Autonomic Computing for Spacecraft Ground Systems

The Glory program is an Earth and Solar science mission designed to broaden science community knowledge of the environment. The causes and effects of global warming have become a concern in recent years and Glory aims to contribute to the knowledge base of the science community. Glory is designed for two functions: one is solar viewing to monitor the total solar irradiance and the other is observing the Earth's atmosphere for aerosol composition. The former is done with an active cavity radiometer, while the latter is accomplished with an aerosol polarimeter sensor to discern atmospheric particles. The Glory program is managed by NASA Goddard Space Flight Center (GSFC) with Orbital Sciences in Dulles, VA as the prime contractor for the spacecraft bus, mission operations, and ground system. This paper describes some of the more unique features of the Glory program including the integration and testing of the satellite and instruments as well as the science data processing. The spacecraft integration and test approach requires extensive analysis and additional planning to ensure existing components are successfully functioning with the new Glory components. The science mission data analysis requires development of mission unique processing systems and algorithms. Science data analysis and distribution will utilize our national assets at the Goddard Institute for Space Studies (GISS) and the University of Colorado's Laboratory for Atmospheric and Space Physics (LASP). The satellite was originally designed and built for the vegetation canopy lidar (VCL) mission, which was terminated in the middle of integration and testing due to payload development issues. The bus was then placed in secure storage in 2001 and removed from an environmentally controlled container in late 2003 to be refurbished to meet the Glory program requirements. Functional testing of all components was done as a system at the start of the program, very different from a traditional program. The plan for Glory is to minimize any changes to the spacecraft in order to meet the Glory requirements. This means that the instrument designs must adhere to the existing interfaces and capabilities as much as possible. Given Glory's unique history and the potential science return, the program is one of significant value to both the science community and the world. The findings Glory promises will improve our understanding of the drivers for global climate change for a minimal investment. The program hopes to show that reuse of existing government assets can result in a lower cost, and a fully successful mission.

Engineering Design and Development DivisionScientific and Commercial Systems CorporationAlexandria, VirginiaABSTRACTThe historically high toll in human lives lost to natural disasters such as hurricanes, tornadoes, floods, and otherprogressive events signals the need for some type of personal warning that alerts people to the need to evacuateor otherwise protect themselves in the face of an advancing threat. Traditional warning services, which rely onbroadcasts by the mass media in the metropolitan areas of the United States, achieve measurable success indisseminating warnings. However, warnings to isolated populations that exist in the U.S. and elsewhere in theworld may be poor to effectively nonexistent, especially in the many archipelagoes. Earth Alert, a joint projectof NASA Goddard Space Flight Center (GSFC) and Scientific and Commercial Systems Corporation (SCSC), istargeted at development of a simple, low-cost means for providing timely warning to otherwise isolated popula-tions. The project uses appropriate relay capabilities of U.S. satellites already in orbit, and thus avoids the high-cost development and launch of dedicated resources.Key words: GOES, emergency warning, WEFAX, repeater1. INTRODUCTIONIn an August 13, 1992 meeting with SCSC managers, the Chief of NASA GSFC International Data SystemsOffice raised the idea of a technology transfer project to provide timely personal warning to isolated populationsthreatened by natural disaster. The specific suggestion was that some capabilities of on-orbit satellite systemscould be diverted to provide enough warning to permit these populations to prepare for the threat of naturaldisasters such as hurricanes, tornadoes, orfloods. The NASA official was armed witha wealth ofexamples ofserious weather

