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I was reading this news article, and it was mentioned that orbit raising is done in early hours. In all the five orbit raising operations, they are raising them only during night. What could be the reason behind this? Do they do them at night time, to minimize signal disturbance, or is there any other reason?

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ISRO calls these "Midnight Maneuvers". This question, why do these maneuvers fall at around midnight Indian Standard Time (IST), has been asked by some of their readers on Mars Orbiter Mission's Facebook page before, and ISRO answered:

“Firing has to happen near the perigee and in the visibility from ISTRAC ground stations. All these orbits have argument of perigee of ~285 deg. When all these constraints are put together, firings time will almost always fall in to midnights of Indian sub continent.”

    enter image description here

    Graphic showing trajectories for the Midnight Maneuvers of ISRO’s Mars Orbiter Mission Spacecraft (Credit: ISRO)

In reality though, not all of these orbital maneuvers were done at midnight IST:

  • First Earth-bound maneuver: 7 Nov. 2013, 01:17 am IST (completed successfully)
  • Second Earth-bound maneuver: 8 Nov. 2013, 02:18 am IST (completed successfully)
  • Third Earth-bound maneuver: 9 Nov. 2013, 02:10 am IST (completed successfully)
  • Fourth Earth-bound maneuver: 11 Nov. 2013, 02:06 am IST (achieved apogee of 78,722 km, planned 117,724 km)
  • Fourth Earth-bound maneuver, supplemental: 12 Nov. 2013, 05:00 am IST (completed successfully)
  • Fifth Earth-bound maneuver: 16 Nov. 2013, 01:27 IST (completed successfully)

All sources: Mars Orbiter Mission on Facebook

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