The document presents a thermal model of the Pioneer 10 spacecraft constructed using finite-element analysis. The model incorporates design documentation and flight telemetry data to model the temperature distribution and thermal radiation across the spacecraft surfaces. It finds that the magnitude, temporal behavior, and direction of the thermal recoil force predicted by the model are similar to the properties of the observed Pioneer anomaly. Independent estimates of parameters characterizing the thermal recoil force from Doppler data analysis show no statistically significant difference from the thermal modeling results, suggesting the anomaly can be explained by thermal radiation without needing to invoke new physics.
This document summarizes a Phase I study on the development of Blacklight rocket engines funded by NASA. The study included:
1) Evaluating previous experimental data showing unusual hydrogen plasma behavior and energy generation.
2) Developing proof-of-concept Blacklight Plasma Thruster (BLPT) and Blacklight Microwave Plasma Thruster (BLMPT) hardware.
3) Developing methods to test thruster performance by measuring specific impulse and efficiency.
4) Conducting initial test firings of the BLPT and BLMPT thrusters.
The document summarizes the heavy-ion physics program using the Large Hadron Collider (LHC) detectors. It discusses probing novel regimes of high density saturated gluon distributions and qualitatively new physics. Key observables include jet quenching, quarkonia suppression, and heavy flavor modification to study the quark-gluon plasma produced in Pb-Pb collisions. The ALICE, ATLAS and CMS experiments are well-suited to measure bulk properties and select hard probes over a wide momentum range.
An open source framework for processing daily satellite images (AVHRR) over l...Sajid Pareeth
An open source framework was developed to process daily satellite images from Advanced Very High Resolution Radiometer (AVHRR) sensors over the last 28 years. The framework uses open source libraries like Pytroll, Orfeo Toolbox, and GRASS GIS to read, calibrate, correct geometrically, and analyze over 22,000 daily AVHRR images. The processed data will be used to study long term warming trends of sub-alpine lakes from derived land surface temperature.
Inter-sensor comparison of lake surface temperatures derived from MODIS, AVHR...Sajid Pareeth
This document discusses a study comparing lake surface water temperatures derived from thermal bands of MODIS, AVHRR, and AATSR sensors. The study aims to develop a daily homogenized lake surface water temperature dataset over the last two decades by leveraging thermal imagery from multiple satellite sensors. The methodology involves processing and calibrating thermal data from the different sensors, developing lake-specific algorithms to derive surface temperatures, and using statistical methods to reconstruct a continuous temperature time series accounting for gaps in the data. Validation is done using in-situ lake temperature measurements. The resulting long-term temperature dataset will be analyzed to study warming trends and links to climatic indices.
The document discusses the NASA Soil Moisture Active Passive (SMAP) mission, which is scheduled for launch in 2014. SMAP will map global soil moisture and freeze/thaw state from space to further understanding of the water, energy, and carbon cycles. The mission involves an L-band radar and radiometer to provide soil moisture measurements. Algorithms are being developed and tested to generate products like soil moisture maps from the radar-radiometer data. Validation efforts and working groups are helping prepare for the mission.
Water vapour absorption in the clear atmosphere of a Neptune-sized exoplanetGOASA
1) The transmission spectrum of the exoplanet HAT-P-11b was observed using Hubble and Spitzer space telescopes.
2) Water vapor absorption was detected at 1.4 micrometers in the atmosphere, indicating a clear atmosphere down to 1 mbar pressure.
3) The detection of water vapor and relatively large atmospheric scale height places an upper limit on the abundance of heavy elements in the atmosphere of around 700 times the solar value, consistent with core accretion planet formation theories.
CERES Flight Model 5 on NPP was prepared for launch with rigorous pre-launch calibration and testing. Post-launch, independent studies will characterize instrument performance across all scales to validate data products. A strategic approach to data release aims to provide quality-controlled data while supporting continuous calibration improvement.
The document summarizes the Level 1 processing pipeline (L1PP) used to process data from the Soil Moisture and Ocean Salinity (SMOS) mission. The L1PP takes raw instrument data and produces calibrated brightness temperature images at three levels - L1a, L1b, and L1c. Key algorithms described include calibration steps, removal of interference sources like sun and moon, image reconstruction, and geolocation. Validation results showed the L1PP algorithms could produce images with well-defined coastlines and improved radio frequency interference mitigation.
This document summarizes a Phase I study on the development of Blacklight rocket engines funded by NASA. The study included:
1) Evaluating previous experimental data showing unusual hydrogen plasma behavior and energy generation.
2) Developing proof-of-concept Blacklight Plasma Thruster (BLPT) and Blacklight Microwave Plasma Thruster (BLMPT) hardware.
3) Developing methods to test thruster performance by measuring specific impulse and efficiency.
4) Conducting initial test firings of the BLPT and BLMPT thrusters.
The document summarizes the heavy-ion physics program using the Large Hadron Collider (LHC) detectors. It discusses probing novel regimes of high density saturated gluon distributions and qualitatively new physics. Key observables include jet quenching, quarkonia suppression, and heavy flavor modification to study the quark-gluon plasma produced in Pb-Pb collisions. The ALICE, ATLAS and CMS experiments are well-suited to measure bulk properties and select hard probes over a wide momentum range.
An open source framework for processing daily satellite images (AVHRR) over l...Sajid Pareeth
An open source framework was developed to process daily satellite images from Advanced Very High Resolution Radiometer (AVHRR) sensors over the last 28 years. The framework uses open source libraries like Pytroll, Orfeo Toolbox, and GRASS GIS to read, calibrate, correct geometrically, and analyze over 22,000 daily AVHRR images. The processed data will be used to study long term warming trends of sub-alpine lakes from derived land surface temperature.
Inter-sensor comparison of lake surface temperatures derived from MODIS, AVHR...Sajid Pareeth
This document discusses a study comparing lake surface water temperatures derived from thermal bands of MODIS, AVHRR, and AATSR sensors. The study aims to develop a daily homogenized lake surface water temperature dataset over the last two decades by leveraging thermal imagery from multiple satellite sensors. The methodology involves processing and calibrating thermal data from the different sensors, developing lake-specific algorithms to derive surface temperatures, and using statistical methods to reconstruct a continuous temperature time series accounting for gaps in the data. Validation is done using in-situ lake temperature measurements. The resulting long-term temperature dataset will be analyzed to study warming trends and links to climatic indices.
The document discusses the NASA Soil Moisture Active Passive (SMAP) mission, which is scheduled for launch in 2014. SMAP will map global soil moisture and freeze/thaw state from space to further understanding of the water, energy, and carbon cycles. The mission involves an L-band radar and radiometer to provide soil moisture measurements. Algorithms are being developed and tested to generate products like soil moisture maps from the radar-radiometer data. Validation efforts and working groups are helping prepare for the mission.
Water vapour absorption in the clear atmosphere of a Neptune-sized exoplanetGOASA
1) The transmission spectrum of the exoplanet HAT-P-11b was observed using Hubble and Spitzer space telescopes.
2) Water vapor absorption was detected at 1.4 micrometers in the atmosphere, indicating a clear atmosphere down to 1 mbar pressure.
3) The detection of water vapor and relatively large atmospheric scale height places an upper limit on the abundance of heavy elements in the atmosphere of around 700 times the solar value, consistent with core accretion planet formation theories.
CERES Flight Model 5 on NPP was prepared for launch with rigorous pre-launch calibration and testing. Post-launch, independent studies will characterize instrument performance across all scales to validate data products. A strategic approach to data release aims to provide quality-controlled data while supporting continuous calibration improvement.
The document summarizes the Level 1 processing pipeline (L1PP) used to process data from the Soil Moisture and Ocean Salinity (SMOS) mission. The L1PP takes raw instrument data and produces calibrated brightness temperature images at three levels - L1a, L1b, and L1c. Key algorithms described include calibration steps, removal of interference sources like sun and moon, image reconstruction, and geolocation. Validation results showed the L1PP algorithms could produce images with well-defined coastlines and improved radio frequency interference mitigation.
This document summarizes VLBI observations of supernova SN 2011dh made 14 days after its discovery, providing the earliest radio image of a supernova. The observations detected SN 2011dh at 22 GHz using a subset of the EVN array. The recovered flux density was approximately half the value measured by the EVLA at the same frequency and epoch, possibly due to extended emission or calibration issues. Precise coordinates for SN 2011dh were determined, linked to the ICRF, which may help improve future VLBI observations of the supernova.
This document discusses the Soil Moisture Active Passive (SMAP) mission and its objectives to map global soil moisture and freeze/thaw state using L-band radar and radiometer instruments. It describes how SMAP measurements will improve understanding of links between terrestrial water, energy and carbon cycles. It also outlines the development of a Level 4 carbon product that will estimate land-atmosphere carbon exchange using SMAP and ancillary data as inputs to models.
Geothermal exploration using remote sensing techniquesSepideh Abadpour
The document discusses using remote sensing to identify geothermal regions. It describes common remote sensing techniques like identifying thermal anomalies and using satellite images to study land surface temperature. The document also discusses a case study in Mexico that used Landsat images to identify areas with potential geothermal activity by enhancing oxide and hydroxyl mineral spectral features while suppressing vegetation. Band ratios and subtractions were used to create color composites that effectively identified altered rocks and geological structures for further field exploration.
WE1.L10 - USE OF NASA DATA IN THE JOINT CENTER FOR SATELLITE DATA ASSIMILATIONgrssieee
The document discusses the use of NASA satellite data in weather and environmental analysis by the Joint Center for Satellite Data Assimilation (JCSDA). The JCSDA is an interagency partnership that works to improve forecast models through better use of satellite observations. It assimilates many NASA sensors operationally, including MODIS, AIRS, and Jason altimetry, and is working to prepare other sensors like SMAP for assimilation testing. Highlights are presented on atmospheric, ocean, and land data assimilation using NASA data to improve analysis and forecasts.
