MGEX
Satellites

The Navigation with Indian Constellation (NAVIC) comprises 3 geostationary (GEO) satellites located at 34°E, 83°E and 129.5°E as well as two pairs of satellites in inclined geosynchronous orbit (IGSO) with their ascending nodes at 55°E and 111.75°E and an inclination of 29°.

Common Name
SVN
Int. Sat. ID
NORAD ID
PRN
Notes
IRNSS-1A I001 2013-034A 39199 I01 IGSO 55°E; launched 1 July 2013
IRNSS-1B I002 2014-017A 39635 I02 IGSO 55°E; launched 4 April 2014
IRNSS-1C I003 2014-061A 40269 I03 GEO 83°E; launched 15 Oct. 2014
IRNSS-1D I004 2015-018A 40547 I04 IGSO 111.75°E; launched 8 Mar. 2015
IRNSS-1E I005 2016-003A 41241 I05 IGSO 111.75°E; launched 20 Jan. 2016
IRNSS-1F I006 2016-015A 41384 I06 GEO 32.5°E; launched 10 Mar. 2016
IRNSS-1G I007 2016-027A 41469 I07 GEO 129.5°E; launched 28 Apr. 2016


Spacecraft Characteristics

A collection of technical information with associated references for the IRNSS spacecraft can be obtained at ESA's eoPortal. Physical key parameters of the spacecraft are summarized below:

Parameter IRNSS-1A/.../-1G
Launch mass 1425 kg
Dry mass 614 kg
Body size 1.58 m x 1.50 m x 1.50 m
Solar array size n/a
Span width n/a
Cross section n/a
SRP acceleration n/a

The NAVIC satellites transmit signals in the L5-band (1176.45 MHz) as well as the S-band (2492.028 MHz). A rubidium atomic clock serves as primary frequency standard. Precise distance measurements using satellite laser ranging are enabled through a laser retroreflector array (LRA).

IRNSS
Fig. 1 NAVIC spacecraft reference system and sensor locations. Reproduced from DOI 10.1016/j.asr.2015.06.019 with permission of Elsevier; satellite image courtesy ISRO.

Phase center coordinates of the GNSS antennas and the LRA as recommended for NAVIC processing 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 IGS14 ANTEX product. All values refer to the spacecraft coordinate system illustrated in Fig. 1. The spacecraft coordinate system is aligned with the main body axes and originates near the center of the launch adapter plane. In accord with IGS conventions, the individual axes are aligned in the following way:
  • the +zIGS-axis is oriented along the boresight direction of the GNSS antenna;
  • the +yIGS-axis is parallel to the rotation axis of the solar panels and oriented such that the LRA is located in the second quadrant of the xIGS/yIGS-plane relative to the GNSS antenna;
  • the +xIGS-axis completes a right handed system;
IRNSS-1
 
Coordinates (w.r.t. origin)
Coordinates (w.r.t. CoM)
Reference
xIGS yIGS zIGS xIGS yIGS zIGS
GNSS L5/S -924.0 mm -0.9 mm +1277.3 mm +11.4 mm +1.1 mm +1280.8 mm [1]
LRA   -1372.0 mm +526.0 mm +1116.5 mm -436.0 mm +528.0 mm +1120.0 mm [2]
CoM   -936.0 mm -2.0 mm -3.5 mm       [2]


During nominal operations the +zIGS-axis is continuously oriented towards a point at +83° East longitude and +5° latitude. In addition, the NAVIC satellites employ a yaw steering to keep the yIGS-axis perpendicular to the Sun direction. The +xIGS-panel remains sunlit at all times, while the -xIGS-panel points to "deep space". Further information and a mathematical formulation of the NAVIC attitude control law are provided in [3] and [4].

References

[1] A.S. Ganeshan, priv. comm. (9-10 Feb. 2015)
[2] ILRS Retroreflector Information for IRNSS
[3] Montenbruck O., Schmid R., Mercier F., Steigenberger P., Noll C., Fatkulin R., Kogure S., Ganeshan A. S. (2015) GNSS satellite geometry and attitude models. Advances in Space Research 56(6):1015-1029. DOI 10.1016/j.asr.2015.06.019


Events

Date
UTC
Satellite
PRN
Description
Notes
2013/09/11 IRNSS-1A I01 Start of L5 signal transmission Chennai station
2014/05/02 IRNSS-1B I02 Start of L5 signal transmission Chennai station
2014/11/10 05:10 IRNSS-1C I03 Start of L5 signal transmission Chennai station
2015/08/01 IRNSS-1D I04 Start of L5 signal transmission Chennai station
2016/02/03 IRNSS-1E I05 Start of L5 signal transmission Chennai station
2016/02/15 IRNSS-1E I05 End of L5 signal transmisssion Chennai station
2016/03/24 IRNSS-1E I05 Restart of L5 signal transmission Chennai station
2016/03/25 IRNSS-1F I06 Start of L5 signal transmission Chennai station
2016/05/16 01:42 IRNSS-1G I07 Start of L5 signal transmission Chennai station
2017/08/31 IRNSS-1H Launch failure ISRO

Last Updated: 2017/11/08 14:49:10
Please include the IGS logo and citation in all websites, presentations, publications, or posters that use IGS data, products, or services. IGS is a service of IAG.