Star Tracker Bright Spots Hourly, 12/01/2022 - 01/15/2023

For this experiment, data were collected from December 1, 2022 to January 15, 2023 across all Starlink satellites that were in the main operational shell of approximately 53 deg. inclination and 550 km altitude. In total, data were collected from the two CMOS Image Sensors (CIS) onboard 2,914 Starlink satellites for a total of 5,828 CIS. Data were filtered to exclude satellites with CIS faults causing out-of-family measurements during the time period.  An algorithm to detect bright spots was developed for the CIS and data were stored on-board each respective Starlink satellite. This algorithm is similar to others previously demonstrated using clustering of pixels to detect single-event effects and ionizing radiation impacts to CIS. On Starlink, an algorithm was written to estimate the number of transient bright spots based on frame subtraction. The algorithm estimated the number of bright spots per second, and this value was collected once a minute from all possible CIS across Starlink satellites.  Earth-centered earth-fixed (ECEF) position data were also captured for each satellite and able to be converted to latitude, longitude, and altitude (LLA) for ease of plotting data onto two dimensional maps. Data were filtered to exclude several factors: temporary CIS faults, presence of stray light sources such as the sun and moon in the image, measurements taken in vehicle maneuver states, and measurements taken outside the operational altitude. In order to filter out such cases, a simple heuristic was derived such that the error between the two sensors on a satellite was less than 100% (relative to the lowest sensor).To visualize behavior across the whole constellation, data were converted to standard deviations from the mean. Overall, the observations from CMOS image sensors indicate they can be utilized to identify periods and locations of increased ionizing radiation. On-orbit data show that the imager sensor registers higher rates of bright spots when passing over the South Atlantic Anomaly. Five minutes of data from the constellation is sufficient to outline the shape of the SAA enabling studies of the LEO environment on much shorter time scales than before. Additionally, it is shown that even with periods as short as a day, high spatial resolution can be achieved.