The Formation Flying Test Bed (FFTB) at NASA Goddard Space Flight Center (GSFC) is being developed as a modular, hybrid dynamic simulation facility employed for end-to-end guidance, navigation, and control (GN&C) analysis and design for formation flying clusters and constellations of satellites. The FFTB will support critical hardware and software technology development to enable current and future missions for NASA, other government agencies, and external customers for a wide range of missions, particularly those involving distributed spacecraft operations. The initial capabilities of the FFTB are based upon an integration of high fidelity hardware and software simulation, emulation, and test platforms developed at GSFC in recent years; including a high-fidelity GPS simulator which has been a fundamental component of the Guidance, Navigation, and Control Center's GPS Test Facility. The FFTB will be continuously evolving over the next several years from a tool with initial capabilities in GPS navigation hardware/software-in-the-loop analysis and closed loop GPS-based orbit control algorithm assessment to one with cross-link communications and relative navigation analysis and simulation capability. Eventually the FFTB will provide full capability to support all aspects of multi-sensor, absolute and relative position determination and control, in all (attitude and orbit) degrees of freedom, as well as information management for satellite clusters and constellations. In this paper we focus on the architecture for the FFTB as a general GN&C analysis environment for the spacecraft formation flying community inside and outside of NASA GSFC and we briefly reference some current and future activities which will drive the requirements and development.

The NASA Goddard Space Flight Center (GSFC) High-altitude Imaging Wind and Rain Airborne Profiler (HIWRAP) is a solid-state dual frequency Doppler radar funded by the NASA Instrument Incubator Program. It uses direct-digital-synthesizer devices to generate versatile waveforms including conventional pulses and linear frequency modulation (LFM) chirps. This letter describes a waveform used by the GSFC and the Remote Sensing Solutions to address the critical limitations of range sidelobes and blind ranges in airborne pulse-compression radar. By utilizing a frequency diversity waveform consisting of two pulses and an LFM chirp at each transmit cycle, this system provides the improved sensitivity and range resolution benefits of pulse compression on targets within the middle and high altitudes while maintaining conventional pulsed data near the radar and the surface. The data obtained by the HIWRAP during the NASA Midlatitude Continental Convective Clouds Experiment using this waveform scheme are presented.

Due to high launch vehicle costs, space instrumentation designers are constantly pressured to decrease weight and increase reliability of flight hardware. To meet these needs in a spectrometer, the infrared products team at Optical Coating Laboratory, Inc. (OCLI) and the NASA Goddard Space Flight Center (GSFC) have developed an infrared logarithmically variable filter for use in NASA's Pluto Fast Fly-by instrument. The filter and diode array combination replaces the multiple optical elements in conventional spectrometers, resulting in lower instrumentation weight and complexity with no moving parts. The choice of logarithmic rather than linear profile yields constant resolving power on every pixel of the array. Filters were produced in which the center wavelength varied from 1.0-1.581 micrometers , and 1.581-2.5 micrometers over a distance of 1.024 cm. Bandwidth was 0.3% FWHM and overall transmittance ranged from 30% to 50%. This paper discusses the major issues and tradeoffs in the design, manufacture, and testing of the filters. Measurement techniques are presented and comparisons are made between theoretical and measured performance of bandwidth, transmittance, and spectral profile.

An application of the Design Structure Matrix to Integrated Concurrent Engineering

X-ray astronomy critically depends on X-ray optics. The capability of an X-ray telescope is largelydetermined by the point-spread function (PSF) and the photon-collection area of its mirrors, the same astelescopes in other wavelength bands. Since an X-ray telescope must be operated above the atmosphere inspace and that X-rays reflect only at grazing incidence, X-ray mirrors must be both lightweight and thin, bothof which add significant technical and engineering challenge to making an X-ray telescope. In this paper wereport our effort at NASA Goddard Space Flight Center (GSFC) of developing an approach to making an Xraymirror assembly that can be significantly better than the mirror assembly currently flying on the ChandraX-ray Observatory in each of the three aspects: PSF, effective area per unit mass, and production cost per uniteffective area. Our approach is based on the precision polishing of mono-crystalline silicon to fabricate thinand lightweight X-ray mirrors of the highest figure quality and micro-roughness, therefore, having thepotential of achieving diffraction-limited X-ray optics. When successfully developed, this approach will makeimplementable in the 2020s and 2030s many X-ray astronomical missions that are currently on the drawingboard, including sounding rocket flights such as OGRE, Explorer class missions such as STAR-X andFORCE, Probe class missions such as AXIS, TAP, and HEX-P, as well as large missions such as Lynx.

