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At least 307 records · Page 17

Two Extremely Red Galaxies

This report concerns one of the major observational studies in the ISO Central Programme, the ISO Normal Galaxy Survey. This is a survey of an unbiased sample of spiral and lenticular galaxies selected from the Revised Shapley-Ames Catalog. It is therefore optically-selected, with a brightness limit of blue magnitude = 12, and otherwise randomly chosen. The original sample included 150 galaxies, but this was reduced to 74 when the allocated observing time was expended because the ISO overheads encountered in flight were much larger than predicted.

Joseph, Robert D.↗

ISOPHOT and SWS spectra of classical novae in outburst

The rationale for making photometric and spectroscopic observations of classical novae using the Infrared Space Observatory (ISO) is reviewed. Special attention is given to the coronal phase in ONeMg novae. The abundances of CNO, Ne, Mg, Al and Si were obtained from ISO's short wavelength spectrometer (SWS) data. The presence of forbidden line and dust emissions after the outburst were investigated with ISO photometer (ISOPHOT) photometry from 5 micrometers to 200 micrometers.

Gehrz, Robert D.↗

The Beta Pictoris Phenomenon in Young Stars With Accreting Gas

Program Hae2BPIC resulted in usable ISO spectra of three young, Herbig Ae stars: HR 5999 (A7e, t=0.6 Myr), SV Cep (al-2e, t=1-3 Myr), and MW Vul (Al-2e, t=1-3 Myr). While too small a sample to pursue our original goal of surveying the silicate emission in these young, protoplanetary disk systems, comparison of these data with ground-based IR spectra, and published ISO observations of other HAe stars (especially the posters at PPIV) reveals the following: The known binary stars in the sample show signatures of partially crystal line silicate features by t=0.6 Myr, at an epoch when ostensibly single Herbig Ae stars have substantially stronger silicate emission dominated by amorphous grains. The known binary stars also show deficits in the optically thick continuum flux relative to coeval single stars. Comparison of ISO spectra indicates that the flux deficit seen in WD 163296 over 10-100 microns relative to AB Aur reflects a real deficit of material interior to 300.

Grady, Carol A.↗

Final Report

This multi-year grant partially supported the Infrared Space Observatory (ISO) data analysis and related activities of three Guest Investigators (Prof. Dan Clemens, Prof. Thomas Bania, and Prof. James Jackson) at Boston University for ten distinct ISO investigations. Support under this grant covered "Years 1 & 2" of the ISO activities at Boston University. "Year 3" activities support is currently in force under a separate JPL contract, with Prof. James Jackson as the Block Grant PI; "Year 4" support has been requested from JPL and that proposal is currently pending.

