In the OSTI Collections: the Space Environment and Space Technology

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Article Acknowledgement:
Dr. William N. Watson, Physicist
DOE Office of Scientific and Technical Information

 

Plasma and radiation

Collision avoidance

Design for missions

Discoveries

References

Reports available from OSTI's SciTech Connect

Reports available from DOE PAGESBeta

Research organizations

Conferences

Scientific journals and publishers

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To explore and make use of outer space with satellites and space probes requires dealing with a sizeable challenge:  namely, the very different environment those satellites and probes are put in.  Space isn’t simply a region of airlessness and weightlessness, but of intense ionizing radiation and significant magnetic fields.   Much of it is also a place of cold temperatures, at least away from the sun, other stars, and objects warmed by them.  And this environment is not an unchanging one.  The radiation and magnetism particularly undergo substantial changes, which constitute phenomena that despite the lack of an atmosphere are known as “space weather”.  Also, the immediate environment of earth satellites includes other satellites, as well as debris from spacecraft. 

 

While the Department of Energy is not the main contributor to the nation’s space efforts, it has long sponsored work at its national laboratories and at other institutions aimed at better understanding the outer space environment.   One reason for this interest, as a 2015 slide presentation about the capabilities of Los Alamos National Laboratory in this field[SciTech Connect] explains, is that “A staggering number of the spacecraft we rely upon daily have to spend a part of their orbit in the harshest of Earth’s radiation environment.”  The presentation describes Los Alamos’ involvement with over 400 space-weather instruments on more than 60 satellites, as well as specific data collection and analysis efforts, and notes that the nation has all the pieces needed for assembly of “an excellent tool” for space situational awareness. 

 

The Energy Department sponsors investigations of the environment beyond earth’s atmosphere, applications of that knowledge to design spacecraft for various purposes, and explorations using those spacecraft.  The range of issues addressed by this work is suggested by the following sample of recent reports.  

 

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Plasma and radiation

 

The magnetic field of the earth’s magnetosphere[Wikipedia]—the region around the earth where the magnetic field significantly affects the motion of electrically charged particles—would more closely resemble the symmetrical field of a bar magnet were it not for the solar wind[Wikipedia] of charged particles emanating from the sun.  But because the solar wind constitutes a plasma with a significant magnetic field of its own[OSTI], this magnetic field combined with the field the earth produces results in an overall magnetic field that looks compressed on the earth’s daylit side and extends into a long tail away from the sun on the earth’s night side.  This combined magnetic field traps some of the charged particles from the sun as well as other charged particles from elsewhere in space, confining them to move within large belts that encircle the earth.  Since these belts of charged particles were discovered using instruments that had been placed aboard early artificial satellites because of explorations instigated by cosmic-radiation researcher James Van Allen[Wikipedia], and since moving charged particles constitute radiation, the belts are known as the Van Allen radiation belts[Wikipedia].  Variations in the solar wind affect the shapes of the magnetic field and radiation belts, and thus affect the “weather” in space near the earth. 

 

Figure 1.  Artist's rendition of Earth's magnetosphere (source:  http://sec.gsfc.nasa.gov/popscise.jpg).[Wikimedia]  Magnetized plasma constituting the solar wind interacts with the magnetic field of the earth, resulting in an overall magnetic field near the earth that’s compressed on the earth’s daylit side and extended on the night side. 

 

The slide presentation “Hazards to satellites from the space environment”[SciTech Connect] discusses three types of hazards:  effects of various radiations on the satellite material, electric charge buildup and discharge that can damage ungrounded and unshielded electronics, and free oxygen atoms’ reaction with satellites’ protective materials.  The hazards are known but not well quantified.  To enable the design of satellites that can endure space weather, the presentation calls for extensive laboratory testing and mathematical analysis to determine the sensitivity to space weather of all electronics.  Experiments with fast-moving heavy ions are needed to duplicate space radiation consisting of such particles.  The presentation notes that current mathematical models are limited by lack of knowledge about certain details of satellites’ interactions with their environment, not accounting for the size and complexity of satellite components, and the fact that no company wants to upload their space-hardware designs to existing web-based modeling tools. 

