Indian Navy's GSAT-7R satellite is at its final destination: ISRO Chief

Indian Navy's GSAT-7R (CMS-03) communication satellite that was launched on Sunday, (Nov 2nd) by the Indian Space agency ISRO's LVM3 rocket, has been sequentially raised into its final orbit. "The spacecraft is in the required circular orbit that is about 36,000kms above the Earth," ISRO Chief Dr. V. Narayanan told WION.

Why is orbit raising crucial for a communication satellite ?

Typically, all communication satellites are launched into an initial, temporary orbit known as Geosynchronous Transfer Orbit (GTO). Think of its like a transit halt. Satellites remain in GTO for barely a week, after which they are gradually pushed to their designated orbits. GTO is an elliptical or egg-shaped orbit, where the satellite circles very close above the Earth and then moves very far away from the Earth, all during a single revolution around the Earth. A satellite in a GTO orbit would be 170-200kms above Earth at its nearest approach (perigee) and about 36,000kms above the Earth at its farthest approach (apogee).

To enable communication or broadcast over a vast region(almost one-third of the Earth), a satellite must be placed in a circular orbit 36,000kms above the Earth's equator, this is known as a Geostationary orbit. Therefore, satellites launched into GTO have to fire their engines while at perigee and raise themselves to the Geostationary orbit.

As the name suggests, Geostationary orbit is one where the satellite is exactly in sync with the Earth's 24-hour rotation period. Therefore, the GSAT-7R satellite which is placed 36,000kms above the Indian landmass would always remain above the Indian landmass, because its rotation is in complete sync with the Earth. Because of its vantage point high above India and the Indian ocean region, it can provide coverage in the vast maritime region surrounding the subcontinent.

For context, this is why DTH TV antennae are all permanently pointing to a fixed location in the sky. The antennae are oriented towards a specific Geostationary satellite, one that appears stationary relative to a region on Earth.

Owing to lifting power limitations of its LVM3 rocket which can only carry 4,000lg to GTO, ISRO hurled the GSAT-7R satellite into a lower-than-GTO orbit. The rocket placed the satellite in an orbit that is 170kms(perigee) at its closest approach to Earth and about 26,700kms(apogee) at its farthest approach to Earth. Thereafter, ISRO had issued multiple commands to fire the satellite's engines and place it in a 36,000kms circular orbit, where it is equidistant from Earth.

Why is GSAT-7R a significant strategic asset ?

Weighing 4,400kg, GSAT-7R or CMS-03 is India's largest military communications satellite. It will enable secure and real-time data, video, voice connectivity between Indian Navy ships, submarines, aircraft, and Maritime Operations Centres. For India, it is also the heaviest satellite launched from home soil.

According to the Indian Navy, the satellite carries components that are specifically developed to meet their operational requirements. The satellite is meant to provide telecommunications coverage across the Indian ocean region, and enhance the Navy's space-based communications and Maritime domain awareness capabilities.

The CMS-03/GSAT-7R is a replacement for the ageing GSAT-7 that ISRO built for the Indian Navy in 2013. The 2,650kg GSAT-7 was launched from overseas aboard Europe's Ariane rocket in August 2013, as ISRO did not possess the rocketry muscle power to lift such a heavy satellite at the time. Therefore, ISRO paid the European firm to ferry the Indian satellite to space.