Clemens, Dan↗

Photochemistry Saturn's Atmosphere: Effects of an Influx of External Oxygen - 2

We use a one-dimensional diurnally averaged model of photochemistry and diffusion in Saturn's stratosphere to investigate the influence of extraplanetary debris on atmospheric chemistry. In particular, we consider the effects of an influx of oxygen from micrometeoroid ablation or from ring-particle diffusion; the contribution from cometary impacts, satellite debris, or ring vapor is deemed to be less important. The photochemical model results are compared directly with Infrared Space Observatory (ISO) observations to constrain the influx of extraplanetary oxygen to Saturn. From the ISO observations, we determine that the column densities of CO2 and H2O above 10 mbar in Saturn's atmosphere are (6.3 +/- 1) x 10(exp 14) and (1.4 +/- 0.4) x 10(exp 15)/ square cm, respectively; our models indicate that a globally averaged oxygen influx of (4+/-2) x 10(exp 6) O atoms /sq cm/s is required to explain these observations. Models with a locally enhanced influx of H20 operating over a small fraction of the projected area do not provide as good a fit to the ISO H2O observations. If volatile oxygen compounds comprise one-third to one-half of the exogenic source by mass, then Saturn is currently being bombarded with (3 +/- 2) x 10(exp -16) g/square cm/s of extraplanetary material. To reproduce the observed CO2/H2O ratio in Saturn's stratosphere, some of the exogenic oxygen must arrive in the form of a carbon-oxygen bonded species such as CO or CO2. An influx consistent with the composition of cometary ices fails to reproduce the high observed CO2/H2O ratio, suggesting that (i) the material has ices that are slightly more carbon-rich than is typical for comets, (ii) a contribution from an organic-rich component is required, or (iii) some of the hydrogen-oxygen bonded material is converted to carbon-oxygen bonded material without photochemistry (e.g., during the ablation process). We have also reanalyzed the 5-micron CO observations of Noll and Larson and determine that the CO lines are most sensitive to the 100- to 400-mbar column density for which we derive a range of (0.7-1.5) x 10(exp 17)/square cm; the CO observations do not allow us to distinguish between an external or internal source of CO on Saturn. If we assume that all the extraplanetary oxygen derives from a micrometeoroid source, then the unfocused dust flux at 9.5 AU must be (i) (1 +/- 0.7) x 10(exp -16) g/square cm/s if interstellar grains are the source of the external oxygen on Saturn, (ii) (4 +/- 3) x 10 (exp -17) g/ sq. cm./s if IDPs on randomly inclined, highly eccentric orbits (e.g., Halley-type comet grains) are the source of the external oxygen, or (iii) (2+/- 1.4) x 10(exp -18)/g/sq cm/s if IDPs on low inclination, low eccentricity orbits (e.g., Kuiper-belt grains) are the source of the external oxygen. These estimates can be used in combination with future Cassini dust detection data to determine the ultimate source of the dust at Saturn's distance from the Sun.

Moses, Julianne I.↗

Capillary Pressure Balance with Repeated Head-Up Tilt in Humans

We measured blood density (BD). plasma density (PD) and hematocrit (Ht) during repeated 70 deg head-up tilt (HUT) consisting of a pre-drink period with two supine (P and P3) and two HUT (P2 and P4) phases of 45 min each. At the end of P4 test subjects (N=8) drank 10 ml/kg body weight of isotonic (290 mOsm/kg) sodium chloride (ISO) or hypotonic (<10 mOsm/kg) unsweetened us (HYP), or nothing (control: CON). The following periods continued the supine (P5, P7) / upright (P6) sequence. Mass density of plasma and whole blood using a "mechanical oscillation" technique were measured from ear lobe blood. Tilting altered (p<0.001) BD, PD, and Ht in all consecutive Phases. BD and PD were different (p<0.05) between CON. HYP. and ISO Phases 6 and 7. The computed mass density of fluid (FD). which moved between intra. and extravascular compartments. averaged 1008 g/l and was the same in any conditions. In the non-drink treatment (P3, P5, P7), supine PV steadly decreased when compared to P1. Tilt-induced PV shifts ranged from 9.7 to 16.7% when compared to PV du. ring the respective previous Phases. After drinking, PV increased above CON values at the end of Phase 7 by 12.9% with ISO, and by 6.6% with HYP. Progressive hemoconcentration. occurred during non-drink supine; isotonic saline ingestion increased supine PV a control level but did not stop or reverse the decrease of upright hemoconcentration. Upright density values were not slowed with repeated upright tilting; decreased fluid loss occurred in consecutive upright periods. Upright capillary pressure balance was achieved with diminished plasma volume loss during repeated tilting.

