Balu
05-30-2015, 11:35 PM
GLONASS
Whereas the Soviet low altitude navigation systems were patterned after the American Transit network, a Soviet counterpart to the US Global Positioning System first appeared in 1982, four years after the launch of the first Navstar GPS satellite. The now Russian Military Space Forces' Global Navigation Satellite System (GLONASS) is designed to provide instantaneous, high precision location and speed information to users throughout most of the world. Deployed in nearly circular orbits at an altitude of 19,100 km by Proton boosters, eachGLONASS satellite emits navigational signals in a 38 degree cone near 1250 MHz (L2). GLONASS positional accuracies (95% confidence) are claimed to be 100 m on the surface of the Earth, 150 m in altitude, and 15 cm/s in velocity.
Like Tsikada, GLONASS spacecraft were developed under the leadership of the Applied Mechanics NPO with the assistance of the Institute for Space Device Engineering. A third party, the Russian Institute of Radio navigation and Time, has been responsible for time synchronization and related equipment. Also following the Tsikada precedent, serial production for GLONASS satellites has been accomplished primarily by the Polet PO. Conceived and promoted in the early 1970's by the former Soviet Ministry of Defense, and in particular by the Soviet Navy, GLONASS is now the centerpiece of the CIS' Intergovernmental Radio navigation Program, which has close ties with the International Civil Aviation Organization (ICAO) and the International Maritime Organization (IMO) (References 446-458) (http://fas.org/spp/guide/russia/nav/glonass.htm#ref446).
By Presidential decree on 24 September 1993, just before the 11th anniversary of the maiden GLONASS mission, the GLONASS program was officially placed under the auspices of the Russian VKS. This organization is responsible not only for the deployment and on-orbit maintenance of GLONASS spacecraft (the latter through the Golitsino-2 Satellite Control Center) but also, through its Scientific Information Center, for certification of GLONASS user equipment.
Since the program began deployments in 1982, four models of GLONASS spacecraft have been flown. Ten Block I satellites were launched during 1982-1985 with design lifetimes of only one year (average actual lifetime of 14 months). Six Block IIa satellites followedin 1985-1986 with new time and frequency standards and increased frequency stability. The Block IIa spacecraft also demonstrated a 20% increase in operational lifetime.
Block IIb spacecraft with 2-year design lifetimes appeared in 1987, and a total of 12 were launched, but half were lost in launch vehicle accidents. The remaining spacecraft worked well, operating for an average of nearly 22 months each. The current GLONASS model, Block IIv, has been in use since 1988 with 12 of the 34 satellites launched during 1993-1994. One Block liv spacecraft, which are expected to operate for at least three years, worked for 50 months before being placed in a standby status.
The 3-axis-stabilized GLONASS spacecraft now possess a mass of about 1,400 kg, a slight increase over the 1,250-kg original model. The diameter and height of the satellite bus are approximately 2.4 m and 3.7 m, respectively, with a solar array span of 7.2 m for an electrical power generation capability of 1.6kW at beginning of life. The aft payload structure houses 12 primary antennas for L-band transmissions. Laser corner-cube reflectors are also carried to aid in precise orbit determination and geodetic research. GLONASS spacecraft are equipped with a modest propulsion system to permit relocation within the constellation andto maintain interplane phasings.
The Phase I GLONASS system was completed in 1991 with seven active satellites in each of two orbital planes separated by 120 degrees.(The official Phase I goal was six satellites in each of two-planes.) Within each plane the spacecraft are spaced 45 degrees apart with a 15 degree phase shift between planes. The Phase II requirement for seven active and one spare satellite in each of three orbital planes separated by 120 degrees is scheduled to be met by 1995.
The two principal GLONASS receivers are the SNS-85 for airborne platforms and the Shkiper for naval vessels. The former unit has amass of only 13.5 kg and dimensions of 201 x 259 x 364 mm, while the latter is somewhat larger at 21.5 kg and 263 x 425 x 426 mm. However, the Shkiper provides a more accurate velocity determination: 15 cm/s compared to 50 cm/s for the SNS-85. The similarity of the GLONASS and GPS frequencies and techniques permits the creation of single, dual-use receivers when the slightly different geodetic (e.g., SGS-85 versus WGS-84, respectively) and time reference frames are taken into account. Such a dual-use receiver has been developed by the Institute of Space Device Engineering. Several concepts have been proposed for integrating the GLONASS and GPS networks, particularly for international civil aviation (References 459-469) (http://fas.org/spp/guide/russia/nav/glonass.htm#ref459).
