GRACE mission which was launched on March 17th, 2002 had a 10 minutes launch window. The mission was to launch a couple of earth observation satellites.

And interestingly, NASA's GRACE Launch Press Kit, March 2002 mentions that the launch window keeps moving earlier by 2mins 12s on every subsequent day.

Launch timing

On March 16, 2002, the 10 minute launch window opens at 12:23 p.m. local time in Plesetsk (4:23 a.m. EST). If launch does not take place on March 16, the window on subsequent days falls earlier by 2 minutes, 12 seconds each day

Given satellites were launched from earth to observe earth, why would it require such a narrow launch window per day?

  • 2
    $\begingroup$ The -2:14 is about how fast sunrise is changing there and then. Perhaps they wanted a constant solar angle during the early part of the flight. Unfortunately, the fact they launched near noon argues against this. $\endgroup$ – Bob Jacobsen Jun 30 '19 at 21:28
  • 1
    $\begingroup$ GRACE is supposed to track the movement of water on earth so maybe they wanted to synchronize it with some kind of meteorological process in the atmosphere. (e.g.: tracking specific could formation over a day?) $\endgroup$ – GittingGud Jul 1 '19 at 6:41
  • $\begingroup$ I'm guessing the mission's trajectory was influenced significantly enough by the Moon and Sun pertubations that there is an ideal condition that needs to be optimised with that in mind. These are two spacecraft flying in formation, so it would not be surprising for there to be an obscure trajectory, lighting, communications, or other requirement on launch. $\endgroup$ – CourageousPotato May 20 at 8:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.