A few days from now, the Earth, moon and sun will perfectly align, shrouding the moon in the shadow of the Earth.
The total lunar eclipse, which is expected to last over three hours starts at 2 a.m. EDT (0600 GMT) on April 15, will also plunge NASA's $504 million probe – the Lunar Reconnaissance Orbiter (LRO) – into darkness.
The spacecraft's batteries need sunlight to recharge, so it will have to operate without charging for longer than usual. Will that be a problem?
In a statement, Noah Petro, Lunar Reconnaissance Orbiter deputy project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., said that the LRO team would be watching the eclipse very closely.
"The spacecraft will be going straight from the moon's shadow to the Earth's shadow while it orbits during the eclipse," Petro said. "We're taking precautions to make sure everything is fine. We're turning off the instruments and will monitor the spacecraft every few hours when it's visible from Earth."
There have been instances when LRO had orbited the moon during an eclipse. In the past, the spacecraft has had to pass through the Earth's shadow for a short period of time. This time, though, LRO has to "to pass through the complete shadow twice" before the eclipse ends.
"For quite a while, people in LRO have been analyzing what's going to happen during this eclipse," Petro said. "We'll make sure the world knows LRO survived with no problems."
Launched in 2009 the robotic mission mostly orbits the moon at an altitude of about 31 miles and maps the moon's surface.
Meanwhile, NASA's $280 million Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft--launched in 2013 – is gradually lowering its orbit and is expected to land on the moon’s surface on or before April 21. But scientists are eagerly watching to see "how LADEE handles the prolonged exposure to the intense cold of this eclipse, and we've used flight data to predict that most of the spacecraft should be fine," said Butler Hine, LADEE project manager at Ames. "However, the eclipse will really put the spacecraft design through an extreme test, especially the propulsion system."
If it survives the eclipse, "we will have nearly a week of additional science at low altitudes before impact," said Dr. Elphic. "For a short mission like LADEE, even a few days count for a lot – this is a very exciting time in the mission."
After LADEE plunges onto the moon's surface NASA's LRO may be able to find the LADEE impact site in a few months.
Meanwhile, NASA is holding a little contest called "Take the Plunge Challenge" to generate public interest in the project. People are encouraged to submit their best guess (by April 11) on when LADEE will impact the lunar surface.