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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1982

Galileo spacecraft power distribution and autonomous fault recovery

There is a trend in current spacecraft design to achieve greater fault tolerance through the implemenation of on-board software dedicated to detecting and isolating failures. A combination of hardware and software is utilized in the Galileo power system for autonomous fault recovery. Galileo is a dual-spun spacecraft designed to carry a number of scientific instruments into a series of orbits around the planet Jupiter. In addition to its self-contained scientific payload, it will also carry a probe system which will be separated from the spacecraft some 150 days prior to Jupiter encounter. The Galileo spacecraft is scheduled to be launched in 1985. Attention is given to the power system, the fault protection requirements, and the power fault recovery implementation.

Detwiler, R. C.↗
NASA NTRS1984

Transonic wind-tunnel investigation of the Galileo Probe parachute configuration

Wind-tunnel tests have been made of 1/4-scale and 1/2-scale models of the Galileo Probe conical ribbon-parachute at flight conditions. For the Galileo mission, the parachute is deployed behind a blunt shape at transonic speed. The investigation was initiated to verify the solutions to the delayed main-parachute opening with squidding that was observed in the 1982 Galileo Probe system balloon drop test. In addition to varying model scale, the forebody shape, angle of attack, dynamic pressure, Mach number, and canopy trailing distance behind the forebody were varied to determine their effect on parachute performance. Both steady-state and deployment tests were conducted. Parachute drag was measured and was seen to degrade severely at canopy trailing distances of 5.5 and 7 forebody diameters. Performance was shown to be good at the trailing distances of 9 and 11 diameters. A second balloon drop test demonstrated the desired parachute performance at the system level.

Corridan, R. E.↗
NASA NTRS1984

Assessment of Galileo modal test results for mathematical model verification

The modal test program for the Galileo Spacecraft was completed at the Jet Propulsion Laboratory in the summer of 1983. The multiple sine dwell method was used for the baseline test. The Galileo Spacecraft is a rather complex 2433 kg structure made of a central core on which seven major appendages representing 30 percent of the total mass are attached, resulting in a high modal density structure. The test revealed a strong nonlinearity in several major modes. This nonlinearity discovered in the course of the test necessitated running additional tests at the unusually high response levels of up to about 21 g. The high levels of response were required to obtain a model verification valid at the level of loads for which the spacecraft was designed. Because of the high modal density and the nonlinearity, correlation between the dynamic mathematical model and the test results becomes a difficult task. Significant changes in the pre-test analytical model are necessary to establish confidence in the upgraded analytical model used for the final load verification. This verification, using a test verified model, is required by NASA to fly the Galileo Spacecraft on the Shuttle/Centaur launch vehicle in 1986.

Trubert, M.↗
NASA NTRS1985

Asteroid amphitrite: Surface composition and prospects for the possible Galileo flyby

Studies of the trajectory of the Galileo mission to Jupiter recently revealed that the spacecraft can pass close to one of the largest asteroids (#29 Amphitrite). NASA has therefore altered the mission plan of the Galileo spacecraft to include a possible close flyby of Amphitrite in early December 1986, if the condition of the spacecraft allows. If this option is actually implemented, Amphitrite will become the only asteroid for which any high-spatial resolution images and reflection spectra will be available. To evaluate the value of this data and place Amphitrite in the context of the more than 600 asteroids for which some compositional information exists. Existing data was reexamined, new telescopic spectra of Amphitrite were obtained, and simulated Galileo data sets were constructed.

Bell, J. F.↗
NASA NTRS1985

Error and erasure probabilities for Galileo uplink code

The Galileo uplink Frame Erasure probability and Undetected Frame Error probability are derived. The performance meets desired specification under normal operations. The Galileo command system will work well even in an emergency condition, where the bit error rate into the command decoder is 1.00 X 0.001 (although Galileo's command threshold error rate is 1.00 X 0.00001).

