The Indian Space Research Organisation (ISRO) recently completed the post-mission disposal (PMD) operation of the communication satellite GSAT-12. The satellite carrying 12 extended C band transponders was launched in 2011 and served for more than a decade. However, after the launch of its replacement satellite CMS-01 in 2020, the GSAT-12 was relocated to 47.96°E longitude from 83° E longitude where it was located till March 2021.
The PDM was successfully completed on March 23.
ISRO said that the Geosynchronous Earth Orbital (GEO) regime is one of the most populated and highly utilised regions and that the internationally accepted space debris mitigation guidelines by the UN and IADC recommend disposing of an object away from the GEO region at its end-of-life.
“The recommended practice is to re-orbit the object to a nearly circular graveyard orbit sufficiently above the GEO region so that the orbit would not decay back into the GEO-protected zone under the influence of perturbation forces, such as non-uniformity of Earth shape, Sun’s Moon’s gravity, solar radiation pressure, etc., within another 100 years,” ISRO said.
For GSAT-12, the required minimum raise in perigee altitude was estimated to be 261 km.
As a result of meticulous operations management by the Master Control Facility (MCF) in Hassan, the available fuel of GSAT-12 was more than sufficient to meet this goal, the space agency said.
A series of seven manoeuvres were carried out to raise the orbit above the GEO altitude of 35786 km and four inclination changing manoeuvres of GSAT-12 were carried out during March 20-22 to spend the remaining propellant.
“On March 23, the final passivation manoeuvre was carried out to vent out the remaining fuel by firing the oppositely mounted thrusters, cancelling the net thrust without affecting the orbit. As part of electrical passivation, all rotating mechanisms, such as the momentum wheels, reaction wheels and gyros, were turned off, and batteries were disconnected from the solar panels and discharged. Finally, the transmitters were switched off to avoid any potential RF interference. The passivation activities were completed on March 23, 2023,” ISRO said.
GSAT-12 is the 23rd GEO satellite to undergo PMD before decommissioning. The space agency added that the PMD operation is fully compliant with the IADC and UN space debris mitigation guidelines, as well as the UN guidelines for the long-term sustainability of outer space activities.
