Aspheres for determining the position of stars
Reference project
Star tracking with aspheric lenses and an optical design from asphericon
Satellites are essential for observing earth, monitoring the climate and navigation. An important success factor for such projects is autonomous positioning of satellites. Together with Terma A/S, a leading provider in the development of position sensors, asphericon was involved in developing the optical system for the star tracker of a satellite. Thanks to its high-quality coating, it can withstand challenging conditions in space, while meeting demanding dimensional requirements and delivering the most accurate results.
Project details
Satellite technologies are indispensable in observing the earth and climate and in navigation. An important factor for measurements with satellites is completely autonomous positioning with the highest accuracy. One of the leading companies in the development of position sensors is Terma A/S. In recent years, the company has succeeded in developing very compact star trackers - autonomous digital cameras with high accuracy that determine the orientation of a satellite in a matter of seconds using star constellation detection. In order to meet the demanding dimensional requirements of a star tracker, a very compact design of all components is required. In the joint project, asphericon’s role was to optimize the optical system as the core. The aim was to make optimal use of the available space by using as few lenses as possible but with excellent optical quality. In addition, the optics had to meet the high requirements for thermal stability without affecting the measurement accuracy.
Parameters
Fig. 1 One of six satellites | © U.S. Air Force
- Six satellites on a temporary circular orbit 720 km above the ground
- Star catalog with more than 5,000 star directions
- Determination of the flight position by tracking cataloged stars at a rate of up to 10 Hz and an accuracy of one arc second (1/3,600 of a degree)
Objectives
Fig. 2 Components of the star tracker | © Terma A/S
- Precise positioning of satellites
- Increasing the reliability and significance of earth observations by satellites on meteorological missions
Optics for Terma A/S at a glance:
- Optical design: ultra-compact system of aspheric and spherical components
- Material: radiation-resistant glass with high-end form tolerances (≤ 0.5 fr), roughness (≤ 0.002 µm) and imperfection tolerances
- Coating: super broadband AR coating (ARSBB 480 - 850nm) to ensure thermal stability
