Workers at Vandenberg AFB help prepare NASA's Terra spacecraft for encapsulation in the rocket faring left.

Workers at Vandenberg AFB, Calif., help prepare NASA's Terra spacecraft (right) for encapsulation in the rocket faring (left). Terra is expected to be launched aboard a Lockheed Martin Atlas IIAS rocket Dec. 16 from Space Launch Complex 3 East at Vandenberg. Terra comprises five state-of-the-art sets of instruments that will collect data for continuous, long-term records of the state of Earth's land, oceans and atmosphere. Together with data from other satellite systems launched by NASA and other countries, Terra will inaugurate a new self-consistent data record that will be gathered over the next 15 years. From an altitude of 438 miles, Terra will circle the Earth 16 times a day from pole to pole (98 degree inclination), crossing the equator at 10:30 a.m. The five Terra instruments will operate by measuring sunlight reflected by the Earth and heat emitted by the Earth