GISAT-1A (EOS-05) Mission

Why in News?

ISRO is planning to launch GISAT-1A in September 2026.

• The mission is significant as it follows the failure of the earlier GISAT-1/EOS-03 mission in 2021 and comes after recent PSLV failures.

GISAT-1A

• Developed by –  Indian Space Research Organisation (ISRO)
• Features
• GISAT – Geo-Imaging Satellite designed for wide-area and near-continuous observation of the Indian subcontinent.
• It is intended to observe the Indian landmass for large parts of the day.
• Applications include –
  • Flood monitoring
  • Cyclone tracking
  • Agriculture
  • Forestry
  • Monitoring rapid changes on the Earth's surface.
• The replacement mission is designated F17.

GISAT-1 Mission Failure

• GISAT-1/EOS-03 was launched in August, 2021 using GSLV Mk-II.
• It was supposed to first enter a Geosynchronous Transfer Orbit (GTO) and then move to a geostationary orbit.
• The mission failed when the cryogenic upper stage did not start.
• The failure was linked to a valve leak, which reduced pressure in the liquid hydrogen tank.
• The cryogenic stage uses liquid hydrogen as fuel and liquid oxygen as oxidiser.

Orbit Concepts

• Geosynchronous Transfer Orbit (GTO) –
  • Highly elliptical orbit (170 km - 36,000 km).
  • Used as an intermediate orbit before reaching geostationary orbit.
• Geostationary Orbit –
  • A satellite in this orbit appears fixed relative to a point on Earth.
  • It is particularly useful for continuous observation and communication.

Different types of launch vehicles

• PSLV and GSLV Mk-II share some design elements, including the S139 first-stage solid motor lineage.
• They also share aspects of avionics, guidance, tracking and separation systems.

Recent ISRO Launch Issues

• PSLV-C61 carrying EOS-09 failed in May 2025.
• PSLV-C62 carrying N1 satellite failed in January 2026.
• Both failures involved anomalies during the third stage.
• ISRO subsequently paused launches while failure causes were investigated.
• GSLV-F15/NVS-02 was intended to strengthen India's NavIC constellation.

NavIC provides Positioning, Navigation and Timing (PNT) services over the Indian subcontinent.

• Following the NVS-02 problem, the constellation had only 3 satellites, whereas at least 4 are required for PNT services.
  • NVS-03 is expected to be launched subsequently.

Human Spaceflight Connection

• LVM-3 is planned to be upgraded into a human-rated LVM-3.
• It is intended to launch Indian astronauts under the Gaganyaan programme.

Reference

The Hindu| GISAT-1A (EOS-05) mission