TERRA ASCENT PLANNING TO MEET LANDSAT-7 PHASING REQUIREMENTS

NASA’ s Earth Observing System (EOS) Terra spacecraft, the flagship of NASA’ s Earth Science Enterprise, was launched on December 18, 1999. Terra’ s mission orbit is a Sun-synchronous frozen orbit with a 16-day repeating groundtrack. The groundtrack is controlled with respect to the World Reference System (WRS). Terra is charged not only with meeting its own orbit requirements, but also with flying on the same WRS path as the Landsat-7 spacecraft to perform coincident scene investigation. This paper describes the trajectory planning efforts of the NASA Goddard Space Flight Center Flight Dynamics team to place Terra in its mission orbit. Pre-mission analysis is discussed, as well as changes to the baseline plan made after launch to accommodate a spacecraft anomaly, which required use of limited maneuver durations to achieve mission orbit.