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Typically, the Lunar Reconnaissance Orbiter (LRO) spacecraft flies over the night side of the Moon every two hours, spending about 45 minutes in darkness. Because LRO is powered by sunlight, it uses a rechargeable battery to operate while on the night side of the Moon and then charges the battery when it comes back around into daylight.
During the total lunar eclipse of April 15, 2014, however, LRO emerges from the night side of the Moon only to find the Sun blocked by the Earth. LRO needs to travel an entire orbit before seeing the Sun again, relying continuously on its battery for almost three hours, longer than it ever has before.
LRO won’t be in any real danger as long as its power consumption is handled carefully. Its scientific instruments will be turned off temporarily, while vital subsystems like the heater will remain on. LRO will be closely monitored throughout the eclipse.
This animation shows the Moon as it might look through a telescope on Earth, with LRO’s orbit, its view of the Sun, and a fuel gauge showing received sunlight and the battery’s charge.