Gravity Recovery and Interior Laboratory

For other uses, see Grail (disambiguation).

Gravity Recovery and Interior Laboratory (GRAIL)

Artist's interpretation of the GRAIL tandem spacecraft above the lunar surface
Operator	NASA / JPL
Major contractors	Lockheed Martin Space Systems Massachusetts Institute of Technology
Mission type	Orbiter
Satellite of	The Moon
Orbital insertion date	December 31, 2011 (2011-12-31) (GRAIL-A), January 1, 2012 (2012-01-01) (GRAIL-B) (planned)
Launch date	2011-09-10, 13:08:52.775 UTC
Launch vehicle	Delta II 7920H-10 configuration (D-356)
Launch site	Space Launch Complex 17B Cape Canaveral Air Force Station
Mission duration	March 2012 (2012-03) - May 2012 (2012-05) (planned)
COSPAR ID	2011-046
Homepage	http://moon.mit.edu
Mass	132.6 kg (292 lb)
Power	(Solar array / Li-ion battery)
References: [1][2]
GRAIL mission logo

The Gravity Recovery and Interior Laboratory (GRAIL) is an American lunar science mission in NASA's Discovery Program, which will use high-quality gravitational field mapping of the Moon to determine its interior structure. The two small spacecraft GRAIL A and GRAIL B were launched on 10 September 2011 aboard a single launch vehicle: the most-powerful configuration of a Delta II, the 7920H-10.^[1][3][4] GRAIL A separated from the rocket about nine minutes after launch, GRAIL B followed about eight minutes later. They will arrive at their orbits around the Moon 24 hours apart.^[5]

The science phase of the mission will last for 90 days. Following the science phase (or extended mission phase), a five-day decommissioning period is planned, after which the spacecraft will impact the lunar surface in about 40 days.^[6] The gravity mapping technique is similar to that used by Gravity Recovery and Climate Experiment (GRACE), and the spacecraft design is based on XSS-11.^[7]

Unlike the Apollo program missions, which took three days to reach the Moon, GRAIL will make use of a three- to four-month low-energy trans-lunar cruise via the Sun-Earth Lagrange point L1 to reduce fuel requirements, protect instruments and reduce the velocity of the two spacecraft at lunar arrival to help achieve the extremely low 50 km (31 mi) orbits with separation between the spacecraft (arriving 24 hours apart) of 175 to 225 km (109 to 140 mi).^[8][9] The very tight tolerances in the flight plan leaves little room for error correction leading to a launch window lasting one second and providing only two launch opportunities per day.^[10]

Maria Zuber of the Massachusetts Institute of Technology is GRAIL's principal investigator. The mission's team of expert scientists and engineers also includes former NASA astronaut Sally Ride, who will lead the mission's public outreach efforts. NASA's Jet Propulsion Laboratory manages the project. As of August 5, 2011, the program has cost US$496 million.^[11]

Objectives

Each spacecraft transmits and receives telemetry from the other spacecraft and Earth-based facilities. By measuring the change in distance between the two spacecraft, the gravity field and geological structure of the Moon can be obtained. The gravitational field of the Moon will be mapped in unprecedented detail.^[12]

Primary objectives

• Map the structure of the lunar crust and lithosphere
• Understand the asymmetric thermal evolution of the Moon
• Determine the subsurface structure of impact basins and the origin of lunar mascons
• Ascertain the temporal evolution of crustal brecciation and magmatism
• Constrain the deep interior structure of the Moon
• Place limits on the size of the Moon's inner core

The data collection phase of the mission will last 90 days, and will be followed by 12 months of data analysis.^[12] Results will begin to become available about 30 days after the collection begins.^[8] The knowledge acquired will aid understanding of the evolutionary history of the terrestrial planets.^[8]

Instruments

• K_a band ranging assembly (KBR)
• Radio science beacon (RSB)
• Moon Knowledge Acquired by Middle school students (MoonKam).^[13] Each MoonKAM system (one per spacecraft) consists of a digital video controller and four camera heads.^[14]

Launch attempts

All times are in EDT (UTC-4).

Attempt	Planned	Result	Turnaround	Reason	Decision point	Weather go %	Notes
1	2011-09-08 08:37:06 !8 Sep 2011, 8:37:06 am	scrubbed[15]	---	high level winds	2011-09-08 08:30:00 !8 Sep 2011, 8:30 am	40%	A weather balloon was released minutes before the decision point to take the latest readings of upper level winds and Air Force weather reconnaissance aircraft were aloft beginning at 7 am.
2	2011-09-08 09:16:12 !8 Sep 2011, 9:16:12 am	scrubbed[15]	0 days, 0 hours, 39 minutes	high level winds	2011-09-08 09:07:12 !8 Sep 2011, 9:07 am	40% [10]	Range was reconfigured for omni antennae instead of tracked ones to support 99 degree azimuth.
3	2011-09-09 08:33:25 !9 Sep 2011, 8:33:25 am	abandoned[15]	0 days, 23 hours, 17 minutes	rocket propulsion		40%	An issue with the rocket's propulsion system was detected while the Delta 2 rocket was drained of fuel.
4	2011-09-10 08:29:45 !10 Sep 2011, 8:29:45 am	scrubbed[15]	0 days, 23 hours, 56 minutes	high level winds	2011-09-10 08:21 !10 Sep 2011, 8:21 am	60%
5	2011-09-10 09:08:52 !10 Sep 2011, 9:08:52 am	Success[15]	0 days, 0 hours, 39 minutes

