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At least 127 records · Page 7

Tether applications in space transportation

The high cost of delivering rocket propellants to orbit for use there makes attractive the use of alternative reaction masses such as other spacecraft, planetary magnetospheres and atmospheres, light, and celestial bodies. Some of these alternatives have already been used in special cases, but tethers may be the key to using all of them on a far more general and ambitious basis. This paper gives a general overview of the many ways tethers might be used in space transportation. There is an emphasis on near-term applications such as payload boosting and space station momentum management.

Carroll, J. A.↗

The determination of physical and dynamical parameters of Pluto/Charon and binary asteroids by least-square formation of a matched filter for a time series of images. I - The operational theory

A theory is derived for the determination of the masses, radii, and orbital elements of the Pluto/Charon, or similar, system based on the prediction of an image distribution over space and time and its comparison with observation. The comparison may be ultimately through the theory of least squares or the application of a matched filter to the observations as a three-dimensional signal stream at an initial or intermediate state. The theory is an approximation correct to fifth order in the diameters of celestial bodies. The theory of astronomical seeing that is used is based on Kolmogorov turbulence in the long-exposure limit. The images must be photometric. Linear tracking errors that can be removed are preferable to either automatic or manual guiding, in the collection of candidate observations.

Wildey, R. L.↗

Reference frame studies at JPL/CALTECH

Studies being undertaken in order to interconnect the three principal celestial coordinate systens are reviewed. These systems are the optical frame (FK4/FK5) based on positions of Galactic stars, the planetary/lunar ephemeris frame based on the major celestial bodies of the solar system, and the radio frame constructed from observations of quasars. The optical frame is being connected to the radio frame by VLBI observations of radio-emitting stars, and the radio frame is being tied to the ephemeris frame in several ways; for example, differential VLBI measurements between quasars and planet-orbiting spacecraft. Prospects for future interconnection studies are briefly discussed.

Dickey, J. O.↗

Spacecraft technology trends - A view from the past

Future spacecraft will be sent on missions to complete the exploration of the solar system, to return samples from celestial bodies, record the process of creation of stars, galaxies, and the universe itself, to provide a continuous record of earth processes, and to maintain vital space communications. A key ingredient to projecting the future is to comprehend the historic record and to understand the significance of trends. This paper focuses on spacecraft cost and life trends, as well as those of the major subsystems. Throughout the history of the 'space age' there has been significant progress in the performance of spacecraft and their subsystems. However, various aspects of spacecraft performance lag behind what is technically feasible by a considerable margin. In addition, examination of the historical trend implies that future spacecraft will likely continue to be relatively unique in their design features. This is in contrast to the technically realizable future attributes such as large space platforms, modularity, system autonomy and on-orbit repair and servicing.

Hudson, Wayne R.↗

Photochemistry of planetary ionospheres

The dominant photochemical reactions taking place in the ionospheres of Venus, Saturn, and Comet P/Halley are presented. It is shown that the differences in the ionospheres of these celestial bodies result from the different chemistry, energetics, and dynamics of the respective atmospheres. The role of photochemistry in the formation of the individual ionospheres is discussed.

Nagy, Andrew F.↗

Search for the Tunguska event in the Antarctic snow

The Tunguska explosion in 1908 is supposed to have been produced by the impact of a small celestial body. The absence of any identifiable crater together with the huge energy released by the event suggest that the impactor exploded in midair and that its material was widely spread over the Earth. The short term contribution of such exceptional events to the total accretion rate of extraterrestrial material by the Earth could be significant. Samples were chosen in a core electromechanically drilled in 1984 near South Pole Station. There, the low temperatures, preventing melting all year long, and the nearly regular snow fall rate provide good conditions for a reliable continuous record of any infalling material. In many samples Ir was below the detection limit of the instrumentation. The iridium infall averaged over 45 samples is given. In a few samples the iridium content is significantly higher than the average: the frequency and amplitude of such fluctuations can be explained by the presence on some filters of finite size cosmic particles. No significant systematic increase above the average level is observed in the part of the core corresponding to the Tunguska event. The two major results of this study are: (1) The presence of Tunguska explosion debris in the Antarctic snow is not confirmed; and (2) The estimate of the average iridium infall, is an order of magnitude lower than the Ganapathy's background but is close to the values measured in Antarctic snow and atmospheric samples by Takahashi et al. The results are also consistent with the flux of micrometeoroids deduced from optical and radar observations or derived from the study of Greenland cosmic dust collection but are lower than the flux at mid-latitude measured in paleocene-oligocene sediments from the central part of the Pacific Ocean.

