StarBaseOC: The Grails A amp B will arrive and enter Moon39s orbit on ...

SPACE. www.SPACE.com Two For the Moon: the GRAIL Mission The Gravity Recovery and Interior Laboratory (GRAIL) mission consists of two identical spacecraft, sent to orbit the moon at 30 miles (50 km) altitude. Rather than observe the surface of the moon directly, the GRAIL satellites constantly monitor a microwave beam transmitted between them. The microwaves are precisely measured to determine the changing distance between the spacecraft as they pass through the moon's gravity field. SOLAR PANELS MICROWAVE EMITTER Earth's Gravity Field Anomales (miligals) 50 -40 30 -20 -10 0 10 20 30 40 50 ANTENNAS A similar set of probes called GRACE (Gravity Recovery and Climate Experiment) Each satellite weighs about 445 pounds (202 kg). After spending three to four months traveling to the moon and an additional three months studying it, the probes has already mapped the Earth's lumpy gravity field. will be crashed into the moon's surface. SOURCES: NASA, MASSACHUSETTS INSTITUTE OF TECHNOLOGY, LOCKHEED MARTIN KARL TATE / SPACE.com