AcknowledgmentsWe wish to thank the Analysis Center of Life Science, Hiroshima University for the use of their facilities. This work was supported in part by Cooperative Link of Unique Science and Technology for Economy Revitalization (CLUSTER) from Hiroshima Prefectural Institute of Industrial Science and Technology, Japan, Innovation Plaza Hiroshima of JST (Japan Science and Technology Corporation), Takeda Science Foundation, Grant-in-Aid for Scientific Research and Program for Promotion of Basic and Applied Researches for Innovation in Bio-oriented Industry.Conflicts of InterestConflicts of InterestThe authors declare no conflict of interest.
As the highest accuracy attitude measurement device, star trackers are capable of providing arcsec level 3-axis attitude and are widely used in many spacecrafts.
A star tracker can be treated as a special electronic camera connected to a microcomputer. It can take star images of a part of the sky and identify these stars in the star image. Based on the position information of these identified stars, the attitude of spacecraft can be determined [1�C4].With the expansion of the application fields, especially on spacecrafts with the capability of rapid and large angle attitude maneuver control, star trackers must still work normally and steadily. Under these highly dynamic conditions, a crucial Drug_discovery problem arises: due to the large angular velocity of the spacecraft, the star-spots in the star image will move across many pixels during the exposure time and ultimately form obvious trails.
This will affect star detection sensitivity and star location accuracy seriously and result in low attitude accuracy and poor stability. This case can be ameliorated by adjusting the dynamic working parameters, especially the exposure time. Increasing the exposure time means more energy is gathered at each star-spot, which enhances high star detection sensitivity, but on the other hand, increasing the exposure time aggravates the movement of the star-spots and makes it more difficult to locate them. By contrast, reducing the exposure time alleviates the movement effect and reduces star location errors, but at the cost of an energy loss. Therefore, under highly dynamic conditions there exists an optimal exposure time and it is necessary to choose this proper exposure time for star trackers.As discussed above, under highly dynamic conditions the exposure time mainly affects two aspects of star trackers: star detection sensitivity and star location accuracy. The exposure time directly determines the total energy and length of each star-spot in the star image, and both of them together affect star detection sensitivity.