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GLONASS Space Segment

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GLONASSGLONASS
Title GLONASS Space Segment
Edited by GMV
Level Basic
Year of Publication 2011
Logo GMV.png

The main functions of the Space Segment are to transmit radio-navigation signals, and to store and retransmit the navigation message sent by the Control Segment. These transmissions are controlled by highly stable atomic clocks on board the satellites.[1]

The space segment is defined by the number of satellites in the constellation (to ensure visibility of, at least, 4 satellites in view at any time and from anywhere on Earth), as well as the characteristics of the satellites in question.

Contents

GLONASS Satellite Constellation

Glonass Constellation

The GLONASS space segment consists nominally of 24 operational satellites, distributed over three orbital planes.[2] The longitude of ascending node differs by 120 deg from plane to plane. There are eight satellites per plane, separated 45 deg in argument of latitude. The difference in the argument of latitude of satellites in equivalent slots in two different orbital planes is 15 deg. Each satellite is identified by its slot number, which defines the orbital plane and its location within the plane.[3]

The GPS space segment also consists of nominally 24 satellites, which are, however, distributed over six orbital planes, differing from plane to plane by 60 deg in longitude of the ascending node.

GLONASS satellites operate in circular orbits at an altitude of 19100-km, an inclination of 64.8 deg and each satellite completes the orbit in approximately 11 hours 15 minutes. This means that for a stationary observer the same satellite is visible at the same point in the sky every eight sidereal days. Since there are eight satellites in each orbital plane, satellite positions in the sky get repeated each (although by different satellites). With the 11 h 58 min orbital period for GPS satellites, the same GPS satellite is visible at the same point in the sky every (sidereal) day.

Satellites carry atomic clocks and the payload needed for handling (receiving, processing and transmitting) navigation data. They also have reflectors to allow laser ranging from dedicated ground stations.

Differences between GPS and GLONASS constellations are summarized in the following table:[4]

GLONASS GPS GALILEO
Number of nominal satellites 24 24 30
Number of orbital planes 3 6 3
Orbital Inclination 64°8' 55° 56°
Orbital altitude 19.140 km 20.180 km 23.222 km
Period of revolution 11h 15m 11h 58m 14h 22m
Launch site Baikonur/Plesetsk Cape Canaveral Kourou (French Guiana)
Date of first launch 02/10/82 22/02/78 N/A
Satellites for launch 1/3 1 2
Datum PZ-90.11 WGS-84 GTRF

GLONASS Satellite Description

GLONASS satellites are divided into blocks. Each block is a set of satellites usually launched within certain time interval. Below there is a brief description of the different blocks:[1]

Glonass K satellite at the CeBIT 2011 Expo in Germany


Finally, the following table gathers the main characteristics of the different GLONASS satellite blocks:[4]

Glonass Glonass-M Glonass-K
Status out of service in service in service
First launch 1982 2003 2011
Lifetime (years) 3 7 10
Mass (Kg) 1250 1480 750
Output power (W) 1000 1600 1600
Number of civil signals 1 2 2
On board clocks stability 5x10-13 1x10-13 1x10-14

Notes

References

  1. ^ a b J. Sanz Subirana, JM. Juan Zornoza and M. Hernández-Pajares, Global Navigation Satellite Systems: Volume I: Fundamentals and Algorithms
  2. ^ Russian system of differentional correction and monitoring
  3. ^ GLONASS SCC Information
  4. ^ a b GLONASS System Description in glonass.it web site
  5. ^ Russia Launches Single GLONASS Satellite, GPS World, GPS Staff, June 16, 2014
  6. ^ Russia Launches CDMA Payload on GLONASS-M, Inside GNSS, June 16, 2014
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