Design of Magneto-Optic Wide-Area Arrays for Deep Space EMF Studies and Power System Control M. J. Dudziak1 and A. Ya. Chervonenkis2 1 MODIS Corporation Richmond, Virginia (USA) 2 MODIS Corporation Moscow, RussiaA technology for the study of magnetic fields in deep space and for possible control of space engineeringplatforms is proposed, based upon based on the interaction between the field and domain structure (DS) inspecial Bi-substituted iron-garnet films (MODE sensors) that have been successfully used in local areamagnetic studies. The MODE sensor is based upon the magneto-optic Faraday effect and is proposed foruse in wide-area (> 1000 km^2) electro-optic arrays that may be deployed by a space platform while inflight. Such operation could be conducted as a long-term process during a 100 A.U. to 1000 A.U. spacemission covering significant and disparate regions of the solar system and beyond.Each element in the array could also incorporate magnetostrictive devices, providing a dual scale formeasurements of changes in magnetic activity in the region of operation. Deployment would be effectiveby programmed release of sensor units from the main spacecraft and self-propulsion according to pre-programmed coordinates relative to the main craft. Communications from the array elements, thus formingthe equivalent of a deep-space towed-array sensing system, would be managed through optical or radiosignal transmission and employing a relay communication mechanism, thereby reducing the need forsignificant power by individual array elements. In-flight redeployment of the entire array into analternative geometrical configuration would also be a possibility enabled by the communication logic.The design and construction of these arrays could also be employed in control and communications withina large-volume space propulsion system such as several that have been proposed for long-range missions,using principles derived from MIMD parallel computing and the spatial light modulation and switchingcapabilities of the magneto-optic devices.1 INTRODUCTION to efficiently and effectively measure magnetic regions that may lie beyond the practical reach ofExploration of magnetic fields and in particular a contemplated spacecraft, even such as could bewide-area magnetic topography in regions of deep engineered for deep space missions. An alternativespace may have several interesting consequences approach may exist through the application ofand may shed important light on the nature and methodologies similar to those employed in suchfabric of regions of space heretofore not possible to diverse signal processing applications as towed-examine from terrestial or near-orbit sources. array sonar, EEG, and magneto-encephelographyThere may also be consequences of merit and (MEG), namely the use of a wide array of point-importance for the study of hypothetical vacuum sensitive sensors the data of which can becurrent or energetic anomaly phenomena that may interpolated to produce useful information on theexist in regions relatively far removed from stars nature of field behavior across a surface that isand planetary bodies. However, one of the obvious otherwise not easily measurable. The approachbarriers to such a study lies in the problem of how suggested herein is to devise such an array that can1 Chairman and Chief Scientist, firstname.lastname@example.org, (804) 329-8704, fax (804) 329-14542 Executive Vice President and Director of Magneto-Optics Laboratory, email@example.com, 7 (095) 121-4303
be deployed across very large regions of space redistribution or reconfiguration of the array duringduring the mission of a deep space vehicle and to the mission flight, then there is an additionalemploy a technology that has proven successful in requirement for power and means of locomotion.the close-range measurement of magnetic fieldsand the detection as well of significant disturbancesin magnetic fields in terrestial environments. The 2 MAGNETO-OPTIC DETECTION ANDmechanism for distribution, transport, relocation, ENCODING (MODE)and communication among these sensor units is aseparate topic partially presented in this discussion, The heart of the matter is in being able to sensethe emphasis here being upon the sensing and very weak magnetic fields and to registerdetecting technology as well as the processing of disturbances and variances that may exist in thethe information collected by such a large-area fields as the sensor is moved through some regionmobile array of sensor modules. of space. It is argued that a new formulation of magneto-optic thin films, an improvement uponThere is an obvious first critical element in any well-known Fe-Ga substrate types, offers such aarchitecture that could be designed for this type of solution.open-ended measurement, a process where quitecontrary to most space-borne experiments, there is The MODE field visualizing film (FVF) is aat the outset uncertainty about how and in what transparent ferromagnetic layer of Bi-substitutedgeometry the sensor elements should be deployed iron-garnet grown by LPE technique on a non-or even what patterns of information may be magnetic substrate. The composition of the FVF isgathered once the mission is underway. This first