NASA Grail Twin Probes Final Flight Path

The NASA GRAIL twin probes' final flight path into their crash site, imaged with data from NASA's Lunar Reconnaissance Orbiter (LRO). 

Credit: NASA/JPL-Caltech/GSFC/ASU

Two space probes that successfully mapped variations in the Moon's gravity field have been deliberately crashed into the lunar surface in a dramatic end to their mission.

They are just the latest in a string of probes to leave their shattered remains on the Moon. The impacts of the GRAIL probes, Ebb and Flow, into a 2.4 km high (1.5 miles) mountain near the lunar north pole, was deliberate and planned in great detail.

NASA decided to destroy the craft in a controlled manoeuvre rather than take the risk, however tiny, that they might later hit one of the historic landing sites of Apollo and unmanned probes.

The two spacecraft, each the size of a washing machine, fired their thrusters one last time to burn up the last of their fuel. They dropped into a lower orbit and hit the peak's southern face, near a crater called Goldschmidt, at 6,050 kph (3,760 mph).

NASA Grail Mission: Twin Probes' Lunar Crash

Two NASA moon probes are slated to slam into the rim of a lunar crater today (Dec. 17), and the space agency will give viewers a behind-the-scenes look at the dramatic action.

The twin Grail spacecraft, known as Ebb and Flow, will crash intentionally near the moon's north pole at 5:28 p.m. EST (2228 GMT) today, bringing their gravity-mapping mission to a spectacular close.

The event will be broadcast on NASA TV and streamed live on the agency's website, beginning at 5 p.m. EST (2200 GMT).

The coverage should last about 35 minutes and will include interviews with Grail team members. The impact site will be in shadow at the time of the crash, so no video of Ebb and Flow's violent demise is expected, NASA officials said.

This graphic highlights locations on the moon NASA considers "lunar heritage sites" and the path NASA's Gravity Recovery and Interior Laboratory spacecraft will take on their final flight. Image released Dec. 13, 2012.

CREDIT: NASA/JPL-Caltech

You can follow along at NASA TV's website www.nasa.gov