Analysis of the Advantages and Disadvantages of ASP CMOS Star Trackers

After half a century of development, the development direction of star trackers has been roughly divided into two directions: CCD and APS CMOS, each with its own advantages. Only by understanding the specific usage environment can we reasonably choose the application method of star trackers.

The application of CCD star sensors in the aerospace field has become increasingly mature, and their prospects are promising. However, the vast majority of high-precision star sensors that have reached the application level currently have relatively high quality, power consumption, volume, etc., making it difficult to directly apply them to the thriving micro/nano satellites. Therefore, many international research institutions and star sensor development units have also focused their main research efforts on new star sensors that are more suitable for the development of small satellites.

APS CMOS image sensor: small size, low power consumption, light weight, high integration, strong anti-interference ability, and flexible data readout method.

APS CMOS star sensors are different from CCD sensors in that their quantum efficiency is generally low. Therefore, it is necessary to increase the exposure time and minimize the processing time as much as possible to ensure the overall update rate. Generally speaking, in the field of star sensors, the overall attitude update rate is inversely proportional to the exposure time. The attitude update rate of a typical CCD star sensor is limited by the sum of the readout time and exposure time of the sensor pixels. Due to the use of a large array image sensor as a photosensitive detector, the readout time is longer, and the update rate is generally around 5Hz. The APSCMOS photodetector can achieve simultaneous readout and exposure, so the main factor affecting the update rate is exposure time.

The exposure time of a star sensor is directly related to the sensitivity of the photosensitive detector, as well as the human pupil diameter and transmittance of the lens. After adopting the fast all sky star map processing method and the fast all sky autonomous star map recognition algorithm, the initial capture time of the star sensor is greatly reduced, and the attitude output can be achieved within 1 second after power on, with a capture attitude capture time of less than 0.5 seconds.

With the emergence and maturity of new sensing and microelectronics technologies, as well as new optical systems, the design and application of new optical systems and the development and application of APS are the two most active hotspots in star tracker technology. Performance and demand complement each other, and with the improvement of performance and the reduction of price, the application field of star trackers is bound to expand day by day.