EOS-05: ISRO's First Earth Observation Satellite in Geosynchronous Orbit

Core Context

India's Earth observation programme has traditionally relied on satellites placed in low earth orbit (LEO) or sun-synchronous polar orbit, such as the Cartosat and RISAT series, which pass over the same location only once every few days. To get near-continuous, real-time imagery of the Indian subcontinent, ISRO conceived a geo-imaging satellite that would instead sit far higher up, at geosynchronous altitude, so that it keeps returning to view the same broad region again and again as Earth rotates beneath it. This satellite was originally developed as GISAT-1 and was renamed EOS-03 under ISRO's unified Earth Observation Satellite (EOS) naming series, which since 2022 has folded older programme names like Cartosat, RISAT, and GISAT into a single EOS numbering scheme. The first attempt to launch this geo-imaging satellite, EOS-03, failed in August 2021 when the cryogenic upper stage of its GSLV rocket underperformed, and the satellite could not reach orbit. EOS-05 is the rebuilt version of that same geo-imaging concept.

Latest Developments

ISRO launched EOS-05 on September 4, 2026, at 2:55 am IST aboard the GSLV-F17 rocket from the Second Launch Pad of the Satish Dhawan Space Centre, Sriharikota. This was the 19th flight of the GSLV and marked ISRO's first successful launch of 2026 after a couple of earlier setbacks in the year. The rocket, standing 51.7 metres tall with a lift-off mass of 420.5 tonnes, used its usual three-stage configuration: a solid-fuelled core with four liquid strap-on boosters, a liquid-fuelled second stage, and the CUS15 cryogenic upper stage burning liquid hydrogen and liquid oxygen. About 18 minutes after lift-off, the 2,367 kg EOS-05 — the heaviest satellite the GSLV has carried so far — separated into a sub-geosynchronous transfer orbit. The satellite will now use its own onboard propulsion system to gradually raise and circularise its orbit until it settles into its final operational geosynchronous position at an altitude of roughly 36,000 km. Built on ISRO's I-2K satellite platform, EOS-05 carries an imaging payload that includes a camera with a spatial resolution of about 42 metres per pixel, which is being described as the highest-resolution imaging capability yet placed at geosynchronous altitude by any country's civilian programme. Once operational, the satellite is expected to support agriculture monitoring, water resource management, urban planning, forestry assessment, ocean resource tracking, disaster management (including tracking of floods, fires, and severe weather systems), and border and other strategic surveillance requirements.

UPSC Prelims Angle

• Examiners love the distinction between a geostationary orbit (equatorial, zero inclination, satellite appears fixed over one point) and a geosynchronous orbit (same 24-hour period as Earth's rotation, but can be inclined, so the satellite traces a repeating figure-eight ground track and can cover higher latitudes). EOS-05 operates in the latter.
• EOS-05 was launched by GSLV (Geosynchronous Satellite Launch Vehicle), not PSLV — remember that GSLV is ISRO's vehicle of choice for heavier payloads headed to geosynchronous transfer orbit, thanks to its indigenous cryogenic upper stage.
• The mission was launched from the Satish Dhawan Space Centre, Sriharikota, in Andhra Pradesh — ISRO's primary spaceport, not to be confused with the upcoming new spaceport being developed at Kulasekharapattinam, Tamil Nadu.
• EOS-05 was formerly known as GISAT-1A and is functionally the successor to the failed EOS-03 (GISAT-1) mission of August 2021, which was lost due to a cryogenic stage anomaly.
• Since 2022, ISRO has consolidated its older, differently-named Earth observation satellite families (Cartosat for high-resolution mapping, RISAT for radar imaging, GISAT for geo-imaging) into a single sequential EOS naming series.