GRAIL
The Gravity Recovery and Interior Laboratory (GRAIL) was an American lunar science mission in NASA's Discovery Program which used high-quality gravitational field mapping of the Moon to determine its interior structure. The two small spacecraft GRAIL A (Ebb) and GRAIL B (Flow) were launched on 10 September 2011 aboard a single launch vehicle: the most-powerful configuration of a Delta II, the 7920H-10. GRAIL A separated from the rocket about nine minutes after launch, GRAIL B followed about eight minutes later. They arrived at their orbits around the Moon 25 hours apart. The first probe entered orbit on 31 December 2011 and the second followed on 1 January 2012. The two spacecraft impacted the Lunar surface on December 17, 2012.
Artist's interpretation of the GRAIL tandem spacecraft above the lunar surface. | |
| Operator | NASA / JPL |
|---|---|
| COSPAR ID | 2011-046 (A, B) |
| SATCAT no. | 37801, 37802 |
| Website | moon |
| Mission duration | 1 year, 3 months, 7 days, 9 hours |
| Spacecraft properties | |
| Manufacturer | Massachusetts Institute of Technology, LMSS |
| Launch mass | 202.4 kg (each) |
| Dry mass | 132.6 kg (292 lb) |
| Power | (Solar array / Li-ion battery) |
| Start of mission | |
| Launch date | September 10, 2011, 13:08:52.775 UTC |
| Rocket | Delta II 7920H-10 D-356 |
| Launch site | Cape Canaveral SLC-17B |
| Entered service | December 31, 2011 (Ebb) January 1, 2012 (Flow) |
| Orbital parameters | |
| Reference system | Selenocentric |
| Regime | Polar orbit |
| Semi-major axis | 1,788.0 kilometres (1,111.0 mi) |
| Periselene altitude | 25 kilometres (16 mi) |
| Aposelene altitude | 86 kilometres (53 mi) |
| Period | 113 minutes |
| Lunar impactor | |
| Impact date | GRAIL A: December 17, 2012, 22:28:51 UTC |
| Impact site | 75.6083°N 33.4043°E |
| Lunar impactor | |
| Impact date | GRAIL B: December 17, 2012, 22:29:21 UTC |
| Impact site | 75.6504°N 33.1643°E |
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