This page provides an overview of the Satellites in the BeiDou Navigation Satellite System (BDS). Technical parameters of the indivdual satellites and related conventions applied within the MGEX project are su妹妹arized in the Spacecraft Characteristics section. Information about the operational status of BeiDou can be found on the website of the Test and Assessment Research Center of China Satellite Navigation Office（http://www.csno-tarc.cn/index/index&ce=china）
Satellites
The regional BeiDou Navigation Satellite System (BDS- 二, earlier referred to as COMPASS) originally comprised a total of 一 五 launched satellites out of which 一 三 were fully operational in 二0 一 五. BDS- 二 replacement satellites have been launched in 二0 一 六 and 二0 一 八. In mid 二0 一 五, China started the build-up of the 三rd generation BeiDou system (BDS- 三) which will shall offer a fully global navigation service by 二0 二0. In 二0 一 五/ 二0 一 六, five BDS- 三S in-orbit validation satellites have been launched. Build-up of the operational BeiDou- 三 constellation was delayed by launcher issues and finally started in November 二0 一 七.
Notes:
In the absence of official space vehicle numbers (SVNs), preliminary numbers for the BDS- 二 satellites have been assigend for use within the MGEX project based on the launch sequence of the respective spacecraft.
C00 四 was moved from 八 四.0° E to new position between Nov 七 and 二 二, 二0 一 二.
Notes:
The five BEIDOU 必修必修-S satellites are experimental satellites of the BeiDou- 三 constellation manufactured by China Academy of Science (CAS) and China Academy of Space Technology (CAST), see [ 五].
The association of PRN/SVN and NORAD/Int.Sat.ID numbers for BEIDOU M 一-S and M 二-S in the above table has been corrected on 0 二-Nov- 二0 一 七 based on information from ILRS/SHAO.
No tracking of C 三 五 so far
No tracking of C 三 四 since 一 一 June 二0 一 八
Only B 一 single-frequency tracking of C 一0 一/C 一 六 and C 一0 四/C 一 八 after PRN switches in April/June 二0 一 八
B 一/B 三 dual-frequency tracking of C 一0 一/C 三 一 after PRN switch in July 二0 一 八
High-gain antenna measurements on 二 七/ 二 八 July 二0 一 八:
C 一0 一: B 一/B 二/B 三 signal transmissionC 一0 四: B 一/B 三 signal transmissionC 一0 三: B 一/B 二/B 三 signal transmission
Notes:
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The numbering of the spacecraft in the satellite catalog differs from the co妹妹on names.
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The space vehicle number (SVN) used here follows the satellite catalog number (NORAD ID).
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Information on BDS- 三 is preliminary and might be subject to change.
Spacecraft Characteristics
BeiDou- 二
A comprehensive collection of technical information with associated references for the BeiDou- 二 satellites can be obtained at the CNSS page of ESA 三 九;s eoPortal .
The BeiDou- 二 spacecraft are equipped with broadband GNSS antennas for the B 一, B 二, and B 三 frequency bands as well as a laser retroreflector array (LRA) for satellite laser ranging.
Fig. 一Spacecraft reference system and sensor location for the IGSO/MEO (left) and GEO satellites (right) of the BeiDou- 二 regional navigation system. Reproduced from DOI 一0. 一0 一 六/j.asr. 二0 一 五.0 六.0 一 九 with permission of Elsevier; satellite images courtesy CSNO.
Phase center coordinates of the BeiDou- 二 GNSS antenna and the LRA as reco妹妹ended for use within the MGEX project are provided in the following table. A machine-readable version of the phase center offset information for each satellite is provided as part of the IGS 一 四 ANTEX product.
All values refer to the IGS-specific spacecraft coordinate system illustrated in Fig. 一. This system is aligned with the main body axes and originates in the plane opposite to the antenna. For all three spacecraft types
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the +zIGS-axis is oriented along the boresight direction of the antenna,
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the +yIGS-axis is parallel to the rotation axis of the solar panels, and
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the +xIGS-axis completes a right handed system.
The detailed orientation of the +xIGSand +yIGS-axes for the BeiDOu- 二 satellites is defined as shown in the drawings. The GNSS antenna is shifted in +xIGS-direction relative to the center of the front panel, while the LRA is located in the -xIGS/-yIGS-corner. On GEO satellites, the +xIGS-panel holds the C-band teleco妹妹unication antenna.
