## 3 On Orbit Operations and Anomaly Analysis
### Critical Anomaly-Loss of Communication  
Contact was lost with IDEASSat during the second pass over the NCU ground station at 13:34 UTC on 15 February, following a successful overpass at 01:40 UTC earlier that day. Despite the high elevation angle of the second overpass, no beacon signals were received by the NCU ground station. The last contact with a SatNOGS ground station was with a ground station in Canada at 04:09 UTC that day [34], after which no further signals were received for a period of close to 1.5 months. Ground stations that were previously able to receive IDEASSat beacon signals were unable to do so during this time, indicating that the fault was on the spacecraft end. Efforts to transmit the system reset command from the NCU ground station were unsuccessful in producing a response from the spacecraft. During this time, geomagnetic and solar activity were quiet (Figure 26), although the spacecraft did pass through the auroral ovals and South Atlantic Anomaly (SAA) multiple times per day. The spacecraft began beaconing again on 2 April 2021, which was detected by the SatNOGS network [35], as well as the NCU ground station. Commands were successfully uplinked to the spacecraft from the NCU ground station the same day resetting the beacon packet format to life, as well as commanding the replay of flight data saved to the CDH SD cards over UHF. The spacecraft remained active for a few days, with the final transmission received on 4 April 2021, after which there was no further contact. The retrieved flight data yielded a number of clues that allowed for the cause of the communications blackout to be identified to a high level of confidence:  
* FSW was not operating and logging data during the blackout, indicating that the spacecraft was likely powered off for the 1.5 month interval. As observed previously during the impedance mismatch anomaly on the ground, FSW would continue to function even in the event of a transceiver anomaly. * The subsystem reset counters in flight data were reset, indicating that a power cycle and FSW reboot had taken place. However, there was no record of commanded reboots of the spacecraft by FSW, indicating that the power cycle and reboot were un-commanded. Figure 25: ADCS reboot count. 0 corresponds to invalid attitudes, 1 corresponds to valid attitudes. * The 1.5-month blackout time, as opposed to a commanded or watchdog reboot, which would be completed within seconds. * The first beacon packet received following the blackout showed an SOC of 85%, which was much lower than that observed during the first 22 days of operation. This suggests the possibility of reboot through full or deep battery discharge. * The second blackout after three days of operation. Following the above findings, an extensive review was performed of the IDEASat EPS to identify single failure points that could result in a systemwide power down that would still be recoverable after an extended period of time. The latter factor ruled out the components in the 3.3 V power bus used by the CDH, as radiation failures in the power MOSFETs used as DC/DC converters and power switches would be nonrecoverable single event burnouts (SEBs) and single event gate ruptures (SEGRs) [36]. Additionally, the aforementioned components had been subject to testing on the ground, were derated according to NASA EEE standards [37], had previous flight heritage from the MinXSS mission [11], and had shown no anomalies in received flight data, making spontaneous on-orbit failure much less likely. The likely cause of the extended power down and communications blackout was identified to be a single gate CMOS Schmitt trigger inverter used in the EPS reset circuit. The purpose of the reset circuit was to allow CDH to power cycle the spacecraft in the event there was an anomaly that could not be resolved by a soft reset, such as watchdog timeout or repeated subsystem resets. Figure 27 is a schematic of the IDEASat EPS reset circuit.