Pattern recognition of star constellations for spacecraftapplications

A software system for a star imager for on-line satellite attitude determination is described. The system works with a single standard commercial CCD-camera with a high aperture lens and an onboard star catalogue. It is capable of both an initial course attitude determination without any prior knowledge of the satellite orientation and a high-accuracy attitude determination based on prediction and averaging of several identified star constellations. In the high accuracy mode the star imager aims at an accuracy better than 2 arc sec with a processing time of less than a few seconds. The star imager is developed for the Danish microsatellite Oersted     

Tracking of planetary terrains

The AFAST project (Autonomously Feature And Star Tracking) at the Jet Propulsion Laboratory, California Institute of Technology is engaged in the attitude determination and tracking of the CCD camera pointing direction on future spacecraft missions. Ground based attitude determination is time-consuming and costly. This implies that the attitude determination and the tracking of the pointing direction must be autonomous and rely exclusively on the CCD sensor. Also, distant observations call for autonomy, as relay times to Earth make ground control infeasible. This paper presents a strategy to track the pointing direction on planetary terrains. The strategy utilizes multiple closed contours in a planetary image. It accomplishes tracking by recognizing a constellation of the closed contours. The strategy is adaptable to both spacecraft and missile applications     

Accuracy performance of star trackers - a tutorial

An autonomous star tracker is an avionics instrument used to provide the absolute 3-axis attitude of a spacecraft utilizing star observations. It consists of an electronic camera and associated processing electronics. The processor has the capability to perform star identification utilizing an internal star catalog stored in firmware and to calculate the attitude quaternion autonomously. Relevant parameters and characteristics of an autonomous star tracker are discussed in detail     

Star trackers for attitude determination

One problem comes to all spacecrafts using vector information. That is the problem of determining the attitude. This paper describes how the area of attitude determination instruments has evolved from simple pointing devices into the latest technology, which determines the attitude by utilizing a CCD camera and a powerful microcomputer. The instruments are called star trackers and they are capable of determining the attitude with an accuracy better than 1 arcsecond. The concept of the star tracker is explained. The obtainable accuracy is calculated, the numbers of stars to be included in the star catalogue are discussed and the acquisition of the initial attitude is explained. Finally the commercial market for star trackers is discussed     

Pattern recognition of star constellations for spacecraftapplications

A software system for a star imager for online satellite attitude determination is described. The system works with a single standard commercial CCD camera with a high aperture lens and an onboard star catalog. It is capable of both an initial coarse attitude determination without any prior knowledge of the satellite orientation and a high-accuracy attitude determination based on prediction and averaging of several identified star constellations. In the high-accuracy mode the star image aims at an accuracy better than 2 arc sec with a processing time of less than a few seconds. The star imager has been developed for the Danish Oersted satellite     

Operation and performance of a second generation, solid state, star tracker, the ASC

The Advanced Stellar Compass (ASC) is a second generation star tracker, consisting of a CCD camera and its associated microcomputer. The ASC operates by matching the star images acquired by the camera with its internal star catalogs. An initial attitude acquisition (solving the lost in space problem) is performed, and successively, the attitude of the camera is calculated in celestial coordinates by averaging the position of a large number of star observations for each image. Key parameters of the ASC for the Ørsted satellite and Astrid II satellite versions are: mass as low as 900 g, power consumption as low as 5.5W, relative attitude angle errors less than 1.4 arcseconds in declination, and 13 arcseconds in roll, RMS, as measured at the Mauna Kea, HI observatories of the University of Hawaii in June 1996.