The research on star sensors began in the 1940s, and the development of star sensors has gone through four stages: embryonic, first generation, second generation, and third generation. The characteristics and typical products of star sensors in each stage are introduced below.
Before the emergence of star sensors using charge coupled devices (CCD) as image sensors, it was the embryonic stage of star sensor development. In the 1940s to 1950s, star sensors mainly used photomultiplier tubes as image sensors. This type of star sensor had a simple structure, limited tracking of stars, and due to the limitations of the image sensor itself, the measurement accuracy of the star sensor was difficult to exceed 30 “. In the 1960s, the former Soviet Union Geophysical Science Production Union (“Geofizika”) was the first to develop a star tracker for spacecraft attitude control. This star tracker and a series of improved star sensors were widely used in subsequent space missions, such as in lunar and Mars exploration and the attitude navigation system of the spacecraft “Granat”. In the 1960s and 1970s, the image sensors of star sensors were mainly composed of image tubes. At this time, the imaging of star sensors was highly susceptible to stray light. It was not until the early 1970s that “Geofizika” improved these types of star sensors to enhance their ability to resist stray light.
In the 1970s, after the invention of the CCD image sensor by Willard S. Boyle and George E. Smith at Bell Laboratories in the United States, Goss first demonstrated the CCD star sensor at the Jet Propulsion Laboratory (JPL) in the United States and verified its advantages over the image tube star sensor. Afterwards, JPL successfully developed a STELLAR star sensor using CCD as the image sensor, with a field of view of 3 ° × 3 °, using Fairchild’s pixel array of 100 × The 100 CCD image sensor and Intel’s 8080 microprocessor can achieve a single star measurement accuracy of 10 ″. Due to the significant performance advantages of CCD, it gradually replaced the image tube as the main photoelectric conversion component of star sensors, and thus entered the first stage of star sensor development. After using CCD as an image sensor, the image resolution of the star sensor has been significantly improved, and a microprocessor has been embedded to enable the star sensor to perform autonomous operations. After the stars in the field of view are mapped onto the target surface of the image sensor, the microprocessor calculates the centroid coordinates of the star points in the star map and transmits the resulting data to the main control computer on the spacecraft, or saves it in memory for processing after returning to the ground. The field of view of the first generation star sensors is generally small, and due to the limitations of microprocessor computing power and memory storage capacity, they cannot perform star map recognition and attitude calculation without coarse attitude. Typical products in the first generation of star sensors include the ASTROS (Advanced Stellar and Target Reference Optical Sensor) star sensor developed by JPL, with a field of view of 5 ° × 5 °; MADAN (Multi Mission Attention Determination and Autonomous Navigation) star sensor developed by TRW in the United States, with a field of view of 7.4 ° × 7.4 °; HD1003 star sensor developed by HDOS in the United States, with a field of view of 8 ° × 8 °.
In the 1990s, with the application of high-speed microprocessors and large capacity memory, Lawrence Livermore National Laboratory developed a matching star sensor for the Clementine lunar probe at the request of the Naval Research Laboratory in the United States. It was able to achieve real-time calibration, star map recognition, and attitude capture on spacecraft, thus entering the second stage of star sensor development. Compared to the first generation star sensors, the second generation star sensors have a larger field of view and significant improvements in computing power and storage capacity. They can use the navigation star library stored internally to perform autonomous star map recognition throughout the sky without the use of other devices to provide initial attitudes. Based on the recognition results, the attitude of the star sensor can be calculated, solving the problem of Lost in Space (LIP). Meanwhile, due to the large number of stars in the field of view, star sensors only need to detect brighter stars during the imaging process, which can meet the requirements of star map recognition for detecting the number of stars. Moreover, a larger number of stars can improve the accuracy and robustness of attitude measurement. In addition, with the application of new technologies in the field of optoelectronics, the volume, mass, and power consumption of the second generation star sensors have been optimized. At this stage, star sensors have gradually matured and have been widely used in various tasks such as ship, missile, and spacecraft. Typical products in the second generation star sensor include the ASTRO-15 star sensor developed by Jena Optronik, with a field of view of 13.8 ° × 13.8 °, data update rate of 4Hz, power consumption of 10W, attitude measurement accuracy of 1 “, 1”, 10 “(1 σ）； The ASC star sensor developed by Technical University of Denmark (DTU) has a field of view of 19 ° × 14 °, data update rate of 4Hz, power consumption of 7.8W, attitude measurement accuracy of 1 “, 1”, 8 “(1 σ）。
The research on CMOS (Complex Metal Oxide Semiconductor) star sensors predates CCD star sensors. However, due to the limitations of CMOS structure and semiconductor manufacturing technology at that time, the problem of low detection sensitivity of CMOS image sensors has not been solved. In the 1990s, with the invention of CMOS Active Pixel Sensor (APS) technology, the detection sensitivity of CMOS image sensors was significantly improved [16]. At the same time, miniaturization has become a trend in the development of spacecraft such as satellites. For such spacecraft, CCD star sensors have large power consumption, volume, and weight, making it difficult to meet the requirements of miniaturization. However, CMOS star sensors have gradually been widely used in spacecraft such as microsatellites due to their large field of view, low power consumption, high integration, and strong spatial radiation resistance, From then on, we entered the third stage of the development of star sensors [17]. Typical products in the third-generation star sensor include the AA-STR star sensor developed by Galileo Avionica, with a field of view of 20 ° × 20 °, data update rate of 10Hz, power consumption of 4-7W, attitude measurement accuracy of 12 ″, 12 ″, 100 ″ (2 σ）； The MAST star sensor developed by JPL has a field of view of 20 ° × 20 °, data update rate of 50Hz, power consumption of 69mW, attitude measurement accuracy of 7.5 ″ (1 σ）。
With the continuous maturity of star sensor technology, it has been widely used in space missions due to its high attitude measurement accuracy and no drift.
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