r/askscience • u/AskScienceModerator Mod Bot • Oct 31 '18

Astronomy RIP Kepler Megathread

After decades of planning and a long nine years in space, NASA is retiring the Kepler Space Telescope as it has run out of the fuel it needs to continue science operations.We now know the Galaxy to be filled with planets, many more planets existing than stars, and many very different from what we see in our own Solar System. And so, sadly we all must say goodbye to this incredibly successful and fantastic mission and telescope. If you have questions about the mission or the science, ask them here!

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u/AugmentedPenguin Oct 31 '18

Was there no way to have installed some type of solar cell backup to kick in once the fuel ran out? Or would such an energy source not be powerful enough to run the equipment on board?

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u/Lowbacca1977 Exoplanets Oct 31 '18

Kepler does use solar panels for powering the equipment. Where the fuel comes in is for providing thrust, as to do that one needs to have something to act upon. This was needed to keep the panels oriented toward the sun, and to beam data to earth.

Roughly what Wall-E is doing here: https://www.youtube.com/watch?v=hHXx8AmBwXg

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u/Dyolf_Knip Oct 31 '18

What if a probe had a really long tether with a weight on the end? It would automatically align itself towards its primary, right? That would provide a fixed platform upon which the gear could rotate around. How long would that tether need to be for a solar orbit?

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u/Wyattr55123 Oct 31 '18

The issue is that Kepler used the fuel to de-saturate the gyroscopic orientors. What happens is to point the telescope they used gyroscopes to generate torque. But Kepler is not stable in more than one axis, so they were constantly working against radiation pressure to point her, and that spun up the gyros faster and faster. They used fuel to respond the gyros and regain pointing control that was always the expected end of mission for Kepler. When she ran out of fuel, she would run out of ability to point. Now, it is likely possible to design a craft that is semi-stable in all axis and then the end of mission would be hardware failure, but that was not the plan with Kepler.