This document provides a multiwavelength summary of GRB 130427A, one of the brightest gamma-ray bursts ever detected. It was observed across the electromagnetic spectrum from gamma-rays to radio wavelengths. Key points:
1) GRB 130427A had an extremely high luminosity and energy release, similar to the most powerful high-redshift bursts.
2) Follow-up observations detected associated supernova SN 2013cq, showing that very energetic bursts can still be accompanied by supernovae.
3) Light curves at X-ray, optical, and ultraviolet wavelengths show evidence for a jet break approximately 37 kiloseconds after the burst.
4) Standard synchrotron shock models
The document describes the SWOT (Surface Water and Ocean Topography) mission and ground system. SWOT will use Ka-band radar interferometry to measure water levels over oceans and inland water bodies. It presents the mission phases from launch to science operations. The ground system will acquire KaRIN instrument data at rates over 600 Mbps and generate large data products like hydrology maps at 50m resolution. Processing will involve geolocation, corrections, and derivation of geophysical parameters from the radar data. The large data volumes and dual ocean/hydrology goals pose challenges for the SWOT ground system.
The document describes using genetic algorithms to calibrate Rothermel's fuel models. It aims to: 1) Test if genetic algorithm calibration improves accuracy of previously published custom fuel models; 2) Use genetic algorithms to calibrate a new heathland fuel model (GA-heath) using experimental fire data; and 3) Evaluate GA-heath against standard fuel models and a model built with average heath fuel characteristics. The genetic algorithm approach is described and applied to published datasets on grass-shrub and heathland fuels to calibrate new fuel models, finding improved accuracy over published custom models in most cases.
Agu chen a31_g-2917_retrieving temperature and relative humidity profiles fro...Maosi Chen
Atmospheric temperature and relative humidity profiles are fundamental for atmospheric research such as numerical weather prediction and climate change assessment. Hyperspectral satellite data contain a wealth of relevant information and have been used in many algorithms (e.g. regression-based methods) to retrieve these profiles. Deep Learning or Deep Neural Network (DNN) is capable of finding complex relationships (functions) between pairs of input and output variables by assembling many simple non-linear modules together and learning the parameters therein from large amounts of observations. DNN has been successfully applied in many fields (such as image classification, object detection, language translation). In this study, we explored the potential of retrieving atmospheric profiles from hyperspectral satellite radiation data using DNN. The requirement for applying the DNN technique is satisfied with large amount of hyperspectral radiance data provided by United States Suomi National Polar (NPP) Cross-track Infrared Sounder (CrIS) and the reanalyzed atmospheric profiles data provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). The proposed DNN consists of two consecutive parts. In the first part, the first 1245 bands of the NPP CrIS hyperspectral radiance data (648.75 to 2555 cm-1) are compressed into a 300-element vector representing their key features by stacked AutoEncoders. Then, in the second part, the multi-layer Self-Normalizing Neural Network (SNN) is used to map the compressed vector (of 300 elements) into 55-layer temperature and relative humidity profiles. The DNN trainable variables are optimized by minimizing the difference of its predictions and the matched ECMWF temperature and humidity profiles (53230 samples). Finally, the DNN retrieved atmospheric temperature and relative humidity profiles and those provided by the NOAA Unique Combined Atmospheric Processing System (NUCAPS, the official retrieval products for CrIS) are compared with the matched radiosonde observations at one location.
The document discusses estimating air and snow surface temperature evolution in East Antarctica using passive microwave remote sensing. Key points:
- Passive microwave sensors have been monitoring Antarctica since the 1980s, providing multiple images per day, but the continent remains undersampled.
- Correlation analysis between brightness temperature (Tb) measurements from sensors and in situ snow/air temperature data show Tb is closely related to snow temperature at different depths.
- Linear regressions were used to retrieve snow temperatures at depths from 0-10 meters using Tb, achieving good correlation (R2 > 0.9) and standard errors around 2°C.
- Air temperature was also retrieved but with lower accuracy (RMSE 4-
Observations of Gamma-Ray Bursts with the Fermi-Large Area TelescopeVlasios Vasileiou
Brief introduction to the history and science of Gamma Ray Bursts and a report of the latest observational results of the Fermi-Large Area Telescope on GRBs.
Editorial – October 2011 – Three of the MyOcean long time series reanalysis products
Greengs all,
This month’s newsleer is devoted to three of the MyOcean long me series Reanalysis products: the In Situ temperature and salinity CORA reanalysis
(1990 to 2010), the reanalysis of the North Atlanc ocean biogeochemistry (1998-2007) and the Arcc Ocean sea-ice dri/ reanalysis (1992-
2010).
The first product described here is the In Situ temperature and salinity CORA reanalysis (1990 to 2010). A new version of the comprehensive and
qualified ocean in-situ dataset (the Coriolis dataset for Re-Analysis - CORA) is released for the period 1990 to 2010. This in-situ dataset of temperature
and salinity profiles, from different data types (Argo, GTS data, VOS ships, NODC historical data...) on the global scale, is meant to be used for
general oceanographic research purposes, for ocean model validaon, and also for inializaon or assimilaon of ocean models. This product is
available from the MyOcean web portal (hp://www.myocean.eu/).
The second product is the reanalysis of the North Atlanc ocean biogeochemistry (1998-2007). A system assimilang Ocean Colour SeaWiFS data
during the period 1998-2007 has been designed to construct a reanalysis of the North Atlanc ocean biogeochemistry based on a coupled physicalbiogeochemical
model at eddy-admi:ng resoluon. The aim of this study is, on the one hand to develop the skeleton of a pre-operaonal coupled
physical-biogeochemical system with real-me assimilave/forecasng capability, and on the other hand to operate this prototype system for producing
a biogeochemical reanalysis covering the 1998-2007 period. This product is not available from the MyOcean web portal yet.
The third reanalysis product is the 1992-2010 winter Arcc Ocean sea ice dri/ me series made at Ifremer/CERSAT from satellite measurements
which consists of several products: the Level 3 products from single sensors and the L4 products from the combinaon of sensors. They are available
at 3, 6 and 30 day-lag with a 62.5 km-grid size during winter. This dataset is available for oceanic and climate modelling as well as various scienfic
studies in the Arcc. The me series is ongoing and will connue for Arcc long term monitoring using the next MetOp/ASCAT operaonal
scaerometers, planned to be operated for the next 10 years. This product is available from the MyOcean web portal (hp://www.myocean.eu/).
The next January 2012 issue will be dedicated to various applicaons using the Mercator Ocean products.
We wish you a pleasant reading!
This document discusses research on measuring reaction rate coefficients for reactions of the CN radical with various hydrocarbon molecules like propane, propylene, and butadiene at high temperatures representative of circumstellar envelopes of asymptotic giant branch stars. The research uses a high enthalpy source to generate a high temperature flow containing CN radicals, which are then reacted with the hydrocarbon species. Laser-induced fluorescence is used to monitor the CN radicals and determine reaction rate coefficients as a function of temperature from 1000-2200 K. The research aims to provide important kinetic data to understand chemical processes in the envelopes of evolved stars.
A. De Simone: The Quest for Dark Matter: Update and NewsSEENET-MTP
The document summarizes the status of dark matter searches from multiple experiments and detection strategies. It discusses evidence that dark matter exists from cosmological measurements and observations of galaxy rotations. It also outlines various dark matter candidate particles and the search strategies used, including direct detection experiments that have seen some positive hints of an annual modulation signal including DAMA/Libra and CoGeNT experiments, but are in tension with null results from Xenon, CDMS, and Edelweiss experiments. Collider searches for dark matter are also discussed.
The document summarizes a study that used closed loop brightness temperature data inversion to retrieve soil hydraulic properties from radiometer measurements over different soil plots. Soil moisture, temperature, and brightness temperature were monitored over several plots. An inverse modeling procedure was used to estimate soil hydraulic parameters by coupling multiple models and minimizing differences between measured and modeled brightness temperatures and soil moisture values. The estimated soil hydraulic parameters from the inversion procedure improved the modeling of the soil moisture dynamics and brightness temperature compared to laboratory-determined parameters.
VariableR jet reclustering is a technique that allows reconstruction of boosted objects over a wide range of kinematic regimes. This enables efficient identification of events with multiple boosted top quarks, a signature of new physics processes like gluino production. The performance of VariableR reclustering is evaluated by comparing reconstructed jets to those from fixed radius reclustering. VariableR performs better at identifying top quarks and W bosons in events with four top quarks, enhancing sensitivity for gluino searches.
This study implements a Bayesian statistical framework to calibrate the SCOPE process-based simulator for simulating gross primary production (GPP) and top-of-canopy reflectance at a spruce flux tower site in the Czech Republic. Markov chain Monte Carlo simulation is used to quantify the uncertainty in SCOPE input parameters by comparing simulated and measured reflectance and GPP data. The results show the posterior parameter distributions have lower uncertainty than the prior distributions. Simulated half-hourly GPP over the growing season using maximum a posteriori parameter estimates matches the measured data. Future work will estimate seasonal parameter variations to improve GPP simulation accuracy.
Fermi lat observations_of_the_gamma_ray_burst_grb_130427aSérgio Sacani
The observations of gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide constraints on the nature of extremely energetic astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon (95 GeV), longest gamma-ray duration (20 hours), and one of the largest isotropic energy releases ever observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge the widely accepted model that the non-thermal high-energy emission in the afterglow phase of GRBs is synchrotron emission radiated by electrons accelerated at an external shock.
Inference of homogeneous_clouds_in_an_exoplanet_atmosphereSérgio Sacani
1) New visible and infrared observations of the exoplanet Kepler-7b were analyzed to determine its atmospheric properties and detect the presence of clouds.
