In congested outer space, ISRO ups collision evasion for satellites

The 2023 data indicated a steady growth in the space object population, with the year reporting the maximum number of on-orbit payload deployments and launches. ISRO also reported the highest-ever number of collision avoidance manoeuvres (CAMs) and close approach alerts.

Bengaluru: The Indian Space Research Organisation (ISRO) carried out 23 collision avoidance manoeuvres (CAMs) for its earth-orbiting satellites in 2023, a new report released by the space agency said. Of these CAMs, 18 were carried out for satellites in the low earth orbit (LEO) and five in the geo-synchronous earth orbit (GEO).

The Indian Space Situational Assessment Report (ISSAR), released earlier this month, underlined an increasing trend in CAMs per year, pointing to “growing congestion” in outer space.

The number of CAMs has steadily increased from 2018 and 2019 (eight each) through 2020 (12), 2021 (19), and 2022 (21).

ISRO said no concerning close approaches with other space objects were detected in the Chandrayaan-3 mission phases or Aditya-L1 during its earth-bound phase.

The number of CAMs has steadily increased from 2018 and 2019 (eight each) through 2020 (12), 2021 (19), and 2022 (21).

During 2023, a total of 3,033 alerts for close approaches within a distance of 1 km were detected for ISRO satellites. The report said around 2,700 close approaches were observed with other operational satellites within 5 km. Some of the approaches were handled in coordination with international agencies like SpaceX and EUMETSAT but none were critical enough to warrant a CAM.

The 2023 data indicated a steady growth in the space object population, with the year reporting the maximum number of on-orbit payload deployments and launches. ISRO also reported the highest-ever number of CAMs and close approach alerts.

Chandrayaan-3 and a 4-sec delay

In a segment on collision avoidance analysis (COLA) for launch vehicles, the report said the Chandrayaan-3 lift-off had to be delayed by four seconds, to avoid close approaches between a debris object and the injected satellites in their orbital phase, due to overlapping operational altitudes.

ISSAR is an annual exercise that details space situational awareness (SSA) which is critical to the assessment of vulnerable conditions in which space assets operate, in the face of both natural objects – like asteroids, meteoroids, comets, and particle flux – and artificial space objects.

SSA activities carried out by ISRO include close approach assessment of satellites and launch vehicles, prediction of atmospheric re-entry, and promoting responsible behaviour while conducting operations in outer space.

The report, compiled by the Isro System for Safe and Sustainable Space Operations Management, was released by Isro Chairman S Somanath, on April 2.

The year saw seven launches from Isro, all successful, placing five Indian and 46 foreign satellites, and eight rocket bodies on their intended orbits. As on December 31, 2023, LEO and GEO have 22 and 29 Government of India-owned satellites, respectively.

In 2023, eight Indian satellites re-entered the atmosphere – one of them, Megha-Tropiques-1, underwent a controlled re-entry in what the report called an “immensely challenging” exercise.

Underscoring the potential challenges to sustainable space operations posed by space tourism and mega constellations, the report proposed the adoption of advanced technologies for active debris removal and on-orbit servicing of satellites.