Two Colorado-built spacecraft will map the moon’s interior from crust to core, with the unprecedented detail expected to greatly advance understanding of its evolution.
Slated for launch Thursday, NASA’s $469 million Gravity Recovery and Interior Laboratory — GRAIL — mission will study the moon for nine months.
The two nearly identical spacecraft will take 3½ months to reach the moon.
The leisurely path gives time for checking out electronics, dissipating gases from instruments and using less fuel for insertion into lunar orbit, said Stuart Spath, GRAIL chief engineer for spacecraft-builder Lockheed Martin Space Systems.
While “simple in concept,” execution of the mission is extremely challenging, said John Henk, Lockheed’s GRAIL program manager.
The two spacecraft will orbit the moon about 34 miles above its cratered surface. Never more than 130 miles apart, the spacecraft will send radio signals to each other.
Measurements of that distance will be made to within a micron — the width of a human hair.
Mountains, craters and subsurface masses will strengthen or lessen gravity, causing the distance between the two washing machine- size spacecraft to widen or narrow.
Scientists will use the information to create a high-resolution map of the moon’s gravitational field, which is called the lumpiest in the solar system.
“GRAIL will unlock lunar mysteries and help us understand how the moon, Earth and other rocky planets evolved as well,” said Maria Zuber, GRAIL principal investigator from the Massachusetts Institute of Technology.
Each spacecraft is equipped with five cameras. Middle-school students will be able to ask for the cameras to photograph specific areas. The photos will be posted on the Internet.
Taking the spacecraft aloft from Cape Canaveral Air Station in Florida will be a Delta II rocket provided by United Launch Alliance of Centennial.
At Lockheed Martin’s Waterton Canyon facility, many of the 140 employees who worked on GRAIL at its peak and their families will gather to watch the early-morning launch.
If severe weather interferes with Thursday’s launch, it can’t be rescheduled until Oct. 19.
Ann Schrader: 303-954-1967 or aschrader@denverpost.com