2) The observations found a westward shift in Kepler-7b's optical phase curve and placed upper limits on its thermal emission that remained undetected in Spitzer bandpasses.
3) The data suggests Kepler-7b has optically thick, high-altitude clouds located west of the substellar point, composed possibly of silicates. The clouds help explain Kepler-7b's unusually high geometric albedo and visible flux that cannot be attributed to thermal emission or molecular hydrogen scattering alone.
1) The document proposes three potential markers for accurately classifying wetland boundaries using polarimetric synthetic aperture radar (PolSAR) imagery: HH-VV phase difference, double-bounce scattering from a four-component decomposition model, and correlation coefficient in the LR basis.
2) Finite-difference time-domain (FDTD) polarimetric scattering analysis of a simple model of vertical dielectric pillars on a dielectric plate representing emergent vegetation on water validated that all three proposed markers can accurately identify wetland boundaries when water levels are relatively high.
3) Future work could include comparing the proposed simple markers to more accurate classification methods, analyzing the effects of varying incident angles and vegetation density, and determining how identified boundary
The ngc1999 dark_globule_is_not_a_globuleSérgio Sacani
The Herschel PACS instrument detected a flux deficit at 70 and 160 microns in the NGC 1999 dark globule. However, follow-up observations with APEX LABOCA, SABOCA, and Magellan PANIC did not detect a submillimeter source or evidence of high extinction at the location of the flux decrement. The authors conclude that the dark patch is actually a cavity or hole in the material producing the NGC 1999 reflection nebula, carved out by protostellar jets from the nearby V 380 Ori multiple star system, rather than an absorbing globule.
Hoag's Object is a peculiar ring galaxy with a central elliptical core. New observations from Hubble Space Telescope and Russian 6-m telescope provide additional data on its structure and kinematics. The data show Hoag's Object has an old stellar core surrounded by a luminous quasi-spiral pattern and massive HI disk. Previous formation scenarios are reviewed in light of the new data. A new scenario is proposed where the elliptical core formed early in the Universe and the HI disk later formed by cold accretion of primordial gas.
This document summarizes research determining the velocity vector of the Andromeda Galaxy (M31) relative to the Milky Way using Hubble Space Telescope measurements of M31's proper motion. N-body models of M31 are used to correct for internal stellar motions within M31. The results imply M31 is on a radial orbit towards the Milky Way. The velocity vector is then used to estimate the mass of the Local Group, obtaining a value of (3.17 ± 0.57) × 1012 M☉. It is also implied M33 is likely bound to M31.
This document summarizes VLBI observations of supernova SN 2011dh made 14 days after its discovery, providing the earliest radio image of a supernova. The observations detected SN 2011dh at 22 GHz using a subset of the EVN array. The recovered flux density was approximately half the value measured by the EVLA at the same frequency and epoch, possibly due to extended emission or calibration issues. Precise coordinates for SN 2011dh were determined, linked to the ICRF, which may help improve future VLBI observations of the supernova.
This document discusses the Soil Moisture Active Passive (SMAP) mission and its objectives to map global soil moisture and freeze/thaw state using L-band radar and radiometer instruments. It describes how SMAP measurements will improve understanding of links between terrestrial water, energy and carbon cycles. It also outlines the development of a Level 4 carbon product that will estimate land-atmosphere carbon exchange using SMAP and ancillary data as inputs to models.
Geothermal exploration using remote sensing techniquesSepideh Abadpour
The document discusses using remote sensing to identify geothermal regions. It describes common remote sensing techniques like identifying thermal anomalies and using satellite images to study land surface temperature. The document also discusses a case study in Mexico that used Landsat images to identify areas with potential geothermal activity by enhancing oxide and hydroxyl mineral spectral features while suppressing vegetation. Band ratios and subtractions were used to create color composites that effectively identified altered rocks and geological structures for further field exploration.
WE1.L10 - USE OF NASA DATA IN THE JOINT CENTER FOR SATELLITE DATA ASSIMILATIONgrssieee
The document discusses the use of NASA satellite data in weather and environmental analysis by the Joint Center for Satellite Data Assimilation (JCSDA). The JCSDA is an interagency partnership that works to improve forecast models through better use of satellite observations. It assimilates many NASA sensors operationally, including MODIS, AIRS, and Jason altimetry, and is working to prepare other sensors like SMAP for assimilation testing. Highlights are presented on atmospheric, ocean, and land data assimilation using NASA data to improve analysis and forecasts.
This document provides a multiwavelength summary of GRB 130427A, one of the brightest gamma-ray bursts ever detected. It was observed across the electromagnetic spectrum from gamma-rays to radio wavelengths. Key points:
1) GRB 130427A had an extremely high luminosity and energy release, similar to the most powerful high-redshift bursts.
2) Follow-up observations detected associated supernova SN 2013cq, showing that very energetic bursts can still be accompanied by supernovae.
3) Light curves at X-ray, optical, and ultraviolet wavelengths show evidence for a jet break approximately 37 kiloseconds after the burst.
4) Standard synchrotron shock models
The document describes the SWOT (Surface Water and Ocean Topography) mission and ground system. SWOT will use Ka-band radar interferometry to measure water levels over oceans and inland water bodies. It presents the mission phases from launch to science operations. The ground system will acquire KaRIN instrument data at rates over 600 Mbps and generate large data products like hydrology maps at 50m resolution. Processing will involve geolocation, corrections, and derivation of geophysical parameters from the radar data. The large data volumes and dual ocean/hydrology goals pose challenges for the SWOT ground system.
The document describes using genetic algorithms to calibrate Rothermel's fuel models. It aims to: 1) Test if genetic algorithm calibration improves accuracy of previously published custom fuel models; 2) Use genetic algorithms to calibrate a new heathland fuel model (GA-heath) using experimental fire data; and 3) Evaluate GA-heath against standard fuel models and a model built with average heath fuel characteristics. The genetic algorithm approach is described and applied to published datasets on grass-shrub and heathland fuels to calibrate new fuel models, finding improved accuracy over published custom models in most cases.
Agu chen a31_g-2917_retrieving temperature and relative humidity profiles fro...Maosi Chen
Atmospheric temperature and relative humidity profiles are fundamental for atmospheric research such as numerical weather prediction and climate change assessment. Hyperspectral satellite data contain a wealth of relevant information and have been used in many algorithms (e.g. regression-based methods) to retrieve these profiles. Deep Learning or Deep Neural Network (DNN) is capable of finding complex relationships (functions) between pairs of input and output variables by assembling many simple non-linear modules together and learning the parameters therein from large amounts of observations. DNN has been successfully applied in many fields (such as image classification, object detection, language translation). In this study, we explored the potential of retrieving atmospheric profiles from hyperspectral satellite radiation data using DNN. The requirement for applying the DNN technique is satisfied with large amount of hyperspectral radiance data provided by United States Suomi National Polar (NPP) Cross-track Infrared Sounder (CrIS) and the reanalyzed atmospheric profiles data provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). The proposed DNN consists of two consecutive parts. In the first part, the first 1245 bands of the NPP CrIS hyperspectral radiance data (648.75 to 2555 cm-1) are compressed into a 300-element vector representing their key features by stacked AutoEncoders. Then, in the second part, the multi-layer Self-Normalizing Neural Network (SNN) is used to map the compressed vector (of 300 elements) into 55-layer temperature and relative humidity profiles. The DNN trainable variables are optimized by minimizing the difference of its predictions and the matched ECMWF temperature and humidity profiles (53230 samples). Finally, the DNN retrieved atmospheric temperature and relative humidity profiles and those provided by the NOAA Unique Combined Atmospheric Processing System (NUCAPS, the official retrieval products for CrIS) are compared with the matched radiosonde observations at one location.
The document discusses estimating air and snow surface temperature evolution in East Antarctica using passive microwave remote sensing. Key points:
- Passive microwave sensors have been monitoring Antarctica since the 1980s, providing multiple images per day, but the continent remains undersampled.
- Correlation analysis between brightness temperature (Tb) measurements from sensors and in situ snow/air temperature data show Tb is closely related to snow temperature at different depths.
- Linear regressions were used to retrieve snow temperatures at depths from 0-10 meters using Tb, achieving good correlation (R2 > 0.9) and standard errors around 2°C.
- Air temperature was also retrieved but with lower accuracy (RMSE 4-
Observations of Gamma-Ray Bursts with the Fermi-Large Area TelescopeVlasios Vasileiou
Brief introduction to the history and science of Gamma Ray Bursts and a report of the latest observational results of the Fermi-Large Area Telescope on GRBs.
Editorial – October 2011 – Three of the MyOcean long time series reanalysis products
Greengs all,
This month’s newsleer is devoted to three of the MyOcean long me series Reanalysis products: the In Situ temperature and salinity CORA reanalysis
(1990 to 2010), the reanalysis of the North Atlanc ocean biogeochemistry (1998-2007) and the Arcc Ocean sea-ice dri/ reanalysis (1992-
2010).
The first product described here is the In Situ temperature and salinity CORA reanalysis (1990 to 2010). A new version of the comprehensive and
qualified ocean in-situ dataset (the Coriolis dataset for Re-Analysis - CORA) is released for the period 1990 to 2010. This in-situ dataset of temperature
and salinity profiles, from different data types (Argo, GTS data, VOS ships, NODC historical data...) on the global scale, is meant to be used for
general oceanographic research purposes, for ocean model validaon, and also for inializaon or assimilaon of ocean models. This product is
available from the MyOcean web portal (hp://www.myocean.eu/).
The second product is the reanalysis of the North Atlanc ocean biogeochemistry (1998-2007). A system assimilang Ocean Colour SeaWiFS data
during the period 1998-2007 has been designed to construct a reanalysis of the North Atlanc ocean biogeochemistry based on a coupled physicalbiogeochemical
model at eddy-admi:ng resoluon. The aim of this study is, on the one hand to develop the skeleton of a pre-operaonal coupled
physical-biogeochemical system with real-me assimilave/forecasng capability, and on the other hand to operate this prototype system for producing
a biogeochemical reanalysis covering the 1998-2007 period. This product is not available from the MyOcean web portal yet.