A total of 12 GLONASS spacecraft were added to the network during 1993-1994 with four launches of three vehicles each: Kosmos 2234-2236 in 1993 and Kosmos 2275-2277, 2287-2289, and 2294-2296 in 1994. The Kosmos 2287-2288 mission was particularly noteworthy with its inauguration of the GLONASS Plane 2. By the end of 1994, 15 GLONASS spacecraft remained operational, although Kosmos 2111 in Plane 1 was in a non-nominal position due to a propulsion system failure early in life. During October, 1993, Kosmos 2206 transferred from slot 20 to slot 21 which was then occupied by Kosmos 2205 which had been moved from slot 18.
While GLONASS is scheduled to reach full operational capability in 1995, the first flight of the improved GLONASS-M Block I spacecraft is anticipated in 1995-1996. Under development since 1990, the 1,480 kg satellite will feature better frequency and timing accuracies as well as an extended operational life of 5-7 years. Further in the future, perhaps after the turn of the century, a 2,000-kg-class GLONASS-M Block II may be available with intersatellite communications and monitoring and capable of autonomous operations for as long as 60 days (References 470-472) (http://fas.org/spp/guide/russia/nav/glonass.htm#ref470).
Within a few years of the debut of GLONASS satellites, the world scientific community, in particular radio astronomers, discovered a harmful side-effect of the system. The heart of the GLONASS L1 band coincides with the weak natural emissions of extra-solar hydroxyl molecules. Consequently, some spacecraft transmissions were interfering with radio astronomy surveys. As the number of operational GLONASS spacecraft increased, the problem became severe and was further accentuated by the fact that the high altitude satellites remain above the horizon for extended periods. However, having been made aware of the problem, the GLONASS program is incorporating measures to minimize the interferences
(References 473-476) (http://fas.org/spp/guide/russia/nav/glonass.htm#ref473).
http://fas.org/spp/guide/russia/nav/glonass.htm
Whereas the Soviet low altitude navigation systems were patterned after the American Transit network, a Soviet counterpart to the US Global Positioning System first appeared in 1982, four years after the launch of the first Navstar GPS satellite. The now Russian Military Space Forces' Global Navigation Satellite System (GLONASS) is designed to provide instantaneous, high precision location and speed information to users throughout most of the world. Deployed in nearly circular orbits at an altitude of 19,100 km by Proton boosters, eachGLONASS satellite emits navigational signals in a 38 degree cone near 1250 MHz (L2). GLONASS positional accuracies (95% confidence) are claimed to be 100 m on the surface of the Earth, 150 m in altitude, and 15 cm/s in velocity.
Like Tsikada, GLONASS spacecraft were developed under the leadership of the Applied Mechanics NPO with the assistance of the Institute for Space Device Engineering. A third party, the Russian Institute of Radio navigation and Time, has been responsible for time synchronization and related equipment. Also following the Tsikada precedent, serial production for GLONASS satellites has been accomplished primarily by the Polet PO. Conceived and promoted in the early 1970's by the former Soviet Ministry of Defense, and in particular by the Soviet Navy, GLONASS is now the centerpiece of the CIS' Intergovernmental Radio navigation Program, which has close ties with the International Civil Aviation Organization (ICAO) and the International Maritime Organization (IMO) (References 446-458) (http://fas.org/spp/guide/russia/nav/glonass.htm#ref446).
By Presidential decree on 24 September 1993, just before the 11th anniversary of the maiden GLONASS mission, the GLONASS program was officially placed under the auspices of the Russian VKS. This organization is responsible not only for the deployment and on-orbit maintenance of GLONASS spacecraft (the latter through the Golitsino-2 Satellite Control Center) but also, through its Scientific Information Center, for certification of GLONASS user equipment.
Since the program began deployments in 1982, four models of GLONASS spacecraft have been flown. Ten Block I satellites were launched during 1982-1985 with design lifetimes of only one year (average actual lifetime of 14 months). Six Block IIa satellites followedin 1985-1986 with new time and frequency standards and increased frequency stability. The Block IIa spacecraft also demonstrated a 20% increase in operational lifetime.
