CloudSat's A-Train Exit and the Formation of the C-Train: An Orbital Dynamics Perspective

NASA's CloudS at mission was launched in 2006 and flew in formation with other earth-observing satellites in NASA's Afternoon Constellation (the “A-Train”)for approximately 12 years. In February 2018, a series of reaction wheel anomalies forced CloudSat to exit the A-Train, but in October 2018, CloudSat established a new formation at a lower altitude with its previous formation-flying partner, the French CALIPSO satellite. This paper outlines the orbital dynamics considerations of the A-Train exit, and the process required to establish the new “C-Train,” which was especially challenging given the constraints on CloudSat operations. Despite battery issues that severely limit CloudSat's allowable maneuver execution windows, CloudSat was able to exit the A-Train safely, re-shape its orbit at a new lower altitude, and work with the CALIPSO team to establish a new formation for coincident science measurements.