Space situational awareness
Also called: SSA · Topic: Remote Sensing, GIS and GNSS · NCERT: Beyond NCERT
Meaning
Space situational awareness (SSA) means keeping watch on everything that circles the earth. This includes working satellites, old rocket parts and broken pieces, called space debris. Experts track where each object is and predict where it will go next. This warns them if two objects may crash, or when an object will fall back into the air and burn up. This fall is called re-entry. SSA matters because one crash can break into hundreds of new pieces, and each one can harm other satellites. In India, ISRO does this work through IS4OM (ISRO System for Safe and Sustainable Space Operations Management). Each year, IS4OM brings out the Indian Space Situational Assessment Report (ISSAR). ISSAR 2024 came out on 22 April 2025, and ISSAR 2025 on 8 April 2026.
Example
In 2001, the upper stage of India's PSLV-C3 rocket broke up into 371 pieces. ISRO still tracks the pieces that remain in orbit. There were 41 at the end of 2024 and 33 at the end of 2025. ISSAR 2024 also recorded that in 2024, 3,665 catalogued objects were added to orbit, while a record 2,095 re-entered the atmosphere.
Don't confuse with
- Active Debris Removal (ADR): SSA only watches and predicts. ADR sends a spacecraft to catch debris and take it out of orbit.
- Debris-Free Space Missions (DFSM): DFSM is ISRO's aim that, by 2030, all Indian missions are planned so they leave no new debris. SSA is the tracking work that makes such safe planning possible.