Block IIb spacecraft with 2-year design lifetimes appeared in 1987, and a total of 12 were launched, but half were lost in launch vehicle accidents. The remaining spacecraft worked well, operating for an average of nearly 22 months each. The current GLONASS model, Block IIv, has been in use since 1988 with 12 of the 34 satellites launched during 1993-1994. One Block liv spacecraft, which are expected to operate for at least three years, worked for 50 months before being placed in a standby status.
The 3-axis-stabilized GLONASS spacecraft now possess a mass of about 1,400 kg, a slight increase over the 1,250-kg original model. The diameter and height of the satellite bus are approximately 2.4 m and 3.7 m, respectively, with a solar array span of 7.2 m for an electrical power generation capability of 1.6kW at beginning of life. The aft payload structure houses 12 primary antennas for L-band transmissions. Laser corner-cube reflectors are also carried to aid in precise orbit determination and geodetic research. GLONASS spacecraft are equipped with a modest propulsion system to permit relocation within the constellation andto maintain interplane phasings.
The Phase I GLONASS system was completed in 1991 with seven active satellites in each of two orbital planes separated by 120 degrees.(The official Phase I goal was six satellites in each of two-planes.) Within each plane the spacecraft are spaced 45 degrees apart with a 15 degree phase shift between planes. The Phase II requirement for seven active and one spare satellite in each of three orbital planes separated by 120 degrees is scheduled to be met by 1995.
The two principal GLONASS receivers are the SNS-85 for airborne platforms and the Shkiper for naval vessels. The former unit has amass of only 13.5 kg and dimensions of 201 x 259 x 364 mm, while the latter is somewhat larger at 21.5 kg and 263 x 425 x 426 mm. However, the Shkiper provides a more accurate velocity determination: 15 cm/s compared to 50 cm/s for the SNS-85. The similarity of the GLONASS and GPS frequencies and techniques permits the creation of single, dual-use receivers when the slightly different geodetic (e.g., SGS-85 versus WGS-84, respectively) and time reference frames are taken into account. Such a dual-use receiver has been developed by the Institute of Space Device Engineering. Several concepts have been proposed for integrating the GLONASS and GPS networks, particularly for international civil aviation (References 459-469) (http://fas.org/spp/guide/russia/nav/glonass.htm#ref459).
A total of 12 GLONASS spacecraft were added to the network during 1993-1994 with four launches of three vehicles each: Kosmos 2234-2236 in 1993 and Kosmos 2275-2277, 2287-2289, and 2294-2296 in 1994. The Kosmos 2287-2288 mission was particularly noteworthy with its inauguration of the GLONASS Plane 2. By the end of 1994, 15 GLONASS spacecraft remained operational, although Kosmos 2111 in Plane 1 was in a non-nominal position due to a propulsion system failure early in life. During October, 1993, Kosmos 2206 transferred from slot 20 to slot 21 which was then occupied by Kosmos 2205 which had been moved from slot 18.
While GLONASS is scheduled to reach full operational capability in 1995, the first flight of the improved GLONASS-M Block I spacecraft is anticipated in 1995-1996. Under development since 1990, the 1,480 kg satellite will feature better frequency and timing accuracies as well as an extended operational life of 5-7 years. Further in the future, perhaps after the turn of the century, a 2,000-kg-class GLONASS-M Block II may be available with intersatellite communications and monitoring and capable of autonomous operations for as long as 60 days (References 470-472) (http://fas.org/spp/guide/russia/nav/glonass.htm#ref470).
Within a few years of the debut of GLONASS satellites, the world scientific community, in particular radio astronomers, discovered a harmful side-effect of the system. The heart of the GLONASS L1 band coincides with the weak natural emissions of extra-solar hydroxyl molecules. Consequently, some spacecraft transmissions were interfering with radio astronomy surveys. As the number of operational GLONASS spacecraft increased, the problem became severe and was further accentuated by the fact that the high altitude satellites remain above the horizon for extended periods. However, having been made aware of the problem, the GLONASS program is incorporating measures to minimize the interferences
(References 473-476) (http://fas.org/spp/guide/russia/nav/glonass.htm#ref473).
http://fas.org/spp/guide/russia/nav/glonass.htm