Rocchia, R.↗

Photometry and polarimetry of Mercury

Information available on the photometric and polarimetric properties of Mercury's surface is discussed, with special consideration given to data concerning the nature of the Mercurial regolith and the comparison of the Mercury's photometric properties with those of the moon. The results from an analysis performed in terms of Hapke's (1981, 1984, 1986) photometric function confirm the remarkable similarity of photometric properties of the two celestial bodies. However, their highland/mare alabedo ratios differs considerably; while the ratio is about 2 on the moon, it is only about 1.4 on Mercury. Mercury also shows slightly lower values of the maximum positive polarization observed, a difference that is consistent with either a slightly higher average reflectance for Mercury, or with a difference in regolith texture, or both.

Veverka, J.↗

Computer graphics aid mission operations

The application of computer graphics techniques in NASA space missions is reviewed. Telemetric monitoring of the Space Shuttle and its components is discussed, noting the use of computer graphics for real-time visualization problems in the retrieval and repair of the Solar Maximum Mission. The use of the world map display for determining a spacecraft's location above the earth and the problem of verifying the relative position and orientation of spacecraft to celestial bodies are examined. The Flight Dynamics/STS Three-dimensional Monitoring System and the Trajectroy Computations and Orbital Products System world map display are described, emphasizing Space Shuttle applications. Also, consideration is given to the development of monitoring systems such as the Shuttle Payloads Mission Monitoring System and the Attitude Heads-Up Display and the use of the NASA-Goddard Two-dimensional Graphics Monitoring System during Shuttle missions and to support the Hubble Space Telescope.

Jeletic, James F.↗

Utilization of space resources: A historical view

While widely accepted today, the use of non-Earth resources in official space planning circles has been long in coming. Popular and governmental acceptance of using extraterrestrial resources, be they asteroids, comets, or other celestial bodies are highlighted. Particular emphasis is placed on those individuals, such as the late Dandridge Cole, who pioneered early discussion and thought on the topic over a period of several decades. The evolution of using extraterrestrial resources in governmental space policy, such as NASA's Outlook for Space (1976) and Pioneering the Space Frontier (1986) is reviewed. Put forward is the view that a redefinition of resources of near-Earth space may be warranted, particularly in consideration of using high vacuum, solar radiation, and magnetospheric phenomenon for experimentation and application purposes. Lastly, a prospective look at public reaction to utilizing space resources is presented.

David, Leonard W.↗

Space civil engineering - A new discipline

Space Civil Engineering is an emerging engineering discipline that focuses on extending and expanding the Civil Engineering know-how and practice to the development and maintenance of infrastructure on celestial bodies. Space Civil Engineering is presently being developed as a new discipline within the Department of Civil Engineering at Colorado State University under a recently established NASA Space Grant College Program. Academic programs geared toward creating Space Civil Engineering Options at both undergraduate and graduate levels are being formulated. Basic ideas and concepts of the curriculum in the Space Civil Engineering Option at both undergraduate and graduate levels are presented. The role of Space Civil Engineering in the Space Program is discussed.