characterized by the formula (R Bi)3 (M Fe)5012,critical element is that there may be something where R is a rare-earth ion (Y, Lu, Tm, Gd, Ho,worth recording and examining. One must take this Dy, Tb, Eu for example) and M is generally Ga oras a hypothesis with enough weight so as to justify Al. Magnetic and magneto-optic properties of thethe experiment; the question then arises as to how FVF are controlled by composition, growthmuch the hypothesis and speculation can justify the conditions and post-epitaxial treatment. Theexpense of the experiment. If the apparatus and specific Faraday rotation of 10^4 deg/sm andarchitecture is cost-effective and can demonstrate absorption coefficient less then 10^3 cm-1 arethe probability of success in the field, then there available in a generic composition (Tm Bi)3 (Femay be a cost justification for incorporating such Ga)5012. High contrast domain structures can bean experiment into a deep space mission. easily observed using a polarizing microscope.The second and subsequent critical elements of this The magneto-optic layer or FVF is created byproposed architecture are related to these mission growing the epitaxial layer on the garnet substrate,engineering and economical issues but they are deposited in a supercooled flux, containing afundamentally a question of physics. It is essential solvent of composition Bi203-PbO-B203 as well asto have the ability to accurately measure low- garnet-formed oxides at a temperature range ofstrength magnetic fields in a manner than will 940K to 1108K.allow the distribution of such sensed information tobe used in an interpolation process that can give By introducing a high level of Bi3+ ion substitutionuseful information about larger regions of space into the FVF a high MO figure of merit can bebeyond the scope of the actual measuring achieved, s.t. Ψ= 2ΘF / α > 10 grad/dB. Aninstrument. The device must have sufficient means important feature of the FVF of value for possiblefor assimilating, storing, and communicating this deep space magnetic anomaly and variation studiesinformation to some type of central (or distributed) is the high domain wall velocity (> 1000m/s)computing apparatus which in turn can obtained in four types of films: (i) high-anisotropic-communicate the final data sets of interest to an oriented films with Y and Lu composition, in theearth-based telemetry center. Furthermore, there is presence only of in-plane magnetic fields, (ii) filmsthe issue of power and drive for the sensor devices with Gd and Tm, with angular momentumthat would compose such an array of instruments. compensation (AMC), (i) films with Y, Lu, and PrTo the extent that they are to be widely distributed (orthohomlical magnetic anisotropy (ORMA), andacross some region of space and probably films with Gd and Eu (both AMC and ORMA).untethered, there is a requirement for power andcontrol for the maneuvering of the devices intotheir respective positions. If there is to be some
These magneto-optic thin films have been encoded with both magnetic and non-magnetic ink.successfully used in a number of applications While these are significantly different in everyincluding but not limited to the following: respect including the sensing apparatus design (cf. Figure 3 below) from what is proposed for the Banknote and cheque anti-counterfeiting space-borne platform, the principle is illustrative of Magnetic barcode authentication the end result in terms of a data image that can be Non-destructive testing of metallic structures renedered and processed to discriminate magnetic Geomagnetic anomaly detection regions in the sensor field. Fiber-optic based magnetized chemotherapeutic agent concentration  Typically, as shown in Figure 3, the sensor apparatus consists of a thin-film crystal element Product security labeling into which a beam of polarized light is introduced, Powerline voltage irregularity measurement with the Faraday effect rendered to the beam as it passes through the plane of the thin-film. ThisTwo simple examples of images produced by a beam, in the sensors employed for surface andprototype measurement device, the MagVision structural sensing and for security applications, isScanner, is shown in Figure 1 and Figure 2 below: then output to a CCD camera for translation into a video (or still frame) signal transmitted to a computer. CCD Camera Polarized beam MODE Crystal Figure 1 – Secure Paper with Magnetic Ink Sample Figure 3 – Basic MagVision Scanner Design 3 MEASUREMENT OF EMF IN DEEP SPACE USING NOVEL SENSOR AND RECOGNITION TECHNIQUES In a related paper also being presented at this conference and included in these proceedings , the theoretical basis for possible generation of coherent states of “vapour phase” photons by lightlike vacuum currents in regions of empty space is presented. This model allows for the possibility Figure 2 – Secure Signature with Magnetic Ink that over a large volume this “topological condensation” process, based upon a fundamentalIn this case the magnified images are taken from a model known as topological geometrodynamicsregion approx. 5mm by 5mm on a paper substrate (TGD) , could result in useful energy to maintain
