1) The document describes thermal remote sensing of Boiling Springs Lake using sensors on Landsat 7 and Terra satellites. 2) Landsat 7's ETM+ sensor collects data every 16 days at 60m resolution, including a single thermal band, while Terra's ASTER sensor collects higher resolution visible, near infrared, shortwave infrared, and thermal infrared data. 3) Preliminary results show seasonal variations in lake temperatures from 26C in February to 42C in August using Landsat data, and from 35C in October to lower temperatures in other months using ASTER data, though issues like atmospheric effects and spatial resolution need further analysis.

1. Satellite Thermal
Remote Sensing of
Boiling Springs Lake
Jeff Pedelty
NASA Goddard Space Flight Center
Goddard Center for Astrobiology

2. Overview
• Work in progress
• Description of sensors
– Landsat 7’s ETM+
– TERRA’s ASTER
• Acquisitions of Boiling
Springs Lake
• Temperature determinations &
issues
• Future aerial thermal remote
sensing
ASTER: October 19, 2002

3. Landsat 7 ETM+
• Landsat 7 launched April 1999
• ETM+ is the Enhanced Thematic Mapper Plus
• 16-day repeat cycle
• ~15% duty cycle
• Conterminous US imaged each overpass
– Approximately 10:30AM acquisition
• Single thermal band (10.4-12.5)
• 60m spatial resolution across 185km area
• Data purchased from USGS EROS Data Center ($250
for new acquisitions, $600 < 5/31/2003)

4. Landsat 7 acquisitions of BSL
• Goal was to acquire
seasonal sampling at
reasonable cost
• Scan Line Corrector failure
in May 2003 introduced
luck into acquisition process
– Jan 12, 2005 (gap)
– Feb 11, 2004
– May 20, 2005
– August 21, 2004
– August 24, 2005 (gap)
– October 12, 2002 (free)
Thermal: Feb 2004 Jan 2005
True Color

5. Landsat atmospheric correction
• Upwelling thermal emission includes atmospheric
contribution and attenuation
• Requires local meteorology (e.g. NOAA’s National Center
Environmental Prediction) + radiative transfer
(MODTRAN)
• LTOA = T + Lu +  (1 - ) Ld
• http://atmcor.gsfc.nasa.gov is a utility to determine , Lu
and Ld for each acquisition
– Barsi (GSFC), Schott (RIT), Hook/Palluconi (JPL)
• Output is land surface temperature (T)
• Vicarious calibration campaigns suggest ~1-2K accuracy

6. Landsat Temperature Results
Date  Lup Ldown Peak T
Feb 2004 0.91 0.55 0.94 26
May 2005 0.81 1.24 2.08 35
Aug 2004 0.75 2.04 3.32 42
Oct 2002 0.91 0.64 1.10 35

7. ASTER instrument
• On EOS TERRA mission (launched 12/99)
• Joint US / Japan instrument (JPL)
• “Zoom Lens” of TERRA
• 15m Vis/NIR, 30m SWIR, 90m Thermal IR
– Total of 14 bands, 5 in the thermal infrared
• <16 day repeat cycle
• 60km swath
• Sophisticated multi-band temperature and
emissivity retrieval algorithms
• Extensive vicarious calibration campaigns

8. ASTER’s Spectral Bands

9. ASTER coverage
<100% coverage: but 925,661 Scenes observed as of 9 Feb 2005

10. ASTER Acquisitions of Lassen
Volcano Monitoring Project (http://www.volcano.si.edu/gvp/volcano/index.htm)

11. ASTER Image Log
• Archived data free to NASA researchers (W.
Turner approval required, NASA HQ)
• 53 Acquisitions from May 2000 - May 2006
• 35 Day
– 15 Clear
– 18 Cloudy or Hazy
• 18 Night
– At least 9 Cloudy or Hazy
• Trying to obtain image concurrent w/ VFG mtg.

12. Sample ASTER Images
October 19, 2002
Bands 321 False Color
BSL Zoom
Bands 321
BSL Zoom
Temperature

13. ASTER Day Temperatures
(Removing 2 hazy dates)
Date Within Year
Temperature

14. ASTER Day/Night Results
Date Within Year
Temperature

15. Issues with ASTER Temperatures
• Spillover to ground?
– Point spread function is not rectangular
– Peak pixel does not measure just lake.
– Lower ground temperatures may be bringing down lake
temperatures. Perhaps indicated in night data?
• Shadowing?
– Lower sun angle in winter could result in shadowing of
hotter parts of the lake.
– Night data indicate this is not a major issue.
• Other unknown systematic effects?

16. Aerial Thermal Remote Sensing
• QWIP detector developed at GSFC
– Quantum Well Infrared Photoconductor
• 1024 x 1024 GaAs array
• 4 bands in thermal IR (T and  retrieval)
• Investigating aerial (or even hillside) data
collection at BSL later this summer/fall
• Data collection in winter could validate the
ASTER/Landsat temperature trends.

17. Sample QWIP Image

18. Multispectral Thermal Imager
(MTI)
• DOE technology development mission
• Launched ca 2000
• “Point and Shoot” mission, ~10 scenes/day
• 20m resolution thermal data (~5m and ~10m)
– Highest resolution thermal imaging from space
• Operated ~2 years, now in storage on orbit
• No acquisitions of Lassen/BSL, but Yellowstone
data do exist and I have some in hand.
– Perhaps of interest to others

19. ASTER Imaging Opportunities
• ASTER needs to be tasked to take specific
images
• I have requested an allocation with NASA
HQ under the name of NAI ViFoG
• See me if ASTER data would be useful for
any upcoming field campaigns.

20. Backup