The third reanalysis product is the 1992-2010 winter Arcc Ocean sea ice dri/ me series made at Ifremer/CERSAT from satellite measurements
which consists of several products: the Level 3 products from single sensors and the L4 products from the combinaon of sensors. They are available
at 3, 6 and 30 day-lag with a 62.5 km-grid size during winter. This dataset is available for oceanic and climate modelling as well as various scienfic
studies in the Arcc. The me series is ongoing and will connue for Arcc long term monitoring using the next MetOp/ASCAT operaonal
scaerometers, planned to be operated for the next 10 years. This product is available from the MyOcean web portal (hp://www.myocean.eu/).
The next January 2012 issue will be dedicated to various applicaons using the Mercator Ocean products.
We wish you a pleasant reading!
This document discusses research on measuring reaction rate coefficients for reactions of the CN radical with various hydrocarbon molecules like propane, propylene, and butadiene at high temperatures representative of circumstellar envelopes of asymptotic giant branch stars. The research uses a high enthalpy source to generate a high temperature flow containing CN radicals, which are then reacted with the hydrocarbon species. Laser-induced fluorescence is used to monitor the CN radicals and determine reaction rate coefficients as a function of temperature from 1000-2200 K. The research aims to provide important kinetic data to understand chemical processes in the envelopes of evolved stars.
A. De Simone: The Quest for Dark Matter: Update and NewsSEENET-MTP
The document summarizes the status of dark matter searches from multiple experiments and detection strategies. It discusses evidence that dark matter exists from cosmological measurements and observations of galaxy rotations. It also outlines various dark matter candidate particles and the search strategies used, including direct detection experiments that have seen some positive hints of an annual modulation signal including DAMA/Libra and CoGeNT experiments, but are in tension with null results from Xenon, CDMS, and Edelweiss experiments. Collider searches for dark matter are also discussed.
The document summarizes a study that used closed loop brightness temperature data inversion to retrieve soil hydraulic properties from radiometer measurements over different soil plots. Soil moisture, temperature, and brightness temperature were monitored over several plots. An inverse modeling procedure was used to estimate soil hydraulic parameters by coupling multiple models and minimizing differences between measured and modeled brightness temperatures and soil moisture values. The estimated soil hydraulic parameters from the inversion procedure improved the modeling of the soil moisture dynamics and brightness temperature compared to laboratory-determined parameters.
VariableR jet reclustering is a technique that allows reconstruction of boosted objects over a wide range of kinematic regimes. This enables efficient identification of events with multiple boosted top quarks, a signature of new physics processes like gluino production. The performance of VariableR reclustering is evaluated by comparing reconstructed jets to those from fixed radius reclustering. VariableR performs better at identifying top quarks and W bosons in events with four top quarks, enhancing sensitivity for gluino searches.
This study implements a Bayesian statistical framework to calibrate the SCOPE process-based simulator for simulating gross primary production (GPP) and top-of-canopy reflectance at a spruce flux tower site in the Czech Republic. Markov chain Monte Carlo simulation is used to quantify the uncertainty in SCOPE input parameters by comparing simulated and measured reflectance and GPP data. The results show the posterior parameter distributions have lower uncertainty than the prior distributions. Simulated half-hourly GPP over the growing season using maximum a posteriori parameter estimates matches the measured data. Future work will estimate seasonal parameter variations to improve GPP simulation accuracy.
Fermi lat observations_of_the_gamma_ray_burst_grb_130427aSérgio Sacani
The observations of gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide constraints on the nature of extremely energetic astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon (95 GeV), longest gamma-ray duration (20 hours), and one of the largest isotropic energy releases ever observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge the widely accepted model that the non-thermal high-energy emission in the afterglow phase of GRBs is synchrotron emission radiated by electrons accelerated at an external shock.
Inference of homogeneous_clouds_in_an_exoplanet_atmosphereSérgio Sacani
1) New visible and infrared observations of the exoplanet Kepler-7b were analyzed to determine its atmospheric properties and detect the presence of clouds.
2) The observations found a westward shift in Kepler-7b's optical phase curve and placed upper limits on its thermal emission that remained undetected in Spitzer bandpasses.
3) The data suggests Kepler-7b has optically thick, high-altitude clouds located west of the substellar point, composed possibly of silicates. The clouds help explain Kepler-7b's unusually high geometric albedo and visible flux that cannot be attributed to thermal emission or molecular hydrogen scattering alone.
1) The document proposes three potential markers for accurately classifying wetland boundaries using polarimetric synthetic aperture radar (PolSAR) imagery: HH-VV phase difference, double-bounce scattering from a four-component decomposition model, and correlation coefficient in the LR basis.
2) Finite-difference time-domain (FDTD) polarimetric scattering analysis of a simple model of vertical dielectric pillars on a dielectric plate representing emergent vegetation on water validated that all three proposed markers can accurately identify wetland boundaries when water levels are relatively high.
3) Future work could include comparing the proposed simple markers to more accurate classification methods, analyzing the effects of varying incident angles and vegetation density, and determining how identified boundary
The ngc1999 dark_globule_is_not_a_globuleSérgio Sacani
The Herschel PACS instrument detected a flux deficit at 70 and 160 microns in the NGC 1999 dark globule. However, follow-up observations with APEX LABOCA, SABOCA, and Magellan PANIC did not detect a submillimeter source or evidence of high extinction at the location of the flux decrement. The authors conclude that the dark patch is actually a cavity or hole in the material producing the NGC 1999 reflection nebula, carved out by protostellar jets from the nearby V 380 Ori multiple star system, rather than an absorbing globule.
Hoag's Object is a peculiar ring galaxy with a central elliptical core. New observations from Hubble Space Telescope and Russian 6-m telescope provide additional data on its structure and kinematics. The data show Hoag's Object has an old stellar core surrounded by a luminous quasi-spiral pattern and massive HI disk. Previous formation scenarios are reviewed in light of the new data. A new scenario is proposed where the elliptical core formed early in the Universe and the HI disk later formed by cold accretion of primordial gas.
This document summarizes research determining the velocity vector of the Andromeda Galaxy (M31) relative to the Milky Way using Hubble Space Telescope measurements of M31's proper motion. N-body models of M31 are used to correct for internal stellar motions within M31. The results imply M31 is on a radial orbit towards the Milky Way. The velocity vector is then used to estimate the mass of the Local Group, obtaining a value of (3.17 ± 0.57) × 1012 M☉. It is also implied M33 is likely bound to M31.
Bright and dark_polar_deposits_on _mercury_evidence_for_surface _volatilesSérgio Sacani
1) Laser albedometer measurements from Mercury's north pole reveal unusually dark and bright surface deposits near permanently shadowed regions.
2) The dark deposits coincide with areas exhibiting low radar backscatter, suggesting a thin, dark material overlies buried ice.
3) Bright deposits are found in the largest craters above 84.9° latitude and match areas predicted to be cold enough for surface ice. This provides evidence that water ice is exposed directly at the surface in these locations.
This document appears to be a citation to a scientific publication from 1959 containing the string "1959ApJS....4..257S" repeated multiple times without any other context or information. There is no clear high-level or essential information that can be summarized from the document.
The relation between_gas_and_dust_in_the_taurus_molecular_cloudSérgio Sacani
This document summarizes a study of the relationship between gas and dust in the Taurus molecular cloud. The authors compare hydrogen column densities derived from dust extinction measurements with carbon monoxide column densities derived from 12CO and 13CO observations. They find a linear relationship between visual extinction (AV) and carbon monoxide column density (N(CO)) between AV of 3-10 magnitudes. However, in other regions the relationship is flattened for AV greater than 4 magnitudes. Accounting for temperature gradients and CO depletion, they estimate the total hydrogen mass of Taurus to be about 1.5x104 solar masses and derive a CO-to-H2 conversion factor.
Delivery of dark_material_to_vesta_via_carbonaceous_chondritic_impactsSérgio Sacani
This document analyzes dark material (DM) observed on the surface of asteroid Vesta by NASA's Dawn spacecraft. Spectral analysis finds the DM has properties similar to carbonaceous chondrite meteorites mixed with Vestan surface materials. Laboratory experiments matching the albedo and absorption bands of DM used mixtures of carbonaceous chondrites and eucrite basalt. Impact modeling suggests the DM was delivered via impacts of carbonaceous chondrite asteroids during the formation of the large Veneneia impact basin on Vesta. This supports the idea that carbonaceous chondrites were an important early source of carbon and volatiles in the solar system.
Mapping the complex_kinematics_of_l_lobjects_in_the_orion_nebulaSérgio Sacani
This document presents a study of the kinematics of two LL Orionis-type objects (LL objects) in the Orion nebula, LL 1 and LL 2, and their associated Herbig-Haro jets HH 888 and HH 505. The authors combine long-slit spectroscopic observations of the objects with proper motion measurements to construct 3D velocity maps. The maps reveal:
1) Low velocities (10-20 km/s) in the stellar bowshocks of LL 1 and LL 2, with LL 1 showing symmetric motions and LL 2 showing asymmetric motions following nebula gradients.
2) Jet knot velocities over 200 km/s near the stars declining to under 100 km/s farther out in HH 8
This document describes observations of Cepheid variables in the host galaxies of two Type Ia supernovae, SN 1995al in NGC 3021 and SN 2002fk in NGC 1309, using the Hubble Space Telescope. The observations aim to increase the sample of reliably calibrated supernovae to improve the measurement of the Hubble constant. New Cepheids were discovered, including many with periods over 60 days. Metallicity measurements of the galaxies' H II regions were also consistent with solar metallicity. The new data on the supernovae and Cepheids will help strengthen the distance ladder and reduce systematic uncertainties in the determination of the Hubble constant.