Hinghofer-Szalkay, H. G.↗

A Matrix Approach to Software Process Definition

The Software Engineering Laboratory (SEL) is currently engaged in a Methodology and Metrics program for the Information Systems Center (ISC) at Goddard Space Flight Center (GSFC). This paper addresses the Methodology portion of the program. The purpose of the Methodology effort is to assist a software team lead in selecting and tailoring a software development or maintenance process for a specific GSFC project. It is intended that this process will also be compliant with both ISO 9001 and the Software Engineering Institute's Capability Maturity Model (CMM). Under the Methodology program, we have defined four standard ISO-compliant software processes for the ISC, and three tailoring criteria that team leads can use to categorize their projects. The team lead would select a process and appropriate tailoring factors, from which a software process tailored to the specific project could be generated. Our objective in the Methodology program is to present software process information in a structured fashion, to make it easy for a team lead to characterize the type of software engineering to be performed, and to apply tailoring parameters to search for an appropriate software process description. This will enable the team lead to follow a proven, effective software process and also satisfy NASA's requirement for compliance with ISO 9001 and the anticipated requirement for CMM assessment. This work is also intended to support the deployment of sound software processes across the ISC.

Schultz, David↗

A Search for Supernova in Star-Burst Galaxies

The rate at which massive supernovae occur in galaxies can be related directly to the rate of formation of massive stars this rate in turn can be computed from measurements and theoretical models of stellar mss distributions. Other measurements such as chemical composition and the dynamical structure of galaxies can also be used to infer the rate of massive supernovae. Various lines of reasoning using these measurements and theories of star formation have predicted a supernova rate which might be as much as ten times the rate of supernovae that had been observed using optical telescopes. The unseen supernovae were thought to be undetected due to a variety of circumstances, with the primary problem being extinction imposed by dust along the line of observation. This research used new infrared observations of the Infrared Space Observatory (ISO) space craft to explore active galaxies with a technique unhindered by dust extinction. New image processing algorithms for ISO point source analysis and cosmic ray deglitching were developed in order to search through a fairly complete set of the ISO data.

Rank, David M.↗

The Far-Infrared Spectral Energy Distributions of Quasars

The origin of the infrared emission in Active Galactic Nuclei (AGN), whose strength is comparable to the optical/ultraviolet (OUV) emission, is generally thought to be a combination of thermal emission from dust and non-thermal, synchrotron emission. Although data are sparse, particularly in the far-infrared, the broad wavelength range of this emission suggests a wide range of temperatures and a combination of AGN and starburst heating mechanisms. The strength of the non-thermal emission is expected to be related to the radio emission. While this scenario is well-established, basic questions, such as the spatial and temperature distribution of the dust, the relative importance of AGN and starburst heating, and the significance of the non-thermal contribution remain largely undetermined. The wide wavelength range of the Infrared Space Observatory (ISO) combined with its arcmin spatial resolution and increased sensitivity facilitated the observation of a larger subset of the AGN population than previously covered, allowing these questions to be investigated in more detail. This paper will review the spectral energy distributions (SED) of AGN with particular emphasis on the infrared emission and on ISO's contributions to our knowledge. Preliminary results from ISO observations of X-ray selected and high-redshift AGN will be described.

