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BeiDou Space Segment

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COMPASSCOMPASS
Title BeiDou Space Segment
Author(s) GMV.
Level Basic
Year of Publication 2011
Logo GMV.png


The Compass Navigation Satellite System (CNSS), also named BeiDou-2, is China’s second-generation satellite navigation system capable of providing positioning, navigation, and timing services to users on a continuous worldwide basis.

On November 2, 2006, China announced the 2nd generation Chinese navigation system, COMPASS[1]. The system is currently under development evolving from a regional system called BeiDou-1, and in the first phase will provide high-accuracy positioning services for users in China and its neighbouring regions. As of April 2011, eight satellites for Compass have been launched. According to an official report[2], " the eighth Beidou/Compass satellite marks the completion of basic function of Beidou (Compass) Navigation Satellite System " .

The long-term goal is to develop an independent global navigation satellite system similar to the GPS and GLONASS.[3]

COMPASS Space Segment

The COMPASS Space Segment will consist of a constellation of 35 satellites, which include 5 geostationary orbit (GEO) satellites and 30 non-GSO satellites; 27 in Medium Earth Orbit (MEO) and 3 in Inclined GSO (IGSO),that will offer complete coverage of the globe.[4]

It is planned that Compass system will have more than 10 satellites by 2012 and may offer services for the Asia-Pacific region. The global navigation system should be finished by 2020.[5]

COMPASS Space Segment

As of April 2011, eight satellites for Compass have been launched. According to an official report [2], " the eighth Beidou satellite marks the completion of basic function of Beidou (Compass) Navigation Satellite System and will collaborate with five navigation satellites launched last year to establish a navigating system of three GEO (geostationary orbit) satellites plus three IGSO (Inclined Geo Synchronous orbit) satellites. The system will be able to provide services to most regions in China after a period of orbiting running tests and system integration. "


List of Compass Satellites at April 2011 (information as appeared in BeiDou article in Wikipedia [5])
Date Launcher Satellite Orbit Usable System
4/14/2007 Long March 3A (LM-3A) Compass-M1 MEO ~21,500 km Testing only Compass
4/15/2009 Long March 3C (LM-3C) Compass-G2 GEO Drifting No
1/17/2010 LM-3C Compass-G1 GEO 144.5°E Yes
6/2/2010 LM-3C Compass-G3 GEO 84°E Yes
8/1/2010 LM-3A Compass-IGSO1 IGSO 118°E incl 55° Yes
11/1/2010 LM-3C Compass-G4 GEO 160°E Yes
12/18/2010 LM-3A Compass-IGSO2 IGSO 118°E incl 55° Yes
04/10/2011 LM-3A Compass-IGSO3 IGSO 118°E incl 55°, 200~35,991km Yes

The nominal constellation includes 35 satellites, 5 GEOs, 3 IGSOs and 27 MEOs. The number of IGSO orbits is 3, and 1 IGSO per plane. The intersection node is 118E. While the MEO constellation is Walker constellation; 24 MEOs in 3 planes plus 3 spares. The orbital parameters of the final constellation are shown in the following table:[6]

Final Compass constellation
Orbit parmts. GEO IGSO MEO
Semi-Major Axis (Km) 42164 42164 27878
Eccentricity 0 0 0
Inclination (deg) 0 55 55
RAAN (deg) 158.75E, 180E, 210.5E, 240E,260E 218E,98E,338E --
Argument Perigee 0 0
Mean anomaly (deg) 0 218E:0,98E:120,338E:240
# Sats 5 3 27
# Planes 1 3 3

Notes

References