GRAIL

GRAIL (for Gravity Recovery and Interior Laboratory) was a NASA lunar mission to study the Moon's gravitational field. Two separately-launched spacecraft (GRAIL A aka Ebb and GRAIL B aka Flow) exchanged timing information with each other and with stations on Earth, to record precise location information of each over time. Through analysis, much information on the gravitational field could be determined, i.e., its gravity anomalies. The primary science data collection required only three months and after some additional data collection, the probes were deliberately crashed into the moon a year after the launch. Instruments:

• LGRS ("Lunar Gravity Ranging System").
• RSB ("Radio Science Beacon").
• MoonKAM ("Moon Knowledge Acquired by Middle school students"), a video system.