Berner, J. B.↗
NASA NTRS1986

The Galileo single-event upset solution and risk assessment

The Galileo probe will be subject to radiation fields and energetic particle bombardment during its outward bound journey and in orbit around Jupiter and its moons. To avoid the occurrence and propagation of effects of single event upset (SEU) bit state changes induced by the bombardments attempts were made to harden the Galileo electronics against SEUs. The hazards are especially acute for Schottky diode and low-power Schottky TTL parts. The preventive action options which were scheduled are reviewed, noting the selection of CMOS chips as replacements for SEU-susceptible devices. The simulation and risk assessment that were performed to evaluate the potential success of the replacements are summarized, with emphasis on the data employed to ensure the accuracy of the assessments and the predicted effects of SEUs in the various Galileo subsystems.

Burdick, Garry M.↗
NASA NTRS1988

Performance of Galileo's concatenated codes with nonideal interleaving

The Galileo spacecraft employs concatenated coding schemes with Reed-Solomon interleaving depth 2. The bit error rate (BER) performance of Galileo's concatenated codes, assuming different interleaving depths (including infinite interleaving depth) are compared. It is observed that Galileo's depth 2 interleaving, when used with the experimental (15, 1/4) code, requires about 0.4 to 0.5 dB additional signal-to-noise ratio to achieve the same BER performance as the concatenated code with ideal interleaving. When used with the standard (7, 1/2) code, depth 2 interleaving requires about 0.2 dB more signal-to-noise ratio than ideal interleaving.

Cheung, K.-M.↗
NASA NTRS1989

Thermal design of the Galileo bus and Retro Propulsion Module

The Galileo spacecraft (S/C) consists of an Orbiter and Probe which have instruments to investigate the chemical composition and physical state of Jupiter's atmosphere, the Jovian satellites and the structure and physical dynamics of the Jovian magnetosphere. Galileo was at the Kennedy Space Center (KSC) preparing for a May 1986 launch at the time of the Challenger accident. The delay and an incraease in mission time has decreased the Radioisotope Thermoelectric Generator power output significantly. A change to the Inertial Upper Stage from the more powerful Centaur G-Prime has resulted in a trajectory that requires gravity assists once by Venus and twice by earth. The resulting peak solar intensity of this roundabout trajectory is more than twice the previous design value for the direct trajectory. Galileo was returned to the Jet Propulsion Laboratory (JPL) from KSC in February 1987 to begin the rework of the S/C thermal design. Verification of the thermal redesign was completed in the JPL 25' space simulator in August and November of 1988. This paper summarizes the thermal design and redesign of the Bus and Retro Propulsion Model.

Avila, A.↗
NASA NTRS1989

Shuttle Atlantis to deploy Galileo probe toward Jupiter

The objectives of Space Shuttle Mission STS-34 are described along with major flight activities, prelaunch and launch operations, trajectory sequence of events, and landing and post-landing operations. The primary objective of STS-34 is to deploy the Galileo planetary exploration spacecraft into low earth orbit. Following deployment, Galileo will be propelled on a trajectory, known as Venus-Earth-Earth Gravity Assist (VEEGA), by an inertial upper stage (IUS). The objectives of the Galileo mission are to study the chemical composition, state, and dynamics of the Jovian atmosphere and satellites, and investigate the structure and physical dynamics of the Jovian magnetosphere. Secondary STS-34 payloads include the Shuttle Solar Backscatter Ultraviolet (SSBUV) instrument; the Mesoscale Lightning Experiment (MLE); and various other payloads involving polymer morphology, the effects of microgravity on plant growth hormone, and the growth of ice crystals.

