GRAIL

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GRAIL-transit-Earth-Moon GRAIL-transit-Earth-Moon.png
GRAIL-transit-Earth-Moon
Animation of GRAIL-A's trajectory around Moon from 31 December 2011 to 30 April 2012 GRAIL-A * Moon Animation of GRAIL-A trajectory around Moon.gif
Animation of GRAIL-A's trajectory around Moon from 31 December 2011 to 30 April 2012
   GRAIL-A ·   Moon

Unlike the Apollo program missions, which took three days to reach the Moon, GRAIL made use of a three- to four-month low-energy trans-lunar cruise well outside the Moon's orbit and passing near the Sun-Earth Lagrange point L1 before looping back to rendezvous with the Moon. This extended and circuitous trajectory enabled the mission 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 25 hours apart) of 175 to 225 km (109 to 140 mi). [22] [29] The very tight tolerances in the flight plan left little room for error correction leading to a launch window lasting one second and providing only two launch opportunities per day. [28]

Science phase

The primary science phase of GRAIL lasted for 88 days, from 7 March 2012 to 29 May 2012. It was followed by a second science phase that ran from 8 Aug 2012 into early Dec 2012.

The gravity mapping technique was similar to that used by Gravity Recovery and Climate Experiment (GRACE), and the spacecraft design was based on XSS-11. [3]

The orbital insertion dates were December 31, 2011 (for GRAIL-A) and January 1, 2012 (for GRAIL-B). [27] The initial lunar orbits were highly elliptical near-polar, and were later lowered to near-circular at about 25-86 km altitude with a period of about 114 minutes. [30]

The spacecraft were operated over the 88-day acquisition phase, divided into three 27.3 day long nadir-pointed mapping cycles. Twice each day there was an 8-hour pass in view of the Deep Space Network for transmission of science and "E/PO MoonKam" data. [31]

The first student-requested MoonKam images were taken by Ebb from 2012 March 15–17 and downlinked to Earth March 20. More than 2,700 schools spanning 52 countries were using the MoonKAM cameras. [32]

Footage of LRO by MoonKam

Flow's MoonKam camera captured LRO as it flew by at a distance of about 12 miles (20 km) on May 3. It's the first footage of a moon-orbiting robotic spacecraft taken by another one. [33]

Terminal phase

Ebb and Flow's Final Moments.jpg
Ebb and Flow's final moments.
GRAIL's Final Resting Spot.jpg
GRAIL's final resting spot.
This animation shows the last three orbits of the spacecraft, with views of the impact site. The impact occurs on the night side of a waxing crescent Moon, so the view shifts from a natural color Moon to a false-color elevation map.
LRO flies over the north pole of the Moon, where it has a very good view of the GRAIL impact. The second part of this video is the view from LRO through LAMP's slit, showing the impact and the resulting plume.

Final experiment and mission end

At the end of the science phase and a mission extension, the spacecraft were powered down and decommissioned over a five-day period. The spacecraft impacted the lunar surface on December 17, 2012. [31] [34] [35] [36] [37] [38] Both spacecraft impacted an unnamed lunar mountain between Philolaus and Mouchez at 75°37′N26°38′W / 75.62°N 26.63°W / 75.62; -26.63 . Ebb, the lead spacecraft in formation, impacted first. Flow impacted moments later. Each spacecraft was traveling at 3,760 miles per hour (1.68 km/s). A final experiment was conducted during the final days of the mission. Main engines aboard the spacecraft were fired, depleting remaining fuel. Data from that effort will be used by mission planners to validate fuel consumption computer models to improve predictions of fuel needs for future missions. [39] NASA has announced that the crash site will be named after GRAIL collaborator and first American woman in space, Sally Ride. [40]

Moon – Oceanus Procellarum ("Ocean of Storms")
14-236-LunarGrailMission-OceanusProcellarum-Rifts-Overall-20141001.jpg
Ancient rift valleys – rectangular structure (visible – topography – GRAIL gravity gradients) (October 1, 2014).
PIA18822-LunarGrailMission-OceanusProcellarum-Rifts-Overall-20141001.jpg
Ancient rift valleys – context.
PIA18821-LunarGrailMission-OceanusProcellarum-Rifts-Closeup-20141001.jpg
Ancient rift valleys – closeup (artist's concept).

