14 July 2019: Lightsail 2 Mission Manager's Log
The LightSail 2 spacecraft was allowed to perform a hard reboot based upon its long-duration watchdog timer on July 14. During the July 14 prime shift, the flight team commanded the spacecraft into ADCS Mode 1, Z-axis alignment. Proper torque rod commanding was observed, and +X magnetometer readings showed that the measured magnetic field was within 20 deg of the spacecraft’s Z-axis.
The ADCS mode was then changed to Mode 2, solar sailing mode, in order to demonstrate the functionality of the attitude actuators. In Mode 2, the momentum wheel is used to rotate the spacecraft about the +Y axis, while the torque rods are used to provide supplemental torques. LightSail 2 successfully transitioned into Mode 2, and the momentum wheel was seen to spin up. The Mode 2 test duration was 20 minutes. Stored telemetry data was downlinked covering the test duration, and is currently being analyzed. The wheel torques commanded by the ADCS algorithm, and the actual wheel torques implemented, are shown below. It is noted that in there is significant chatter in the commanded torque, and the wheel is not very responsive in keeping up with the commanded torque. Additional analysis is being done on the ADCS algorithm to evaluate the behavior.