Source record↗
NASA NTRS1989

Final environmental impact statement for the Galileo Mission (Tier 2)

This Final Environmental Impact Statement (FEIS) addresses the proposed action of completing the preparation and operation of the Galileo spacecraft, including its planned launch on the Space Transportation System (STS) Shuttle in October 1989, and the alternative of canceling further work on the mission. The only expected environmental effects of the proposed action are associated with normal launch vehicle operation, and are treated in published National Environmental Policy Act (NEPA) documents on the Shuttle (NASA 1978) and the Kennedy Space Center (NASA 1979), and in the KSC Environmental Resources Document (NASA 1986) and the Galileo Tier 1 EIS (NASA 1988a). The environmental impacts of a normal launch were deemed insufficient to preclude Shuttle operations. Environmental impacts may also result from launch or mission accidents that could release plutonium fuel used in the Galileo power system. Intensive analysis of the possible accidents associated with the proposed action reveal small health or environmental risks. There are no environmental impacts in the no-action alternative. The remote possibility of environmental impacts of the proposed action must be weighed against the large adverse fiscal and programmatic impacts inherent in the no-action alternative.

Source record↗
NASA NTRS1991

Orientale and South Pole-Aitken basins on the Moon: Preliminary Galileo imaging results

During the Earth-Moon flyby the Galileo Solid State Imaging System obtained new information on the landscape and physical geology of the Moon. Multicolor Galileo images of the Moon reveal variations in color properties of the lunar surface. Using returned lunar samples as a key, the color differences can be interpreted in terms of variations in the mineral makeup of the lunar rocks and soil. The combined results of Apollo landings and multicolor images from Galileo allow extrapolation of surface composition to areas distant from the landing sites, including the far side invisible from Earth.

Head, J.↗
NASA NTRS1991

Galileo: The Earth encounter

The following subject areas are covered: Galileo Veega trajectory to Jupiter; lunar science objectives; Earth science objectives; Santa 2 data flow; Galileo - the U.S./Canada connections and European connections; UV spectrometer observations during close encounter periods; phase angle and cone angle of the Earth during the Earth encounters; Lunar orbit traverse at EGA1; Moon imaging - EGA1; Galileo imaging Earth after EGA1; and Earth 1 flyby geometry.

Clarke, Theodore C.↗
NASA NTRS1990

Galileo spacecraft power management and distribution system

The Galileo PMAD (power management and distribution system) is described, and the design drivers that established the final as-built hardware are discussed. The spacecraft is powered by two general-purpose heat-source-radioisotope thermoelectric generators. Power bus regulation is provided by a shunt regulator. Galileo PMAD distributes a 570-W beginning of mission (BOM) power source to a user complement of some 137 load elements. Extensive use of pyrotechnics requires two pyro switching subassemblies. They initiate 148 squibs which operate the 47 pyro devices on the spacecraft. Detection and correction of faults in the Galileo PMAD is an autonomous feature dictated by requirements for long life and reliability in the absence of ground-based support. Volatile computer memories in the spacecraft command and data system and attitude control system require a continuous source of backup power during all anticipated power bus fault scenarios. Power for the Jupiter Probe is conditioned, isolated, and controlled by a Probe interface subassembly. Flight performance of the spacecraft and the PMAD has been successful to date, with no major anomalies.

Detwiler, R. C.↗
NASA NTRS1991

Galileo ultraviolet spectrometer experiment - Initial Venus and interplanetary cruise results

The Galileo Extreme Ultraviolet Spectrometer obtained a spectrum of Venus atmospheric emissions in the 55.0- to 125.0-nm wavelength region. Emissions of helium (58.4 nm), ionized atomic oxygen (83.4 nm), and atomic hydrogen (121.6 nm), as well as a blended spectral feature of atomic hydrogen (Lyman-beta) and atomic oxygen (102.5 nm), were observed at 3.5-nm resolution. During the Galileo spacecraft cruise from Venus to earth, Lyman-alpha emission from solar system atomic hydrogen (121.6 nm) was measured. The dominant source of the Lyman-alpha emission is atomic hydrogen from the interstellar medium. A model of Galileo observations at solar maximum indicates a decrease in the solar Lyman-alpha flux near the solar poles. A strong day-to-day variation also occurs with the 27-day periodicity of the rotation of the sun.