Wilkes, Belinda J.↗

NASA's Geospatial Interoperability Office(GIO)Program

NASA produces vast amounts of information about the Earth from satellites, supercomputer models, and other sources. These data are most useful when made easily accessible to NASA researchers and scientists, to NASA's partner Federal Agencies, and to society as a whole. A NASA goal is to apply its data for knowledge gain, decision support and understanding of Earth, and other planetary systems. The NASA Earth Science Enterprise (ESE) Geospatial Interoperability Office (GIO) Program leads the development, promotion and implementation of information technology standards that accelerate and expand the delivery of NASA's Earth system science research through integrated systems solutions. Our overarching goal is to make it easy for decision-makers, scientists and citizens to use NASA's science information. NASA's Federal partners currently participate with NASA and one another in the development and implementation of geospatial standards to ensure the most efficient and effective access to one another's data. Through the GIO, NASA participates with its Federal partners in implementing interoperability standards in support of E-Gov and the associated President's Management Agenda initiatives by collaborating on standards development. Through partnerships with government, private industry, education and communities the GIO works towards enhancing the ESE Applications Division in the area of National Applications and decision support systems. The GIO provides geospatial standards leadership within NASA, represents NASA on the Federal Geographic Data Committee (FGDC) Coordination Working Group and chairs the FGDC's Geospatial Applications and Interoperability Working Group (GAI) and supports development and implementation efforts such as Earth Science Gateway (ESG), Space Time Tool Kit and Web Map Services (WMS) Global Mosaic. The GIO supports NASA in the collection and dissemination of geospatial interoperability standards needs and progress throughout the agency including areas such as ESE Applications, the SEEDS Working Groups, the Facilities Engineering Division (Code JX) and NASA's Chief Information Offices (CIO). With these agency level requirements GIO leads, brokers and facilitates efforts to, develop, implement, influence and fully participate in standards development internationally, federally and locally. The GIO also represents NASA in the OpenGIS Consortium and ISO TC211. The OGC has made considerable progress in regards to relations with other open standards bodies; namely ISO, W3C and OASIS. ISO TC211 is the Geographic and Geomatics Information technical committee that works towards standardization in the field of digital geographic information. The GIO focuses on seamless access to data, applications of data, and enabling technologies furthering the interoperability of distributed data. Through teaming within the Applications Directorate and partnerships with government, private industry, education and communities, GIO works towards the data application goals of NASA, the ESE Applications Directorate, and our Federal partners by managing projects in four categories: Geospatial Standards and Leadership, Geospatial One Stop, Standards Development and Implementation, and National and NASA Activities.

Weir, Patricia↗

Evidence for increased beta-adrenoreceptor responsiveness induced by 14 days of simulated microgravity in humans

We studied hemodynamic responses to alpha- and beta-receptor agonists in eight healthy men before and after 14 days of 6 degrees head-down tilt (HDT) to test the hypothesis that increased adrenoreceptor responsiveness is induced by prolonged exposure to simulated microgravity. Steady-state infusions of isoproterenol (Iso) at rates of 0.005, 0.01, and 0.02 microgram.kg-1.min-1 were used to assess beta 1- and beta 2-adrenoreceptor responsiveness. Infusions of phenylephrine (PE) at rates of 0.25, 0.50, and 1.00 microgram.kg-1.min-1 were used to assess responsiveness of alpha 1-vascular adrenoreceptors. Slopes calculated from linear regressions between Iso and PE doses and changes in beat-to-beat heart rate, blood pressure, and leg vascular resistance (occlusion plethysmography) for each subject were used as an index of alpha- and beta-adrenoreceptor responsiveness. HDT increased the slopes of heart rate (1,056 +/- 107 to 1,553 +/- 83 beats micrograms-1.kg-1.min-1; P = 0.014) and vasodilation (-469 +/- 111 to -1,446 +/- 309 peripheral resistance units.microgram-1.kg-1.min-1; P = 0.0224) to Iso infusion. There was no alteration in blood pressure or vascular resistance responses to PE infusion after HDT. Our results provide evidence that simulated microgravity causes selective increases in beta 1- and beta 2-adrenoreceptor responsiveness without affecting alpha 1-vascular adrenoreceptor responses.

