# Why did NASA intentionally crash the Lunar Atmosphere and Dust Environment Explorer (LADEE) on the moon?

The Lunar Atmosphere and Dust Environment Explorer (LADEE) was intentionally crashed into the moon by NASA but why did they crash the craft instead of leaving it in orbit, or was it a part of some mission to study how the impact takes place?

• I am by no means an expert, but it seems logical to me to avoid as much space debris as possible. Crashing a craft that's no langer needed into the moon (or let it vaporize in earth's atmosphere) is a good way to get rid of it and lessen the risk for further missions to get in contact with debris. - I could be totally wrong, but this is logic in my head. – Padarom Apr 23 '14 at 14:03
• this was the first thing that came to my mind , but they have this on their website nasa.gov/ames/… "NASA Completes LADEE Mission with Planned Impact on Moon's Surface" , but no where it is mentioned why ! – Randomizer Apr 23 '14 at 14:24

Once in orbit, always in orbit doesn't apply to the moon--the gravity is too uneven. Stuff left in lunar orbit generally crashes into the moon after a while. (All the Apollo landers that were left in lunar orbit are gone by now.)

In addition to observing the crash they also wanted to control the crash--make sure it didn't happen on top of anything sitting on the moon.

LADEE was going to run out of fuel, and they wanted - and succeeded - to collect data of Moon's atmosphere and levitated dust. (LADEE means 'Lunar Atmosphere and Dust Environment Explorer'.)

Fuel is needed to compensate orbital degradation due to Moon's non-symmetric gravitational field.

Online communication was possible due to superfast laser data transmission (Lunar Laser Communication Demonstration, or LLCD).

More details here and here.

• Not data from the moon's atmosphere! The moon has no atmosphere, they were examining the moons surface and underlying layers in hope for water molecules and stuff. – harogaston Apr 24 '14 at 3:52
• So did they do it because it ran out of fuel (Once it's in orbit, it pretty much is in orbit- So they don't really need any more fuel, do they?), or because they wanted levitated dust? And if latter is the case, how can they examine it, if the craft is destroyed? – Padarom Apr 24 '14 at 7:28
• @harogaston Wrong. Moon has an atmosphere. A tiny one. csmonitor.com/Science/2013/0906/… – Envite Apr 24 '14 at 9:47
• Mission was already over. They just take the chance of crashing the probe to gather extra data about the dust after the crash. Of course those data were not gathered by LADEE. – Envite Apr 24 '14 at 9:51
• @Padarom They do need fuel, otherwise the orbit degrades due to Moon's non-symmetric gravitational field; data have been sent online. 'A' in LADEE is for 'Atmosphere', 'D' is for 'Dust'. More reading about the mission here: americaspace.com/?p=55743 – Gerald Apr 24 '14 at 13:36

Several reasons:

1. The space probes are orbiting around the moon, below a certain altitude, and definitely at altitudes as low as 1 - 2 miles, fuel must be used to keep it in orbit. After it has completed its mission, there will be no/little more fuel left for it to escape the moon's gravity pull again. (Quote from previous reference At the time of impact, the spacecraft will have used all of its fuel.) So the probes will crash anyways.
2. From this New York Times article about a previous planned (of Grail), the purpose of a planned crash is so that the crash site does not destroy a historic landmark, such as Neil Armstrong's footprints. A less sentimental reason is that the crash site can also be strategically planned to help further missions locate a specific place on the moon, using the indentation the impact will create.