ALBERT

Description: NASA's Magellan mission to understand the geological and geophysical processes that have shaped the planet Venus is reviewed. Through synthetic aperture radar, radiometric, altimetric, and gravity measurements, the scientific community hopes to improve its knowledge of the planet's topography and internal mass distribution. The spacecraft sequence software design, development, and test are described and the nominal operational flow of stored sequence design and generation are addressed. The ground processing of engineering telemetry and imaging data are described and the Magellan operational experience with nonroutine behavior of the spacecraft during the cruise and mapping portions of the prime mission is summarized.

Description: Two spacecraft dedicated to Very Long Baseline Interferometry (VLBI) will be launched in 1996 and 1997 to make observations using baselines between the space telescopes and many of the world's ground radio telescopes. The Japanese Institute of Space and Astronautical Science (ISAS) will launch VSOP (VLBI Space Observatory Program) in September 1996, while the Russian Astro Space Center (ASC) is scheduled to launch RadioAstron in 1997. Both spacecraft will observe radio sources at frequencies near 1.7, 4.8, and 22 GHz; RadioAstron will also observe at 0.33 GHz. The baselines between space and ground telescopes will provide 3-10 times the resolution available for ground VLBI at the same observing frequencies. Ground tracking stations on four continents will supply the required precise frequency reference to each spacecraft measure the two-way residual phase and Doppler on the ground-space link, and record 128 Megabit/s of VLBI data downlinked from the spacecraft. The spacecraft data are meaningless without cross-correlation against the data from Earth-bound telescopes, which must take place at special-purpose VLBI correlation facilities. Therefore, participation by most of the world's radio observatories is needed to achieve substantial science return from VSOP and RadioAstron. The collaboration of several major space agencies and the ground observatories, which generally follow very different models for allocation of observing time and for routine operations, leads to great complexity in mission planning and in day-to-day operations. This paper describes some of those complications and the strategies being developed to assure productive scientific missions.

Description: During the past decade, both NASA and the DOD have conducted numerous space servicing studies. These studies have shown that fluid resupply of on-orbit spacecraft is feasible and would allow for extended spacecraft utilization. In order to prove that the studies have validity, an on-orbit flight demonstration of automatic fluid resupply is required. To embark on this flight demonstration, the system concepts, operational procedures, and conceptual service and target vehicles must be identified. Hernandez Engineering, Inc. (HEI), under the direction of the Space Servicing System Project Office of the NASA/JSC New Initiatives Office, has conducted a systems engineering and integration study. The study objective was to develop preliminary concepts for a flight demonstration of automatic rendezvous, proximity operations, capture, and fluid transfer utilizing servicer and target vehicles. The results show that a servicer vehicle/target kit can be launched to orbit with an ELV and automatically rendezvous and dock with the explorer platform (EP). The servicer vehicle can then separate from the EP/kit, perform proximity maneuvers, redock with the EP/kit, and perform fluid transfer operations. After the on-orbit flight demonstration is completed, the servicer/kit can be separated from the EP and be deorbited into the Earth's atmosphere.

Description: The Satellite Servicer Flight Demonstration Program is NASA's first definitive attempt at addressing the problems associated with the supervised autonomous servicing of satellites in orbit. NASA has completed a study of its on-orbit requirements for the next decade. Utilizing the results of this study, the necessary key servicing functions, which require on-orbit demonstration before a program would commit to servicing capability, were determined. These capabilities are: (1) autonomous rendezvous and docking; (2) supervised autonomous orbital replacement unit exchange; and (3) supervised autonomous fluid transfer. A satellite servicer system plan to conduct a series of on-orbit flight demonstrations of these capabilities utilizing the Orbital Maneuvering Vehicle, elements of the Flight Telerobotic Servicer and other applicable hardware has been developed. This paper surveys the A&R technologies that must be matured from the laboratory to flight status prior to conducting these on-orbit flight demonstrations.

Description: The major hardware elements, demonstration objectives, and technical approaches, as well as existing and developing technologies for applicability to the Satellite Servicer System (SSSFD) program are presented. In a project to develop the capability of servicing satellites in remote locations, NASA and SDI have planned a series of flights to demonstrate autonomous rendezvous and docking, supervised autonomous fluid transfer, and supervised autonomous orbital replacement unit exchange. Program objectives, design reference mission, and flight demonstrations are described. The expanded capability demonstrated by the SSSFD program will provide alternatives to excessive dependence on ground operations personnel and training, increase the reach into unique space environments, and decrease the costs of managing and operating space assets.