IRNSS-1d in Making (ISRO Photo)

All Set for Countdown to Launch of IRNSS-1D on Saturday, March 28 (PHOTOS)

ISRO said the launch of India’s fourth Navigation Satellite IRNSS-1D onboard PSLV-C27 that was postponed from March 9 will be lifted off at 17:19 hrs IST in the evening on Saturday, March 28, 2015 from Satish Dhawan Space Centre, Sriharikota in Andhra Pradesh.

The Indian Regional Navigation Satellite System 1D (IRNSS-1D) is the fourth navigation satellite of the 7 satellites constituting the IRNSS space segment, weighing 1,425 kg. The configuration of IRNSS-1D is similar to its predecessors — IRNSS-1A, 1B and 1C — and the new launch is being taken up within five months after the launch of the IRNSS-1c last year.

To be launched into a sub-Geosynchronous Transfer Orbit (sub GTO) with a 284 km perigee (nearest point to Earth) and 20,650 km apogee (farthest point to Earth) with an inclination of 19.2 deg with respect to the equatorial plane, the satellite was built by the ISRO Satellite Applications Centre in Bangalore at a cost of about Rs.150 crore.

Once injected into the preliminary orbit, the two solar panels of IRNSS-1D will be automatically deployed and the Master Control Facility (MCF) at Hassan near Bangalore will take over the ground control of the satellite.

The ground control will immediately perform the initial orbit raising manoeuvres consisting of one manoeuvre at perigee (nearest point to earth) and three at apogee (farthest point to earth), using the Liquid Apogee Motor (LAM) of the satellite. In the next phase, it will place the satellite in the circular geostationary orbit at the designated location.

Similar to Europe’s Galileo satellites, India’s IRNSS navigation system will be independent and the country need not depend on third parties. The IRNSS-1D predecessors, IRNSS-1A, 1B and 1C were launched by PSLV-C22, PSLV-C24 and PSLV-C26 in July 2013, April 2014 and October 2014 respectively.


The two solar panels of IRNSS-1D consisting of Ultra Triple Junction solar cells generate about 1660 Watts of electrical power. Sun and Star sensors as well as gyroscopes provide orientation reference for the satellite.

Special thermal control schemes have been designed and implemented for some of the critical elements such as atomic clocks. The Attitude and Orbit Control System (AOCS) of IRNSS-1D maintains the satellite’s orientation with the help of reaction wheels, magnetic torquers and thrusters. Its propulsion system consists of a Liquid Apogee Motor (LAM) and thrusters.


Since this is an independent Indian Satellite-based positioning system for critical National security and private applications, its main objective is to provide Reliable Position, Navigation and Timing services all over India and its neighbourhood, to provide 10 to 20 meres of accuracy to the user.

Essentially, the IRNSS will provide services called Standard Positioning Service (SPS) and
Restricted Service (RS) for the private and government use respectively.

Of the seven satellites, three IRNSS satellites are in GEO stationary orbit (GEO) and four satellites in Geo Synchronous Orbit (GSO) orbit with inclination of 29° to the equatorial plane. All the satellites will be launched by 2016 and they will be visible at all times in the Indian region and they will be monitored by the Hassan Ground Control for both maintenance and operation.

The Ground control provides the monitoring of the constellation status, computation of the orbital and clock parameters and navigation data uploading. The Ground segment comprises of TTC & Uplinking Stations, Spacecraft Control Centre, IRNSS Timing Centre, CDMA Ranging Stations, Navigation Control Centre and Data Communication Links.

Space segment is compatible with single frequency receiver for Standard Positioning Service (SPS), dual frequency receiver for both SPS & RS service and a multi mode receiver compatible with other GNSS providers.

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