So what does an eclipse look like from the Moon?

In the wee hours of Tuesday morning, we’ll be treated to a total lunar eclipse.  But the spacecraft at the Moon will get a solar eclipse instead, as the Earth crosses in front of the Moon.  The ringside observers at present consist of Lunar Reconnaissance Orbiter (which has already observed others, but spent its efforts looking at the Moon instead of the Earth, to see how the sunlight was changed by its passage through the Earth’s atmosphere), the Change’e 3 lander and rover Yutu*, and NASA’s LADEE spacecraft.  This last is the one that scientists and engineers are most nervous about.  LADEE is already near the end of its mission, due to declining hydrazine and nitrogen tetroxide reserves to maintain its orbit through the Moon’s lumpy gravity field.  But unlike Change’e 3, which is built to survive two weeks of total darkness, LADEE is only built to survive very brief trips through the Moon’s shadow.  Tuesday morning, it will be spending four hours transiting the various portions of the Earth’s shadow — penumbra, umbra, and then the other side of the penumbra.  Its batteries will probably endure this, though it’s outside design parameters, but the hydrazine fuel has a fairly good chance of freezing.  If it does, the mission will be effectively over as it will have no means of orienting itself.  And if so, it is not a big loss, for the spacecraft has already completed its mission.  Any science it uncovers during the eclipse is pure gravy, though gravy the team is anxiously awaiting all the same, like proud parents watching their child’s team strive to defeat the star team, ready to proud of whatever they achieve, but hoping against hope they do better than anyone had expected.

The various spacecraft at the Moon will attempt to observe the eclipse, or to observe the Moon during the eclipse.  What will it look like?  Well, here’s what the Japanese Kaguya probe saw during a penumbral eclipse (a relatively gentle occurance compared to a total lunar eclipse, as it’s over more quickly) in 2009, watching as the Earth rose over the lunar horizon due to the spacecraft’s orbital motion:



*Yutu has survived the long lunar night after all, but is now stationary.  I have no information on how much science it is currently able to perform.


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