We are developing a submillimeter continuum camera for the Caltech Submillimeter Observatory (CSO) located on Mauna Kea. The camera will employ a monolithic Si bolometer array which was developed by Mosley et al. at the NASA Goddard Space Flight Center (GSFC). The camera will be cooled to a temperature of about 300 mK in a <SUP>3</SUP>He cryostat, and will operate primarily at wavelengths of 350 and 450 micrometers . We plan to use a bolometer array with 1 x 24 directly illuminated pixels, each pixel of dimension 1 x 2 mm<SUP>2</SUP>, which is about half of the F/4 beam size at these wavelengths. Each pixel is 10 - 12 micrometers thick and is supported only by four thin Si legs formed by wet chemical etch. The pixels are doped n-type by phosphorus implantation, compensated by boron implantation. Signals from the bolometer pixels are first amplified by cryogenically cooled FETs. The signals are further amplified by room-temperature amplifiers and then separately digitized by 16 bit A/D converters with differential inputs. The outputs of the A/D converters are fed into a digital signal processing board via fiber-optic cables. The electronics and data acquisition system were designed by the Goddard group. We will report the status of this effort.

The Thermal Infrared Sensor (TIRS) is a pushbroom sensor that will be a part of the Landsat Data Continuity Mission (LDCM), which is a joint mission between NASA and the USGS. The TIRS instrument will continue to collect the thermal infrared data that are currently being collected by the Thematic Mapper and the Enhanced Thematic Mapper Plus on Landsats 5 and 7, respectively. One of the key requirements of the new sensor is that the dark and background response be stable to ensure proper data continuity from the legacy Landsat instruments. Pre launch testing of the instrument has recently been completed at the NASA Goddard Space Flight Center (GSFC), which included calibration collects that mimic those that will be performed on orbit. These collects include images of a cold plate meant to simulate the deep space calibration source as viewed by the instrument in flight. The data from these collects give insight into the stability of the instrument’s dark and background response, as well as factors that may cause these responses to vary. This paper quantifies the measured background and dark response of TIRS as well as its stability.

The General Mission Analysis Tool (GMAT) is an open-source space mission design, analysis and trajectory optimization tool. GMAT is developed by a team of NASA, private industry, public and private contributors. GMAT is designed to model, optimize and estimate spacecraft trajectories in flight regimes ranging from low Earth orbit to lunar applications, interplanetary trajectories and other deep space missions. GMAT has also been flight qualified to support operational maneuver planning for the Advanced Composition Explorer (ACE) mission. ACE was launched in August, 1997 and is orbiting the Sun-Earth L1 libration point. The primary science objective of ACE is to study the composition of both the solar wind and the galactic cosmic rays. Operational orbit determination, maneuver operations and product generation for ACE are conducted by NASA Goddard Space Flight Center (GSFC) Flight Dynamics Facility (FDF). This paper discusses the entire engineering lifecycle and major operational certification milestones that GMAT successfully completed to obtain operational certification for the ACE mission. Operational certification milestones such as gathering of the requirements for ACE operational maneuver planning, gap analysis, test plans and procedures development, system design, pre-shadow operations, training to FDF ACE maneuver planners, shadow operations, Test Readiness Review (TRR) and finally Operational Readiness Review (ORR) are discussed. These efforts have demonstrated that GMAT is flight quality software ready to support ACE mission operations in the FDF.

The Space Exploration Synthetic Aperture Radar (SESAR) is a P-band radar instrument for planetary applications being developed at the NASA Goddard Space Flight Center (GSFC). This radar will enable unprecedented surface and near-subsurface measurements of planetary bodies including the Moon, Mars, and asteroids. The radar will measure full polarimetry at meter-scale resolution while featuring a low power, lightweight, beamforming design, specifically developed to meet stringent requirements of planetary instruments. The ongoing prototype development is maturing the SESAR technology for upcoming planetary mission opportunities.

