Thomas Chrien, Millennium Space Systems, A Boeing Company; Richard Pepe, Millennium Space Systems, A Boeing Company
Keywords: Dark offset correction, Low cost Star Trackers, Resident space object detection performance, Data Mining, Synthetic dark signal
Abstract:
Optical Cameras used for space situational awareness missions must consider the performance limiting impacts of dark current. Dark current comes from thermally excited defects localized in detector elements. It adds to photocurrent to increase the reported signal from each detector element. If not removed, dark signal will increase spatial noise in the image, and impede the ability to reduce noise by the averaging together multiple frames. There are several strategies for eliminating the negative impact of dark current, but each approach comes with regrets. Very high-quality detector material may be used with low-defect densities, however this drives the cost of the detector arrays. The detector may be cryogenically cooled to reduce the dark current rate, but this requires the addition of a cooling device and a means to control the temperature. Dark current offset correction calibrations typically require adding hardware such as a shutter, and during dark calibration collection, the camera is not available for the SSA mission.
We have developed a new technique that estimates the dark signal from a detector array over a range of temperatures from routine SSA image data. We form a synthetic dark correction term from this data that does not require a dark field measurement. The technique is significant in that it enables the use of lower cost SSA cameras, without impacting the sensor availability to perform dark calibrations.
In this presentation, we will describe the method, including how we sample the dark current data over time and temperature variations, and how the synthetic corrections are applied. We also evaluate the performance of these corrections.
Date of Conference: September 27-20, 2022
Track: Optical Systems & Instrumentation