or sustain low-power long-range activities in a regions of space that would be stronger sources ofspace mission. the condensate photon currents than some other regions.It is proposed that in a fashion analogous to thepurely classical environments of sailing or Given, it is conjectural at this point that suchwindsurfing there are some mechanisms that might variations in the vacuum current do exist andaid in the detection of regions of space where such within any “controllable” region of space such asvacuum current activity and coherence might be could be managed by the rearrangement of somestronger than in others. In sailing one must seek type of collector units in a geometric configurationout better wind and draft as well as currents by that has proximity to the main body of ansome combination of sensing techniques, one of interstellar spaceship, for instance. However, therewhich is to observe the effects of the wind upon the seems to be one reasonable method and set of toolsdistant surface of the water and to observe the for exploring this speculation, and that is throughresulting optical effects. From such observation measurement of variations in the magnetic field asone can, with some level of expertise, develop a some prototype spaceship is navigating throughsystem for seeking out and also predictively comparable regions of space.changing course in order to obtain maximum windand to optimally take advantage of currents and We propose that there is justification to attemptother navigational aids, as well as to avoid regions such an experiment and that the mechanism toof doldrum or excessive storm conditions. In conduct it is not as complicated as may at firstsailing, moreover, the navigator uses as large a data seem to be required. One possible means forspace as possible, and the best set of tools are those detecting some anomalies in space that could bethat would conceivably allow one to examine wind indicative of variations in vacuum current would beand draft conditions across the largest possible through the measurement of magnetic fields.area. MODE sensors equipped with transmitters and distributed across a region that could span severalUniformity across all of empty space may not be at tens of kilometers in the xy plane and which couldall the case and one would do well to not adhere to be expanded into a third dimension without anythe assumption that what is measured within the significant impact on the sensing andvicinity of large masses such as stars and planets is communication capabilities – such devices wouldindicative of deep space. How deep space regions likely be able to provide a mapping of magneticmay vary and fluctuate in terms of hypothetical regions that has never been contemplated before.vacuum currents is precisely one object for possiblestudy using a massive-area deployed system such Naturally the fields as well as the variation factoras is contemplated herein. may be extremely low in strength, of the order of 10-10 T or less. A shift in field strength may beWe envision a craft, or more precisely a set of useful as a tool in determining where a region ofunits, with the capability of some such variation in interest (from the perspective of vacuum currentcourse, allowing a matter of a few degrees’ change activity) may exist.in course over a period of hours, days, weeks, oreven longer. This craft may also consist of a In order to complement the sensitivity of magneto-spatially distributed system navigating through optic Faraday effect devices a sensing unit mayspace as a network of communicating components, include magnetostrictive measurement technologyheterogenous in function and autonomous in terms as well. The Faraday device can attain sensitivitiesof local navigation. One could imagine the self- in the nT/Hz range, and but possibly lower to theorganized and cybernetically capable equivalent of pT/Hz range due to increase of the uniaxialan asteroid cloud, moving in a given direction but anisotropic field Hk=2Ku/Ms, where Ku = uniaxialcapable of reconfiguration or redirection. anisotropy constant and Ms = saturation magnetization. The increase of Hk > 10 3 kA/m canThese units could communicate via RF or MW be attained through the increase of Bi content in thefrequencies or using an optically-based method. epitaxial growth process. However the limits ofSome or all of these physically dispersed units may spatial resolution are of the order of cubicbe capable of capturing the current flow described millimeters and there may be difficulty intheoretically in  and these units may also have assimilating sufficient field data for any usefulthe capability of adjusting position in order to interpolation process. For this reason it is proposedmodify and attenuate their collectors toward or into to also include some variant of a magnetostrictive