Results

Gravity passes through matter. In addition to surface mass, a high-resolution gravity field gives a blurred, but useful, look below the surface. Analyses of the GRAIL data have produced a series of scientific results for the Moon.

See also

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References

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  2. ↑ "The GRAIL Mission: A Fact Sheet". Sally Ride Science. 2010. Archived from the original on 28 April 2010. Retrieved 15 April 2010.
  3. 1 2 Taylor Dinerman (31 December 2007). "Is XSS-11 the answer to America's quest for Operationally Responsive Space?". The Space Review. Retrieved 31 August 2011.
  4. ↑ Asif Siddiqi (2018). Beyond Earth: A Chronicle of Deep Space Exploration, 1958–2016 (PDF) (second ed.). NASA History Program Office. ISBN   978-1-626-83043-1 . Retrieved 30 November 2022.
  5. 1 2 3 "About GRAIL". moon.mit.edu. MIT . Retrieved 12 March 2011.
  6. ↑ Gail Schontzler (18 January 2012). "Bozeman class wins contest to name satellites orbiting moon". Bozeman Daily Chronicle. Retrieved 18 December 2018.
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  10. ↑ Laura Dattaro (10 September 2011). "Moon-bound twin GRAIL spacecraft launch success". EarthSky.org. Retrieved 23 July 2024.
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  13. 1 2 "GRAIL Launch Press Kit" (PDF). solarsystem.nasa.gov. NASA. Archived from the original (PDF) on 5 October 2012. Retrieved 31 August 2011.
  14. ↑ M. T. Zuber; D. E. Smith; S. W. Asmar; Alomon; A. S. Konopliv; F. G. Lemoine; et al. (19–23 March 2012). Gravity Recovery and Interior Laboratory (GRAIL) Mission: Status at the Initiation of the Science Mapping Phase. 43rd Lunar and Planetary Science Conference. Texas, USA: NASA. GSFC.CP.00105.2012.
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  23. 1 2 "GRAIL: Spacecraft and Payload". moon.mit.edu. MIT . Retrieved 24 July 2024.
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  26. ↑ "GRAIL (Gravity Recovery and Interior Laboratory)". eoPortal.org. Retrieved 3 December 2022.
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Gravity Recovery and Interior Laboratory
GRAIL.jpg
Artist's interpretation of the GRAIL tandem spacecraft above the lunar surface.
NamesGRAIL
Mission type Lunar orbiters
Operator NASA  / JPL [1] [2]
COSPAR ID 2011-046A
2011-046B
SATCAT no. 37801
37802
Website moon.mit.edu
Mission duration1 year, 3 months and 7 days
Spacecraft properties
Bus XSS-11 [3]
Manufacturer MIT
Lockheed Martin
Launch mass202.4 kg (each) [4]
Dry mass132.6 kg (292 lb)
Power(Solar array / Li-ion battery)
Start of mission
Launch dateSeptember 10, 2011, 13:08:52.775 (2011-09-10UTC13:08:52Z) UTC
Rocket Delta II 7920H-10
D-356
Launch site Cape Canaveral SLC-17B
Contractor United Launch Alliance
Entered serviceDecember 31, 2011 (Ebb)
January 1, 2012 (Flow)
End of mission
DisposalDeorbited
Decay dateDecember 17, 2012
Orbital parameters
Reference system Selenocentric
Regime Polar orbit [5]
Semi-major axis 1,788.0 km (1,111.0 mi)
Periselene altitude 25 km (16 mi)
Aposelene altitude 86 km (53 mi)
Period 113 minutes
Lunar impactor
Spacecraft componentEbb
Impact dateDecember 17, 2012, 22:28:51 UTC
Impact site 75°36′30″N33°24′15″E / 75.6083°N 33.4043°E / 75.6083; 33.4043
New Horizons spacecraft model 1.png
Proposals
Finalists
Candidates
  • Underline indicates active current missions
  • Italics indicate missions yet to launch
  • Symbol † indicates failure en route or before intended mission data returned

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