Our deep, wide-field imaging of M101 and its surrounding environment reveals:
1) M101's disk extends to nearly 25 arcminutes (50 kpc), three times the measured optical radius, with an asymmetric plume of light to the northeast following the extended HI disk.
2) This outer plume has very blue colors, suggesting a somewhat evolved young stellar population, while another redder spur is detected to the east.
3) No evidence is found of very extended tidal tails around M101 or its companions despite signs of past interactions shaping M101's asymmetry.
4) The detection of starlight at such large radii allows studying the stellar populations and star formation histories in M101's outer disk
This document analyzes trajectories to reach the heliopause and exit the solar system using nuclear thermal propulsion (NTP) and Oberth maneuvers. It finds that NTP, which can provide much higher specific impulse than chemical propulsion, enables significantly faster trajectories when combined with Oberth maneuvers where the spacecraft fires its engines near the closest approach to the Sun. The document models trajectories from various launch vehicles that take the spacecraft close to the Sun, where it executes a large velocity change to enter an hyperbolic orbit leaving the solar system. It finds that lower perihelion distances and higher Oberth burns result in higher exit velocities from the solar system.
This document presents a problem set related to investigating the unexplained Pioneer anomaly. The anomaly is an anomalous small constant Doppler frequency drift observed in radio-metric tracking data from the Pioneer 10 and 11 spacecraft between 20-70 AU from the Sun.
The problem set provides calculations to analyze how the anomaly would affect the trajectories and velocities of the Pioneer spacecraft over time. It also discusses potential error sources both external and onboard the spacecraft, as well as computational errors, that could contribute to the observed anomaly. The document concludes that the anomaly remains unexplained and that a dedicated test is needed given limitations of other spacecraft to provide an independent verification.
Herman mosquera2011 nonlinear electrodynamics and the pioneer 1011 spacecraftSOCIEDAD JULIO GARAVITO
1) The document discusses the unexplained "Pioneer anomaly" - an anomalous blueshift in radio signals from the Pioneer 10/11 spacecraft that suggests they are accelerating under an unexplained force.
2) Conventional explanations like gravitational effects, solar radiation pressure, and modified dynamics have been ruled out. The anomaly appears to be related to the electromagnetic sector rather than gravity.
3) The document proposes that nonlinear electrodynamics (NLED), where the electromagnetic field depends nonlinearly on the field strength, could explain an anomalous frequency shift in photons as they propagate through space without interacting with matter. This effect is called "photon acceleration".
1) NREL is a national laboratory operated by the Alliance for Sustainable Energy, LLC that focuses on energy efficiency and renewable energy.
2) The presentation discusses options for quantifying solar resource from measurements including horizontal and inclined surfaces, and methods for transposing horizontal irradiance data to plane of array irradiance.
3) It notes that isotropic models used to approximate this transposition can underestimate plane of array irradiance by 5-20% compared to using anisotropic physics models that better simulate cloud conditions and solar radiances.
The document describes an imaging Fourier transform spectrometer (IFTS) intended to provide atmospheric measurements of the Arctic region from a highly elliptical orbit. The IFTS would measure pressure, temperature, and concentrations of gases like O2, CH4, and CO2 to improve understanding of climate change, methane hydrate releases, and air quality in the Arctic. A balloon mission is planned to test the instrument at a technology readiness level of 7. The IFTS design uses a commercial Michelson interferometer with a diode laser, beam splitter, and double-axis mirror pointing system to collect interferograms at 100 frames per second with 0.25 cm-1 spectral resolution across two wavelength channels.
33 Measurement of beam-recoil observables Ox, Oz and target asymmetry T for t...Cristian Randieri PhD
Measurement of beam-recoil observables Ox, Oz and target asymmetry T for the reaction γρ → K+Λ - The European Physical Journal A, Hadrons and Nuclei, February 2009, Vol. 39, N. 2, pp. 149–161, ISSN: 1434-6001, doi: 10.1140/epja/i2008-10713-4
di A. Lleres, O. Bartalini, V. Bellini, J. P. Bocquet, P. Calvat, M. Capogni, L. Casano, M. Castoldi, A. D’Angelo, J. P. Didelez, R. Di Salvo, A. Fantini, D. Franco, C. Gaulard, G. Gervino, F. Ghio, B. Girolami, A. Giusa, M. Guidal, E. Hourany, R. Kunne, V. Kuznetsov, A. Lapik, P. Levi Sandri, F. Mammoliti, G. Mandaglio, D. Moricciani, A. N. Mushkarenkov, V. Nedorezov, L. Nicoletti, C. Perrin, C. Randieri, D. Rebreyend, F. Renard, N. Rudnev, T. Russew, G. Russo, C. Schaerf, M. L. Sperduto, M. C. Sutera, A. Turinge, V. Vegna (2009)
Abstract
The double polarization (beam-recoil) observables Ox and Oz have been measured for the reac- tion γp → K+Λ from threshold production to E ∼ 1500MeV. The data were obtained with the linearly polarized beam of the GRAAL facility. Values for the target asymmetry T could also be extracted despite the use of an unpolarized target. Analyses of our results by two isobar models tend to confirm the necessity to include new or poorly known resonances in the 1900MeV mass region.
1. The document describes observations of the Seyfert-1 galaxy Mrk 509 using XMM-Newton and Swift.
2. It analyzes the optical-UV and X-ray variability over a 100 day monitoring campaign with a few day resolution.
3. The results suggest that on these timescales, the soft X-ray excess in Mrk 509 is produced by warm Comptonization of thermal optical-UV photons from the accretion disk by a warm, optically thick corona surrounding the inner disk regions.
Analysis of Anomalous Thrust Experiments from an Asymmetric CavityBrian Kraft
1) Several institutions have tested novel propulsion devices called EM Drives and Cannae Drives that produce thrust without propellant by using resonant microwave cavities. Results have ranged from 0.02 N/kW to 1.03 N/kW of thrust.
2) The document analyzes differences between experiments such as cavity design, materials, power levels, measurement techniques, and number of test runs. It finds variations in these factors likely contributed to differing results.
3) Specifically, NASA JSC Eagleworks obtained the lowest thrust of 0.0021 N/kW using a tapered cylindrical cavity with a dielectric insert, while other experiments excluding Tajmar obtained over 0.1 N/kW
On the-mechanism-of-proton-conductivity-in-h-sub3sub o-sbteo-sub6sub_2012_jou...Javier Lemus Godoy
This document summarizes a study investigating the proton conductivity mechanism in H3OSbTeO6 using neutron diffraction, quasielastic neutron scattering, and NMR experiments at various temperatures. H3OSbTeO6 has an outstanding proton conductivity even at room temperature. It consists of a three-dimensional framework of corner-sharing SbO6 and TeO6 octahedra forming cages where H3O+ ions are located. Three types of ion motion were observed: rotations of the H3O group, jumps between equivalent positions within cages, and long-range translational diffusion between cages. Structural changes reflected the onset of ionic conductivity. Details of the complex diffusion mechanism are provided.
Detection of an atmosphere around the super earth 55 cancri eSérgio Sacani
We report the analysis of two new spectroscopic observations of the super-Earth 55 Cancri e, in the near
infrared, obtained with the WFC3 camera onboard the HST. 55 Cancri e orbits so close to its parent
star, that temperatures much higher than 2000 K are expected on its surface. Given the brightness
of 55 Cancri, the observations were obtained in scanning mode, adopting a very long scanning length
and a very high scanning speed. We use our specialized pipeline to take into account systematics
introduced by these observational parameters when coupled with the geometrical distortions of the
instrument. We measure the transit depth per wavelength channel with an average relative uncertainty
of 22 ppm per visit and nd modulations that depart from a straight line model with a 6 condence
level. These results suggest that 55 Cancri e is surrounded by an atmosphere, which is probably
hydrogen-rich. Our fully Bayesian spectral retrieval code, T -REx, has identied HCN to be the
most likely molecular candidate able to explain the features at 1.42 and 1.54 m. While additional
spectroscopic observations in a broader wavelength range in the infrared will be needed to conrm
the HCN detection, we discuss here the implications of such result. Our chemical model, developed
with combustion specialists, indicates that relatively high mixing ratios of HCN may be caused by a
high C/O ratio. This result suggests this super-Earth is a carbon-rich environment even more exotic
than previously thought.
The document summarizes research on modeling the annealing kinetics of latent tracks in solid state nuclear track detectors (SSNTDs). It describes the historical development and limitations of existing models. A single activation energy (SAE) model is proposed to overcome limitations. The SAE model relates the annealing rate to time and temperature using an empirical equation involving a single activation energy, Ea, which is a material-dependent property. Experimental validation of the SAE model involves isothermal and isochronal annealing experiments to determine Ea and other parameters. The SAE model provides a better description of annealing in SSNTDs compared to previous models.
This document summarizes an experiment that measured the temperature-dependent responsivity of plasmonic terahertz detectors. The experiment measured the response of gallium nitride chips under terahertz pulses in both free space and liquid nitrogen conditions. The results showed lower response amplitudes in liquid nitrogen, consistent with decreased electron excitation and conductivity at lower temperatures according to plasmonics and semiconductor physics models. Understanding these material properties allows for optimizing devices that use plasmonic materials.
Experimental study of evaporation in a tubular solar stillIAEME Publication
This document summarizes an experimental study on evaporation in a tubular solar still. The study aims to determine the heat transfer coefficients in the still and their relationship to variables like temperature. An outdoor experiment is conducted using a prototype tubular solar still constructed with a PVC cover. Temperature readings are recorded. Theoretical models are analyzed to predict evaporation rate based on factors like humidity and vapor pressure. Constants C and n are evaluated using experimental data to better model heat transfer rate equations for this still design compared to previous models.