 

Two other slide presentations deal with one specific set of mathematical models, for disturbances in the earth’s magnetosphere that affect the buildup of electric charge on spacecraft.  “SHIELDS project:  Space Hazards Induced near Earth by Large, Dynamic Storms”[SciTech Connect] briefly describes the SHIELDS software and how it was able to describe a brief July 2013 magnetospheric disturbance (a “substorm”[Wikipedia]) with dramatically more accuracy than a previous model, assimilating information from one set of satellites about the flow of protons in their vicinity.  “Shields - Code Coupling”[SciTech Connect] describes the software’s structure in more detail, as well as the techniques used by disparate groups of programmers to develop and integrate its components to ensure their compatibility. 

 

More information about how spacecraft become electrically charged, due in this case to electron fluxes, comes from instruments aboard the Van Allen Probes A and B[Wikipedia], which were launched in 2012 to explore the Van Allen radiation belts and designed to maximize their electrical conductivity.  While observations of how the probes became positively and negatively charged over the course of their mission didn’t lead to complete conclusions about exactly what parameters will produce intense negative charging to such spacecraft, some information was gained.  As reported in the Space Weather paper “Spacecraft surface charging within geosynchronous orbit observed by the Van Allen Probes”[DoE PAGES], the probes tended to charge slightly positive although they sometimes charged negative.  Greater and lesser positive and negative charging tended to occur in different regions of space.  Also, intense negative charging was more likely if the local electron flux passed a certain threshold, though significant negative charging did not always occur then.  Electron density and pressure (and thus electron temperature) were generally elevated when significant charging occurred, with the strongest connection being between electron pressure and spacecraft charging, though again these didn’t always correlate.  While an earlier investigation led to reporting that charging events’ intensities depend on the average electron temperature, the Van Allen probes didn’t find as strong a relationship between these variables. 

Figure 2.  Top:  Van Allen Probes A and B as depicted on page 6 of 21, “LANL Space Environment Capability”[SciTech Connect].  Bottom:  maps of locations around the earth where the probes were charged to various potentials within the specified voltage ranges, as measured by the probes’ Electric Fields and Waves instrument (from “Spacecraft surface charging within geosynchronous orbit observed by the Van Allen Probes”[SciTech Connect], Space Weather, Volume 14, Issue: 2, pp. 154 and 156). 

 

The Van Allen Probes also provided data for a preliminary study of the orientations of radiation-belt electron paths relative to the local magnetic field.  This study was one of eight preliminary studies of various space weather features conducted during a 2015 summer school for graduate students held at Los Alamos National Laboratory and described in a single technical report.[SciTech Connect]  Van Allen Probe A also provided data used in two of the other studies.  One dealt with the sudden flux increases of charged particles having many different energies that occur on the night side of the earth’s magnetosphere at the beginning of magnetospheric substorms, while the other explored increases and decreases of electron density in the inner magnetosphere.  Another pair of studies examined whistler waves, radio waves generated by lightning that propagate into the magnetosphere; these affect the heating of the plasmas they propagate in and accelerate and precipitate electrons in the Van Allen belts.  Simulations of different instabilities in the solar wind and the earth’s magnetosphere, one of which has been suggested as a mechanism of interaction between the solar wind and magnetosphere, resulted from two more studies.  And another study explored how measurements of the solar wind passing a space probe stationed between the earth and the sun[Wikipedia] could be used to forecast the space weather produced when that wind reaches the earth’s magnetosphere soon thereafter. 

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Collision avoidance

 

If satellites moved in pure vacuum, knowledge of the local gravitational field would suffice to determine their orbits.  However, earth satellites are subject to a slight but significant drag from the very thin upper atmosphere they pass through, which changes as variations in heating from the sun’s rays induce the atmosphere to expand and contract.  This means that a satellite’s orbit cannot be predicted over the long term without up-to-date information about the state of the atmosphere and how the satellite is slowed or deflected by the thin gas it does encounter.  “IMPACT Project:  Integrated Modeling of Perturbations in Atmospheres for Conjunction Tracking”[SciTech Connect] describes a recent effort to mathematically model the atmosphere’s state and the drag it induces on satellites moving through it.  The model allows determination of the upper atmosphere’s density with the help of current data and of the induced drag in terms of the upper atmosphere’s density, temperature, and chemical composition. 