NASA Discipline Cardiopulmonary↗

Infrared Spectroscopy of Star Formation in Galactic and Extragalactic Regions

Last year we submitted and had accepted a paper entitled "The Far-Infrared Emission Line and Continuum Spectrum of the Seyfert Galaxy NGC 1068," by Spinoglio, L., Malkan, M., Smith. HA, Gonzalez-Alfonso, E., and Fischer, J. This analysis was based on the SWAS Monte Carlo code modeling of the OH lines in galaxies observed by ISO. Since that meeting last spring considerable effort has been put into improving the Monte Carlo code. A group of European astronomers, including Prof. Eduardo Gonzalez-Alfonso, had been performing Monte Carlo modeling of other molecules seen in ISO galaxies. We used portions of this grant to bring Prof. Gonzalez-Alfonso to Cambridge for an intensive working visit. A second major paper on the ISO IR spectroscopy of galaxies, "The Far Infrared Spectrum of Arp 220," Gonzalez-Alfonso, E., Smith. H., Fischer, J., and Cernicharo, J., is in press. Spitzer science development was the major component of this past year;s research. This program supported the development of five Early Release Objects for Spitzer observations on which Dr. Smith was Principal Investigator or Co-Investigator, and another five proposals for GO time. The early release program is designed to rapidly present to the public and the scientific community some exciting results from Spitzer in the first months of its operation. The Spitzer instrument and science teams submitted proposals for ERO objects, and a competitive selection process narrowed these down to a small group with exciting science and realistic observational parameters. This grant supported Dr. Smith's participation in the ERO process, including developing science goals, identifying key objects for observation, and developing the detailed AOR (observing formulae) to be use by the instruments for mapping, integrating, etc.). During this year Dr. Smith worked on writing up and publishing these early results. The attached bibliography includes six of Dr. Smith's articles. During this past year Dr. Smith also led or helped to develop proposals for ten Spitzer GO Programs, and three others. Appendix B lists the programs involved.

Smith, Howard A.↗

WISE-2005: Adrenergic Responses Before and After 60 Days of 6 Degree Head-Down Bed-Rest in Women

Sixteen women who participated in the WISE-2005 headdown bed rest (HDBR) were studied before and on day 56 of bed rest to test the hypothesis that chronic changes in circulating norepinephrine (NOR) would change the response to adrenergic receptor agonists. Five minute infusions of 2 doses of isoproterenol (ISO), and 2 doses of NOR were administered while heart rate (HR), mean arterial pressure (MAP) and total peripheral resistance (TPR) were measured. Before HDBR, the higher dose of ISO increased HR by 13 beats/min (P<O.OOl) and decreased TPR by -50% (P<O.OOl) with no changes in MAP, the higher dose of NOR increased MAP by 8 mmHg (P<O.OOl) and increased TPR -20% (P=0.007) with no change in HR. On HDBR day 56, subjects who took part in daily exercise+lower body negative pressure (EX+LBNP) countermeasures had no change in HR response to ISO while the control group (CON) had greater increases in HR. MAP tended to be lower post-HDBR in CON but not in EX+LBNP, while TPR was higher in both groups. In response to NOR, MAP increased with elevated TPR with no change in HR. Post-HDBR TPR increased more in the EX+LBNP group. These studies indicate that HDBR alters the HR response to IS0 but that EX+LBNP countermeasure prevented this change. The greater TPR response to NOR in the post-HDBR for the EX+LBNP group might reflect enhanced peripheral vasoconstrictor response that could reduce the risk of orthostatic intolerance after this countermeasure.

Edgell, H.↗

Clean Assembly of Genesis Collector Canister for Flight: Lessons for Planetary Sample Return

Measurement of solar composition in the Genesis collectors requires not only high sensitivity but very low blanks; thus, very strict collector contamination minimization was required beginning with mission planning and continuing through hardware design, fabrication, assembly and testing. Genesis started with clean collectors and kept them clean inside of a canister. The mounting hardware and container for the clean collectors were designed to be cleanable, with access to all surfaces for cleaning. Major structural components were made of aluminum and cleaned with megasonically energized ultrapure water (UPW). The UPW purity was >18 M resistivity. Although aluminum is relatively difficult to clean, the Genesis protocol achieved level 25 and level 50 cleanliness on large structural parts; however, the experience suggests that surface treatments may be helpful on future missions. All cleaning was performed in an ISO Class 4 (Class 10) cleanroom immediately adjacent to an ISO Class 4 assembly room; thus, no plastic packaging was required for transport. Persons assembling the canister were totally enclosed in cleanroom suits with face shield and HEPA filter exhaust from suit. Interior canister materials, including fasteners, were installed, untouched by gloves, using tweezers and other stainless steel tools. Sealants/lubricants were not exposed inside the canister, but vented to the exterior and applied in extremely small amounts using special tools. The canister was closed in ISO Class 4, not to be opened until on station at Earth-Sun L1. Throughout the cleaning and assembly, coupons of reference materials that were cleaned at the same time as the flight hardware were archived for future reference and blanks. Likewise reference collectors were archived. Post-mission analysis of collectors has made use of these archived reference materials.

