ObjectiveFor all-time star sensors, traditional wide optical response bandwidth design can easily cause imaging chromatic aberration, which is not conducive to star detection and extraction; Some bands have low atmospheric transmittance, and excessively wide response bandwidth can easily reduce the signal-to-noise ratio of star detection. With the rapid development of infrared sensor technology, these issues have gradually become important bottlenecks that limit the further improvement of the accuracy of all-time star sensors. Due to the significant spectral correlation between atmospheric background radiation and transmittance, there are significant differences in the number of observable stars in different bands, resulting in significant differences in the actual star measurement capabilities of all-time star sensors using different optical sensitive bands. Therefore, according to the characteristics of the near-infrared band atmospheric window, it is of great significance to select an appropriate optical response band to improve the star detection capability of the all-time star sensor.
MethodsBased on the definition of 0 magnitude star radiation flux in different optical response bands, and taking into account factors such as atmospheric background radiation and transmittance in different bands, the signal-to-noise ratio relationship of 0 magnitude star corresponding to different optical response bands under the same hardware conditions is derived (Tab.5); Using Modtran software to simulate and calculate atmospheric parameters in relevant bands, and combining with the statistical number of stars in different bands, the quantitative analysis adopts the relationship between the number of star detections in different optical response bands (Fig.3, Tab.7). A daytime star observation platform is built and the model of the relationship between the number of star detections is verified by taking pictures of Polaris and Sadr. On this basis, based on the distribution of stars in different bands of the same magnitude (Fig.5), combined with the attitude determination conditions of the star sensor, Monte Carlo simulation was used to calculate the actual success rate of the star sensor's attitude determination using different optical response bands.
Results and DiscussionsUnder the same hardware conditions, the star detection ability of the all-time star sensor using the
H-band as the optical response band is about 17 times, 10 times, and 2 times that of the
R,
I, and
J bands (Fig.4). The correctness of this conclusion was verified through actual observations of one or two stars in North Star and Sadr (Fig.9). The field of view of the star sensor is taken as 5°×5°, when the signal-to-noise ratio of the star sensor to
R-band 0 magnitude stars reaches 100. Using the
H-band can achieve the detection of more than 3 stars in a field of view of 99.23%, while under the same conditions, the
R-band,
I-band, and
J-band are only 6.09%, 48.30%, and 77.28%, respectively (Tab.8).
ConclusionsIn order to reduce the chromatic aberration of the all-time star sensor imaging and improve the daytime star measurement signal-to-noise ratio of the all-time star sensor, a comparative analysis was conducted on the star measurement capabilities of the all-time star sensor in various optical response bands. Through comparative analysis, it is found that the use of different optical response bands has a significant impact on the actual star measurement ability of all-time star sensors; Under the same hardware conditions, the all-time star sensor has the most outstanding ability to detect stars in the
H-band, with a detection number of stars about 17 times, 10 times, and 2 times that of the
R,
I, and
J bands. The success rate of attitude determination also has a significant advantage. A daytime star observation platform was built, and the actual star measurement capabilities using different optical band platforms were experimentally calculated. The experimental results showed that the
H-band all-time star sensor has significantly stronger star measurement capabilities than other optical bands, making it the optimal optical response band for all-time star sensors.
