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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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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

The internal reference source (IRS) for diffuse infrared background experiment (DIRBE)

A means is described for providing internal calibration for the detectors for DIRBE, which is the Diffuse Infrared Background Experiment (a part of the Cosmic Background Explorer). The internal reference source (IRS) that is used consists of four thermal graybody sources coupled to an integrating sphere. The relative insensitivity of the DIRBE bolometers and the linear temperature dependence of the Rayleigh-Jeans law made bolometer stimulation over five orders of magnitude difficult, so four different sources were used with emitting areas varying by a factor of 10 to the 8th. A low heat capacity design with the necessary stability appears to be thin nichrome films on a sapphire substrate. Voltage stability to 0.01 percent is required for those near infrared bands that required stimulation on the Wien portion of the blackbody curve.

Silverglate, P.↗
NASA NTRS1986

Heat trap with flare as multimode antenna

A heat trap, also called a Winston cone or compound parabolic concentrator, has been designed and built to serve as the beam defining optic for the far-infrared absolute spectrophotometer on the Cosmic Background Explorer satellite. This quasi-optical multimode antenna is coupled to a flared entrance section shaped like a trumpet bell to reduce response to off-axis radiation. The antenna has very low sidelobes over a two-decade frequency range from 1 to 100/cm. Fabrication is described, and stray light data are presented and compared to theory. A novel optical figure test for concentrators is presented.

Mather, J. C.↗
NASA NTRS1986

Surface scattering characteristics and the measurement of particulate contamination

Surface scattering measurement techniques can be adopted for use in spacecraft contamination control programs. A witness mirror measurement program was developed and implemented for the NASA Cosmic Background Explorer (COBE) spacecraft. Scattering measurements were obtained before and after a qualification level vibration test for several COBE prototype instruments. The measurements indicate that a significant amount of particle redistribution occurred during the vibration test. The methodology used and the results obtained from this monitoring program are discussed.

Carosso, Paolo A.↗
NASA NTRS1987

Cryogenics program overview

An overview of the cryogenics program of the Goddard Space Flight Center is given in viewgraph form. Goddard's role and the flight programs requiring cryogenics are outlined. Diagrams are given of the Cosmic Background Explorer, the Broad Band X-Ray Telescope, the Hubble Space Telescope, an adiabatic demagnetization refrigerator, a liquid cryogenic cooler for the Shuttle Glow Experiment, a liquid helium dewar, and the X-ray spectrometer on the Advanced X-Ray Astrophysics Facility.

Castles, Stephen H.↗
NASA NTRS1987

Space Infrared Telescope Facility (SIRTF) design and thermal analysis

The design and performance characteristics of an observatory are compared with those of a storage dewar. The critical design technologies required to increase cryogen dewar lifetime are discussed. In particular, outer shell temperature, vapor cooled shields, multilayer insulation performance, and tank support systems are analyzed to assess their impact on cryogen lifetime for both the observatory and the storage dewar. The cryogen lifetime and cryogen mass loss rate of the Space Infrared Telescope Facility (SIRTF) are compared with that of the Infrared Astronomy Satellite and the Cosmic Background Explorer Satellite. A 0.1 percent mass loss per day of superfluid helium dewar can be designed using current state-of-the-art dewar technology. Space-based liquid hydrogen and liquid oxygen tanks can be designed for a 5-year lifetime.

Lee, Jeffrey H.↗
NASA NTRS1987

Space station Platform Management System (PMS) replanning using resource envelopes

One of the responsibilities of the Space Station Platform Management System (PMS) is to maintain constraint-free, short-term plans for platform and free-flyer activities. Both the replanning function and the associated constraint-checking function are viewed as potentially requiring expert system assistance. The PMS Resource Envelope Scheduling System (PRESS) expert system, which is currently under development, is described. The PRESS capabilities will include the following: plan, replan, and perform constraint checking using resource envelopes resembling those required for telescience; initialize itself using the results fo a previous run; infer the replanning needs associated with a change in resource availability; allow the user to determine the level of interaction (including an advisory capability) with the system during execution; and generate both a graphic timeline and a report as output. The PRESS is being developed on an IBM PC/AT using TeKnowledge, Inc.'s M.1 expert system shell. The PRESS activity definitions and constraints are based on those defined for the Cosmic Background Explorer (COBE) mission scheduled for launch in early 1989.