Experimental study of evaporation in a tubular solar stillIAEME Publication
This document summarizes an experimental study on evaporation in a tubular solar still. The study aims to determine heat transfer coefficients in the still and develop a model to predict evaporation. Experiments were conducted on a prototype tubular solar still in April 2012. Temperature and distillate output data were collected. Heat transfer coefficients were calculated using a modified Nusselt number approach. The constants C and n were determined through regression analysis of experimental data. The developed model was found to provide closer results to experiments compared to an existing Dunkle model. The tubular solar still design was found to improve distillate yield by 166% over a double slope solar still of the same basin area.
Some possible interpretations from data of the CODALEMA experimentAhmed Ammar Rebai PhD
The purpose of the CODALEMA experiment, installed at the Nan\c{c}ay Radio Observatory (France), is to study the radio-detection of ultra-high energy cosmic rays in the energy range of 10^{16}-10^{18} eV. Distributed over an area of 0.25 km^2, the original device uses in coincidence an array of particle detectors and an array of short antennas, with a centralized acquisition. A new analysis of the observable in energy for radio is presented from this system, taking into account the geomagnetic effect. Since 2011, a new array of radio-detectors, consisting of 60 stand-alone and self-triggered stations, is being deployed over an area of 1.5 km^2 around the initial configuration. This new development leads to specific constraints to be discussed in term of recognition of cosmic rays and in term of analysis of wave-front.
This document reports on a study analyzing the molecular structure, vibrational spectra, and nonlinear optical properties of 4-Chloro-DL-phenylalanine (4CLPA) using density functional theory calculations. Specifically, the researchers recorded and analyzed the FTIR and FT-Raman spectra of 4CLPA. They investigated the equilibrium geometry, bonding features, and harmonic vibrational wavenumbers using DFT calculations. They also analyzed the predicted electronic absorption spectra from TD-DFT calculations compared to the measured UV–Vis spectrum. In addition, they calculated properties like the first order hyperpolarizability and frontier molecular orbitals to understand the charge interactions and reactivity of 4CLPA.
A. Investigation and Analysis of Anomalous Thrust ExperimentsKurt Zeller
NASA and several independent researchers have conducted experiments testing a novel propulsion technology called the EM Drive, which produces thrust without ejecting propellant by utilizing a resonant microwave cavity. Key findings include:
1) Experiments by NASA, NWPU in China, SPR Ltd., and Guido Fetta observed thrust-to-power ratios ranging from 0.021 N/kW to 1.03 N/kW, exceeding ion thrusters.
2) NASA's tests in a hard vacuum matched results from initial atmospheric tests, finding thrust from both an EM Drive and Cannae Drive configuration.
3) Device designs and test parameters like power level, frequency, cavity material, and inclusion of a dielectric varied between experiments
Pablo Estevez: "Computational Intelligence Applied to Time Series Analysis" ieee_cis_cyprus
This document summarizes a presentation on analyzing astronomical time series data using information theoretic learning approaches. It discusses challenges with irregularly sampled and noisy light curve data from astronomical surveys. It proposes using correntropy, a generalized correlation measure, within a periodic kernel to create a Correntropy Kernelized Periodogram (CKP) for discriminating periodic vs non-periodic light curves and estimating periods of periodic curves. It applies this approach to real survey data from MACHO and EROS, achieving high classification accuracy and ability to process billions of light curves efficiently using GPU clusters.
Towards the identification of the primary particle nature by the radiodetecti...Ahmed Ammar Rebai PhD
To contact the author use ahmed.rebai2@gmail.com
Radio signal from extensive air showers EAS studied by the CODALEMA experiment have been detected by means of the classic short fat antennas array working in a slave trigger mode by a particle scintillator array. It is shown that the radio shower wavefront is curved with respect to the plane wavefront hypothesis. Then a new fitting model (parabolic model) is proposed to fit the radio signal time delay distributions in an event-by-event basis. This model take into account this wavefront property and several shower geometry parameters such as: the existence of an apparent localised radio-emission source located at a distance Rc from the antenna array of and the
radio shower core on the ground. Comparison of the outputs from this model and other reconstruction models used in the same experiment show: 1)- That the radio shower core is shifted from the particle shower core in a statistic analysis approach. 2)- The capability of the radiodetection method to reconstruct the curvature radius
with a statistical error less than 50 g.cm−2 . Finally a preliminary study of the primary particle nature has been performed based on a comparison between data and Xmax distribution from Aires Monte-Carlo simulations for the same set of events.
1. This document describes a multiwavelength campaign on the Seyfert 1 galaxy Mrk 509 using five satellites and two ground-based facilities.
2. The campaign aims to study several open questions about active galactic nuclei (AGN), including the location and physics of outflows from AGN, the nature of continuum emission, the geometry and physical state of the X-ray broad emission line region, and the Fe-K line complex.
3. The observations cover more than five decades in frequency, from 2 μm to 200 keV, and include a simultaneous set of deep XMM-Newton and INTEGRAL observations over seven weeks. This allows the authors to disentangle different components and study time variability
Similar to Support for the_thermal_origin_of_the_pioneer_anomaly (20)
The binding of cosmological structures by massless topological defectsSérgio Sacani
Assuming spherical symmetry and weak field, it is shown that if one solves the Poisson equation or the Einstein field
equations sourced by a topological defect, i.e. a singularity of a very specific form, the result is a localized gravitational
field capable of driving flat rotation (i.e. Keplerian circular orbits at a constant speed for all radii) of test masses on a thin
spherical shell without any underlying mass. Moreover, a large-scale structure which exploits this solution by assembling
concentrically a number of such topological defects can establish a flat stellar or galactic rotation curve, and can also deflect
light in the same manner as an equipotential (isothermal) sphere. Thus, the need for dark matter or modified gravity theory is
mitigated, at least in part.
EWOCS-I: The catalog of X-ray sources in Westerlund 1 from the Extended Weste...Sérgio Sacani
Context. With a mass exceeding several 104 M⊙ and a rich and dense population of massive stars, supermassive young star clusters
represent the most massive star-forming environment that is dominated by the feedback from massive stars and gravitational interactions
among stars.
Aims. In this paper we present the Extended Westerlund 1 and 2 Open Clusters Survey (EWOCS) project, which aims to investigate
the influence of the starburst environment on the formation of stars and planets, and on the evolution of both low and high mass stars.
The primary targets of this project are Westerlund 1 and 2, the closest supermassive star clusters to the Sun.
Methods. The project is based primarily on recent observations conducted with the Chandra and JWST observatories. Specifically,
the Chandra survey of Westerlund 1 consists of 36 new ACIS-I observations, nearly co-pointed, for a total exposure time of 1 Msec.
Additionally, we included 8 archival Chandra/ACIS-S observations. This paper presents the resulting catalog of X-ray sources within
and around Westerlund 1. Sources were detected by combining various existing methods, and photon extraction and source validation
were carried out using the ACIS-Extract software.
Results. The EWOCS X-ray catalog comprises 5963 validated sources out of the 9420 initially provided to ACIS-Extract, reaching a
photon flux threshold of approximately 2 × 10−8 photons cm−2
s
−1
. The X-ray sources exhibit a highly concentrated spatial distribution,
with 1075 sources located within the central 1 arcmin. We have successfully detected X-ray emissions from 126 out of the 166 known
massive stars of the cluster, and we have collected over 71 000 photons from the magnetar CXO J164710.20-455217.
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
Continuum emission from within the plunging region of black hole discs
Support for the_thermal_origin_of_the_pioneer_anomaly
1. Support for the thermal origin of the Pioneer anomaly
Slava G. Turyshev1 , Viktor T. Toth2 , Gary Kinsella1 , Siu-Chun Lee3 , Shing M. Lok3 , and Jordan Ellis1
1
Jet Propulsion Laboratory, California Institute of Technology,
4800 Oak Grove Drive, Pasadena, CA 91109-0899, USA
2
Ottawa, ON K1N 9H5, Canada and
3
Applied Sciences Laboratory, 13111 Brooks Drive, Suite A, Baldwin Park, CA 91706-7902, USA
We investigate the possibility that the anomalous acceleration of the Pioneer 10 and 11 space-
craft is due to the recoil force associated with an anisotropic emission of thermal radiation off the
vehicles. To this end, relying on the project and spacecraft design documentation, we constructed
a comprehensive finite-element thermal model of the two spacecraft. Then, we numerically solve
thermal conduction and radiation equations using the actual flight telemetry as boundary condi-
arXiv:1204.2507v1 [gr-qc] 11 Apr 2012
tions. We use the results of this model to evaluate the effect of the thermal recoil force on the
Pioneer 10 spacecraft at various heliocentric distances. We found that the magnitude, temporal
behavior, and direction of the resulting thermal acceleration are all similar to the properties of the
observed anomaly. As a novel element of our investigation, we develop a parameterized model for
the thermal recoil force and estimate the coefficients of this model independently from navigational
Doppler data. We find no statistically significant difference between the two estimates and conclude
that once the thermal recoil force is properly accounted for, no anomalous acceleration remains.
