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At least 1,207 records · Page 67

Statistical interference prediction for ground stations from orbiting satellites. I - Simulation of interference duration and analytical approach for the determination of protection ratios

The authors describe simulation and analytical techniques for predicting the interference durations and protection ratios for deep-space ground stations from satellites in circular orbits. The simulation approach employs the characteristics of the ground station receivers in addition to the satellite specifications to calculate the daily statistics of the interference duration. On the other hand, the analytical method employs the ground station specifications to statistically predict the protection ratios as a function of the number of interference satellites and their associated probabilities. The results presented here can be used for both planning the missions and designing satellite communication links. The results can be also be used by spectrum managers and operations personnel to minimize the risk of harmful interference from satellites in low earth orbit to the deep space frequency band.

Gevargiz, John M.↗

Scientific use of Space Station Freedom

Space Station Freedom extends the NASA Office of Space Science and Applications capabilities for critical, on-orbit/long-duration microgravity and space researches; it also represents a stage beyond the capabilities of existing ground-based, suborbital, Space Shuttle, and Spacelab activities. Spacelab can be used as a developmental precursor for the development of microgravity and life sciences research facilities associated with Space Station Freedom. A survey is made of attached Station payloads that plausibly enhance science/applications perspectives.

Tyson, Richard W.↗

Space Station Payload Adaptation System

The development and design of a system of containers for the efficient integration of Space Station payloads is described called the Space Station Payload Adaptation System (SSPAS). The SSPAS was developed to address the incorporation of multiple payloads, the use of a small payload carrier, large numbers of samples, and on-orbit servicing. SSPAS subsystems such as the Spacelab rack are modular and designed for integration into the 'Quick Is Beautiful' (QIB) facility. The QIB is designed to provide access to space for small- and medium-sized microgravity research projects and proof-of-concept investigations. The power-distribution and heat-rejection potential of the QIB are described, and an improved experiment-apparatus container is proposed. The SSPAS rack-mounting and container concepts are concluded to make up an efficent system that can effectively exploit the R&D potential of the Space Station.

Taylor, Kenneth R.↗

Impact of restructuring on Space Station Freedom assembly sequence

The Space Station Freedom program and the process used to develop an assembly sequence are overviewed, with special attention given to the outcome of the recent restructuring activity and the positive impact it had on the Space Station design and the assembly sequence. The many technically complex and challenging aspects of the assembly sequence planning are examined, including the launch vehicle integration, the spacecraft systems capability development, and the availability of resources. It is shown that the restructuring reduced the size and the complexity of the Space Station, while the increase of ground integration through the use of preintegrated truss and shortened modules offers a reduced program risk and reduced demands on the STS.

Chung, Steven Y.↗

Operability of Space Station Freedom's meteoroid/debris protection system

The design of Space Station Freedom's external structure must not only protect the spacecraft from the hazardous environment, but also must be compatible with the extra vehicular activity system for assembly and maintenance. The external procedures for module support are utility connections, external orbital replaceable unit changeout, and maintenance of the meteoroid/debris shields and multilayer insulation. All of these interfaces require proper man-machine engineering to be compatible with the extra vehicular activity and manipulator systems. This paper discusses design solutions, including those provided for human interface, to the Space Station Freedom meteoroid/debris protection system. The system advantages and current access capabilities are illustrated through analysis of its configuration over the Space Station Freedom resource nodes and common modules, with emphasis on the cylindrical sections and endcones.

Kahl, Maggie S.↗

Guidelines for developing spacecraft maximum allowable concentrations for Space Station contaminants

The National Aeronautics and Space Administration (NASA) is preparing to launch a manned space station by the year 1996. Because of concerns about the health, safety, and functioning abilities of the crews, NASA has requested that the National Research Council (NRC) through the Board on Environmental Studies and Toxicology (BEST) provide advice on toxicological matters for the space-station program. The Subcommittee on Guidelines for Developing Spacecraft Maximum Allowable Concentrations for Space Station Contaminants was established by the Committee on Toxicology (COT) to address NASA's concerns. Spacecraft maximum allowable concentrations (SMAC's) are defined as the maximum concentrations of airborne substances (such as gas, vapor, or aerosol) that will not cause adverse health effects, significant discomfort, or degradation in crew performance.