 

Tracking the hundreds of thousands of known earth-orbiting objects with sizes of one centimeter or more requires automatic processing of their telescopic images.  Like any electronic devices, the image-processing electronics heretofore used produce a certain irreducible amount of static.  In audio devices, electronic static makes noise; in imaging devices, static blurs the images but is still called “noise”.[Wikipedia]  Making images that are clear enough to track satellites and space debris despite the noise has required the use of large telescopes.  The larger the area is of the telescope’s light-collecting lens or mirror, the brighter the image it produces, and the less that image will be deteriorated by noise in the processing electronics. 

 

Yet the demands on orbital tracking systems have increased, not only to steer satellites away from collision courses but to monitor compliance with the Outer Space Treaty’s[Wikipedia] ban on weapons of mass destruction in outer space.  Large telescopes, though, are expensive.  At the same time, new electronic image processors have been designed to work in a way that makes them less noisy.[Wikipedia]  Accordingly, analysis and experiment demonstrate the feasibility of “A New Approach to Space Situational Awareness using Small Ground-Based Telescopes”[SciTech Connect], as described in a technical report of that title.  “Small” in the two experiments described means that the telescopes’ main mirrors have widths of 0.8 and 0.4 meters, instead of the 2.5 meters typical of telescopes currently used for satellite and debris tracking.  With such telescopes, cameras using the new image-processor designs, and data-analysis methods described in the report, the researchers were able to find and track very faint satellites.  Future tasks to further demonstrate and extend the techniques involve observing small targets with rapid motion across the field of view, using a new tracking system with high speed and precision on the 0.8-meter telescope, evaluating other imaging camera and commercial technologies, and exploring technical interchanges with Russian counterparts involved in orbital tracking. 

Figure 3.  As a test of how well satellites can be found and tracked by telescopes whose main mirrors are much less than 2.5 meters wide, the Galaxy 14 C band communications satellite was located and tracked with the 0.4-meter Schmidt-Cassegrain telescope of the Moore Observatory at Columbia Basin College.  Top:  apparent orbital path of the Galaxy 14 satellite, from a sequence of images with the star field moving left to right, in which the satellite positions are rendered as dark blue dots for improved clarity.  Bottom:  the satellite’s apparent brightness can be estimated using a reference star (GSC 5189:2425) and a nearby binary star (UCAC3 169.291215 and UCAC3 169.291196).  (From “A New Approach to Space Situational Awareness using Small Ground-Based Telescopes”[SciTech Connect], pp. 12 and 13.) 

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Design for missions

 

Engineers need information about conditions encountered in space travel to design spacecraft that will function as intended.  Designs based on such information are described in the following reports. 

 

Electronic system designs for spacecraft have to account for not only high radiation levels, but for the mechanical shocks and vibrations of being launched and steered into orbit, and for a greater temperature range than many ground-based systems function in.  A less essential but important desideratum is to base the designs on standard foundational components.  While the components need not be standard to actually work, the time and cost of developing a successful system can be decreased if the design incorporates as many tried-and-tested components as possible.  These considerations inform the decisions described in “MicroTCA for Space Applications”[SciTech Connect], which discusses a new commercial standard for telecommunication electronics, and why engineers at Los Alamos National Laboratory chose it instead of a different standard to meet new hardware requirements. 

 

Satellites that carry sensors, processors for analyzing the sensors’ signals, and gimbals[Wikipedia] which can pivot to allow arbitrary relative orientations of onboard components present a particular design problem:  how to transfer signals between the sensors and the processors that convey large numbers of bits per second, if the most efficient placement for both sensors and processors requires the signals to cross a gimbal that might move into any configuration at any time.  Optical fibers might convey those signals, if they don’t crack with all the bending they might be subjected to.  A further problem is that some satellites’ electronics are assembled in humid air to inhibit electrostatic discharge, but humid air drastically reduces the strength of optical fiber.  The Sandia National Laboratories technical report “Large motion high cycle high speed optical fibers for space based applications”[SciTech Connect] describes experiments with optical fibers under various conditions, including irradiation, that answered questions about how much bending an optical fiber can stand in what humidity, and whether fatigue[Wikipedia] develops at the surfaces or internal interfaces of optical fibers that are subjected to cycles of bending, in terms of a mathematical model.  The author concluded [p. 60] that in the three-year lifetime desired for the application in question, “the large safety factor in current designs would most likely preclude failure”. 