Sadeh, Willy Z.↗

Applications of living systems theory to life in space

The conceptual system and methodology of living systems theory appear to be of value to research on life in isolated environments. A space station, which must provide suitable conditions for human life in a stressful environment that meets none of the basic needs of life, is an extreme example of such isolation. A space station would include living systems at levels of individual human beings, groups of people engaged in a variety of activities, and the entire space crew as an organization. It could also carry living systems of other species, such as other animals and plants. Using the subsystem analysis of living systems theory, planners of a station, either in space or on a celestial body, would make sure that all the requirements for survival at all these levels had been considered. Attention would be given not only to the necessary matter and energy, but also the essential information flows that integrate and control living systems. Many variables for each subsystem could be monitored and kept in steady states. Use of living systems process analysis of the five flows of matter energy and information would assure that all members of the crew received what they needed.

Miller, James Grier↗

Space Civil Engineering option - A progress report

Space Civil Engineering is an emerging engineering discipline that focuses on extending and expanding Civil Engineering to the development, operation, and maintenance of infrastructures on celestial bodies. Space Civil Engineering is presently being developed as a new discipline within the Department of Civil Engineering at Colorado State University and with support of the NASA Space Grant College Program. Academic programs geared toward creating Space Civil Engineering Options at both undergraduate and graduate levels are being formulated. Basic ideas and concepts and the current status of the curriculum in the Space Civil Engineering Option primarily at the undergraduate level are presented.

Criswell, Marvin E.↗

SEQ-POINTER: Next generation, planetary spacecraft remote sensing science observation design tool

Since Mariner, NASA-JPL planetary missions have been supported by ground software to plan and design remote sensing science observations. The software used by the science and sequence designers to plan and design observations has evolved with mission and technological advances. The original program, PEGASIS (Mariners 4, 6, and 7), was re-engineered as POGASIS (Mariner 9, Viking, and Mariner 10), and again later as POINTER (Voyager and Galileo). Each of these programs were developed under technological, political, and fiscal constraints which limited their adaptability to other missions and spacecraft designs. Implementation of a multi-mission tool, SEQ POINTER, under the auspices of the JPL Multimission Operations Systems Office (MOSO) is in progress. This version has been designed to address the limitations experienced on previous versions as they were being adapted to a new mission and spacecraft. The tool has been modularly designed with subroutine interface structures to support interchangeable celestial body and spacecraft definition models. The computational and graphics modules have also been designed to interface with data collected from previous spacecraft, or on-going observations, which describe the surface of each target body. These enhancements make SEQ POINTER a candidate for low-cost mission usage, when a remote sensing science observation design capability is required. The current and planned capabilities of the tool will be discussed. The presentation will also include a 5-10 minute video presentation demonstrating the capabilities of a proto-Cassini Project version that was adapted to test the tool. The work described in this abstract was performed by the Jet Propulsion Laboratory, California Institute of Technology, under contract to the National Aeronautics and Space Administration.

Boyer, Jeffrey S.↗

Proceedings of the 2nd INTEGRAL Workshop: The Transparent Universe

Progress made in hard X-ray and gamma ray astronomy is reported on. The following topics are covered: nucleosynthesis in various celestial bodies and its gamma ray line emission; the center of the Galaxy and Galactic compact objects; extragalactic sources; surveys in various bands, and the International Gamma Ray Astrophysical Laboratory (INTEGRAL) program and hardware.

Kaldeich-Schuermann, B.↗

Landsat-7 Simulation and Testing Environments

A spacecraft Attitude Control and Determination Subsystem (ACDS) is heavily dependent upon simulation throughout its entire development, implementation and ground test cycle. Engineering simulation tools are typically developed to design and analyze control systems to validate the design and software simulation tools are required to qualify the flight software. However, the need for simulation does not end here. Operating the ACDS of a spacecraft on the ground requires the simulation of spacecraft dynamics, disturbance modeling and celestial body motion. Sensor data must also be simulated and substituted for actual sensor data on the ground so that the spacecraft will respond by sending commands to the actuators as they will on orbit. And finally, the simulators is the primary training tool and test-bed for the Flight Operations Team. In this paper various ACDS simulation, developed for or used by the Landsat 7 project will be described. The paper will include a description of each tool, its unique attributes, and its role in the overall development and testing of the ACDS. Finally, a section is included which discusses how the coordinated use of these simulation tools can maximize the probability of uncovering software, hardware and operations errors during the ground test process.

