Since joining the A-Train in May 2006, CloudSat actively maintained its orbit and flew in tight formation with CALIPSO. This required CloudSat to perform orbit maintenance burns approximately every two to three weeks and to also perform larger inclination burns approximately once a year in conjunction with the other vehicles in the A-Train. On

th April 17 of 2011 CloudSat experienced a severe battery anomaly which caused the vehicle to fault into a passive but power positive spin, and it could no longer maintain itself within its control box. Over the next several months, the team diagnosed the issue with the spacecraft battery, and developed a new method of operations which involved hibernating during eclipse, but allowed the vehicle to collect science data for 55 minutes during the sunlit portion of the orbit. By November 2011 the vehicle was returned to operational status, and the team then began working on a methodology to return the vehicle to its slot within the A-Train. After a lengthy series of burns, the vehicle rejoined the A-Train in May 2012. I Prior to the anomaly, CloudSat had sufficient battery capacity to operate normally in eclipse and, for the most part, burns were performed in eclipse to simplify burn planning by eliminating instrument and star tracker sun constraints. The lack of sun constraints also made it relatively easy to avoid Moon and Earth interference. After the anomaly occurred, the battery could not support the loads required to conduct burns which meant all the burns now had to be performed while the vehicle is in the sun. In addition, the battery was so weak that it could not be relied on to provide any power at all during burns which imposed many more constraints on the maneuvers to the burn attitude and on the orientation of the spacecraft during the burn. The new limitation included keeping the solar arrays pointed at the sun at all times and, in order for the new safe modes to work properly, it was necessary to keep the momentum axis pointed within 90 degrees of the sun. Due to orbital conditions, the CloudSat team was under a tight time constraint to develop a maneuver and burn strategy that dealt with these new constraints. The initial method selected resulted in the trackers being removed from the attitude solution during the maneuver to the burn attitude because they were blinded by the Earth. The potential unavailability of trackers was a cause for concern because the only available backup method for attitude determination relied on coarse sun sensors and magnetometers, which are significantly less accurate and if any issue occurred