 

Irradiation by protons in space, as well as cryogenic temperature cycling, could affect a different space-based instrument.  The James Webb Space Telescope (JWST)[Wikipedia] is to have an instrument for spreading out light of different frequencies into a spectrum around the telescope’s images of celestial objects.  Since atoms of each chemical element can be identified by which frequencies of light the atoms emit and absorb most strongly, separating light from a light source by frequency manifests the source’s chemical composition.  Light can be separated into beams of different frequencies by a prism[Wikipedia], which refracts different frequencies in different directions, or by a diffraction grating[Wikipedia], a set of grooves that filters light into a pattern of waves whose intensities add along certain paths and largely cancel along other paths, with the paths determined by the waves’ frequencies and the groove spacing.  In the Webb Telescope instrument, both a prism and a diffraction grating are to be used:  the frequencies are to be separated by a grating engraved into one surface of a zinc selenide[Wikipedia] prism (i.e., a grism = grating + prism).[Wikipedia] 

 

However, zinc selenide fails to transmit about 18% of the light sent through it since that 18% is reflected off one surface—which in this design would be the surface with the diffraction grating—which would result in a significant loss of information about the objects to be imaged and analyzed.  The grating could be given an antireflective coating to greatly reduce this loss, but the coating would occupy a large fraction of the grating’s grooves, which only function properly if their shape is maintained.  Experiments to check whether an antireflective coating would help or hurt were described in the report “Space qualification of an antireflection coating on the surface of a ruled grating prism - Increasing the throughput of the Single Object Slitless Spectroscopy mode of NIRISS onboard JWST”[SciTech Connect].  Specifically, experiments were done to see whether using an electron beam to evaporate an antireflection coating material onto the grating would adversely affect the shape of its grooves, reduce the grism’s durability under cryogenic temperature cycling, or mechanically stress the grism enough to distort the analyzed light waves.  The authors concluded that coating the grism “poses no measureable risk and improves the grism design by an amount of 10-14%, depending on wavelength.” [P. 9 of 11] 

 

Figure 4.  Left:  a flat 1-inch sample of zinc selenide with some sections ruled to make them into diffraction gratings, which was used to qualify an antireflective-coating process.  Right:  magnifications of a grating section before and after a test of the antireflective coating that took the sample through three cycles of slow cooling from room temperature to 16 kelvins, maintaining the cold temperature for 24 hours, and slow rewarming.  The “after” picture shows two of a few dozen similar objects that appeared after the test, which remained after blowing dry air on them and thus pose minimal contamination risk; they resemble particles formed when the surface is scratched with a blade.  According to the experimenters, the objects are most probably “tiny substrate chips dislodged during cryo cycling.”  (From “Space qualification of an antireflection coating on the surface of a ruled grating prism - Increasing the throughput of the Single Object Slitless Spectroscopy mode of NIRISS onboard JWST”[SciTech Connect], pages 5 and 8 of 11.) 

 

Another hardware design problem has less to do with any special characteristics of the space environment per se than with the requirements to be faced at the hardware’s remote location.  People working on the moon or Mars for any great length of time will need a large-capacity power source.  Getting one to either place will take a great deal of fuel and cargo space no matter how the power source is designed, so for a long stay to be at all feasible at either place requires making the size and mass of the power source as small as possible.  This makes a nuclear reactor—in particular, a nuclear reactor that itself is compact—a prime candidate for a power source.  One way to keep a nuclear reactor small would be to use a liquid metal for its coolant, which would require the pipes and heat exchangers it flowed through to maintain their integrity at temperatures above 600°C.  Confidence in the use of liquid mixtures of sodium and potassium (NaK) in contact with stainless steel has come from extensive experience, both with earlier space reactors and with reactors that change nonfissile atoms into atoms that can sustain fission chain reactions.  However, this same experience includes observing welds in the steel corroding and cracking in less time than the eight-year design goal for long-mission reactors’ use.  Hence a project was undertaken to determine the optimal weld configuration for a stainless-steel sodium-potassium cooling system, as reported in “Study of Compatibility of Stainless Steel Weld Joints with Liquid Sodium-Potassium Coolants for Fission Surface Power Reactors for Lunar and Space Applications”[SciTech Connect]

 

Since the most difficult weld to make and to evaluate is the tube to tube sheet weld in the intermediate heat exchangers, it was the focus of this research. A pumped loop of flowing NaK was fabricated for exposure of candidate weld specimens at temperatures of 600°C, the expected temperature within the intermediate heat exchangers. Since metal transfer from a high-temperature region to a cooler region is a predominant mode of corrosion in liquid metal systems, specimens were placed at zones in the loop at the above temperature to evaluate the effects of both alloy component leaching and metal deposition. Microstructural analysis was performed to evaluate weld performance on control weld specimens.

