9 July 2019: Lightsail 2 Mission Manager's Log
During prime shift on July 8, the flight team updated an attitude determination and control subsystem (ADCS) configuration table, to provide a positive current to the Z-axis torque rod during Z-axis alignment (ADCS Mode 1). This will result in the +Z axis aligning with the Earth’s magnetic field when in Mode 1.
The +Y magnetometer was disabled, leaving the +X magnetometer as the sole magnetometer used for attitude determination. The total angular rate threshold for ADCS Mode 2 (solar sailing mode) was increased to 8 deg/sec. If the root-sum-squared of the angular rates exceeds this threshold while in Mode 2, the ADCS system will autonomously change to detumble to reduce angular rates.
A command was sent to re-enable battery charging, producing the desired result.
The flight team determined that the x- and y- torque rods are not being properly activated in response to commands from ADCS. This was traced to a magnetic torquer initialization error in the spacecraft flight software. The problem will require a software patch to fix. It was also determined that the attitude determination algorithm was not correctly incorporating the sun sensor measurements. Additionally, the sun sensors report invalid values for the Sun direction when the Sun is not in the sensor field of view. These invalid measurements are not being properly filtered from the attitude determination process.
Based upon these new findings, project management has decided to delay solar sail deployment to no earlier than July 21. This will allow the team to methodically work through the ADCS issues, perform the necessary flight software updates, and compare flight system performance with simulations to ensure proper performance.
The spacecraft remains healthy. LightSail 2 has been identified by the 18th Space Control Squadron, and has been given the identifier 44420.