A satellite constellation is a collection of satellites that can be launched into orbit and function normally. Star trackers provide high-precision attitude data and other navigation data for the satellite constellation.Using satellites to complete tasks such as global communication, global navigation, and global environmental monitoring, including in the polar regions, must enable satellite coverage at any time from any location on Earth. To achieve this, it is not enough to use a single satellite or a satellite ring. Several satellite rings need to be configured in a certain way to form a satellite network – a constellation. The main satellite constellations include GPS satellite constellations, GLONASS satellite constellations, Galileo satellite constellations, and Beidou satellite constellations.
The composition of the officially working GPS space satellite constellation: 24 satellites are deployed in 6 orbital planes, with the right ascension point of each orbital plane separated by 60°. The inclination angle of the orbital plane relative to the equatorial plane is 55 °, and 4 satellites are evenly distributed in each orbit. The satellites between adjacent orbits are separated by 30 ° from each other, thus ensuring global coverage requirements.
The average height of GPS satellite orbit is about 20200km, and the operating period is 11h58min. Therefore, the distribution pattern of GPS satellites appears the same every day over GPS receivers at the same location on Earth, only about 4 minutes in advance each day. The number of satellites located above the horizon varies with time and location, with a minimum of 4 and a maximum of 11.
There are 21+3 working satellites and 3 backup satellites in the space satellite constellation of the GLONASS system. Satellites are distributed in three equally spaced elliptical orbital planes, with 8 satellites distributed on each orbital plane, and satellites on the same orbital plane are spaced 45 ° apart. The inclination angle of the satellite orbital plane relative to the equatorial plane is 64.8 °, the orbital eccentricity is 0.001, and the right ascension of each orbital plane differs by 120 °. The average height of the satellite is 19100km, and the operating period is 11h and 15min. Due to the fact that the inclination angle of the GLONASS satellite’s orbit is greater than that of the GPS satellite, it has better visibility in high latitude areas.
The Galileo satellite constellation is composed of 30 medium altitude orbit satellites evenly distributed in three orbits, with 10 satellites on each orbital plane, 9 for normal use and 1 for backup. The satellite orbit has an altitude of 23222km, an inclination angle of 56 °, and a satellite operation period of approximately 14 hours.
According to the planning and design, the Beidou satellite constellation consists of 5 geostationary orbit satellites and 30 non geostationary orbit satellites. The 30 non geostationary orbit satellites include 27 medium orbit satellites and 3 tilt synchronous satellites. The average distribution of 27 medium orbit satellites is on three planes with an inclination angle of 55 °, with an orbital spacing of 120 °, an orbital height of 21500km, and a satellite operating period of 12h50min.
Star trackers are high-precision attitude positioning optical sensor on satellites, capable of outputting satellite attitude data with sub arcsec level accuracy, playing a core role in the precise orientation of each satellite in the satellite constellation.
In the formation flight of constellations, satellites need more precise navigation and relative positioning in close proximity. Star trackers provide important data for performing complex maneuvers and maintain the required formation shape during formation flying missions.
Due to almost every satellite being equipped with Star trackers, redundancy and fault detection functions can be provided for satellite constellations. If there is a problem with one, others can seamlessly take over, ensuring uninterrupted task operation and data collection.
Reconfiguring or rebalancing satellite constellations is necessary in constantly evolving tasks. Star trackers provide valuable data, optimize constellation layout, and ensure efficient task reconfiguration.
TYspace Techology is a leading star tracker manufacturer in China. Over the past 8 years, it has provided over 400 units star trackers successfully in orbit to dozens of countries such as China, the United States, Japan, and South Africa,etc. The products are mature and reliable, and have undergone various satellite in orbit verifications. The Star trackers produced by it have been widely used in satellite constellations such as remote sensing satellite constellations, meteorological satellite constellations, laser communication satellite constellations, Internet of Things satellite constellations, etc. We believe that the products of the TYspace Techology can have unique advantages in determining the pose and formation of individual satellites in satellite constellations.
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TY-Space Technology (Beijing) Ltd. is professional focusing on advanced attitude optical sensors, especially Star Trackers for space industry.