 

The research was coordinated with Oak Ridge National Laboratory (ORNL) where most of the weld samples were prepared. In addition, ORNL participated in the loop operation to assist in keeping the testing relevant to the project and to take advantage of the extensive experience in liquid metal research at ORNL.  [P. 2, op.cit.] 

 

Results at the time of the report indicate that the problem of adequate welds remained to be solved: 

 

The original goal of the project was to recommend a weld configuration for space reactors based upon NaK exposure extrapolated to eight years. Making a very high temperature compact NaK test loop proved far more difficult than originally anticipated. Such a loop was fabricated but failed to maintain flow for extended periods at the highest temperature. Much useful information was gained in the process, and some guidance on the weld configuration was obtained based upon the unexposed welds. The system is being modified to correct the deficiencies and will continue to be operated to obtain exposure data using overhead funds and volunteer work.  [P. 3, ibid.]

 

Since crevice corrosion is a major concern in liquid metal systems, the necessary crevice between the tube and the plate should be kept as narrow as possible. As shown … electron beam welding results in a very narrow crevice. It is believed that thermal expansion and contraction during the arc welding process resulted in a more open crevice. From this result, it is recommended that electron beam welds be used wherever possible in the heat exchangers. The effect of NaK exposure will be determined by further testing.  [P. 6, ibid.]

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Discoveries

 

Spacecraft able to function in space are designed to execute a wide variety of functions.  A sample of this variety can be seen in recent reports on spacecraft-based observations of the earth’s surface, the earth’s immediate neighborhood, and objects well beyond the solar system. 

 

One way to slow the accumulation of carbon dioxide in the atmosphere, and thus slow down the increase of heat trapping, is to store CO2 generated by fuel combustion in an underground reservoir.[OSTI]  Making sure the CO2 is actually staying underground and not leaking out requires some way to monitor the reservoir.  Experiments with four different monitoring methods, two of them using satellites, are described in a report entitled “Combining Space Geodesy, Seismology, and Geochemistry for Monitoring Verification and Accounting of CO2 in Sequestration Sites”[SciTech Connect]

 

One of the satellite-based methods involves sending a radar wave—an oscillating electromagnetic field—out from the satellite to the surface of the reservoir and comparing the outgoing wave with the returning echo.  Depending on the exact distance between the reservoir’s surface and the satellite when the satellite passes over, the outgoing oscillation may peak when the echo’s oscillation peaks, or when the echo’s oscillation “troughs” (that is, when the echo’s electromagnetic field is exactly opposite to that of the outgoing wave’s), or when the echo field’s phase is somewhere between, with some intermediate strength and orientation.  Since a certain whole-plus-fractional number of wave oscillations will fit between any given point of the reservoir’s surface and the satellite, a slight change in the distance between them will result in a change in the number of oscillations fitting in that space, and thus a change in the phase difference between the returning echo and the outgoing radar wave.   A distance increase from one pass of the satellite to the next may signal that the reservoir surface has subsided because CO2 has leaked out and the ground has sunk slightly as a result.  The distance may also be affected by other factors, such as the satellite’s orbit not going over the exact same ground path at the same altitude every time around, but if these differences are known and accounted for, any remaining differences in satellite-reservoir distance should indicate changes in the reservoir’s CO2 content. 

 

The other satellite-based method is to place Global Positioning System (GPS) devices[Wikipedia] at various points on the reservoir surface and measure their positions using GPS satellite signals.  Again, if the surface is found to subside, it may be because CO2 is getting out and there’s less pressure supporting the reservoir surface.  A GPS device’s calculation of its position involves calculating the differences between whatever time signals it receives at any moment from GPS satellites.  The farther away a GPS satellite is from a GPS device, the longer ago it was when the most recently received signal was sent from the satellite.  If the current signals from two different satellites have timestamps that differ by x tens of milliseconds, the satellite that sent the earlier signal is about 3x thousand kilometers further away than the other satellite.  Comparing the timestamps between satellite signals in this way, and comparing the results with the information they broadcast about where they were when they sent those signals, allows the GPS device to work out its own position.  While many GPS devices only display latitude and longitude, the same calculations also allow computation of altitude above average sea level.  Detecting altitude decreases in GPS devices placed on a CO2 reservoir indicates possible CO2 leakage. 

