Gravity Recovery and Interior Laboratory
| Gravity Recovery and Interior Laboratory | |
|---|---|
 Mission logo |
|
| Type: | Pair of space probes |
| Country: |
 United States
|
| Organization: |
 NASA
|
| COSPAR designation : |
2011-046A 2011-046B |
| Mission dates | |
| Start date: | September 10, 2011 at 13: 08: 52.775 UTC |
| Starting place: | Cape Canaveral Air Force Station |
| Launcher: | Delta-7920H-10C |
| Mission duration: | 464 days |
| End date: | December 17, 2012 at 10:29:21 PM UTC |
| Landing place: | Controlled crash in the North Pole region (crashed on an unnamed mountain) |
| Orbit data | |
| Origin of coordinates: | moon |
| Track height: | 55 km (initially) |
| Rotation time : | 113 min (initially) |
| General spacecraft data | |
| Takeoff mass: | 307 kg each |
| Empty mass: | 201 kg each |
| Dimensions: | (H × W × D) 1.09 × 0.95 × 0.76 m |
| Manufacturer: | Lockheed Martin Space Systems |
Gravity Recovery and Interior Laboratory ( GRAIL ) was a lunar mission of NASA , as part of the Discovery Program was conducted. The name alludes to English. (Holy) Grail = (Holy) Grail on.
GRAIL consisted of two space probes launched together in September 2011 , which orbited the moon between early 2012 and December 2012. The aim of the mission was to precisely measure the lunar gravity field and the gravity anomalies in order to gain information about the internal structure of the moon.
Structure of the probes
The mission was led by the Jet Propulsion Laboratory . The probes were built by Lockheed Martin Space Systems based on the XSS-11 satellite. The power supply was provided by two fold-out, but non-pivoting solar modules (763 W) that charged lithium-ion batteries (30 Ah at 28 V). For position control served hot gas thrusters and reaction flywheels . The data was transmitted to the Deep Space Network (DSN) via an S-band radio link .
The probes worked as the GRACE satellites, according to the SST-principle ( Satellite-to-Satellite Tracking ): They rounded the moon on the same path, and measured with the Lunar Gravity Ranging System (LGRs) by means of electromagnetic waves in the Ka-band continuously the mutual distance. This allowed irregularities in the gravity field to be analyzed with high precision.
As an additional payload, for educational purposes for schoolchildren, there was the E / PO MoonKam camera system on each of the two probes, each with five individual cameras that transmitted images of the moon's surface, the earth and the probes themselves. The probes were named after a nationwide competition for school classes “Ebb” (ebb) and “Flow” (flood).
Mission history
The two GRAIL probes launched together on a two-stage Delta-7920H-10C rocket on September 10, 2011 at 13: 08: 52.775 UTC from Cape Canaveral Air Force Station .
After the start, a three-and-a-half-month transfer phase took place via the Lagrange point L 1 of the earth-sun system to the moon in order to keep the required speed change small and, on the other hand, to achieve the very low lunar orbit of only about 50 km height as precisely as possible. The orbital time of the probes around the moon was 113 minutes. At this altitude, the two satellites followed each other at a distance of about 175–225 km.
The actual science mission began on March 7, 2012 and lasted 82 days. This was divided into three cycles of 27.3 days each. Twice a day, the probes were in contact with the Deep Space Network (DSN) for eight hours each and transmitted the data.
After completing the primary science phase, it was decided to extend the mission, which was to last from August 30 to December 3, 2012. To do this, the probes reduced their height to an average of 23 km in order to be able to carry out even more precise measurements. After the mission ended in December 2012, there was a five-day decommissioning phase, after which the two satellites should later hit the moon to prevent an uncontrolled crash on possibly significant sites such as B. to avoid the Apollo landing sites.
At the scheduled end of the mission on December 17th, 2012, both space probes collided with an unnamed mountain between Philolaus and Mouchez near the North Pole of the Moon. At 22:28:51 UTC, GRAIL A (“Ebb”) first hit the surface of the moon, about 30 seconds later GRAIL B (“Flow”) followed. The location of the impact of both satellites was named by NASA after the late astronaut Sally Ride .
The GRAIL probes preparing for take-off
The GRAIL probes on the launcher
The Delta-7920H-10C before take-off
The Delta 7920H-10C about to take off
Thickness of the lunar crust
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Web links
- GRAIL @ nasa.gov, accessed January 1, 2012
- WITH GRAIL Home Page
- NASA News: New NASA Mission to Reveal Moon's Internal Structure and Evolution , December 11, 2007
- Kennedy Space Center: Media archive for the GRAIL mission
- hda: NASA mission, probe duo to solve puzzles about the second earth moon , in Spiegel Online Date: September 7, 2011, accessed: September 10, 2011
- NASA: GRAIL-A reaches moon on December 31, 2011
Videos
- Parting Moon Shots from NASA's GRAIL mission. Images of the back of the moon in December 2012, JPLnews @ youtube, accessed on January 16, 2013
Individual evidence
- ↑ Lockheed Martin spacecraft to be flown for NASA's GRAIL lunar mission ( Memento from December 29, 2007 in the Internet Archive )
- ↑ NASA: Gravity Recovery and Interior Laboratory (GRAIL) Launch Kit (PDF; 1.2 MB)
- ↑ a b GRAIL: Spacecraft & Payload. MIT, accessed September 5, 2011 .
- ↑ GRAIL: Education & Outreach. MIT, accessed September 5, 2011 .
- ↑ NASA: Montana Students Submit Winning Names for NASA Lunar Spacecraft , January 17, 2012
- ↑ a b c GRAIL: Mission Design. MIT, accessed September 5, 2011 .
- ↑ NASA: NASA's Twin GRAIL Spacecraft Begin Collecting Lunar Science Data
- ↑ NASA: NASA's GRAIL Moon Twins Begin Extended Mission Science , dated August 31, 2012
- ↑ NASA: NASA's GRAIL Lunar Impact Site Named for Astronaut Sally Ride , December 17, 2012