An Online Tilt Estimation and Compensation Algorithm for a Small Satellite Camera
In the case of a satellite camera designed to execute an Earth observation mission, even after a pre-launch precision alignment process has been carried out, misalignment will occur due to external factors during the launch and in the operating environment. In particular, for high-resolution satellite cameras, which require submicron accuracy for alignment between optical components, misalignment is a major cause of image quality degradation. To compensate for this, most high-resolution satellite cameras undergo a precise realignment process called refocusing before and during the operation process. However, conventional Earth observation satellites only execute refocusing upon de-space. Thus, in this paper, an online tilt estimation and compensation algorithm that can be utilized after de-space correction is executed. Although the sensitivity of the optical performance degradation due to the misalignment is highest in de-space, the MTF can be additionally increased by correcting tilt after refocusing. The algorithm proposed in this research can be used to estimate the amount of tilt that occurs by taking star images, and it can also be used to carry out automatic tilt corrections by employing a compensation mechanism that gives angular motion to the secondary mirror. Crucially, this algorithm is developed using an online processing system so that it can operate without communication with the ground.
KeywordsTilt algorithm Online algorithm Small satellite camera Refocusing
This work was supported by the Global Surveillance Research Center (GSRC) program funded by the Defense Acquisition Program Administration (DAPA) and Agency for Defense Development (ADD).
- 3.http://www.telescope-optics.net. Accessed 21 May 2017
- 6.http://www.edmundoptics.co.kr. Accessed 21 May 2017
- 8.Raval A (2015) A detail review of optical misalignment and corrected by refocusing mechanism. Int J Sci Res Dev 3(4):2321-0613Google Scholar
- 9.Verhoeff P, Van Mierlo HA, Braam BC, Hopman JC, van Werhoven WP, Le Kluse M (1998) Development of an in-orbit refocusing mechanism for the Meteosat second-generation weather satellites. In: SPIE’s international symposium on optical science, engineering, and instrumentation. International Society for Optics and Photonics, pp 92–103Google Scholar
- 10.Yang HS, Lee YW, Kim ED, Choi YW, Rashed AAA (2004) Alignment methods for Cassegrain and RC telescope with wide field of view. Proc SPIE 5528:335Google Scholar
- 12.Lee J, Kim Y, Lee E, Yoo S, Kim E, Choi Y, Park D (2000) Optical design of high-resolution optical camera for small satellite. Korean J Opt Photonics 11(1):6–12Google Scholar
- 14.Gehrz RD, Romana EA, Hoffmann WF, Schwenker JP, Mentzell JE, Hora JL, Eisenhardt PR, Brandl BR, Armus L, Stapelfeldt KR, Hines DC, Mainzer AK, Young ET, Elliott DG (2004) The state of the focus and image quality of the Spitzer space telescope as measured in orbit. Proc SPIE 5487:166–176CrossRefGoogle Scholar