Session
Session V: Orbital Debris, SSA & STM
Location
Utah State University, Logan, UT
Abstract
Compact Total Irradiance Monitor (CTIM) is a 6U cubesat that deployed in July of 2022 to continue forty years of continuous total solar irradiance measurements across multiple missions. In November of 2023, CTIM’s orbit began showing signs of accelerated decay in the form of inconsistent pass start times and noisier S-band downlinks, despite intensive orbital decay analysis. This unexpected decay, along with CTIM’s lack of GPS, presented the Smallsat Operations (SMOPS) team at the University of Colorado’s Laboratory for Atmospheric and Space Physics (CU-LASP) with a big challenge: rapidly revise CONOPs, all while remaining at or under a 1.5k weekly hiatus budget. This also presented big opportunities: it provided valuable experience the team could leverage for end-of-life operations for future missions, and a chance to give a successful mission a heartfelt farewell. Once CTIM’s decay was confirmed, the SMOPS team’s main goal was to perform end-of-life calibrations and downlink remaining scientific data onboard. The approaching deadline of re-entry allowed operators to prioritize short term science over any potential hardware degradation. Due to CTIM’s highly unpredictable orbital decay, Celestrak’s daily official TLE publications became ineffective within hours. This prompted ground station operations (GSOPS) engineers to generate in-house Two Line Element (TLE) sets in real-time based on the doppler shifted downlink signals, which were cross-verified with both the official Celestrak TLE source as well as the SatNOGS amateur radio community’s observations. This in turn necessitated a shift in the cadence of the ground station contact schedule creation process from from once a week to once every two days, demonstrating the highly flexible and reactive paradigm of the GSOPS team and automation software. As atmospheric drag continued to increase on CTIM, the team observed insurmountable momentum build-up on the spacecraft as the torque rods struggled to overcome the increased effects of drag, leading to attitude excursions, safe mode transitions, and even undervoltage events. Finally, to celebrate years of development and nearly 18 months of successful operations, the SMOPS team “sung” a farewell song to CTIM, which the satellite then “echoed” back to the rest of the world (via uplink and downlink commands). This “song”, transmitted over the amateur radio waves, was captured and decoded by the enthusiastic SatNOGS community, demonstrating the effectiveness of public outreach and collaboration on small satellites like CTIM. The final weeks of a mission are challenging, but they also provide numerous opportunities: to implement new processes that ensure mission success, to discover new ways of assessing rapid orbital decay, and for a dedicated team to give a tiny mission with a big legacy a proper sendoff.
SmallSat End-of-Life Operations: Opportunities and Challenges
Utah State University, Logan, UT
Compact Total Irradiance Monitor (CTIM) is a 6U cubesat that deployed in July of 2022 to continue forty years of continuous total solar irradiance measurements across multiple missions. In November of 2023, CTIM’s orbit began showing signs of accelerated decay in the form of inconsistent pass start times and noisier S-band downlinks, despite intensive orbital decay analysis. This unexpected decay, along with CTIM’s lack of GPS, presented the Smallsat Operations (SMOPS) team at the University of Colorado’s Laboratory for Atmospheric and Space Physics (CU-LASP) with a big challenge: rapidly revise CONOPs, all while remaining at or under a 1.5k weekly hiatus budget. This also presented big opportunities: it provided valuable experience the team could leverage for end-of-life operations for future missions, and a chance to give a successful mission a heartfelt farewell. Once CTIM’s decay was confirmed, the SMOPS team’s main goal was to perform end-of-life calibrations and downlink remaining scientific data onboard. The approaching deadline of re-entry allowed operators to prioritize short term science over any potential hardware degradation. Due to CTIM’s highly unpredictable orbital decay, Celestrak’s daily official TLE publications became ineffective within hours. This prompted ground station operations (GSOPS) engineers to generate in-house Two Line Element (TLE) sets in real-time based on the doppler shifted downlink signals, which were cross-verified with both the official Celestrak TLE source as well as the SatNOGS amateur radio community’s observations. This in turn necessitated a shift in the cadence of the ground station contact schedule creation process from from once a week to once every two days, demonstrating the highly flexible and reactive paradigm of the GSOPS team and automation software. As atmospheric drag continued to increase on CTIM, the team observed insurmountable momentum build-up on the spacecraft as the torque rods struggled to overcome the increased effects of drag, leading to attitude excursions, safe mode transitions, and even undervoltage events. Finally, to celebrate years of development and nearly 18 months of successful operations, the SMOPS team “sung” a farewell song to CTIM, which the satellite then “echoed” back to the rest of the world (via uplink and downlink commands). This “song”, transmitted over the amateur radio waves, was captured and decoded by the enthusiastic SatNOGS community, demonstrating the effectiveness of public outreach and collaboration on small satellites like CTIM. The final weeks of a mission are challenging, but they also provide numerous opportunities: to implement new processes that ensure mission success, to discover new ways of assessing rapid orbital decay, and for a dedicated team to give a tiny mission with a big legacy a proper sendoff.
