New Delhi: India is set for an important space mission in the early hours of September 4, when the Indian Space Research Organisation (ISRO) will launch its EOS-05 imaging satellite aboard the GSLV-F17 rocket from Sriharikota.
The mission is also the second attempt to put an imaging satellite of this type into its intended high orbit. The launch began normally, but the mission failed after a problem with the cryogenic upper stage prevented it from functioning as required. The ISRO then began developing an indigenous cryogenic propulsion system. These fuels allow the engine to produce the high performance needed for the upper stages of heavy launch vehicles. The successful operation of the indigenous cryogenic upper stage eventually became an important part of the GSLV programme.
The mission therefore has importance for ISRO’s GSLV programme, which has had a mixed record since its first flights. Also known as GISAT-1A, the EOS-05 is being sent up five years after an earlier attempt to launch a similar satellite ended in failure. In August 2021, the ISRO launched GSLV-F10 carrying GISAT-1, now referred to in the mission history as EOS-03. A cryogenic engine operates at extremely low temperatures, below minus 250 degrees Celsius, and uses liquid hydrogen and liquid oxygen as propellants. If the launch and subsequent orbital manoeuvres go according to plan, the EOS-05 will first enter its transfer orbit before using its own propulsion system to reach the geosynchronous orbit around 36,000 km above earth. Earlier reporting noted: The GSLV-F17/EOS-05 mission is scheduled for launch at 2:55 am on September 4 from the Satish Dhawan Space Centre at Sriharikot. Earlier reporting noted: When most of India will be asleep in the early hours of September 4 at 2.55 am, the Indian Space Research Organisation (ISRO) will be at a crucial crossroads. From the Second Launch Pad at Sriharikota, the Geosynchronous Satellite Launch Vehicle (GSLV-F17) will thunder into the darkness carrying EOS-5, India’s first imaging satellite to operate from geosynchronous orbit, 36,000 kilometers above India.
The process involved years of testing, design changes and failures before the technology became operational. Earlier reporting noted: And yet this same rocket remains one of the crown jewels of India’s space programme.
What EOS-05 will be used for
This will be the 19th flight of the GSLV. The rocket will first release the spacecraft into a sub-geosynchronous transfer orbit. Satellites operating in low earth orbit, by comparison, pass over a particular location at intervals and can observe it for limited periods during each pass. The satellite is expected to support detailed weather monitoring and help track events such as cyclones, floods and forest fires. Its imagery can also be used for environmental observation and agricultural management. Another area of use will be monitoring strategic activity in border regions. From its high orbit, it will be able to observe large areas without waiting for repeated passes over a particular location. The mission is part of India’s effort to build greater imaging capability from geosynchronous orbit. Countries such as the United States, China and Russia have used satellites in high orbits for large-scale observation, while India has had fewer such imaging satellites. The GSLV-F17 mission comes at a time when the ISRO has also been dealing with problems in another part of its launch programme. The problems led the government to order checks and additional testing of the launcher. However, those setbacks are not directly related to the GSLV-F17 mission. The PSLV and GSLV Mk II use different propulsion and engine systems. The GSLV programme has also been part of India’s efforts to develop its own cryogenic propulsion technology. During the 1990s, the country sought cryogenic technology from Russia to help launch heavier satellites. The United States strongly opposed the transfer over fears about missile technology and proliferation. International restrictions eventually prevented India from gaining access to the technology it had sought. The GSLV-F10 had been tasked with sending the imaging satellite into orbit, but the mission ended after the cryogenic upper stage failed to ignite properly. That failure prevented it from reaching its planned orbit and brought an end to the mission. Five years later, the GSLV-F17 is being prepared for another attempt with an imaging satellite built for high-altitude, continuous observation. It will support weather monitoring, disaster tracking, environmental observation, agricultural applications and surveillance across India and its surrounding areas.
Because a satellite placed there can track the same broad area of earth continuously as the planet rotates, the orbit is important. The launch is scheduled for 2:55 am from the second launch pad at the Satish Dhawan Space Centre in Andhra Pradesh. The mission will place the 2,367-kg EOS-05 in a geosynchronous orbit around 36,000 km above earth and give the country an imaging satellite built to keep a continuous watch over the country and nearby regions. The GSLV-F17/EOS-05 is ISRO’s first major GSLV mission in about eight months. The 51.7-metre-long rocket weighs around 420.5 tonnes and will carry the satellite towards a sub-geosynchronous transfer orbit. Of its first 18 missions, six did not achieve full success. The GSLV-F17 will not place EOS-05 directly into its final geosynchronous orbit. From there, it will use its onboard propulsion system to gradually raise its orbit until it reaches its planned position around 36,000 km above earth. EOS-05 is built to provide a continuous view of the Indian landmass and surrounding areas. The Polar Satellite Launch Vehicle (PSLV), which has built a reputation as one of ISRO’s most dependable rockets, suffered a series of failures in 2025 and 2026. The rocket standing on the Sriharikota launch pad for the EOS-05 mission belongs to the GSLV programme. The upcoming EOS-05 launch has a direct link to the August 2021 GISAT-1 mission.
The rocket has earned the informal nickname “Naughty Boy” within the ISRO because of the unpredictable results seen during parts of its development.
