초록 ▼

A method for determining the attitude of a spacecraft (1) by observing stars (2) within a starfield (3). A detector (13), camera electronics (14), and computer (15) located on board the spacecraft (1) are used to generate a set of star match groups by matching pairs of stars observed by the detector

A method for determining the attitude of a spacecraft (1) by observing stars (2) within a starfield (3). A detector (13), camera electronics (14), and computer (15) located on board the spacecraft (1) are used to generate a set of star match groups by matching pairs of stars observed by the detector (13) with pairs of guide stars from a stored database (18) of guide stars. Match groups having small numbers of stars are eliminated. Non-eliminated match groups are validated. Redundant match groups are eliminated. A match group having the largest number of stars is selected. Finally, the attitude of the spacecraft (1) is derived from positions of guide stars within the selected match group. The guide star database (18) can be broken into an acquisition guide star database (8) and a supplementary guide star database (9). The field of view (20) of detector (13) can be broken into a grid of pixels overlaid by a grid of superpixels (21). The guide star pairs are preferably presorted in order of increasing angular separation. An identification matrix (IDGRP) can be used to speed the star identification process.

대표청구항 ▼

[ What is claimed is:] [1.] A method for determining the attitude of a spacecraft by observing stars, the method comprising the steps of:at a first time, observing a set of stars within a preselected field of view by a camera on board the spacecraft to obtain a first set of observations;matching sai

[ What is claimed is:] [1.] A method for determining the attitude of a spacecraft by observing stars, the method comprising the steps of:at a first time, observing a set of stars within a preselected field of view by a camera on board the spacecraft to obtain a first set of observations;matching said first set of observations against original guide stars within a guide star database stored on board the spacecraft;deriving a first approximation of the attitude of the spacecraft from positions of original guide stars that matched with observed stars from the first set of observations;selecting a first set of additional stars from the guide star database and predicting the location of said first set of additional guide stars within the field of view;deriving an improved approximation of the attitude of the spacecraft from positions of the original guide stars and the first set of additional guide stars;using an angular rate of the spacecraft and a needed time for star identification and attitude determination to predict which stars from the first time, called propagation guide stars, will be present in the field of view of the camera at a subsequent time;selecting several of said propagation guide stars;at said subsequent time, determining which stars in the field of view correspond to the selected propagation guide stars;deriving a first approximation of the attitude of the spacecraft from positions of the propagation guide stars so determined in the previous step;selecting a second set of additional guide stars from the guide star database and predicting the location of said second set of additional guide stars within the field of view;deriving an improved approximation of the attitude of the spacecraft from positions of the determined propagation guide stars and the second set of additional guide stars; andselecting a second set of propagation guide stars from among stars that are expected to be within the field of view at yet another future time.