Bush, Joy Lee↗
NASA NTRS1987

CLEAR: Communications Link Expert Assistance Resource

Communications Link Expert Assistance Resource (CLEAR) is a real time, fault diagnosis expert system for the Cosmic Background Explorer (COBE) Mission Operations Room (MOR). The CLEAR expert system is an operational prototype which assists the MOR operator/analyst by isolating and diagnosing faults in the spacecraft communication link with the Tracking and Data Relay Satellite (TDRS) during periods of realtime data acquisition. The mission domain, user requirements, hardware configuration, expert system concept, tool selection, development approach, and system design were discussed. Development approach and system implementation are emphasized. Also discussed are system architecture, tool selection, operation, and future plans.

Hull, Larry G.↗
NASA NTRS1988

The Instrument Test Dewar (ITD): Testing satellite instruments at 1.5 K

The Instrument Test Dewar (ITD) is a cryogenic facility designed and built to test Cosmic Background Explorer (COBE) satellite instruments at 1.5 K. The facility provides a high vacuum and thermal environment with payload thermal, electrical and optical interfaces. There are two concentric vacuum spaces which are not hermitically sealed. The instrument vacuum space is 81.28 cm by 243.84 cm and is cooled by an LHe shroud. The guard vacuum space surrounds an LN2 shroud. There are two separate cryosorption pumping systems and a mechanical LHe pumping system. The data acquisition systems provide payload and housekeeping data. There have been various problems with the facility, and changes and improvements have been made to assure optimum test conditions. COBE instrument testing has been completed on structural, thermal model hardware and the protoflight units.

Milam, Laura J.↗
NASA NTRS1988

Preliminary Orbit Determination System (PODS) for Tracking and Data Relay Satellite System (TDRSS)-tracked target Spacecraft using the homotopy continuation method

The Preliminary Orbit Determination System (PODS) provides early orbit determination capability in the Trajectory Computation and Orbital Products System (TCOPS) for a Tracking and Data Relay Satellite System (TDRSS)-tracked spacecraft. PODS computes a set of orbit states from an a priori estimate and six tracking measurements, consisting of any combination of TDRSS range and Doppler tracking measurements. PODS uses the homotopy continuation method to solve a set of nonlinear equations, and it is particularly effective for the case when the a priori estimate is not well known. Since range and Doppler measurements produce multiple states in PODS, a screening technique selects the desired state. PODS is executed in the TCOPS environment and can directly access all operational data sets. At the completion of the preliminary orbit determination, the PODS-generated state, along with additional tracking measurements, can be directly input to the differential correction (DC) process to generate an improved state. To validate the computational and operational capabilities of PODS, tests were performed using simulated TDRSS tracking measurements for the Cosmic Background Explorer (COBE) satellite and using real TDRSS measurements for the Earth Radiation Budget Satellite (ERBS) and the Solar Mesosphere Explorer (SME) spacecraft. The effects of various measurement combinations, varying arc lengths, and levels of degradation of the a priori state vector on the PODS solutions were considered.

Kirschner, S. M.↗
NASA NTRS1988

Remote chance of recontact

The ejection of appendages with uncertain drag characteristics presents a concern for eventual recontact. Recontact shortly after release can be prevented by avoiding ejection in a plane perpendicular to the velocity. For ejection tangential to the orbit, the likelihood of recontact within a year is high in the absence of drag and oblateness. The optimum direction of ejection of the thermal shield cable and an overestimate of the recontact probability are determined for the Cosmic Background Explorer (COBE) mission when drag, oblateness, and solar/lunar perturbations are present. The probability is small but possibly significant.

