NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) has been orbiting Earth’s Moon since October 6, 2013, and has been accruing data since November 10. Although the probe’s original 100-day scientific mission has concluded, LADEE is still transmitting information back to Earth. However, LADEE’s odyssey will soon come to an end.
According to a NASA press release, LADEE will crash into the lunar surface on or before April 21. , By mid-April, ground controllers at Ames Research Center will have adjusted LADEE’s orbit so that it flies about one to two miles in altitude. A final maneuver on April 11 will guarantee that LADEE’s impact site is on the far side of the Moon. After this, the probe will have depleted its supply of fuel and its orbit will begin to decay naturally.
However, before LADEE’s orbit fully decays, the probe will experience a total lunar eclipse on April 15. This eclipse will last about four hours and will test LADEE’s endurance to its limits. The eclipse will expose LADEE to extreme cold and will take an especially severe toll on the propulsion system. If LADEE survives the eclipse, it will continue to gather and send back data right up to the moment it falls into the lunar surface.
LADEE has gather over 700,000 measurements of the thin lunar atmosphere. In its prior orbit, LADEE’s closest approach to the surface was between 12.5 and 31 miles, and its greatest distance from the surface was between 47 and 93 miles. This orbit permitted LADEE to pass from lunar day to lunar night every two hours, providing information on all the fluctuations that occur in the lunar atmosphere between night and day.
LADEE’s data are expected to elucidate what caused a puzzling pre-sunrise glow observed above the lunar horizon during several Apollo missions; the strongest possibility is that the glow was caused by lunar dust with an electoral charge imparted by sunlight. LADEE is also studying the structure and makeup of the Moon’s atmosphere. Scientists hope that detailed knowledge of the lunar atmosphere will allow better understanding of other bodies with tenuous atmospheres, such as Mercury, some of the moons of the gas giants, and large asteroids.