GRAIL B (Discovery 11B)

Spacecraft nr:

US spacecraft nr:

Launch data: Designation  37802 / 11046B Launch date  10 Sept 2011 - 13:08 UT Launch site  CC, SLC-17B Launch vehicle  Delta-7920H-10C Mission  Lunar gravity field mapping Perigee / Apogee   km Eccentricity   Inclination   deg Period   min

Spacecraft data: Prime manufactor   NASA Jet Propulsion Laboratory (Prime) Lockheed Martin Space Systems (Spacecraft) Platform  LM-300 Operator   NASA Jet Propulsion Laboratory Mass at launch   kg Dry Mass  202 kg Basic shape   Dimension (m)   Equipment   Solar array  2 deployable fixed solar arrays Stabilization   Propulsion   DC power   Design lifetime  270 days

Communication with Earth

Orbits

Trajectories of the satellites

End of live:

Description:

• The lunar mission will use two identical spacecraft orbiting the moon in a low, polar orbit. The spacecraft are based on the flight-proven XSS-11 technology demonstration satellite developed for the Air Force Research Laboratory. They will use Ka-band ranging instruments to send signals between one another, and then relay the data back to Earth to be analyzed. Scientists will examine the minute differences in distance the signals traveled between spacecraft. This will give unprecedented insight into the gravitational changes over the entire moon.
• GRAIL's principal investigator is Maria Zuber of the Massachusetts Institute of Technology. Zuber's team of expert scientists and engineers includes former NASA astronaut Sally Ride, who will lead the mission's public outreach efforts. A camera aboard each spacecraft will allow students and the public to interact with observations from the satellites. Each GRAIL spacecraft will carry the cameras to documents their views from lunar orbits.

Mission details:

• GRAIL, a NASA Discovery mission, was launched from Cape Canaveral on Sep 10, 2011. The Delta rocket reached Earth orbit at 1316 UTC and a deep space coast trajectory at 1419 UTC. The two GRAIL spacecraft were attached to the Delta rocket's second stage; GRAIL-A was deployed at 1428 UTC and GRAIL-B at 1437 UTC.
• The spacecraft will reach the Sun-Earth L1 point 1.5 million km from Earth and then fall back towards the Moon, reaching lunar orbit at New Year. GRAIL-A lunar insertion is scheduled for 0100 UTC on Jan 1, with GRAIL-B at 0200 UTC on Jan 2.
• The two GRAIL spacecraft are on their way to Sun-Earth L1; the Delta second stage is in a 0.88 x 1.05 AU x 0.01 deg heliocentric orbit with a period of around 347 days. (Oct 2011)
• The GRAIL-A and GRAIL-B spacecraft entered lunar orbit on Dec 31, 201 and Jan 1, 2012. The planned capture orbits were 88 x 8378 km x 87.2 deg for GRAIL-A, and 111 x 8359 km x 88.3 deg for GRAIL-B. According to spaceflightnow.com the actual orbit for GRAIL-A is 90 x 8362 km.
  The GRAIL probes will now manoeuvre close to each other to begin their gravity mapping mission.
• On Jan 17, 2012, NASA announced the names Ebb and Flow for the probes, following a competition in which school students suggested names.
• The two GRAIL spacecraft, Ebb and Flow, in a 25 x 86 km lunar orbit, completed their primary mission on May 29, 2012 and their science instruments were turned off until Aug 30, when they will begin a several-month extended mission in a 23-km altitude orbit.
• The two GRAIL spacecraft, completed their gravity mapping mission and impacted the lunar surface at 75.62N 26.63W at 2229 UTC on Dec 17, 2012. On Dec 6 their orbit was lowered to only 15 km above the surface for a final low-altitude data take. NASA is giving the impact region the unofficial (non-IAU) name of 'Sally Ride Impact Site'. The name appears to apply to the general region of the impact, which consists of the two impact points several km apart and any associated secondary debris. The impact velocity was 1.7 km/s.