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Space Station communications and tracking systems modeling and RF link simulation

In this final report, the effort spent on Space Station Communications and Tracking System Modeling and RF Link Simulation is described in detail. The effort is mainly divided into three parts: frequency division multiple access (FDMA) system simulation modeling and software implementation; a study on design and evaluation of a functional computerized RF link simulation/analysis system for Space Station; and a study on design and evaluation of simulation system architecture. This report documents the results of these studies. In addition, a separate User's Manual on Space Communications Simulation System (SCSS) (Version 1) documents the software developed for the Space Station FDMA communications system simulation. The final report, SCSS user's manual, and the software located in the NASA JSC system analysis division's VAX 750 computer together serve as the deliverables from LinCom for this project effort.

Tsang, Chit-Sang↗

Space Station Freedom user's guide

This guide is intended to inform prospective users of the accommodations and resources provided by the Space Station Freedom program. Using this information, they can determine if Space Station Freedom is an appropriate laboratory or facility for their research objectives. The steps that users must follow to fly a payload on Freedom are described. This guide covers the accommodations and resources available on the Space Station during the Man-Tended Capability (MTC) period, scheduled to begin the end of 1996, and a Permanently Manned Capability (PMC) beginning in late 1999.

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Space Station Freedom Utilization Conference: Executive summary

From August 3-6, 1992, Space Station Freedom Program (SSFP) representatives and prospective Space Station Freedom researchers gathered at the Von Braun Civic Center in Huntsville, Alabama, for NASA's first annual Space Station Freedom (SSF) Utilization Conference. The sessions presented are: (1) overview and research capabilities; (2) research plans and opportunities; (3) life sciences research; (4) technology research; (4) microgravity research and biotechnology; and (5) closing plenary.

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Opportunities for research on Space Station Freedom

NASA has allocated research accommodations on Freedom (equipment, utilities, etc.) to the program offices that sponsor space-based research and development as follows: Space Science and Applications (OSSA)--52 percent, Commercial Programs (OCP)--28 percent, Aeronautics and Space Technology (OAST)--12 percent, and Space Flight (OSF)--8 percent. Most of OSSA's allocation will be used for microgravity and life science experiments; although OSSA's space physics, astrophysics, earth science and applications, and solar system exploration divisions also will use some of this allocation. Other Federal agencies have expressed an interest in using Space Station Freedom. They include the National Institutes of Health (NIH), U.S. Geological Survey, National Science Foundation, National Oceanic and Atmospheric Administration, and U.S. Departments of Agriculture and Energy. Payload interfaces with space station lab support equipment must be simple, and experiment packages must be highly contained. Freedom's research facilities will feature International Standard Payload Racks (ISPR's), experiment racks that are about twice the size of a Spacelab rack. ESA's Columbus lab will feature 20 racks, the U.S. lab will have 12 racks, and the Japanese lab will have 10. Thus, Freedom will have a total of 42 racks versus 8 for Space lab. NASA is considering outfitting some rack space to accommodate small, self-contained payloads similar to the Get-Away-Special canisters and middeck-locker experiment packages flown on Space Shuttle missions. Crew time allotted to experiments on Freedom at permanently occupied capability will average 25 minutes per rack per day, compared to six hours per rack per day on Spacelab missions. Hence, telescience--the remote operation of space-based experiments by researchers on the ground--will play a very important role in space station research. Plans for supporting life sciences research on Freedom focus on the two basic goals of NASA 's space life sciences program: to ensure the health, safety, and productivity of humans in space and to acquire fundamental knowledge of biological processes. Space-based research has already shown that people and plants respond the same way to the microgravity environment: they lose structure. However, the mechanisms by which they respond are different, and researchers do not yet know much about these mechanisms. Life science research accommodations on Freedom will include facilities for experiments designed to address this and other questions, in fields such as gravitational biology, space physiology, and biomedical monitoring and countermeasures research.

Phillips, Robert W.↗

Space Station Freedom Utilization Conference. Executive summary

The Space Station Freedom Utilization Conference was held on 3-6 Aug. 1992 in Huntsville, Alabama. The purpose of the conference was to bring together prospective space station researchers and the people in NASA and industry with whom they would be working to exchange information and discuss plans and opportunities for space station research. Topics covered include: research capabilities; research plans and opportunities; life sciences research; technology research; and microgravity research and biotechnology.

