Encyclopedia Astronautica

Gravity Recovery and Interior Laboratory. Twin lunar orbiters, versions of the earth-orbit Grace spacecraft, launched together. The mission was to use high-quality gravity field mapping of the moon to determine the moon's interior structure.

The two Grail satellites perfored high-precision range-rate measurements between them using a Ka-band payload in a 50-km circular lunar orbit. Earth-based data analysis of range-rate data provided a direct measure of the lunar gravity. The 270-day mission included a 90-day gravity mapping Science Phase.

The spacecraft were derived from the Lockheed XSS-11 design. Each spacecraft bus had a rectangular composite structure with two fixed solar arrays. Maneuver was was via a 22N thruster system and orientation via three reaction wheels. Additional attitude sensing components include an IMU, sun sensor and star tracker. To measure the inter-spacecraft range-rate, each spacecraft had a Ka-band Lunar Gravity Ranging System (LGRS) derived from the GRACE instrument.

First Launch: 2011.09.10.
Last Launch: 2011.09.10.
Number: 2 .

More... - Chronology...

Grail Chronology

2011 September 10 - . 13:08 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17B. Launch Pad: SLC17B. LV Family: Delta. Launch Vehicle: Delta 7920H.
  • Grail A - . Nation: USA. Class: Moon. Type: Lunar probe. Spacecraft: Grail. USAF Sat Cat: 37801 . COSPAR: 2011-046A. NASA dual-spacecraft lunar mission. Grail A was deployed from the Delta upper stage at 14:28 GMT and Grail B at 14:37 GMT. The spacecraft will reach the Sun-Earth L1 point 1.5 million km from Earth and then fall back towards the Moon. Lunar orbit insertion is scheduled for 01:00 GMt on 1 January 2012 for Grail A, and at 02:00 GMT on 2 January for Grail B.
  • Grail B - . Nation: USA. Class: Moon. Type: Lunar probe. Spacecraft: Grail. USAF Sat Cat: 37802 . COSPAR: 2011-046B.

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