Holmes, E.↗

NASA'S Great Observatories

Why are space observatories important? The answer concerns twinkling stars in the night sky. To reach telescopes on Earth, light from distant objects has to penetrate Earth's atmosphere. Although the sky may look clear, the gases that make up our atmosphere cause problems for astronomers. These gases absorb the majority of radiation emanating from celestial bodies so that it never reaches the astronomer's telescope. Radiation that does make it to the surface is distorted by pockets of warm and cool air, causing the twinkling effect. In spite of advanced computer enhancement, the images finally seen by astronomers are incomplete. NASA, in conjunction with other countries' space agencies, commercial companies, and the international community, has built observatories such as the Hubble Space Telescope, the Compton Gamma Ray Observatory, and the Chandra X-ray Observatory to find the answers to numerous questions about the universe. With the capabilities the Space Shuttle provides, scientist now have the means for deploying these observatories from the Shuttle's cargo bay directly into orbit.

Source record↗

Remembering Apollo 11: The 30th Anniversary Data Archive CD-ROM

On July 20, 1969, the human race accomplished its single greatest technological achievement of all time when a human first set foot on another celestial body. Six hours after landing at 4:17 p.m. Eastern Standard Time (with less than thirty seconds of fuel remaining), Neil A. Armstrong took the "small step" into our greater future when he stepped off the Lunar Module, named Eagle, onto the surface of the Moon, from which he could look up and see Earth in the heavens as no one had done before him. He was shortly joined by Edwin "Buzz" Aldrin, and the two astronauts spent twenty-one hours on the lunar surface and returned forty-six pounds of lunar rocks. After their historic walks on the Moon, they successfully docked with Michael Collins, patiently orbiting the cold but no longer lifeless Moon alone in the Command module Columbia. This CR-ROM is intended as a collection of hard to find technical data and other interesting information about the Apollo 11 mission, as well as the apollo program in general. It includes basic overviews, such as a retrospective analysis, an annotated bibliography, and history of the lunar-orbit rendezvous concept. It also contains technical data, such as mission operations reports, press kits, and news references for all of the Apollo missions, the Apollo spacecraft, and the Saturn V launch vehicle. Rounding out this CD-ROM are extensive histories of the lunar Orbiter program (the robotic predecessor to Apollo, biographies of the Apollo astronauts and other key individuals, and interesting audio-visual materials, such as video and audio clips, photo galleries, and blueprint-like diagrams of the Apollo spacecraft.

Edgar M Cortright↗

Photon-Counting Microlaser Rangers, Transponders, and Altimeters

Unlike current manned systems, NASA's next generation SLR2000 Satellite Laser Ranging (SLR) station is fully autonomous. eye-safe, relatively compact and inexpensive. and, during daytime tracking operates at signal-to-noise ratios several orders of magnitude below unity. Tiny, passively Q-switched microlasers generate ultra-short pulses with output energies on the order of 100 micron-J at few kHz rates to achieve mm-level ranging precision to satellite altitudes of 20,000 km. Special ranging receivers, combined with Poisson statistical analysis of the received photon distribution, enable the system to rapidly and reliably identify and extract the single photon laser echoes from the solar background. The enhanced rate of return, combined with a uniform signal strength, can actually drive down both systematic and random range errors. The new SLR2000 technology has already spawned exciting new applications. Compact microlaser altimeters, capable of mapping the surface of a planet or other celestial body at multikilohertz rates, is one such application, and a high altitude, airborne version is currently being developed under NASA's Instrument Incubator Program. Interplanetary microlaser transponders would be capable of performing decimeter ranging or subnanosecond time transfer to spacecraft throughout the inner Solar System. resulting in improved knowledge of planetary motions and liberations and enhanced General Relativity experiments.

Degnan, John J.↗