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Orbit determination error analysis and comparison of station-keeping costs for Lissajous and halo-type libration point orbits and sensitivity analysis using experimental design techniques

Spacecraft in orbit near libration point L1 in the Sun-Earth system are excellent platforms for research concerning solar effects on the terrestrial environment. One spacecraft mission launched in 1978 used an L1 orbit for nearly 4 years, and future L1 orbital missions are also being planned. Orbit determination and station-keeping are, however, required for these orbits. In particular, orbit determination error analysis may be used to compute the state uncertainty after a predetermined tracking period; the predicted state uncertainty levels then will impact the control costs computed in station-keeping simulations. Error sources, such as solar radiation pressure and planetary mass uncertainties, are also incorporated. For future missions, there may be some flexibility in the type and size of the spacecraft's nominal trajectory, but different orbits may produce varying error analysis and station-keeping results. The nominal path, for instance, can be (nearly) periodic or distinctly quasi-periodic. A periodic 'halo' orbit may be constructed to be significantly larger than a quasi-periodic 'Lissajous' path; both may meet mission requirements, but perhaps the required control costs for these orbits are probably different. Also for this spacecraft tracking and control simulation problem, experimental design methods can be used to determine the most significant uncertainties. That is, these methods can determine the error sources in the tracking and control problem that most impact the control cost (output); it also produces an equation that gives the approximate functional relationship between the error inputs and the output.

Gordon, Steven C.↗

Fuel cell energy storage for Space Station enhancement

Viewgraphs on fuel cell energy storage for space station enhancement are presented. Topics covered include: power profile; solar dynamic power system; photovoltaic battery; space station energy demands; orbiter fuel cell power plant; space station energy storage; fuel cell system modularity; energy storage system development; and survival power supply.

Stedman, J. K.↗

Space teleoperations technology for Space Station evolution

Viewgraphs on space teleoperations technology for space station evolution are presented. Topics covered include: shuttle remote manipulator system; mobile servicing center functions; mobile servicing center technology; flight telerobotic servicer-telerobot; flight telerobotic servicer technology; technologies required for space station assembly; teleoperation applications; and technology needs for space station evolution.

Reuter, Gerald J.↗

The electromagnetic environment at S- and Ku-band frequencies for the Space Station Freedom

The purpose of this paper is to quantify the electric field strength around the Space Station Assembly/Contingency Subsystem (ACS) S-band conical horn antenna and the Space-to-Ground Subsystem (SGS) Ku-band 6-ft diameter reflector antenna. The regions in which the electric fields exceed the specified maximum permitted RF exposure of the Extravehicular Mobility Unit electronics equipment and EVA astronaut are identified for the Space Station ACS S-band conical horn antenna and the SGS Ku-band 6-ft diameter reflector antenna, respectively. The scattering effects of a flat metal plate, a representative Space Station structural element, were also examined. It was shown that the reflected waves from the reflecting structure cause both destructive and constructive interference of the electric fields in the intersection region between the incident and reflected waves.

Hwu, Shian U.↗

Networked simulation for team training of Space Station astronauts, ground controllers, and scientists - A training and development environment

The purpose of this paper is to describe plans for the Space Station Training Facility (SSTF) which has been designed to meet the envisioned training needs for Space Station Freedom. To meet these needs, the SSTF will integrate networked simulators with real-world systems in five training modes: Stand-Alone, Combined, Joint-Combined, Integrated, and Joint-Integrated. This paper describes the five training modes within the context of three training scenaries. In addition, this paper describes an authoring system which will support the rapid integration of new real-world system changes in the Space Station Freedom Program.

Hajare, Ankur R.↗

Methods for evaluation of the microgravity environment aboard Space Station Freedom

Space Station Freedom will be a platform for microgravity research. For superior microgravity science, the experiment locations must experience very little acceleration in the quasi-steady, structural dynamic, and vibroacoustic frequency ranges. This paper presents the methods that were developed for evaluation of the microgravity environment in the structural dynamic range. An integrated finite element model of the space station was used to conduct analysis for the on-orbit microgravity environment. Methods were developed to evaluate sinusoidal, random, and transient disturbances. Sources of disturbances aboard the Space Station were quantified and forcing functions were assembled. The resulting acceleration levels at the experiment locations due to these disturbances were computed and assessed against the microgravity acceleration requirement curve.

Wetzel, John P.↗

Space Station Freedom food management

This paper summarizes the specification requirements for the Space Station Food System, and describes the system that is being designed and developed to meet those requirements. Space Station Freedom will provide a mix of frozen, refrigerated, rehydratable, and shelf stable foods. The crew will pre-select preferred foods from an approved list, to the extent that proper nutrition balance is maintained. A galley with freezers, refrigerators, trash compactor, and combination microwave and convection ovens will improve crew efficiency and productivity during the long Space Station Freedom (SSF) missions.

Whitehurst, Troy N., Jr.↗