Elkin, D.↗
NASA NTRS1989

Overview of battery usage in NASA/GSFC LEO and GEO missions

In July, 1989, Cosmic Background Explorer (COBE) will be launched from a Delta rocket to study the big bang theory. The COBE, which is in a LEO/Polar orbit, will have two 20 Ah NiCd batteries, and 18 cells per battery, made by McDonnell Douglas Company. In December, 1989, National Oceanic and Atmospheric Administration (NOAA-D) will be launched from an Atlas rocket for weather observation purposes. NOAA-D, which is in a LEO/Polar morning orbit, will have two 26.5 Ah NiCd batteries, and 17 cells per battery, made by Ge-Astro East Windor. NOAA-I, which is scheduled for May, 1991 launch in a LEO/Polar afternoon orbit, will have three 26.5 Ah NiCd batteries, 17 cells per battery, made by GE-Astro East Windor. In April, 1990, Gamma Ray Observatory (GRO) will be launched from STS37 to study the gamma ray radiation phenomenon. GRO, which is in a LEO orbit, will have two modular power systems (MPS) made by McDonnell Douglas, each MPS consisting of three 50 Ah NiCd batteries, 22 cells per battery. In July, 1990, Geostationary Operational Environmental Satellite (GOES-I) will be launched from an Atlas I rocket for weather observation purposes. GOES-I, which is in a GEO orbit, will have two 12 Ah NiCd batteries, 28 cells per battery, made by Ford Aerospace and Communications Company. In December, 1990, Tracking and Data Relay Satellite (TDRS-E) will be launched from STS43 for communication purposes. TDRS-E, which is in a GEO orbit, will have three 40 Ah NiCd batteries, 24 cells per battery, made by TRW. In August, 1991, Extreme Ultraviolet Explorer (EUVE) will be launched from a Delta rocket. EUVE, which is in a LEO orbit, will have one modular power system (MPS) made by McDonnell Douglas. In December, 1991, Upper Atmosphere Research Satellite (UARS) will be launched from STS50 to study the Earth's ozone layer and other environmental concerns. UARS, which is in a 56 deg inclination LEO orbit, will have one modular power systems (MPS) made by McDonnell Douglas.

Yi, Thomas↗
NASA NTRS1989

Measurements of very low-sidelobe conical horn antennas

A description is given of conical corrugated-horn antennas that were designed for millimeter-wave radiometers with a 7 degree field of view, namely the Differential Microwave Radiometers (DMRs) that will measure the large-angular-scale anisotropy of the cosmic background radiation that is generally thought to be the remnant of the primeval explosion, the Big Bang. The DMRs will be part of the Cosmic Background Explorer (COBE) satellite. Measured test results for three radiometers at 31.4, 53, and 90 GHz are reported along with those of a circular polarization orthomode transducer designed and characterized at 31.4 GHz. The measurement techniques and facilities are described, including an outdoor far-field facility where measurements down to levels 90 dB below the main beam maximum were achieved. The goal of achieving very low-sidelobe antennas with good symmetry has been demonstrated.

Toral, Marco A.↗
NASA NTRS1989

COBE nonspinning attitude propagation

The Cosmic Background Explorer (COBE) spacecraft will exhibit complex attitude motion consisting of a spin rate of approximately -0.8 revolution per minute (rpm) about the x-axis and simultaneous precession of the spin axis at a rate of one revolution per orbit (rpo) about the nearly perpendicular spacecraft-to-Sun vector. The effect of the combined spinning and precession is to make accurate attitude propagation difficult and the 1-degree (3 sigma) solution accuracy goal problematic. To improve this situation, an intermediate reference frame is introduced, and the angular velocity divided into two parts. The nonspinning part is that which would be observed if there were no rotation about the X-axis. The spinning part is simply the X-axis component of the angular velocity. The two are propagated independently and combined whenever the complete attitude is needed. This approach is better than the usual one-step method because each of the two angular velocities look nearly constant in their respective reference frames. Since the angular velocities are almost constant, the approximations made in discrete time propagation are more nearly true. To demonstrate the advantages of this nonspinning method, attitude is propagated as outlined above and is then compared with the results of the one-step method. Over the 100-minute COBE orbit, the one-step error grows to several degrees while the nonspinning error remains negligible.

