MT1 – Behind The Black – Robert Zimmerman

ISRO successfully de-orbits defunct satellite

March 8, 2023 9:09 am Robert Zimmerman

Last orbit of MT1

ISRO announced today that it successfully de-orbited the defunct Earth observation MT1 satellite on March 7, 2023, bringing it down over the Pacific Ocean.

The map to the right shows the timing of the last two de-orbit burns during the satellite’s last orbit.

MT1’s orbit was high enough so that it would have remained in space for about 100 more years, with a lot of fuel that might have caused an explosion and the release of many pieces of space junk. ISRO managers decided to allocate the funds to use that fuel to de-orbit it, as a test for making this a routine part of any satellite end-of-mission.

ISRO attempting controlled reentry of old satellite originally lacking in such plans

March 6, 2023 9:54 am Robert Zimmerman

India’s space agency ISRO has been attempting the controlled reentry of an old India-French climate satellite that had originally been placed in a high enough orbit that de-orbit was not expected.

An uninhabited area in the Pacific Ocean between 5°S to 14°S latitude and 119°W to 100°W longitude has been identified as the targeted re-entry zone for the [Megha-Tropiques-1 (MT1)]. Since Aug 2022, 18 orbit manoeuvres have been performed to progressively lower the orbit and on March 7 the ground impact is expected to take place between 4.30 p.m. and 7.30 p.m. IST.

The satellite, once no longer able to do its primary function, still had a lot of fuel left that left it a threat. ISRO managers decided to use that fuel to lower the high orbit — where MT1 was expected to remain for at least 100 years — so that the satellite could be brought down safely now.

The real story here is ISRO’s decision to commit funds to pay for this work. Until recently, most satellites are launched without any funding to remove them once launched. SpaceX changed this with its Starlink constellation, with deorbit always included as part of each satellite’s operational plan.