The current LEO geodetic system, known as GEO-IK, is a second generation design which debuted in 1981 and has averaged one new launch each year of the Musson class satellites. With normally one or two satellites operational, the GEO-IK network can assist the user in
- "creating of regional geodetic nets, including:
- -islands geodetic fixation
- -basis for topographic survey of large building objects
- -geodetic basis for working onto shelf of the World Ocean
- working by request of coordinate fixation of the points in required coordinate system
- working to research the topography of the World Ocean" (Reference 447).
- -islands geodetic fixation
GEO-IK satellites are deployed in nearly circular orbits with a mean altitude of 1,500 km at inclinations of 73.6 degrees or 82.6 degrees. (Since 1986 only the former inclination has been utilized.) Each spacecraft is launched by the Tsyklon-3 booster from the Plesetsk Cosmodrome. The Applied Mechanics NPO of Krasnoyarsk is the principal designer and manufacturer of the 1,500-kg GEO-IK. The satellite bus is similar in appearance to the Tsikada navigation satellites, i.e., primarily a right cylinder with a gravity-gradient stabilization system at the top and payload antennas, etc., attached to the bottom (Figure 4.60). However, eight panels extend like petals from the bottom of the spacecraft to provide additional electrical power in conjunction with nickel-hydrogen storage cells. Also like Tsikada, payload and support systems are primarily contained within a pressurized, temperature-controlled container located inside the cylindrical, solar-cell array.
Geodetic analyses can be performed with any one of five payload systems. A 9.4 GHz radar provides altitude determination above the sea surface with an accuracy of 3-5 m. A two frequency (150 MHz and 400 MHz) doppler system (1-3 cm/s accuracy) operates up to 12 hours per day, and a 5.7/3.4 GHz transponder is also available on demand to provide ranging data to within 3-5 m. Laser corner reflectors with a total area of 0.024 m2 are installed on the spacecraft permitting range determinations to within 1.5 m. Finally, a light signaling system producing a series of nine high intensity (800-1200 J) flashes at a rate of 1/3 Hz can be used in conjunction with ground-based observatories to determine the satellite's position against the star background to within 1.5 arc seconds. The light signaling system can be activated up to 55 times per day (References 477-482).
Normally, GEO-IK geodetic measurements are performed five days per week, permitting two days of mission planning and satellite position forecast preparation. Typical spacecraft lifetimes are only 1-2 years. The principal civilian processor of and clearinghouse for geodetic data is now the Russian Ministry of Ecology and National Resources (which absorbed the former Soviet Main Administration for Geodesy and Cartography), working in conjunction with the Russian Academy of Sciences, in particular the Institute of Terrestrial Magnetism, ionosphere, and Radiowave Propagation (IZMIRAN).
The 14th Musson satellite was launched on 29 November 1994 (the first was lost in a launch failure on 23 January 1981) and was the first to be officially designated GEO-IK rather than Kosmos. GEO-IK 1 was inserted into a 73.6 degree orbit like the three previous spacecraft of this series. Moreover, the newcomer's orbital plane was approximately 60 degrees to the east of its immediate predecessor, also a pattern followed since 1989. As noted in Section 4.1.22, GEO-IK1 carried as an auxiliary package the Elekoncommunications test transponder.
In contrast to GEO-IK, the Russian Etalon satellites reside in high altitude (19,100 km) orbits and are completely passive in nature. Each 1,415-kg satellite is a 1.294 m diameter sphere covered with 306 antenna arrays which in turn each contain 14 corner cubes for laser interrogation and reflecting. Asmall number of reflectors are made of germanium for "future infrared interferometric measurements" (Reference 483). To date only two Etalon satellites have been orbited, Kosmos 1989 (10 January 1989) and Kosmos 2024 (31 May 1989), and each accompanied a pair of GLONASS satellites on Proton launch vehicles.
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