Hord, C. W.↗
NASA NTRS1989

The Galileo PPS expert monitoring and diagnostic prototype

The Galileo PPS Expert Monitoring Module (EMM) is a prototype system implemented on the SUN workstation that will demonstrate a knowledge-based approach to monitoring and diagnosis for the Galileo spacecraft Power/Pyro subsystems. The prototype will simulate an analysis module functioning within the SFOC Engineering Analysis Subsystem Environment (EASE). This document describes the implementation of a prototype EMM for the Galileo spacecraft Power Pyro Subsystem. Section 2 of this document provides an overview of the issues in monitoring and diagnosis and comparison between traditional and knowledge-based solutions to this problem. Section 3 describes various tradeoffs which must be considered when designing a knowledge-based approach to monitoring and diagnosis, and section 4 discusses how these issues were resolved in constructing the prototype. Section 5 presents conclusions and recommendations for constructing a full-scale demonstration of the EMM. A Glossary provides definitions of terms used in this text.

Bahrami, Khosrow↗
NASA NTRS1993

Proposed data compression schemes for the Galileo S-band contingency mission

The Galileo spacecraft is currently on its way to Jupiter and its moons. In April 1991, the high gain antenna (HGA) failed to deploy as commanded. In case the current efforts to deploy the HGA fails, communications during the Jupiter encounters will be through one of two low gain antenna (LGA) on an S-band (2.3 GHz) carrier. A lot of effort has been and will be conducted to attempt to open the HGA. Also various options for improving Galileo's telemetry downlink performance are being evaluated in the event that the HGA will not open at Jupiter arrival. Among all viable options the most promising and powerful one is to perform image and non-image data compression in software onboard the spacecraft. This involves in-flight re-programming of the existing flight software of Galileo's Command and Data Subsystem processors and Attitude and Articulation Control System (AACS) processor, which have very limited computational and memory resources. In this article we describe the proposed data compression algorithms and give their respective compression performance. The planned image compression algorithm is a 4 x 4 or an 8 x 8 multiplication-free integer cosine transform (ICT) scheme, which can be viewed as an integer approximation of the popular discrete cosine transform (DCT) scheme. The implementation complexity of the ICT schemes is much lower than the DCT-based schemes, yet the performances of the two algorithms are indistinguishable. The proposed non-image compression algorith is a Lempel-Ziv-Welch (LZW) variant, which is a lossless universal compression algorithm based on a dynamic dictionary lookup table. We developed a simple and efficient hashing function to perform the string search.

Cheung, Kar-Ming↗
NASA NTRS1993

The flight performance of the Galileo orbiter USO

Results are presented in this article from an analysis of radio metric data received by the DSN stations from the Galileo spacecraft using an Ultrastable Oscillator (USO) as a signal source. These results allow the health and performance of the Galileo USO to be evaluated, and are used to calibrate this Radio Science instrument and the data acquired for Radio Science experiments such as the Redshift Observation, Solar Conjunction, and Jovian occultations. Estimates for the USO-referenced, spacecraft-transmitted frequency and frequency stability were made for 82 data acquisition passes conducted between launch (Oct. 1989) and Nov. 1991. Analyses of the spacecraft-transmitted frequencies show that the USO is behaving as expected. The USO was powered off and then back on in Aug. 1991 with no adverse effect on its performance. The frequency stabilities measured by Allan deviation are consistent with expected values due to thermal wideband noise and the USO itself at the appropriate time intervals. The Galileo USO appears to be healthy and functioning normally in a reasonable manner.

Morabito, D. D.↗
NASA NTRS1993

System design aspects and flight experience of the electrical interfaces across the Galileo spacecraft spin bearing assembly

The Galileo spacecraft design uses a dual-spin general configuration with spun and despun sections; the mechanical connection between the two sections is accomplished by means of a spin bearing assembly (SBA) whose electrical interfacing uses both slip rings/brushes and rotary transformers that are located within the SBA. Attention is presently given to the design features of the SBA, the electrical interface flight anomaly and investigation experience with Galileo to date, and the responses of the Galileo Flight Team to those anomalies.

Landano, Matthew R.↗