Mars Orbiter Mission (MOM) spacecraft experienced the ‘whiteout’ geometry during May 18 to May 30, 2016. The planets continuously in motion can align with the sun causing ‘whiteout’ or 'blackout' causing communication disruptions. In this particular geometry, the Earth came in between the Sun and Mars causing a ‘whiteout’.

A ‘whiteout’ occurs when the Earth is between the Sun and Mars and too much solar radiation may make it impossible to communicate with the Earth. The maximum duration of ‘whiteout’ is around 14 days. MOM spacecraft experienced the ‘whiteout’ during last month (May, 2016). However, MOM is built with full autonomy to take care of itself for long periods without any ground intervention.

Angular separation between Earth and Mars at Sun centre

(Ref: CURRENT SCIENCE, VOL. 109, NO. 6, 25 SEPTEMBER 2015)

The entire planning and commanding for the ‘whiteout’ was completed 10 days before the actual event. No commanding was carried out on the satellite in the ‘whiteout’ period. Payload operations were suspended. Fault Detection, Isolation and Recovery were kept enabled, so as to take care of any contingency on the spacecraft. Master Recovery Sequencer was programmed, to acquire the attitude of the spacecraft and ensure communication with earth even in case of loss of attitude.

The spacecraft came out of ‘whiteout’ geometry successfully on May 30, 2016 and has been normalised for regular operations.

It may be recalled, MOM went through a communication 'blackout' as a result of solar conjunction from June 2, 2015 to July 2, 2015. Telemetry data was received during most of the conjunction period except for 9 days from June 10-18, during superior conjunction. MOM was commanded with autonomy features starting from May 18, 2015, which enabled it to survive the communication 'blackout' period without any ground commands or intervention. The spacecraft emerged out of 'blackout' period with auto control of the spacecraft systems successfully. This experience had enabled the mission team to program a spacecraft about one month in advance for all operations.