PACS numbers: 04.80.-y, 95.10.Eg, 95.55.Pe
INTRODUCTION In this Letter we report on the completion of a finite-
element thermal model of the Pioneer 10 spacecraft. This
The anomalous acceleration of the Pioneer 10 and 11 model relies extensively on the project and spacecraft
spacecraft [1] is a discrepancy between modeled and ob- design documentation and was validated using redun-
served radio-metric Doppler data received from the two dant flight telemetry data. A parameterized form of the
vehicles. The discrepancy can be eliminated by incorpo- thermal force model [11] was also incorporated into a
rating a constant sunward acceleration of unknown origin Doppler analysis, which yielded an independent estimate
with magnitude of aP = (8.74 ± 1.33) × 10−10 m/s into
2 of coefficients characterizing the thermal recoil force. We
the orbital model [2]. The presence of this acceleration, compare the outputs of the two independent analyses –
which became known as the Pioneer anomaly, was seen Doppler and thermal – to show that no statistically sig-
by many as a breakdown in the gravitational inverse- nificant anomalous acceleration remains in the data.
square law of general relativity that reveals itself in the
dynamics of the outer solar system. There were also pro- FINITE-ELEMENT THERMAL MODEL
posals that this anomaly was due, at least in part, to the
waste heat emitted by the spacecrafts’ radioisotope ther- A comprehensive finite-element (FE) thermal model
moelectric generators (RTGs) [3], their electrical subsys- (Fig. 1) of the Pioneer 10 and 11 spacecraft was con-
tems [4], or both [5], motivating a thorough investigation structed at the Jet Propulsion Laboratory (JPL) in col-
of the spacecraft systematics (for review, see [6]). laboration with the Applied Sciences Laboratory (ASL).
Our current investigation began with the recovery of The geometric and thermal models of the spacecraft were
the entire telemetry record of both spacecraft, substan- constructed using the SINDA/3D thermal modeling soft-
tial project documentation, and additional Doppler data ware [15]. While the software provides the capability
[7]. The analysis of the extended Doppler data set was to build a numerical model directly from CAD drawing
completed recently [8], confirming the existence of the files, no such files exist for a spacecraft designed 40 years
anomaly. This analysis also showed that although the ago. For this reason, the model was built in a more te-
direction of the anomalous acceleration cannot be deter- dious manner by specifying the coordinates of the ver-
mined unambiguously, the Doppler residuals improve if tices of each modeled spacecraft surface, using available
one considers a temporally varying acceleration in the blueprints and recovered project documentation. The
direction of the Earth, which is consistent with earlier, spacecraft geometric model was built with a Monte Carlo
similar results [9, 10]. These results are suggestive: If the based radiation analyzer (TSS) to calculate the radia-
acceleration were due to thermal recoil force, it would be tive exchange factors using infrared emittance values for
along the spacecraft spin axis, which generally points in modeled surfaces specified within it. The model incorpo-
the direction of the Earth and would have temporally rated approximately 3,300 surface elements, 3,700 nodes,
decreasing magnitude consistent with the decay of the and 8,700 linear conductors. The spacecraft thermal-
on-board radioisotope fuel (Pu238 ). mechanical configuration is simulated by a network of
2. 2
Earth
Heliocentric distance (AU)
10 20 30 40 50 60 70 80
100
Thermal power (W)
0
−100
−200
−300
−400
1975 1980 1985 1990 1995 2000
FIG. 2: Pioneer 10 thermal power contributing to sunward
acceleration, including solar heating and reflected solar ra-
diation (hollow circles), solar heating only (hollow squares)
with reflected solar radiation removed, and all solar effects
FIG. 1: Illustrative representation of the thermal model of the removed (filled circles). Positive values indicate radiation di-
Pioneer 10 spacecraft evaluated at 40 AU. Top left: spacecraft rected away from the Sun, resulting in a sunward acceleration
body interior (temperature range: blue −16◦ C, red +10◦ C); of the spacecraft.
Bottom left: spacecraft exterior (blue −155◦ C, red −108◦ C);
Right: entire spacecraft (blue −213◦ C, red +136◦ C). Un-
modeled struts that connect the RTGs to the spacecraft body a large (i.e., with radius of 40 high-gain antenna, or HGA,
are indicated with yellow-black dashed lines. diameters), black spherical control surface. The amount
of spacecraft radiative emission absorbed by each element
TABLE I: Pioneer 10 telemetered power at select heliocentric of this control surface corresponds to the amount of mo-
distances. Externally vs. internally located components are mentum carried in this direction.
indicated where applicable (only 5 out of 11 distances shown). The model incorporated some parameters the values of
Power (W) which were less well known: e.g., the effective emissivities
Description 3 AU 10 AU 25 AU 40 AU 70 AU of multilayer insulation blankets or conductive couplings
Science, internal 12.6 12.6 11.9 8.8 0.8 of certain structural elements. Redundancies in the flight
Science, external 6.4 8.4 6.4 6.4 0.0 telemetry were used to refine the estimates of these pa-
Subsystems 20.2 20.2 20.4 20.2 19.5 rameters and validate the model. The primary objective
Electrical, internal 63.2 46.3 35.5 28.4 17.5
Electrical, external 8.1 4.7 2.7 2.3 0.1
was to reproduce the known thermal power of the RTGs
TWTa thermal 18.6 18.6 19.8 19.5 21.2 by choosing suitable temperature boundary conditions
Transmitter 9.2 9.2 8.0 8.3 6.6 that, in turn, had to agree with telemetered temperature
Total consumed 138.3 120.0 104.7 93.9 65.8 readings. In the final results, the modeled RTG thermal
RTG generated 148.5 127.1 107.1 94.0 67.2 power was within 1% of the known value, while modeled
Cable loss 6.9 5.3 4.0 3.2 1.7 RTG fin root temperatures were always within ±2 K of
Total available 141.6 121.8 103.1 90.8 65.5 the flight telemetry.
Difference +3.4 +1.8 −1.6 −3.1 −0.4 Both spacecraft utilized a louver system for thermal
a Traveling wave tube amplifier. management [6]. Louvers mounted on bimetallic springs
opened in response to high interior temperatures, al-
lowing excess thermal radiation to escape the spacecraft
thermal capacitance, conductive couplings, and radiative more freely. Louver geometry for twelve two-blade and
exchange factors between all surfaces and to deep space. two three-blade louver assemblies was integrated into the
The software numerically solves the energy equation model. Movements of the modeled blade positions (and
using equipment power dissipation from the spacecraft the resulting calculated louver effective emittance) were
fight telemetry records (see Table I). RTG power was esti- based on the average temperature of the two nodes on the
mated using the well-known half-life, τ = 87.74 yr, of the edge of the element that corresponded to the physical lo-
238
Pu radioisotope fuel: Qrtg (t) = 2−(t−t0 )/τ Qrtg (t0 ), cation of the actuator housings for each louver assembly.
where t0 = July 1, 1972 and Qrtg (t0 ) = 2578.179 W. The In addition to the internally generated heat, the Sun
objective was to calculate the temperature distribution of was also a significant source of heating, particularly at
all spacecraft surfaces. To accommodate the limitations the smaller heliocentric distances. Since the spacecraft
imposed on us by thermal modeling software, the angular was facing the Sun, the solar energy was absorbed pri-
distribution of the radiative emission from the spacecraft marily by the HGA which largely shadowed the rest of
to space was calculated by solving the thermal radiation the spacecraft from direct solar irradiation except for
equations with the spacecraft positioned at the center of the RTGs. The solar effect became evident as the ab-
3. 3
TABLE II: Error budget for the Pioneer 10 thermal model; TABLE III: Doppler residuals (in mHz) after incorporating
the contributions shown in percentages, relative to aP . a thermal model, varying the efficiencies of RTG (ηrtg ) and
Description Error electrical (ηelec ) heat conversion into a recoil force.
Other sources < 0.1% ηrtg
Quantization error in telemetry data 2.2% ηelec 0.0000 0.0096 0.0120 0.0132 0.0144 0.0156 0.0288
11 1-W radioisotope heater units 2.2% 0.000 5.57
Discrepancy in TWT telemetry 2.5% 0.295 10.80 9.03 7.37
Inaccuracy of geometric modela 5.0% 0.369 8.75 7.11 5.70
Modeling of instrument openingsb 5.0% 0.443 6.87 5.50 4.62
Subtotal: 8.1% 0.480 4.57 4.45 4.54
RTG surface degradation 25.0% 0.517 4.57
TOTAL: 26.3% 0.886 4.52
a Assuming a fore-aft positional uncertainty of 2.5 cm.
b Heat escaping through instrument openings is ill-documented.
ficiency factor”; its value is 1 if the beam is collimated in
the direction of the acceleration. It was recognized ear-
sorbed energy increased the HGA temperature and was lier [11] that the two main contributions to the thermal
then emitted as IR radiation. recoil force are the waste heat generated by the RTGs,
The model was evaluated for Pioneer 10 at eleven dif- Qrtg , and the waste heat produced by electrical equip-
ferent heliocentric distances ranging from 3 AU to 80 AU ment inside the spacecraft compartments, Qelec , yielding
(see Fig. 2). Four temperature telemetry locations on the anomalous acceleration
the equipment compartment and two on the instrument
compartment were examined. The deviation between the aP = ηrtg (Qrtg /mc) + ηelec (Qelec /mc). (1)
predicted values from the model and the flight telemetry
was tracked in each of the eleven cases. The differences Our earlier investigation [11] found that the correspond-
between telemetered temperature values at the six plat- ing efficiency factors, ηrtg and ηelec , depend only on the
form temperature sensors on board vs. values computed geometry of the spacecraft, and remain constant over
from the model reveal a root-mean-square (RMS) error of time; this result was confirmed by the present analysis.
5.1%. This discrepancy is consistent with, and is likely The thermal recoil force is well fitted by the model equa-
a consequence of, the known sources of error listed in tion using ηrtg = 0.0104 and ηelec = 0.406, with a RMS
Table II. Of these, the most significant is the effect of error of only 0.78 W, much smaller than the inherent
possible surface degradation of the sun-facing RTG sur- quantization error present in the telemetry.
faces.