Observations from over a decade of experience in developing faster, better, cheaper missions for the NASA small explorer program

We present a new global time-variable gravity mascon solution derived from Gravity Recovery and Climate Experiment (GRACE) Level 1B data. The new product from the NASA Goddard Space Flight Center (GSFC) results from a novel approach that combines an iterative solution strategy with geographical binning of inter-satellite range-acceleration residuals in the construction of time-dependent regularization matrices applied in the inversion of mascon parameters. This estimation strategy is intentionally conservative as it seeks to maximize the role of the GRACE measurements on the final solution while minimizing the influence of the regularization design process. We fully reprocess the Level 1B data in the presence of the final mascon solution to generate true post-fit inter-satellite residuals, which are utilized to confirm solution convergence and to validate the mascon noise uncertainties. We also present the mathematical case that regularized mascon solutions are biased, and that this bias, or leakage, must be combined with the estimated noise variance to accurately assess total mascon uncertainties. The estimated leakage errors are determined from the monthly resolution operators. We present a simple approach to compute the total uncertainty for both individual mascon and regional analysis of the GSFC mascon product, and validate the results with comparisons to independent mascon solutions and calibrated Stokes uncertainties. Lastly, we present the new solution and uncertainties with global analyses of the mass trends and annual amplitudes, and compute updated trends for the global ocean, and the respective contributions of the Greenland Ice Sheet, Antarctic Ice Sheet, Gulf of Alaska, and terrestrial water storage. This analysis highlights the successful closure of the global mean sea level budget; i.e. the sum of global ocean mass from the GSFC mascons and the steric component from Argo floats agrees well with the total determined from sea surface altimetry.

The Solar Probe science team at NASA Goddard Space Flight Center (GSFC) is considering enhance science observations by adding the nadir viewing Plasma Spectrometer instrument and using heat shields to protect the Plasma Wave Antennas to permit full extension at 3 solar radii (Rs). The main components of the thermal protection system for these nadir viewing instruments are high temperature multi-layer insulation (MLI) blankets and carbon-carbon (C-C) composite sunshields that have an aluminum oxide (Al2O3) coating on the sun facing surfaces. A thermal test on the Plasma Wave Antenna sample was performed in September 2006 using a small and specially designed vacuum chamber and a Vortek Lamp. A 12.7 cm x 12.7 cm low-cost high temperature MLI blanket was built. It consists of 15 layers of 0.01524 mm tantalum foils which are interspaced with a 0.00508 mm carbon fiber mesh. Although the MLI blanket is much thicker than that proposed in the original design, the thermal test results show that the MLI effective emittance is about the same as the 0.03 value assumed for the original design. The highest temperatures of the MLI and hot side C-C measured in the test were 1,000oC and 1,300oC respectively. Higher temperatures were not pursued because the chamber pressure increased as the temperature increased. The pressure increase was caused by outgassing from the test sample and thermocouple connectors. An inspection of the MLI blanket after the test revealed that it had no degradation. The Al2O3 coating on the hot side C-C was discolored, possibly by contaminants from outgassing. When the hottest hot side C-C thermocouple was 700°C or warmer, the C-C warped. The Al2O3 coating delaminated, possibly due to the C-C warping.

The feasibility of performing an on-orbit refueling (OOR) operation to extend the orbital lifetime of the NASA Goddard Space Flight Center (GSFC) Gamma Ray Observatory (GRO) was investigated by TRW, the GRO mission contractor. This study shows that an OOR capability could be integrated into the GRO operational design early in the Phase D development with only minor cost impact and no schedule impact. In this approach, the GRO OOR design would be developed to achieve operational compatibility with the JSC/STS-developed Orbital Refueling System.