Twin spacecraft are undergoing final tests at Lockheed Martin’s Waterton Canyon facility for an extremely precise mission that will map the moon from crust to core.
Scheduled for shipment May 20 to Cape Canaveral, Fla., the nearly identical probes will work together to measure tiny variations in the moon’s gravitational field.
The aim of NASA’s $469 million mission called GRAIL — which stands for Gravity Recovery and Interior Laboratory — is to answer puzzling questions about the moon.
More than 140 Lockheed Martin employees worked on the GRAIL orbiters at the project’s peak, with hundreds more involved in the planning, design and construction. Once GRAIL is in its science phase, the two spacecraft — labeled A and B — will be flown from Lockheed’s mission-support area.
GRAIL “is simple in concept,” said John Henk, Lockheed’s GRAIL program manager, and draws on technology developed for previous missions. The execution is decidedly challenging.
From about 34 miles above the moon’s cratered surface, the two spacecraft will spend three months in polar orbit — never farther apart than 130 miles.
Both spacecraft — each about the size of a washer-dryer combo — carry Ka-band microwave-ranging instruments that will send signals between them, what Henk calls “a fancy telecom system.”
The twins won’t scan the moon but instead will use the microwave system to measure the distance between them to within a micron — the width of a human hair.
The blips and bumps will reveal information about such issues as the moon’s thermal evolution and its well-known but poorly understood gravitational unevenness, details that can be applied to the formation of other rocky planets and for maps of landing sites and safe vehicular routes.
The precise work means anything that can affect the distance between the spacecraft — such as temperature variations — must be known, predicted or eliminated, said Stuart Spath, Lockheed’s GRAIL chief engineer.
Launch is scheduled for Sept. 8, with the two hoisted aloft by a Delta II rocket from Centennial-based United Launch Alliance.
And then GRAIL A and B will take their time getting to the moon. Instead of traveling the 238,000 miles between the moon and Earth in an Apollo program-style beeline in three days, the GRAIL spacecraft will take a leisurely 3 1/2-month roundabout route.
Spath said the long route is intended so electronics can be checked out, gases can be dissipated and less fuel can be used to enter orbit Jan. 1.
GRAIL will wrap up work next May. Plans call for the spacecraft to crash on the moon’s surface.
Ann Schrader: 303-954-1967 or aschrader@denverpost.com