Allton, J. H.↗

Space Systems - Safety and Compatibility of Materials - Method to Determine the Flammability Thresholds of Materials

Spacecraft fire safety emphasizes fire prevention, which is achieved primarily through the use of fire-resistant materials. Materials selection for spacecraft is based on conventional flammability acceptance tests, along with prescribed quantity limitations and configuration control for items that are non-pass or questionable. ISO 14624-1 and -2 are the major methods used to evaluate flammability of polymeric materials intended for use in the habitable environments of spacecraft. The methods are upward flame-propagation tests initiated in static environments and using a well-defined igniter flame at the bottom of the sample. The tests are conducted in the most severe flaming combustion environment expected in the spacecraft. The pass/fail test logic of ISO 14624-1 and -2 does not allow a quantitative comparison with reduced gravity or microgravity test results; therefore their use is limited, and possibilities for in-depth theoretical analyses and realistic estimates of spacecraft fire extinguishment requirements are practically eliminated. To better understand the applicability of laboratory test data to actual spacecraft environments, a modified ISO 14624 protocol has been proposed that, as an alternative to qualifying materials as pass/fail in the worst-expected environments, measures the actual upward flammability limit for the material. A working group established by NASA to provide recommendations for exploration spacecraft internal atmospheres realized the importance of correlating laboratory data with real-life environments and recommended NASA to develop a flammability threshold test method. The working group indicated that for the Constellation Program, the flammability threshold information will allow NASA to identify materials with increased flammability risk from oxygen concentration and total pressure changes, minimize potential impacts, and allow for development of sound requirements for new spacecraft and extravehicular landers and habitats. Furthermore, recent research has shown that current normal gravity materials flammability tests do not correlate with flammability in ventilated, micro- or reduced-gravity conditions. Currently, the materials selection for spacecraft is based on the assumption of commonality between ground flammability test results and spacecraft environments, which does not appear to be valid. Materials flammability threshold data acquired in normal gravity can be correlated with data obtained in microgravity or reduced-gravity experiments, and consequently a more accurate assessment of the margin of safety of the material in the real environment can be made. In addition, the method allows the option of selecting better or best space system materials, as opposed to what would be considered just acceptable from a flammability point of view and realistic assessment of spacecraft fire extinguishment needs, which could result in significant weight savings. The knowledge afforded by this technique allows for limited extrapolations of flammability behavior to conditions not specifically tested and that could potentially result in significant cost and time savings. The intent of this Technical Specification is to bring to the attention of International Aerospace Community the importance of correlating laboratory test data with real-life space systems applications. The method presented is just one of the possibilities that are believed will lead to better understanding the applicability of laboratory aerospace materials flammability test data. International feedback on improving the proposed method, as well as suggestions for correlating other laboratory aerospace test data with real-life applications relevant to space systems are being sought.

Hirsch, David↗

Intra-Seasonal Monthly Oscillations in Stratospheric NCEP Data and Model Results

Intra-seasonal oscillations (ISO) are observed in the zonal-mean of mesospheric wind and temperature measurements-and the numerical spectral model (NSM) generates such oscillations. Relatively large temperature ISO are evident also in stratospheric CPC (NCEP) data at high latitudes, where the NSM produces amplitudes around 3 K at 30 km. Analyzing the NCEP data for the years 1996-2006, we find in Fourier spectra signatures of oscillations with periods between 1.7 and 3 months. With statistical confidence levels exceeding 70%, the spectral features are induced by nonlinear interactions involving the annual and semi-annual variations. The synthesized data show for the 10-year average that the temperature ISO peak in winter, having amplitudes close to 4 K. The synthesized complete spectrum for periods around 2 months produces oscillations, varying from year to year, which can reach peak amplitudes of 15 and 5 K respectively at northern and southern polar latitudes.

