What is a Star Tracker?

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Jul 27, 2022

Star trackers or star sensors are optical devices that are used by satellites as a navigational tool to determine their orientation/attitude to the stars. The positions of stars are measured using a camera, photocells, and other onboard processing systems which identify the images and process the measured position in the reference frame of the spacecraft.

There are around 50-60 navigational stars that have been mapped by astronomers and are primarily used to determine the satellite’s position. Star trackers can scan the starscape to pick out stars and constellations and compare them with these pre-defined navigational stars. But for complex missions such as the Mars mission, the entire starfield database has to be referenced to determine the orientation of a spacecraft.

Star trackers are primarily used for the attitude and orbit control systems of spacecraft but they have temporary outages due to interference effects of light reflecting from the satellite’s surfaces or exhaust plumes during propulsion sequences or by strong light from sources such as the sun, or the sun’s reflection off parts of the spacecraft. Therefore to reduce these effects, star trackers work in tandem with gyroscopes, as the latter provides temporary, and attitude information during star tracker outages. Sometimes two or more star trackers are used for redundancy or to increase the accuracy so that a spacecraft will have more accurate knowledge of its position.

Click here to learn more about Star Trackers featured on SatNow.

Space Missions - A list of all Space Missions

esa

Name Date
Altius 01 May, 2025
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Eutelsat Quantum 30 Jul, 2021
Sentinel 6 21 Nov, 2020
Cheops 18 Dec, 2019
EDRS 06 Aug, 2019
BepiColombo 20 Oct, 2018
Aeolus 22 Aug, 2018
Sentinel 3B 25 Apr, 2018
Sentinel 5 13 Oct, 2017

isro

Name Date
INSAT-3DS 17 Feb, 2024
XPoSat 01 Jan, 2024
Aditya-L1 02 Sep, 2023
DS-SAR 30 Jul, 2023
Chandrayaan-3 14 Jul, 2023
NVS-01 29 May, 2023
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OneWeb India-2 26 Mar, 2023
EOS-07 10 Feb, 2023
EOS-06 26 Nov, 2022

jaxa

Name Date
XRISM 07 Sep, 2023
SLIM 07 Sep, 2023
ALOS-3 07 Mar, 2023
ISTD-3 07 Oct, 2022
HTV9 21 May, 2020
HTV8 25 Sep, 2019
HTV7 23 Sep, 2018
HTV6 09 Dec, 2016
HTV5 19 Aug, 2015
HTV4 04 Aug, 2013

nasa

Name Date
NEO Surveyor 01 Jun, 2028
Libera 01 Dec, 2027
Europa Clipper 10 Oct, 2024
SpaceX CRS-29 09 Nov, 2023
Psyche 13 Oct, 2023
DSOC 13 Oct, 2023
Psyche Asteroid 05 Oct, 2023
Expedition 70 27 Sep, 2023
SpaceX Crew-7 25 Aug, 2023
STARLING 18 Jul, 2023