ISRO's GSLV places EOS-05 imaging satellite in geosynchronous orbit

What happened

The Geosynchronous Satellite Launch Vehicle lifted off at 2:55 a.m. India time on 4 September 2026 from the second launch pad at the Satish Dhawan Space Centre in Sriharikota. It was the 19th flight of this rocket type. About 18 minutes after liftoff, the rocket placed the satellite in a sub-geosynchronous transfer orbit. That is a long oval orbit whose highest point is still below the final height the satellite needs.

The satellite then used its own engine to climb. ISRO reported that the first engine burn, on 5 September, lasted 5,406.4 seconds, or about one and a half hours. After it, the orbit ran from about 20,000 km to 31,129 km above Earth. The Indian Aerospace and Defence Bulletin later reported that after three burns the orbit was about 34,903 by 35,884 km. ISRO plans to park the satellite at 85.5 degrees East longitude.

The mission replaces EOS-03, also known as GISAT-1, which was lost on 12 August 2021 on the GSLV-F10 flight. According to Kalinga TV, ISRO's failure study found a leak in a vent and relief valve. The leak let the upper stage lose tank pressure, so its engine could not start. EOS-05 was also ISRO's first launch since a PSLV rocket failed on 12 January 2026, losing 16 satellites, as Spaceflight Now reported.

That January failure was the second PSLV failure in a row. The earlier one, in May 2025, also involved the rocket's third stage. The Wire described the months without a launch as a hiatus and said the EOS-05 success should help rebuild confidence at the agency. ISRO chairman V. Narayanan confirmed the satellite had reached orbit about 25 minutes after liftoff, according to India TV News.

The engineering behind it

Most Earth imaging satellites fly in low orbits a few hundred kilometres up. They see fine detail, but each one passes over a given place only at certain times. A satellite in geosynchronous orbit takes exactly one day to go around Earth, so it stays over roughly the same area all the time. The cost of this view is distance. At about 36,000 km, the same camera sees far less detail, so engineers need a larger telescope and very sensitive detectors.

The Indian Aerospace and Defence Bulletin lists four sensors on EOS-05. A multispectral camera for visible and near-infrared light gives a resolution of about 42 metres, meaning each pixel covers a square about 42 metres wide on the ground. A hyperspectral sensor splits visible and near-infrared light into 158 narrow channels. A second hyperspectral sensor covers short-wave infrared in 256 channels. A thermal sensor measures long-wave infrared, the heat given off by land, water and clouds.

Hyperspectral data is useful because different materials reflect light in different patterns across many narrow bands. Healthy crops, dry grass, muddy floodwater and burnt ground each have their own pattern. The price is data volume. Hundreds of channels for every pixel produce very large files, which must be compressed on board, sent down over a radio link and then processed on the ground before anyone can use them.

The launch itself was a test of the rocket's cryogenic upper stage, which burns liquid hydrogen and liquid oxygen kept at extremely low temperatures. Kalinga TV gives the rocket's height as 51.7 metres and its liftoff mass as 420.5 tonnes. The Wire notes that this rocket had 10 successes in 12 flights before this mission, and that every GSLV flight since the 2021 failure had worked. The satellite is designed for a working life of nine years.

What it means in Nepal

Kalinga TV reports that ISRO wants EOS-05 to watch fast-changing events such as cyclones, floods, cloudbursts and forest fires, as well as farms and forests. These are the same kinds of hazards that affect hill and plains regions across South Asia. A low-orbit satellite may pass over a valley only once or twice a day. An image every 30 minutes, or every few minutes over a chosen area, means a growing flood or a spreading fire can be followed as it develops.

The 85.5 degrees East slot is close to the longitude of central Nepal. However, the sources describe EOS-05's coverage only in terms of India. They do not say whether Nepal will be imaged, or whether the data will be shared with other countries or the public. Students should not assume access to this data. They can still learn the methods using free satellite data from other missions.

The skills behind this mission sit in two places. One is the satellite itself: sensors, cooling, onboard data handling and the radio links that carry images to the ground. The other is the ground: turning raw pixels into flood maps, burn maps or crop reports that a planning office can act on. The second skill needs both programming and an understanding of rivers, soils and land use, which is why civil and electronics engineers often work on the same remote sensing projects.