Chu, D.↗
NASA NTRS1990

CLEAR: Automating control centers with expert system technology

The Communications Link Expert Assistance Resource (CLEAR) is a fault-isolation expert system to be utilized in the operational environment of the Cosmic Background Explorer (COBE) Mission Operations Room (MOR). CLEAR will assist the COBE Flight Operations Team (FOT) during periods of real-time data acquisition by isolating faults in the spacecraft communication link with the Tracking and Data Relay Satellite (TDRS), providing advice on how to correct them, and logging the events for post-pass evaluation. After a brief introduction to the problem domain, the system requirements, tool selection, development approach, system operation and lessons learned during the transformation of the system from the prototype to the delivered, operation system are described.

Hughes, Peter M.↗
NASA NTRS1989

Cryogenic optical systems and instruments III; Proceedings of the Meeting, San Diego, CA, Aug. 17-19, 1988

Topics considered include the Space Infrared Telescope Facility (SIRTF) and superfluid helium on-orbit transfer (SHOOT), SIRTF cryogenic optics technology, and Cosmic Background Explorer scientific instruments, and the Advanced X-ray Astrophysics Facility (AXAF) cryogenic subsystem. Attention is also given to the Stratospheric Observatory for Infrared Astronomy (SOFIA), high-volume IR array testing and detector coolers, the development of IR detectors and associated electronics, and the Cryogenic Limb Array Etalon Spectrometer (CLAES).

Melugin, Ramsey K.↗
NASA NTRS1989

Effects of ionizing radiation on cryogenic infrared detectors

The Diffuse Infrared Background Experiment (DIRBE) is one of three experiments to be carried aboard the Cosmic Background Explorer (COBE) satellite scheduled to be launched by NASA on a Delta rocket in 1989. The DIRBE is a cryogenic absolute photometer operating in a liquid helium dewar at 1.5 K. Photometric stability is a principal requirement for achieving the scientific objectives of this experiment. The Infrared Astronomy Satellite (IRAS), launched in 1983, which used detectors similar to those in DIRBE, revealed substantial changes in detector responsivity following exposure to ionizing radiation encountered on passage through the South Atlantic Anomaly (SAA). Since the COBE will use the same 900 Km sun-synchronous orbit as IRAS, ionizing radiation-induced performance changes in the detectors were a major concern. Here, ionizing radiation tests carried out on all the DIRBE photodetectors are reported. Responsivity changes following exposure to gamma rays, protons, and alpha particle are discussed. The detector performance was monitored following a simulated entire mission life dose. In addition, the response of the detectors to individual particle interactions was measured. The InSb photovoltaic detectors and the Blocked Impurity Band (BIB) detectors revealed no significant change in responsivity following radiation exposure. The Ge:Ga detectors show large effects which were greatly reduced by proper thermal annealing.

Moseley, S. H.↗
NASA NTRS1989

Characterization of feedback resistors for cryogenic applications

Results are presented on the testing of feedback resistors selected for use in the transimpedance amplifiers (TIAs) in the Diffuse Infrared Background Experiment (DIRBE) to be flown on the NASA's Cosmic Background Explorer satellite planned for a launch in 1989. The resistors without encapsulation were found to be reliable as cryogenic circuit elements. Their resistance is sufficiently high (so that their Johnson noise does not dominate amplifier noise at the signal frequency), and they are sufficiently linear; no correction need to be made for signals up to 1.5 V, the 100,000 signal-to-noise level for the DIRBE, which covers most of the signals expected to be seen on the sky.

Lakew, B.↗
NASA NTRS1989

Flight worthy infrared bolometers with high throughput and low NEP

This paper describes the features of flight-worthy IR bolometers that were developed to meet the requirements of the Far Infrared Absolute Spectrometer (FIRAS) and the Diffuse Infrared Background Experiment (DIRBE) on the Cosmic Background Explorer of a short time constant, high throughput, and low noise equivalent power (NEP). The new bolometers use small chips of doped and compensated silicon as sensing elements, and diamond wafers coated with thin layers of Cr and Au as the absorbing substrate. The throughput values for the FIRAS bolometers and for DIRBE are 1.28 sr-sq cm, and 0.21 sr-sq cm, respectively. At 1.6, the time constants range from 3 to 40 ms, and their NEP range from 4 x 10 to the -15th to 1 x 10 to the -14th W/sq rt of Hz.

Serlemitsos, Aristides T.↗