ISRO is preparing for a landmark mission with the launch of EOS-05, also known as GISAT-1, aboard the GSLV-F17 rocket on 4 September at 2:55 AM IST. This mission is historic because it will be the first time India places an imaging satellite in geosynchronous orbit, nearly 36,000 kilometres above Earth.

The rocket will initially place EOS-05 into a Sub-Geosynchronous Transfer Orbit, or Sub-GTO. This elliptical orbit will have a perigee of about 170 kilometres and an apogee of nearly 28,934 kilometres. 

From this position, the satellite will use its onboard propulsion system to gradually raise its orbit until it reaches its final geosynchronous altitude of 35,786 kilometres above the equator.

A geosynchronous orbit allows the satellite to remain synchronised with Earth’s rotation. Unlike low-Earth-orbit satellites that move rapidly across different regions, EOS-05 will continuously observe the same broad area. This capability is vital for India, as it enables persistent monitoring of the subcontinent and surrounding regions.

The GSLV-F17 rocket, making its 19th flight, will lift off from the Second Launch Pad at the Satish Dhawan Space Centre in Sriharikota. It will fly in its four-metre-diameter ogive composite payload fairing configuration. The mission is a major test of ISRO’s resilience, especially after setbacks with earlier PSLV launches and the failure of GISAT-1 (EOS-03) in 2021 due to a cryogenic stage anomaly.

EOS-05 is designed to provide frequent imaging in multispectral and hyperspectral bands. It can deliver images of selected regions every five minutes and cover the entire Indian landmass every 30 minutes, with a spatial resolution of about 42 metres.

This will support disaster management, cyclone tracking, flood monitoring, forest fire detection, agriculture, environmental observation, and national security surveillance.

The Sub-GTO trajectory is a carefully planned step. Instead of placing the satellite directly at its final altitude, the rocket delivers it into an intermediate orbit, allowing EOS-05 to complete the climb using its own engines. This approach reduces the rocket’s workload and ensures precise orbital insertion.

From its high vantage point, EOS-05 will give India a new eye in space, capable of watching the same region far more continuously than conventional Earth-observation satellites. This persistent observation will be crucial for both civilian and strategic applications, strengthening India’s space-based monitoring infrastructure.

The mission cost is estimated at around ₹450 crores, reflecting India’s commitment to expanding its space capabilities. Live streaming of the launch will begin at 2:25 AM IST, and visitors can witness the event from the Launch View Gallery at SDSC SHAR.

Agencies