Mayr, H. G.↗

Development of an Integrated Countermeasure Device for Use in Long-Duration Space Flight

Prolonged weightlessness is associated with declines in musculoskeletal, cardiovascular, and sensorimotor health. Consequently, in-flight countermeasures are required to preserve astronaut health. We developed and tested a novel exercise countermeasure device (CCD) for use in spaceflight with the aim of preserving musculoskeletal and cardiovascular health along with an incorporated balance-training component. Additionally, the CCD features a compact footprint, and a low power requirement. Methods: After design and development of the CCD, we carried out a training study to test its ability to improve cardiovascular and muscular fitness in healthy volunteers. Fourteen male and female subjects (41.4+/-9.0 years, 69.5+/-15.4Kg) completed 12 weeks (3 sessions per week) of concurrent strength and endurance training on the CCD. Subjects were tested at baseline and after 12 weeks for 1-repetition max leg press strength (1RM), peak oxygen consumption (VO2peak), and isokinetic joint torque (ISO) at the hip, knee, and ankle. Additionally, we evaluated subjects after 6 weeks of training for changes in VO2peak and 1RM. Results: VO2peak and 1RM improved after 6-weeks, with additional improvements after 12 weeks (1.95+/-0.5, 2.28+/-0.5, 2.47+/-0.6 LY/min and 131.2+/-63.9,182.8+/-75.0, 207.0+/-75.0 Kg) for baseline, 6 weeks, and 12 weeks respectively. ISO for hip adduction, adduction, and ankle plantar flexion improved after 12 weeks of training (70.3+/-39.5, 76.8+/-39.2 and 55.7+/-21.7 N-m vs. 86.1+/-37.3, 85.1+/-34.3 and 62.1+/-26.4 N-m respectively). No changes were observed for ISO during hip flexion, knee extension, or knee flexion. Conclusions: The CCD is effective at improving cardiovascular fitness and isotonic leg strength in healthy adults. Further, the improvement in hip adductor and abductor torque provides support that the CCD may provide additional protection for the preservation of bone health at the hip.

Streeper, Tim↗

Age Induced Effects on ESD Characteristics of Solar Array Coupons After Combined Space Environmental Exposures

A set of multi-junction GaAs/Ge solar array test coupons provided by Space Systems/Loral were subjected to a sequence of 5-year increments of combined space environment exposure tests. The test coupons capture an integrated design intended for use in a geosynchronous (GEO) space environment. A key component of this test campaign is performing electrostatic discharge (ESD) tests in the inverted gradient mode. The protocol of the ESD tests is based on the ISO standard for ESD testing on solar array panels [ISO-11221]. The test schematic in the ISO reference has been modified with Space System/Loral designed circuitry to better simulate the on-orbit operational conditions of its solar array design. Part of the modified circuitry is to simulate a solar array panel coverglass flashover discharge. All solar array coupons used in the test campaign consist of four cells constructed to form two strings. The ESD tests were performed at the beginning-of-life (BOL) and at each 5-year environment exposure point until end-of-life (EOL) at 15 years. The space environmental exposure sequence consisted of ultra-violet radiation, electron/proton particle radiation, thermal cycling, and Xenon ion thruster plume erosion. This paper describes the ESD test setup and the importance of the electrical test design in simulating the on-orbit operational conditions. Arc inception voltage results along with ESD test behavior from the BOL condition through the 15th year age condition are discussed. In addition, results from a Xenon plasma plume exposure test with an EOL coupon under the full ESD test condition will be discussed.

Wright, Kenneth H.↗