The Gravity Recovery and Interior Laboratory (GRAIL) - a program for studying the gravitational field and the internal structure of the moon , reconstruction of its thermal history. GRAIL will provide more complete information about the formation of the moon and other solid planets of the solar system. This mission is similar to the previously launched Gravity Recovery and Climate Experiment ( GRACE ) project, which studied the Earth's gravitational field.
| Gravity Recovery and Interior Laboratory (GRAIL) | |
|---|---|
| Gravity Recovery and Interior Laboratory | |
 | |
| Customer |  NASA |
| Manufacturer | Lockheed Martin Space Systems Massachusetts institute of technology |
| Operator | NASA |
| Tasks | moon exploration, photographing |
| Satellite | The moon |
| Launch pad | Cape Canaveral Playground SLC-17B |
| Carrier rocket | Delta-2 (7290N-10) |
| Launch | September 10, 2011 at 13:08:52 UTC (17:08:52 Moscow time) |
| Going into orbit | January 1, 2012 at 01:21 Moscow time (GRAIL-A), January 2 at 02:44 Moscow time (GRAIL-B) |
| Flight duration | several months |
| Descent from orbit | December 18 at 05:28 Moscow time |
| NSSDC ID | 2011-046A |
| SCN | 37801 |
| Specifications | |
| Weight | 132.7 kg |
| Power supplies | Solar cells, Li-ion batteries |
| Mission logo | |
 | |
| Project site | |
The program was implemented by a pair of spacecraft ("Ebb" and "Flow" ("tide" and "low tide")), which were launched on September 10, 2011 using a Delta II rocket. [1] [2] [3] [4] The design of the probes is based on the development of USA-165 .
The project is led by Maria Zuber, head of the Earth, Atmospheric and Planetary Sciences department of the Macca of the Chisinau Institute of Technology . [5] The project budget is $ 496 million, including design, development, launch and staffing. [6]
Mission Description
It is known that on the moon there are large gravitational anomalies (see - mascones ).
Using two devices GRAIL-A and GRAIL-B, following each other in almost the same orbit, at a distance from each other from 175 to 225 km, a map of the anomalies of the gravitational field of the moon will be compiled. The probes will conduct their research autonomously, without constant monitoring from Earth. A microwave ranging system will parameterize the distance between the two satellites. Changes in this distance characterize the gravitational map of the moon. To increase the accuracy of measurements, the height of the lunar orbit will be kept very low, about 50 km, which roughly corresponds to the average LRO altitude.
Each of the probes is also equipped with a small MoonKAM camera, which transmits images of not the highest quality. Its work will be managed not by NASA employees, but by simple schoolchildren who will be able to choose a specific time and place for shooting, monitor the progress of their application on the MoonKAM website and view photos of the lunar surface prepared in accordance with the application.
Working in orbit and completing a mission
The orbit took place on January 1, 2012 (GRAIL-A, 01.21 MSK ) and January 2, 2012 (GRAIL-B, 06.05 MSK). It was carried out according to the ballistic capture scheme with the passage of the point L1 , which does not require a large braking impulse near the Moon (about 800 m / s), but increases the flight time to the Moon from 3 days to 3.5 months.
The initial near-polar orbit of the probes had an elliptical shape with a height of ~ 90 to ~ 8,360 km, and they completed one complete revolution around the Moon in about 11.5 hours. At first, GRAIL-A switched to such a trajectory of movement, having completed its maneuver on January 1 at 02:00 Moscow time. The next day at 02:43 Moscow time, GRAIL-B joined him.
Initially, the GRAIL mission was to last until May 2012. At the end of August 2012, it was decided to extend the mission until December 2012.
Devices from an orbit 55 kilometers high were lowered to an orbit about 23 kilometers high. This made it possible to obtain more accurate data despite the fact that already now the resolution of the map of the gravitational field of the moon created according to GRAIL data exceeds its analogs by three to four times.
Specialists will begin to reduce the height of the GRAIL orbit, gradually leading it to a circular view. In March, when the scientific observation program started, the spacecraft moved at a distance of ~ 55 km from the lunar surface and circled it in about two hours.
The Ebb and Flow probes crashed into the lunar surface near the Goldschmidt crater on December 18, 2012 at about 05:30 Moscow time (December 17 at about 17:30 US Eastern time) [7] .
Research Results
Using the GRAIL apparatus, it was found that the thickness of the lunar crust was markedly overestimated. Seismographs installed during the Apollo expeditions yielded a result of 60 kilometers (after repeated analysis - about 45 kilometers). New results say that its thickness is “only” about 30 kilometers.
See also
- Lunar Quest (space program)
Notes
- ↑ NASA launched satellites to the moon . Lenta.ru (September 10, 2011). Archived March 22, 2012.
- ↑ Delta II Set to Launch NASA's GRAIL Mission (link unavailable) . United Launch Alliance. Archived March 22, 2012.
- ↑ GRAIL probes set off for the Moon (inaccessible link) . Compulent (September 10, 2011). Date of treatment September 12, 2011. Archived on October 7, 2011. (Retrieved September 12, 2011)
- ↑ NASA satellites will be engaged in the measurement of lunar gravity . BBC Russian (September 11, 2011). Archived January 31, 2012. (Retrieved September 12, 2011)
- ↑ NASA To Launch Two 'Grail' Moon Probes To Measure Gravity Huffington Post (September 5, 2011). Archived March 22, 2012.
- ↑ The cost of the Phobos-Grunt project amounted to 5 billion rubles , Lenta.ru (January 2, 2012).
- ↑ NASA GRAIL Twins Complete Their Moon Impact . NASA (12.17.12). Archived December 20, 2012.