Session
Weekend Session III: Science/Mission Payloads Research & Academia 1
Location
Utah State University, Logan, UT
Abstract
The Colorado Ultraviolet Transit Experiment (CUTE) is NASA's first 6U NASA Astrophysics CubeSat built by the Laboratory for Atmospheric and Space Physics (LASP). Its primary purpose is to observe the evolving atmospheres of short-period exoplanets in the near-ultraviolet. It was launched in September 2021 into a ~560 km, polar orbit with a 98.5° inclination. The spacecraft bus, featuring avionics and an attitude determination and control system (ADCS) with a single star tracker, was supplied by Blue Canyon Technologies (BCT). Since its launch, CUTE has experienced an unusually high frequency of ADCS-driven safe mode events, occurring up to three times per week. An investigation into the issue revealed the frequent safe mode events to be due to a timing issue of the Inertial Measurement Unit (IMU) information packets before being sent to the Guidance, Navigation and Control system (GNC). This issue is described as a "glitch" due to the sudden jump discontinuity in certain spacecraft telemetry data following an IMU timing issue. Telemetry analysis revealed significant discrepancies between commanded and reported attitude quaternions, casting doubt on the spacecraft's reported attitude and telemetry values during these glitch events. By conducting a thorough analysis of Sun sensor photodiode counts, battery cycles, spacecraft body rate, and magnetic field vectors, we concluded that the spacecraft's reported quaternions did not accurately reflect its actual orientation following the glitch events. The team utilized basic attitude determination methods, such as integrating the spacecraft's body rate, to further approximate its attitude around the glitches. This calculated attitude revealed that, at times, the glitch was causing the spacecraft's telescope to partially orient towards the Sun, likely leading to the degradation of the primary science instrument over time. This paper explores the pivotal role of ground-truth telemetry points in conjunction with simple attitude verification methods in identifying and understanding anomalies in satellite attitude and on-orbit behavior. This work is likely to assist other teams facing similar challenges and highlights the effectiveness of simple yet powerful spacecraft attitude determination methods.
Untangling Safe-Mode Anomalies on the CUTE CubeSat
Utah State University, Logan, UT
The Colorado Ultraviolet Transit Experiment (CUTE) is NASA's first 6U NASA Astrophysics CubeSat built by the Laboratory for Atmospheric and Space Physics (LASP). Its primary purpose is to observe the evolving atmospheres of short-period exoplanets in the near-ultraviolet. It was launched in September 2021 into a ~560 km, polar orbit with a 98.5° inclination. The spacecraft bus, featuring avionics and an attitude determination and control system (ADCS) with a single star tracker, was supplied by Blue Canyon Technologies (BCT). Since its launch, CUTE has experienced an unusually high frequency of ADCS-driven safe mode events, occurring up to three times per week. An investigation into the issue revealed the frequent safe mode events to be due to a timing issue of the Inertial Measurement Unit (IMU) information packets before being sent to the Guidance, Navigation and Control system (GNC). This issue is described as a "glitch" due to the sudden jump discontinuity in certain spacecraft telemetry data following an IMU timing issue. Telemetry analysis revealed significant discrepancies between commanded and reported attitude quaternions, casting doubt on the spacecraft's reported attitude and telemetry values during these glitch events. By conducting a thorough analysis of Sun sensor photodiode counts, battery cycles, spacecraft body rate, and magnetic field vectors, we concluded that the spacecraft's reported quaternions did not accurately reflect its actual orientation following the glitch events. The team utilized basic attitude determination methods, such as integrating the spacecraft's body rate, to further approximate its attitude around the glitches. This calculated attitude revealed that, at times, the glitch was causing the spacecraft's telescope to partially orient towards the Sun, likely leading to the degradation of the primary science instrument over time. This paper explores the pivotal role of ground-truth telemetry points in conjunction with simple attitude verification methods in identifying and understanding anomalies in satellite attitude and on-orbit behavior. This work is likely to assist other teams facing similar challenges and highlights the effectiveness of simple yet powerful spacecraft attitude determination methods.