device. A magnetostrictive substance changes its MODE CCD Imagephysical dimensions when exposed to a magnetic Sensor Capture Logicfield. An instrument based upon a Mach-Zehndr orFabry-Perot interferometer, with sensitivity also inthe pT/Hz range but extending to cubic centimeters,could be incorporated into this sensor module. Magneto- PowerTogether the two types of device may be able to strictive (Battery)produce readings that in tandem will be useable for Sensorprojecting the strengths of fields in the generalvicinity. Image Position AnalysisWhy should both effects be employed rather than (GPS) Computerone? The thought here is that while the sensitivity Logic & Memoryof both may be high, the accuracy of readings maybe difficult to attain due to a number ofunforeseeable events particularly in the stability of 3-Axis Communications Thrusterthe apparatus after long periods of operation and and Transmissionexposure during the mission. Redundancy and System Logicparallelism are the guiding principals, and it isthought that by choosing two complementary Fuel Storagetechniques rather than two of the same model onecan attain more accurate readings overall. Figure 4 – Basic Sensor Module Architecture4 SENSOR MODULE ARCHITECTURE There are many obvious “packaging” issues that arise immediately on hand as possible problems.Each sensor module must be capable of operating The entire thrusting system, however, is requiredthe sensor units but also processing the data only to the extent that the initial geometry of thecollected. This must also be transmitted to some sensor array must be established upon deploymentreceiver unit and ultimately to a computer for and then periodically rearranged according to theprocessing and transmission of results. The module experiment or the requirements to hold onehas the requirement of being mobile and therefore particular position. Fuel consumption and thereforemust have some form of onboard propulsion storage requirements may be minimized.system. Although there is speculation about thepossibilities of identifying vacuum current regions The role of the microprocessor system and memoryfrom whence useful energy could be extracted is to receive image data and obtain somethrough a process based upon a topological classification or categorization of the magneticdynamical model of photon “condensation” and state as measured into a schema that can be“vapourization” [5,6,7] it is not intended at this compactly transmitted and used onboard the maintime at least to consider how such a power source space vehicle or subsequently transmitted to acould be tapped and used for sensor module “mothership” (which may be an Earth Station). Anpropulsion and power systems. A more centralized embedded low-power 32-bit microprocessor with aion drive type of engine might be designed to take small configuration (e.g., 1 MB or less) of RAMadvantage of cauum current energy sources in the could be sufficient, and a FLASH array couldlarger vicinity of the space vehicle but such an suffice for local data storage.apparatus, similar to space sails and ion drives as awhole is likely to be enormous in size relative to The communication system may inded be thethe sensor modules. largest and most power-hungry component. However the range for transmission is only asFigure 4 illustrates the possible design of such a distant as the maximum distance from a module tomodule – it will have sensors, power, navigation, its nearest neighbor module, as discussed in theand communication all compactly packaged much next section. All communications can be handledlike some of the “insect” robots conceived for lunar through a network relay system very similar to thator planetary exploration. employed in the early but very effective MIMD parallel systems such as the transputer.
The power supply clearly will have demands upon handling their own processing assignments as wellit, as the likelihood of obtaining any useful power as shunting data passed through for otherfrom the environment (e.g., through solar panels) destinations.would be minimal and the cost factor wouldoutweigh their use. Therefore, power minimizationcontrol within all of the digital and also analoglogic will be of the utmost importance. ρNaturally there must be considered the post-measurement problem of communicating all 0 σrequired information from the sensor platform to ρ 2the main part of the ship. In order to do this .effectively, with some fault-tolerance in the overall 2 1network, and power-wise efficiently, an older andproven architecture will be employed.5 A MASSIVELY DISTRIBUTING σ σ 3 ρ COMPUTING PLATFORM IN SPACE ρ 1 σ .The Communicating Sequential Process (CSP) 1 .1 1 3architecture was first devised by C. A. R. Hoare 1 .and the Oxford Computing Group in the early1980’s  as a model for concurrent or parallel 2 Figure 5 Abstract CSP Modelcomputing. It employed the MIMD model – [ρ(n) is a process and σ(q) aremultiple instruction, multiple data – enhanced with processes within ρ(n)]a process algebra that was fundamentallycharacterized by asynchronous and autonomous Following this scheme, the magnetic field sensorhierarchical processes communicating discrete data module encapsulates a data set consisting of 1 – nsets via fixed channels connecting processors. bytes that has been produced from processing theFigure 5 illustrates the basic characteristics of the output of the paired magneto-optic andCSP paradigm, allowing for hierarchies of parallel magnetostrictive sensors. This data is transmittedprocesses embedded within processes and all by the module and received by one or more nearestcommunications handled among adjacent processes neighbors. With a time stamp and other