Testing of the Lunar Reconnaissance Orbiter Attitude Control System Re-Design Without a Gyro

Halverson, Julie ; Calhoun, Phil ; Hsu, Oscar ; Dongmo, Jean-Etienne ; Besser, Rebecca ; Ellis, Ben ; De Hart, Russell ; Tedla, Yohannes ; Rosney, Sean ; Snell, Scott T

关键词: LUNAR SPACECRAFT;    RECONNAISSANCE SPACECRAFT;    LUNAR RECONNAISSANCE ORBITER;    ATTITUDE CONTROL;    SATELLITE ATTITUDE CONTROL;    APPLICATIONS PROGRAMS (COMPUTERS);    GYROSCOPES;    STAR TRACKERS;   

RP-ID  :  GSFC-E-DAA-TN65164

学科分类：航空航天科学

美国|英语

来源: NASA Technical Reports Server

【 摘 要 】

The Lunar Reconnaissance Orbiter (LRO) was launched in 2009 and, with itsseven science instruments, has made numerous contributions to our understandingof the moon. LRO is in an elliptical, polar lunar orbit and nominally maintainsa nadir orientation. There are frequent slews off nadir to observe various sciencetargets. LRO attitude control system (ACS) has two star trackers and a gyro forattitude estimation in an extended Kalman filter (EKF) and four reaction wheelsused in a proportional-integral-derivative (PID) controller. LRO is equipped withthrusters for orbit adjustments and momentum management. In early 2018, thegyro was powered off following a fairly rapid decline in the laser intensity on theX axis. Without the gyro, the EKF has been disabled. Attitude is provided by asingle star tracker and a coarse rate estimate is computed by a back differencingof the star tracker quaternions. Slews have also been disabled. A new rate estimationapproach makes use of a complementary filter, combining the quaterniondifferentiated rates and the integrated PID limited control torque (with reactionwheel drag and feedforward torque removed). The filtered rate estimate replacesthe MIMU rate in the EKF, resulting in minimal flight software changes. The paperwill cover the preparation and testing of the new gyroless algorithm, both inground simulations and inflight.