FROM THE BRIGHT SUN TO THE FAINTEST STARS: THE EUROPEAN ROUTE TO STATE OF THE ART MINIATURIZED ATTITUDE SENSORS

摘要

Following the recent trend for miniaturization and the latest innovation steps in the CMOS technology, the integration on the same chip of a detector pixel array as well as the driving & processing logic has become mature for applications in the space field. In the star tracker application a real optics is needed to image the stars on the detector, but the relevant telescope cannot be integrated directly on the chip. However, the processing logic can be embedded on the silicon and, with a suitable optics, a miniaturized star sensor optical head can be realized. The design of a suitable miniaturized optics is therefore necessary to perform a step forward in the sensor miniaturization. A contract was then awarded to SELEX Galileo by ESA to carry out a preliminary study on a miniaturized optics suitable to be used for a future STAR TRACKER ON CHIP (STRoC). This paper describes in detail the design of such optics for a star tracker application, developed keeping in mind the need for small dimensions and low recurring cost, mandatory for such kind of application to gain attractiveness on a wide range of applications and market opportunities, not only limited to micro and nano satellites. The analyses show encouraging results both in terms of optics performance and stability of the assembly in temperature given the proposed radiative thermal design. A prototype will be manufactured early in 2012 and tested on an optical test bench using an image detector used for star tracker products. The next step in the miniaturized sensor road map is the design of a dedicated chip and supporting off chip electronics. The latter will take advantage of the work realized for the development of a miniaturized Sun Sensor on Chip by SELEX Galileo, like '4T' pixel design, on chip signal processing, thresholding and clustering, algorithms for cluster identification and unwanted objects rejection, feasibility of a true on chip DC/DC converter.