Development status of star trackers

Current status of technological development of star trackers

The development and application of star trackers have gone through more than half a century. With the continuous development of detection devices, star trackers have also been updated. Initially, star trackers used image dissector as detection devices, but problems such as analog stability, size, mass, magnetic effects, and high-voltage breakdown of the image dissector limited its use and development.

Since the 1970s, solid-state image sensor technologies such as CCD and charge injection devices (CID) have gradually matured, promoting the research and development of a new generation of star trackers. CCD image sensors have the characteristics of wide spectral response, high quantum efficiency, small size, low operating voltage, high sensitivity, low noise, high resolution and good spatial stability, and have dominated imaging technology for decades. However, CCD has poor resistance to space radiation; it needs to provide many types of power supplies; image charges are output serially and sequentially, which increases the power consumption of the CCD, the charge transfer rate is less than 1, and the signal is attenuated during the transmission process; the CCD manufacturing process is complex and is not compatible with general purpose Integrated circuits have poor process compatibility.

In the 1990s, the Jet Propulsion Laboratory in the United States invented the APSCMOS image sensor. APS adopts standard CMOS semiconductor production technology and can integrate multiple functional circuits onto one chip. It has the characteristics of small size, low power consumption and light weight. Compared with CCD image sensors, APSCMOS image sensors have the following characteristics: high integration, which can fully integrate the photosensitive array, drive, control circuit, analog signal processing circuit, analog/digital (A/D) conversion, and full digital interface, making it The electronic design of the star tracker is simplified and the peripheral circuits are reduced, which is conducive to the miniaturization of the star tracker: single power supply, low power consumption: strong anti-interference ability, the pixel signal does not require charge transfer and can be read directly; data reading The exit method is flexible.

Parameter characteristics of star tracker

The basic level of star tracker: pointing accuracy 3~10″ (3σ), mass 3~7kg, power consumption 9~15W, data update rate 1~10Hz, initial capture time 2~10s. In terms of dynamic performance, full performance Generally, the movement angular speed is required to be within 0.5(°)/s, and it can reach 2(°)/s or higher without losing some accuracy.

The basic level of star trackers: pointing accuracy of 3-10 “(3 σ), Mass 3-7kg, power consumption 9-15W, data update rate 1-10Hz, initial capture time 2-10s. In terms of dynamic performance, full performance generally requires a motion angular velocity within 0.5 (°)/s, and can reach 2 (°)/s or higher without losing some accuracy.

In order to improve the dynamic performance of star trackers, some star trackers themselves integrate MEMS inertial sensor components, such as HYDRA, to improve the update rate and dynamic performance, and reduce the initial acquisition time.

If a multi-field-of-view star tracker is used, it can effectively avoid sunlight interference and also help improve the rolling accuracy of the star tracker; if a single-field-of-view star tracker is used, the appropriate installation position needs to be adjusted to avoid sunlight and other interference. Failure condition when light is incident.