 

The experiments reported tested both space-based methods to see if CO2injection into the reservoir could be detected by a rise in the reservoir’s surface level, and found both methods potentially workable.  “However,” the report concludes, “it is important to have deformation data well in advance of injection, in order to understand the background deformation associated with hydrological and other near-surface processes unrelated to injection.  It is also important to sample adequately in time (~weekly or better) in order to capture transient events.”  The report also describes experiments with two ground-based reservoir monitoring methods, involving seismometers and geochemical sensors, which also exhibited similar potential.  The report’s authors suggested that some or all of the techniques be used to augment more expensive techniques using monitors below the reservoir surface, with the optimum surface and subsurface sensor arrangements to be determined by further study. 

 

Satellites able to operate in various space weather conditions can also be used to observe that same space weather.  Atmospheric weather near the earth’s surface is well monitored by a dense network of weather stations as well as several satellite-based instruments aimed downward, not to mention its monitoring by ourselves who experience that weather directly.  Instruments for observing space weather, on the other hand, are relatively scarce, so we are relative beginners at learning how space weather works or even what sort of phenomena it can display.  Yet people are learning.  The nature of one space weather event that occurred June 27, 2007 was found by a new computational method using data from two satellites designed for observations of magnetospheric substorms, as reported in “Dual-spacecraft reconstruction of a three-dimensional magnetic flux rope at the Earth's magnetopause ”[DoE PAGES].  The computations showed that in this event, magnetic field lines at the point of the earth’s magnetopause directly under the sun were changing their pattern of connections, and that a large ropelike magnetic field structure about 3000 kilometers wide formed between two reconnection regions.  Older, more limited computational methods failed to reveal the event’s three-dimensional features. 

Figure 5.  Three-dimensional reconstructions of the magnetic field and pressure found by THEMIS satellites C and D.  Top (a):  magnetic field lines, with field intensity indicated in color; white arrows represent approximate magnetic-field orientation in surrounding regions.  Bottom (b):  cyan field lines; plasma pressure in color; white, yellow, and blue arrows have roots on the paths of THEMIS satellites D, C, and E respectively, and show the velocities of positively-charged atoms.  (After “Dual-spacecraft reconstruction of a three-dimensional magnetic flux rope at the Earth's magnetopause ”[DoE PAGES], Annales Geophysicae (Online), Volume 33, Issue 2, p. 173.) 

 

Space telescopes are another type of instrument built for the outer space environment that can reveal natural phenomena that could not be observed well, or even observed at all, from our more familiar environment near the earth’s surface.  While the earth’s atmosphere is transparent to the light we see by, it still scatters some of that light, and is much less transparent to electromagnetic waves of other frequencies, so putting telescopes in space can give us clearer views of the rest of the universe than we might otherwise have. 

 

But, as the previous report’s discussion of a space weather phenomenon exemplifies, viewing things more clearly is only a first step towards understanding them.  This is made even more plain by a report on observations made with the Kepler space observatory[Wikipedia].  Kepler was originally built and placed in orbit about the sun to detect planets orbiting other stars from the way those stars are slightly dimmed when their planets orbit in front of them.  But since stars’ brightnesses can also vary for quite different reasons—namely because of changes in their internal light-generating processes—Kepler has provided new clues about those processes by resolving fine details of stars’ brightness variations, as shown by a 2015 report[SciTech Connect] describing observations of two very dim variable stars.  However, the report also shows that analyses to connect these variations to the internal processes that produced them required significant effort for each star, and finding patterns or drawing a general conclusion from a set of stars looked difficult. 

 

Important as it is to get equipment to function in the space environment, it’s only a beginning.  

 

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References

 

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  • “IMPACT Project Integrated Modeling of Perturbations in Atmospheres for Conjunction Tracking A New Orbital Prediction Model to Avoid Collisions in Space” [slides] [Metadata]
    2014-05-09
    Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)

 

 

 

 

 

 

 

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Last updated on Thursday 16 March 2017