The RTGs were coated with “three mils of zirconia
(ZrO2 ) in a sodium silicate binder” [12]. No information DOPPLER ANALYSIS AND COMPARISON
is available in the literature about the performance of this
particular type of paint when exposed to solar radiation, The parameterized thermal recoil force model pre-
especially at the relatively high temperatures present on sented in Eq. (1) can be incorporated easily into the
the RTG outer surfaces. Similar paints [13] have experi- force model used for Doppler analysis. This presented
enced both an increase and a decrease of up to 5% in in- us with the opportunity to go beyond simply using a re-
frared emissivity. Approximately 25% of the RTG coated coil force estimate in trajectory modeling; the Doppler
surfaces were exposed to solar irradiation. A calculation analysis can also be used to estimate the values of the
that takes into account the relative contribution of RTG parameters ηrtg and ηelec completely independently from
heat to the total anisotropy yields a corresponding error the thermal analysis.
figure of 25% in the overall error budget. Results of this part of our analysis are shown in Ta-
Other, significant error sources (see Table II) include ble III. The spacecraft trajectory was calculated using a
the FE modeling uncertainty (obtained by comparing the variety of values for ηrtg and ηelec . The Doppler anal-
FE model output to redundant telemetry), insufficient ysis yielded the lowest residuals at ηrtg = 0.0144 and
detail in the documentation about the amount of heat ηelec = 0.480; the residuals, parameterized by ηrtg and
escaping through instrument openings, and limited accu- ηelec , lie on an elongated elliptical paraboloid surface.
racy in the available engineering drawings. Consequently, the Doppler analysis is sensitive to the
The thermal power Q emitted in a certain direction is overall magnitude of the recoil force: a ∼ 20% change in
related to the acceleration ath resulting from the corre- the overall magnitude nearly doubles the residual. How-
sponding thermal recoil force as ath = η (Q/mc), where ever, the Doppler analysis cannot disambiguate between
m is the mass of the object being accelerated and c is the the RTG and electrical contributions to the recoil force:
velocity of light. The dimensionless quantity η is an “ef- an increase in one accompanied by a decrease in the other
4. 4
Heliocentric distance (AU)
10 20 30 40 50 60 70 80 0.8
Thermal
Anomalous acceleration
14 Doppler
0.6
12
(10−10 m/s2)
10
ηelec
0.4
8
6
0.2
20 0 0.01 0.02 0.03
ηrtg
Residuals
(mHz)
0
FIG. 4: Comparison of the RTG (ηrtg ) and electrical (ηelec )
−20 efficiency factors estimated independently from the Doppler
1975 1980 1985 1990 1995 2000 and thermal analysis using Eq. (1). The 1σ error ellipse for
FIG. 3: Comparison of the thermally-induced and anomalous the thermal analysis corresponds to the values in Table II. For
accelerations for Pioneer 10. The estimated thermal acceler- the Doppler analysis, the error ellipse corresponds to values of
ation is shown with error bars. The stochastic acceleration ηrtg and ηelec in Table III for which the excess in the Doppler
estimate from [8] appears as a step function. For reference, residual exceeds the best-fit residual.
the Doppler residuals of the stochastic acceleration are also
shown in the bottom panel. Inner and outer error bars corre- The comprehensive thermal model yields a recoil force
spond to the subtotal and total shown in Table II. characterized by the parameters ηrtg = 0.0104 and ηelec =
0.406. The Doppler analysis yielded the lowest residual
results in a small or insignificant increase in the Doppler at ηrtg = 0.0144 and ηelec = 0.480. Numerically, the ther-
residual, as can be seen from the off-diagonal elements in mal analysis based estimate of the recoil force is ∼80%
Table III. (of which ∼35% is produced by the RTGs and ∼45% by
The uncertainty of the thermal recoil force estimate electrical heat) of the magnitude estimated from Doppler
is large. The magnitude of the estimated thermal re- analysis.
coil force is smaller than the observed acceleration, but
To determine if the remaining 20% represents a sta-
the stochastic acceleration estimate derived from Doppler
tistically significant acceleration anomaly not accounted
data is within 1σ (see Fig. 3). An error ellipse of the
for by conventional forces, we analyzed the various error
thermal recoil force estimate in the ηrtg − ηelec parameter
sources that contribute to the uncertainties in the accel-
space of Eq. (1) is shown in Fig. 4. This error ellipse
eration estimates using radio-metric Doppler and ther-
takes into account the fact that the largest source of er-
mal models. On the Doppler side, a significant noise
ror (RTG coating) affects only ηrtg . Fig. 4 also shows the
floor exists which is believed to be due to systematics (in-
error of the stochastic acceleration, estimated using the
cluding the interplanetary charged particle environment,
best-fit Doppler residual as the 1σ noise floor. The ori-
etc.) For the thermal analysis, the biggest source of un-
entation of this error ellipse corresponds to Table III and
certainty is the unknown change in the properties of the
reflects the fact that the using the Doppler data alone,
RTG coating, which results in differences in fore-aft emis-
the RTG and electrical contributions to the thermal re-
sivity and an additional contribution to the recoil force
coil force cannot be well distinguished.
in the spin axis direction. When we plot these uncertain-
Lastly, we mention that both the thermal recoil force ties in the ηrtg , ηelec parameter space, the 1σ error ellipses
and the Doppler data can be well modeled using an ex- overlap. We therefore conclude that at the present level
ponential decay model in the form a = 2−(t−t0 )/τ a0 . of our knowledge of the Pioneer 10 spacecraft and its tra-
Using t0 = January 1, 1980, the best fit parameters jectory, no statistically significant acceleration anomaly
for the Doppler data are [8] τ = (28.8 ± 2.0) yr, a0 = exists.
(10.1±1.0)×10−10 m/s2 . In contrast, the calculated ther-
In closing, we must briefly mention additional avenues
mal recoil force can be modeled, with an RMS error of
that may be explored in future studies. First, the case
0.1 × 10−10 m/s2 , using the parameters τ = 36.9 ± 6.7 yr,
of Pioneer 11 was not analyzed at the same level of de-
a0 = (7.4 ± 2.5) × 10−10 m/s2 .
tail, albeit we note that spot analysis revealed no sur-
prises for this spacecraft. Second, the question of the
anomalous spin-down of both spacecraft remains unad-
CONCLUSIONS dressed, even though it is plausible that the spin-down
is due to heat that is reflected asymmetrically off instru-
We presented results from a thermal analysis of the ment sunshades. Third, Fig. 2 is strongly suggestive that
Pioneer 10 spacecraft and an independently performed the previously reported “onset” of the Pioneer anomaly
analysis of their trajectories using Doppler radio-metric may in fact be a simple result of mismodeling of the so-
data that also incorporated a parameterized on-board lar thermal contribution; this question may be resolved
force model. with further analysis of early trajectory data. Fourth, an
5. 5
as-yet unaddressed issue is the possibility of outgassing (1998), gr-qc/9808081.
from surface materials, which was shown to have a poten- [2] J. D. Anderson, P. A. Laing, E. L. Lau, A. S. Liu, M. M.
tially observable contribution to the anomalous accelera- Nieto, and S. G. Turyshev, Phys. Rev. D 65 (2002), gr-
qc/0104064.
tion [14]. Fifth, our understanding of systematics in the
[3] J. I. Katz, Phys. Rev. Lett. 83, 1892 (1999), arXiv:gr-
Doppler tracking data can be improved by a detailed au- qc/9809070.
tocorrelation analysis. Sixth, the properties of the RTG [4] E. M. Murphy, Phys. Rev. Lett. 83, 1890 (1999),
paint are, in principle, measurable by a thermal vacuum arXiv:gr-qc/9810015.
chamber test of a hot RTG analogue. Finally, yet an- [5] L. K. Scheffer, Phys. Rev. D 67 (2003), arXiv:gr-
other redundant data set exists in the form of Deep Space qc/0107092.
Network signal strength measurements, which could be [6] S. G. Turyshev and V. T. Toth, Living Rev. Relativity
used to improve our understanding of the spacecraft’s 13, 4 (2010), arXiv:1001.3686.
[7] S. Turyshev, V. Toth, L. Kellogg, E. Lau, and K. Lee,
precise orientation. Nonetheless, it is unlikely that any Int. J. Mod. Phys. D 15, 1 (2006), gr-qc/0512121.
re-analysis of the Pioneer 10 and 11 data set will alter [8] S. G. Turyshev, V. T. Toth, J. Ellis, and C. B. Mark-
our main conclusion: the anomalous acceleration of these wardt, Phys. Rev. Lett. 107, 081103 (2011), 1107.2886
spacecraft is consistent with known physics. [gr-qc].
[9] C. B. Markwardt (2005), gr-qc/0208046.
[10] V. T. Toth, Int. J. Mod. Phys. D 18, 717 (2009),
Acknowledgments arXiv:0901.3466.
[11] V. T. Toth and S. G. Turyshev, Phys. Rev. D 79, 043011
(2009), arXiv:0901.4597 [physics.space-ph].
We thank G.L. Goltz, K.J. Lee, and N.A. Mottinger [12] Teledyne Isotopes Energy Systems Division, SNAP 19
of JPL for their indispensable help with the Pioneer Pioneer F & G Final Report (1973), IESD 2873-172.
Doppler data recovery. We thank W.M. Folkner, T. P. [13] N. J. Broadway, Tech. Rep. (1971), NASA Contractor
McElrath, M. M. Watkins, and J.G. Williams of JPL Report CR-1786.
for their interest, support, and encouragement. We also [14] B. Schl¨ppi, K. Altwegg, T. Riesen, and M. Rubin, Ad-
a
thank L.K. Scheffer and C.B. Markwardt for many help- vances in Space Research 49, 579 (2012).
ful conversations. We thank The Planetary Society for [15] Network Analysis Inc., Tempe, Arizona
their long-lasting interest and support. This work in part
was performed at the Jet Propulsion Laboratory, Cali-
fornia Institute of Technology, under a contract with the
National Aeronautics and Space Administration.
[1] J. D. Anderson, P. A. Laing, E. L. Lau, A. S. Liu, M. M.
Nieto, and S. G. Turyshev, Phys. Rev. Lett. 81, 2858