codes, theover formal channels with defined data types. data is further transmitted and thereby relayed through the network of modules, with checkWhile the first microprocessor that truly mechanisms to restrict duplicate and unnecessaryincorporated a system-on-a-chip (SOC) transmissions. Ultimately the data is collected in aarchitecture, the INMOS transputer, was readily repository that is onboard the main spacecraft orsupplanted in the early 1990’s by the rise of the “mothership,” the master vehicle of the mission andPentium, Sparc, MIPS, and Alpha RISC the original delivery ship on which the modulestechnologies, the concept of the embedded and were stored prior to their release.reconfigurable array of parallel processors becamewell established and has paved the way for such With the modules deployed, the main ship canmodern innovations as thin-client and thin-server continue to monitor the EMF state of its smallnetworks for manufacturing, transport, and home universe around it and issue moduleusage. One of the features introduced into the reconfiguration instructions through a similarcomputing world by this processor family was the network broadcast protocol, thereby propagatingdistribution of data through network worm some change in the geometry of the sensorprograms, similar to those employed today in most network, but without dependence upon havingdistributed networks and within web search transmitter and receiver systems capable ofengines. With a root program resident on all reaching the farthest and most remote sensorprocessors, itself the outcome of a successful worm modules, since again only nearest-neighborprogram navigation through the net, other programs “hearing distance” is essential.and data can be loaded and unloaded anywhere inthe net, and processors can do double-duty for
Modulators”, Proc. 2nd Int. Symp. Magneto-6 CONCLUSIONS Optics, Fiz. Nizk. Temp., Vol. 18, Supplement, No. S1 (1992), pp. 435-438The entire concept of large-scale reconfigurable 3. Nikerov, V. A., Kirukhin, N. N., Polyakova,EMF measurement and the utility of such Yu. A., Chervonenkis, A. Ya., Ayrapetov, A.information is admittedly speculative. There are A., “Spatial Filtering on the Base of Twoserious challenges to the system architecture that Magnetooptical SLMs”, Proc. 2nd Int. Symp.would be required to enable such a network of Magneto-Optics, Fiz. Nizk. Temp., Vol. 18,sensors to produce reliable information given that Supplement, No. S1 (1992), pp. 449-452the processing of the network data also requires 4. Fitzpatrick G. L. “Novel eddy current fielddoing extensive interpolation, and a certain amount modulation if magneto-optic films for real timeof extended extrapolation! This implies that imaging of fatigue cracks and hiddenposition data of the sensor modules will be accurate corrosion”, SPIE Proceedings, Vol. 2001, pp.within some measure relative to the overall scale of 210-222, 1993.the deployed network. 5. Dudziak, M., Pitkanen, M., “How Topological Condensation of Photons Could Make PossibleNonetheless, the engineering of the sensor modules Energy Extraction in Deep Space”, 2nd IAAis within near-term feasibility given current SOC Symposium on Realistic Near-Term Advancedtechnology, low-power digital technology, and Scientific Space Missions, Aosta, IT, Juneultra-scalar advances in microprocessors and 1998memory devices. The sensitivity of the magneto- 6. Pitkanen, M., Topological Geometrodynamics,optic and magnetostrictive devices is Internal Report HU-TFT-IR-95-4 (Helsinkiexperimentally demonstrated and can be refined. Univ.), 1995, with web links atThe pattern recognition and field expansion http://blues.helsinki.fi/~matpitka/tgd.html.algorithms that are needed to make the collected 7. Pitkanen, M., Topological Geometrodynamicsdata useful to any degree have been well and p-Adic Numbers, Internal Report HU-demonstrated in other but similar fields and TFT-IR-95-5 (Helsinki Univ.), 1995, with webapplications and there is no particular reason to links atbelieve the computational processing would not http://blues.helsinki.fi/~matpitka/padtgd.html.suffice for this data, provided that the collected data 8. Davis, C. and Wagreich, R., University ofis accurate enough and that the sampling size, Maryland Dept. of Electrical Engineering,granularity, and frequency is sufficient. work reported on optical magnetic sensors. Web site URL:Besides the motivation for basic “classical” www.ee.umd.edu/LaserLab/research.htmlinvestigations into EMF activities and anomalies, 9. Hoare, C. A. R., Communicating Sequentialthere are other attractors for this proposed system. Processes, Princeton University Press, 1985The potential for opening up novelty and discoverypertaining to vacuum currents, black holes, darkmatter, unique useable energy sources, and otherpossibilities is a significant and tantalizingmotivation to explore further this technologicaldesign, perhaps the most unusual but probably notthe last that has been suggested for magneto-opticsensors.7 REFERENCES1. Randoshkin V.V., Chervonenkis A. Ya., “Applied Magnetooptics”, Energoatomizdat, Moscow, 1990 (in Russian);2. Chervonenkis, A. Ya., Kirukhin, N. N., Randoshkin, V. V., Ayrapetov, A. A., “High Speed Magnetooptical Spatial Light