All eyes on GISAT-1A mission as ISRO aims to mend faulty launch streak
The Indian Space Research Organisation (ISRO) is preparing to launch GISAT-1A, an earth-observation satellite also designated EOS-05, aboard a Geosynchronous Satellite Launch Vehicle (GSLV Mk II) from the Satish Dhawan Space Centre, Sriharikota.
The mission is significant because it is ISRO's second attempt at placing this class of satellite in orbit — the original satellite, GISAT-1 (EOS-03), was destroyed in August 2021 when the GSLV-F10 rocket's cryogenic upper stage failed to ignite.
The launch follows a run of setbacks in ISRO's PSLV programme as well, including the PSLV-C61/EOS-09 mission failure in May 2025 (traced to an irregularity in the rocket's third stage) and the PSLV-C62 mission failure in January 2026 (an anomaly in the same PS3 stage), making GISAT-1A's success a closely watched marker of ISRO's technical recovery.
Once operational, GISAT-1A would give India continuous, near-real-time geostationary imaging of the subcontinent, aiding disaster response, agriculture monitoring, and border surveillance.
Geostationary Earth-Observation Satellites — the GISAT/EOS Series
Most Indian earth-observation satellites (the IRS/RESOURCESAT/CARTOSAT/RISAT family) orbit in Low Earth Orbit (LEO) or Sun-Synchronous Polar Orbit (SSPO), imaging a location only during periodic passes. A satellite placed in Geostationary Orbit (GEO) — roughly 36,000 km above the equator, matching Earth's rotation — instead stays fixed over one region continuously, enabling near-real-time monitoring rather than periodic snapshots.
Key Details
- GISAT stands for "GEO Imaging Satellite" — ISRO's designation for its geostationary-orbit earth-observation satellites, distinct from its polar-orbiting IRS/CARTOSAT/RISAT series.
- Satellites in this programme also carry the EOS ("Earth Observation Satellite") numbering used by ISRO for its post-2020 earth-observation missions generally (e.g., EOS-01, EOS-04, EOS-06).
- A geostationary imaging satellite can provide continuous surveillance of a fixed footprint (in this case, the Indian landmass and neighbourhood) for applications like cyclone tracking, flood monitoring, and border/coastal surveillance — tasks a polar-orbiting satellite cannot do continuously.
GISAT-1A/EOS-05 is ISRO's operational realisation of the GEO-imaging concept, replacing the satellite lost in the 2021 GSLV-F10 failure and completing India's transition toward always-on geostationary earth observation.
GSLV — India's Cryogenic-Stage Launch Vehicle
The Geosynchronous Satellite Launch Vehicle (GSLV) is ISRO's launch vehicle designed to place heavier payloads (typically 2,000-2,500 kg class) into geostationary transfer orbit, a capability the lighter Polar Satellite Launch Vehicle (PSLV) does not have. GSLV Mk II is a three-stage vehicle using four liquid strap-on boosters and an indigenously developed cryogenic upper stage (CUS) — a technology India developed independently after a US-led international technology-denial regime blocked cryogenic transfer in the 1990s.
Key Details
- GSLV Mk II is currently ISRO's largest operational launch vehicle short of the LVM3 (formerly GSLV Mk III), which is used for heavier GEO and human-spaceflight (Gaganyaan) payloads.
- The cryogenic upper stage, using liquid hydrogen and liquid oxygen, is the technically most demanding component of the vehicle; its indigenous development (after the 1992 US sanctions blocked Russian cryogenic technology transfer) was a landmark self-reliance milestone for ISRO.
- GSLV-F10 (2021 GISAT-1 launch) failed specifically because the cryogenic upper stage did not ignite; ISRO's investigation attributed this to a technical anomaly in the stage.
GISAT-1A's launch vehicle is again the GSLV, making its cryogenic-stage performance the central technical risk of this mission, given that the same subsystem caused the loss of the original GISAT-1 in 2021.
India's Earth-Observation Satellite Programme and Recent Launch Anomalies
ISRO's earth-observation programme spans decades, beginning with the IRS series in the 1980s-90s and expanding into RISAT (radar imaging), CARTOSAT (cartographic mapping), and now the EOS-numbered satellites launched on both PSLV and GSLV depending on orbit and payload class. Reliability of the launch vehicle fleet is critical since a single launch failure can destroy a satellite years in the making.
Key Details
- PSLV, ISRO's most reliable workhorse historically, suffered back-to-back mission failures — PSLV-C61/EOS-09 (May 2025) and PSLV-C62 (January 2026) — both linked to anomalies in the vehicle's third stage (PS3), an unusual reliability dip for a vehicle with an otherwise strong track record since the 1990s.
- These failures, combined with the earlier 2021 GSLV-F10/GISAT-1 loss, form the "faulty launch streak" context against which GISAT-1A's success or failure will be measured.
- ISRO had targeted an ambitious launch cadence for 2025-26 and 2026-27, including PSLV, GSLV, and LVM3 flights alongside Gaganyaan-related test launches, making restoring reliability operationally urgent.
GISAT-1A's launch is being watched as a test of whether ISRO has resolved the underlying quality-control issues that caused consecutive failures across both its PSLV and GSLV vehicle families.
- GISAT-1A (EOS-05): earth-observation satellite to be placed in Geostationary Orbit via GSLV Mk II from Satish Dhawan Space Centre, Sriharikota, targeted for launch around September 2026.
- Original GISAT-1 (EOS-03) was destroyed on 12 August 2021 when the GSLV-F10 cryogenic upper stage failed to ignite.
- PSLV-C61 (carrying EOS-09) failed on 18 May 2025 due to a third-stage (PS3) anomaly; PSLV-C62 (carrying EOS-N1 and co-passenger satellites) failed in January 2026, also linked to the PS3 stage.
- GSLV Mk II is a three-stage vehicle with four liquid strap-on boosters and an indigenously developed cryogenic upper stage.
- Reported satellite mass for the GISAT/GEO-imaging class is in the approximate 2,100-2,268 kg range across sources [Unverified — exact figure for GISAT-1A not independently confirmed].