[AR] Re: It still works.
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Wed, 6 Dec 2017 22:56:00 -0500 (EST)
On Wed, 6 Dec 2017, Robert Steinke wrote:
TCM and DSN (Deep Space ???) meaning?
TCM - Trajectory Correction Manuver (I'm guessing)DSN - Deep Space Network,
NASA's system of radio dishes for communicating with beyond-earth-orbit
missions.
Correct, on both.
On Wed, Dec 6, 2017 at 7:24 AM, John Dom <johndom@xxxxxxxxx> wrote:
Is the Kepler probe still being used, in part? Years ago I read
it was crippled.
Kepler is still observing, although with some major limitations on which
way it can point. The original mission target area was inaccessible as
soon as the second reaction wheel failed, but targets in a limited range
of directions can be observed for limited lengths of time using a tricky
strategy. With sunlight hitting the spacecraft from a certain small range
of directions, light pressure on its solar arrays gives it passive
pointing stability on one axis -- the one the two surviving reaction
wheels can't cover!
So if you use the spacecraft's thrusters to point it in the right
direction and carefully bring it to a perfect stop, it'll naturally hold
its position on the axis that's no longer covered by a wheel, while the
wheels handle the other two. There's a time limit, because the spacecraft
needs to point in a constant direction to watch the same stars
continuously, but the angle of the sunlight changes constantly as the
spacecraft goes around the Sun, so the passive stability for a particular
target only lasts a few months at most. But it's better than nothing.
If memory serves, their last funding extension runs until summer 2019, but
the spacecraft will almost certainly run out of thruster fuel sometime in
2018, definitively ending the mission.
Henry
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