The Incident

2021 June 26, Measat announced that it had detected an "anomaly" with its Measat 3 comsat (29648/2006-056A) at 91°.5 east on June 21 but that it had been resolved by June 24. That statement turned out to be optimistic

The following day, A Measat press release rowed back on it and said that it would take more time to resolve.

On July 17, Measat said it had control of the satellite but investigation was ongoing. All of Measat 3's communications services were transferred to two companion satellites at the same location, and other nearby satellites.

On August 6 came the announcement that the problem was insurmountable and the satellite would be "de-orbited" in the next few weeks. No explanation was given but other sources indicated that the satellite had insufficient reserves of propellant for station-keeping.

The use of the term "de-orbited" resulted in some interesting reactions. In reality it meant a move to a graveyard orbit. Unfortunately, some authors, including a writer for one of the more-august spaceflight websites (SPACE.com) jumped to the erroneous conclusion that a destructive re-entry into the Earth's atmosphere was on the cards.

Such a course of action is impractical given the amounts of fuel and oxidizer needed for the manoueuvre.


Chronology of Events

June 21 - Measat 3 was drifting slowly westwards but was within its geosynchronous operations "box". Orbit eccentricity was also increasing slowly. At that time its orbit was 35,772 x 35,801 kilometres with a period of 1436.1 minutes and it was overhead 91°.5 east longitude. Its station-keeping thrusters apparently fired in order push it back to the centre of the box. It was probably when the thrusters stopped firing that controllers realised propellant reserves were critically low.

Users of Measat 3 became aware that there were service outages, possibly due to it being slightly "off station".

June 24 - Engineers decided that the situation was under control and some communications services were restored. The orbit was 35,778 x 35,797 kilometres, still with a period of 1436.1 minutes and it was still drifting very slowly westward.

June 25 - Engineers realised the situation was not as expected, Measat 3 was continuing to drift very slowly and its services were once again intermittent. At that point, or very soon afterwards, Measat 3's owners began to transfer its communications services to a pair of companion comsats at the same location and to other satellites in the region.

June 27 - Measat 3 was settled into orbit 35,774 x 35,838 kilometres with a period of 1437.1 minutes. Its westward drift had been increased deliberately to about 0.3° per day. One effect of the increased apogee was to reduce the risk of collision with other satellites in the geosynchronous belt.

July 26 - Measat 3 commenced a series of manouevres over a period of about four days designed to raise perigee. At the time the orbit was 35,790 x 35,837 kilometres, 1437.5 minutes.

July 27 - Measat announced that the satellite was alive and under control but all of its transponders had been turned off in order to avoid causing radio interference on other satellites as it drifted past. A decision had been made to use remaining propellant in the orbit manoeuvring system to take it to a graveyard orbit.

July 30 - Orbit reached 35,817 x 35,838 kilometres, 1438.2 minutes and controllers took a rest from thruster firing.

Aug 1 - Some news outlets and Social Media accounts reported incorrectly that Measat 3 was tumbling and out of control.

Aug 3 - Thruster firings began again and the orbit started to rise further.

Aug 12 - Thruster firings ceased. Measat 3 had reached its graveyard orbit - 35,860 x 35,877 kilometres, 1440.3 minutes

Aug 24 - Thruster firing(s) resulted in apogee being raised by about 10 km.

Aug 27 - Thruster firing(s) resulted in perigee being raised by about 20 km. Orbit now 35883 x 35897 kilometres, 1441.4 minutes, 0.2° inclination.

Sep 2 - A further series of thruster firings commenced.

Sep 9 - Settled into new orbit 130 km above the geosynchronous ring. Inclination 0°.3, having increased slowly throughout all manoeuvres from its original 0°.1.


Orbit Activity

The chart below documents the orbit changes as reflected in the data from Space-Track.

Seemingly inconsistent and erratic values visible around June 26 - June 27 are probably due to Measat 3's unanticipated drift off-station confusing tracking sensors. They would have had difficulty locking onto it because of the presence of Measat 3a and Measat 3b in the same area.

Page Date - 2021 Aug 15
Chronology updated as indicated
Plots updated in real time