Mission status

The two small spacecraft which compose GRAIL were launched on 10 September 2011.^[1][15] GRAIL will make use of a three- to four-month low-energy trans-lunar cruise via the Sun-Earth Lagrange point L1 to reduce fuel requirements, protect instruments, and reduce the velocity of the two spacecraft at lunar arrival to help achieve the extremely low 50 km (31 mi) orbits with separation between the spacecraft (arriving 24 hours apart) of 175 to 225 km (109 to 140 mi).^[8][9] The planned orbital insertion dates are December 31, 2011 (2011-12-31) (for GRAIL-A) and January 1, 2012 (2012-01-01) (for GRAIL-B).^[15]

• 

  Spacecraft technicians close the payload fairing around GRAIL before launch.

• 

  GRAIL awaits launch at Cape Canaveral Air Force Station.

• 

  Fire and smoke light up a blue sky as a United Launch Alliance Delta II Heavy rocket propels GRAIL into space.

References

1. ^ ^{a b c} "Delta II Set to Launch NASA's GRAIL Mission". United Launch Alliance. 2011. http://www.ulalaunch.com/site/pages/Launch.shtml#/21/. Retrieved 2 September 2011. 
2. ^ "The GRAIL Mission: A Fact Sheet". Sally Ride Science. 2010. http://www.grailmoonkam.com/about/grail_fact_sheet. Retrieved 2010-04-15. 
3. ^ Delta II: The Industry Workhorse. United Launch Alliance. 2010. http://www.ulalaunch.com/site/docs/product_cards/DII_product_card.pdf. Retrieved 2 August 2011. 
4. ^ Grey Hautaluoma (10 December 2007). "New NASA Mission to Reveal Moon's Internal Structure and Evolution". NASA. http://www.nasa.gov/home/hqnews/2007/dec/HQ_07274_Grail_Mission.html. Retrieved 31 August 2011. 
5. ^ Moon-bound twin GRAIL spacecraft launch success
6. ^ GRAIL web page. "Mission Design". MIT. http://moon.mit.edu/design.html. Retrieved 13 April 2011. 
7. ^ Taylor Dinerman (Monday, 31 December 2007). "Is XSS-11 the answer to America’s quest for Operationally Responsive Space?". The Space Review. http://www.thespacereview.com/article/1026/1. Retrieved 31 August 2011. 
8. ^ ^{a b c d} "Mission Overview". MIT. http://moon.mit.edu/overview.html. Retrieved 10 September 2011. 
9. ^ ^{a b} "Mission Design". NASA. http://solarsystem.nasa.gov/grail/missiondesign.cfm. Retrieved 10 September 2011. 
10. ^ ^{a b} Justin Ray (17 August 2011). "GRAIL Launch Window Chart". SpaceFlight Now. http://www.spaceflightnow.com/delta/d356/windows.html. Retrieved 9 September 2011. 
11. ^ Marcia Dunn, AP Aerospace Writer (Friday, 5 August 2011). "NASA Spacecraft Begins 5-Year Trip to Jupiter". Yahoo News. http://news.yahoo.com/nasa-spacecraft-begins-5-trip-jupiter-211124283.html. Retrieved 07 September 2011. 
12. ^ ^{a b} "About GRAIL". MIT. http://moon.mit.edu/index.html. Retrieved 2011-03-12. 
13. ^ "About GRAIL MoonKAM". Sally Ride Science. 2010. http://www.grailmoonkam.com/about. Retrieved 2010-04-15. 
14. ^ "GRAIL Launch Press Kit". NASA. http://solarsystem.nasa.gov/grail/docs/GRAIL%20launch%20press%20kit1.pdf. Retrieved 31 August 2011. 
15. ^ ^{a b c d e f g} Harwood, William. "NASA launches GRAIL lunar probes". CBS News. http://www.cbsnews.com/stories/2011/09/10/scitech/main20104282.shtml. Retrieved 11 September 2011. 

External links

• MIT GRAIL Home Page
• NASA 360 New Worlds New Discoveries 2/2 Retrieved 6/3/2011.
• Behind The Scenes of My NASA GRAIL Experience – Day One (AM)