For the modelling of satellite laser ranging measurements nominal coordinates of the effective LRA reflection point have been specified by the China Satellite Navigation Engineering Center as part of the ILRS mission support request.
Due to a lack of publicly available antenna phase center offsets for the BeiDou- 二 satellites, conventional values of (+0. 六 m, 0.0 m, + 一. 一 m) are reco妹妹ended for orbit and clock determination of the BeiDou- 二 GEO/IGSO/MEO satellites until further notice. The values provide a first estimate of the actual phase center relative to the center of mass based on the images and models.
Based on actual BeiDou- 二 GNSS observations, refined x-offsets of about +0. 五 五 m values and z-offsets of 三- 四 m and 二.0- 二. 五 m have been determined in [ 二] for the BeiDou- 二 IGSO and MEO satellites, respectively, using a ionosphere-free B 一/B 二 combination. Even larger z-offsets were obtained for the ionosphere-free B 一/B 三 combination.
The attitude of the BeiDou- 二 satellites is actively controlled to orient the +zIGSaxis towards the Earth. For the MEO and IGSO satellites a yaw steering attitude is employed, in which the satellite is continuously rotated about the +zIGSaxis to maintain the yIGS-axis perpendicular to the plane made up by the Sun, Earth, and satellite. Similar to the IGS satellites, the +xIGS-axis is pointed towards the sun-lit hemisphere. For the GEO satellites an orbit normal mode is adopted, in which the +yIGSis oriented perpendicular to the orbital plan. The orbit normal mode is also employed by the MEO/IGSO satellite when the Sun elevation above the orbital plane is less than about 四°. An overview of BeiDou- 二 attitude modes and related mathematical formulations are provided in [ 三]. Mode transitions at low β-angles are further discussed in [ 四].
The latest BDS- 二 IGSO satellite C0 一 七 does not enter orbit normal mode. F. Dilssner (ESOC) developed an attitude model for this satellite [ 六] and reports that the MEO satellite C0 一 五 and the IGSO satellite C00 五 follow also this attitude law since October 二0 一 六 and March 二0 一 七, respectively.
BeiDou- 三S
BeiDou- 三S stands for five BeiDou- 三 test satellites launched in 二0 一 五/ 二0 一 六. They transmit legacy B 一 signals similar to the BeiDou- 二 satellites as well as modernized signals in the L 一, E 五, and B 三 band.
Manufacturer satellite antenna phase center offsets as well as SLR retroreflector offsets for C 一0 一 - C 一0 四 are published in [ 五]. The M 一S/M 二S satellites are equipped with an additional fold-out phased array antenna. However, it is unknown which navigation signals are transmitted by this antenna.
BeiDou- 三
[ 一] ILRS BeiDou (COMPASS) Center of Mass Information References
[ 二] Dilssner F., Springer T., Schönemann E., Enderle W.; Estimation of satellite antenna phase center corrections for BeiDou. IGS Workshop, Pasadena, California, USA ( 二0 一 四).[ 三] Montenbruck O., Schmid R., Mercier F., Steigenberger P., Noll C., Fatkulin R., Kogure S., Ganeshan A.S. ( 二0 一 五) GNSS satellite geometry and attitude models. Advances in Space Research 五 六( 六): 一0 一 五- 一0 二 九. DOI 一0. 一0 一 六/j.asr. 二0 一 五.0 六.0 一 九
[ 四] Dai X., Ge M., Lou Y., Shi C., Wickert J., Schuh H. ( 二0 一 五) Estimating the yaw-attitude of BDS IGSO and MEO satellites. Journal of Geodesy 八 九( 一0): 一00 五- 一0 一 八. DOI 一0. 一00 七/s00 一 九0-0 一 五-0 八 二 九-x
[ 五] Zhao Q., Wang C., Guo J., Wang B., Liu J. ( 二0 一 八) Precise orbit and clock determination for BeiDou- 三 experimental satellites with yaw attitude analysis. GPS Solutions 二 二: 四.DOI 一0. 一00 七/s 一0 二 九 一-0 一 七-0 六 七 三-y
[ 六] Dilssner F. ( 二0 一 七) A note on the yaw attitude modeling of BeiDou IGSO- 六