Geostationary tether satellite system and its application tocommunication systems

The geostationary tether satellite system expands the geostationary orbit resource from a one-dimensional arc into a two-dimensional disk. The tethered satellites, each several thousand kilometers apart and aligned along the local vertical, are stabilized at the altitude of the geosynchronous orbital speed. When this system is applied to communications systems, it is estimated that the number of satellites can be increased as much as thirteenfold and the communication capacity can be increased more than seventeenfold, compared with a conventional geostationary satellite orbit system     

Low cost orbit transfer of inoperative satellites by a service vehicle

Tumble Orbit Transfer, which is an effective method of re-orbiting inoperative satellites is described. This is done by an independent service vehicle equipped with a long arm and a grapple mechanism on top of it. After grappling the target satellite, the service vehicle orients its axis perpendicular to the orbit velocity vector. Then a thruster is activated to give an impulse on the service vehicle, which simultaneously causes velocity change and tumbling of the combined system. Since the angular momentums of two masses are exchanged periodically, separation at a selected instance will bring each mass into different orbits, one with a higher energy and the other with a lower. Separation soon after the impulse application puts the target satellite into an elliptical orbit, and separation after a half orbital period puts it into a higher circular orbit, assuming the original orbit is circular. The amount of total impulse is exactly half of that required in a conventional method. In case the service vehicle returns to the original orbit after injecting the target into the new orbit. The required total impulse is further reduced to one-third maximum. Another important feature of this method is the ease of capturing. Because the dominant force during and after the impulse application is tension through the arm, bending rigidity in the capture mechanism is not required. Therefore, a simple grapple will be enough for this maneuver. Small fuel requirements and simple capturing make this method attractive for transferring orbiting objects, and only this will provide a method of re-orbiting inoperative satellites of arbitrary shape.     

Searching for lost fragments in GEO

This paper attempts to search the lost fragments from the near-synchronous US TitanIIIC transtage explosion of February 21, 1992, known as the second major fragmentation of a TitanIIIC transtage. This breakup was accidentally observed by the Maui GEODSS sensor, and then a total of 23 objects were reported from the breakup, no orbital data on any fragments has been generated by the SSN. In order to evaluate the debris cloud orbital evolution, we demonstrate the actual US TitanIIIC transtage explosion by using breakup model and orbit propagator. The perturbing accelerations, considered in this analysis are the non-spherical part of the Earth's gravitational attraction, the gravitational attraction due to the Sun and Moon, and the solar radiation pressure effects. Finally, we will present a search strategy based on distribution of the right ascension of the ascending node about the catalogued objects and the debris particles from the US TitanIIIC transtage explosion.     

Orbital debris - status and possibilities for control

This article is a shortened version of a position paper on orbital debris compiled by an Ad hoc Expert Group of the International Academy of Astronautics' Committee on Safety, Rescue and Quality. Its objectives were to elaborate on the need and urgency for action and to indicate ways for its implementation. The article reviews debris control options and methods ranging from those requiring no technology development to those which require new and thus far untried developments.     

On-board multibeam deployable antennas using Ka,C, andS frequency bands

The configuration, on-ground tests, and design verification results for the multibeam antenna flight model for Engineering Test Satellite-VI (ETS-VI) are described for onboard multibeam antennas with thirteen and five beams for the Ka- and S-bands, respectively. The antennas feature Ka-band frequency reuse in alternate beams through use of a cluster horn; shared use of a reflector for two frequency bands using a novel frequency selective surface (FSS); large, lightweight deployable main reflectors with diameters of 3.5 m and 2.5 m; and a highly accurate antenna-pointing control system consisting of RF sensors and an antenna-pointing mechanism to drive the subreflector