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... > Instruments > Earth Remote Sensing Instruments > Active Remote Sensing > Altimeters > Radar Altimeters > Star Tracker

Preferred term

Star Tracker  

Definition

  • the star tracker calculates a coarse attitude by matching triangle patterns of stars with patterns stored in its catalog. Subsequently, in attitude update mode it calculates precise attitude at a rate of 1.7 Hz. The star tracker attitude serves also as reference for determining the orientation of the SIRAL interferometric baseline. The orientation of the interferometric baseline needs to be very accurately measured in-flight: small errors in knowledge of the roll-angle translate into substantial errors in the elevation of off-nadir points. The HE-5AS star tracker of Terma A/S, originally developed and qualified for the NEMO (Navy EarthMap Observer) and FCT (Foreign Comparative Test) projects, is selected for CryoSat. It is a fully autonomous star tracker capable of delivering high-accuracy inertial attitude measurements from a lost-in-space condition with no external attitude information. The EOL performance of the star tracker is < 3.2 arcsec in the lateral axes and < 16 arcsec about the roll axis under worst-case conditions. 13) The star tracker baffle has been designed to meet the required sun exclusion angle of 30º and the moon exclusion angle of 25º. These exclusion angles ensure together with the star tracker accommodation on the antenna bench that during the whole mission sun and moon can only blind one star tracker head at any time. (en)

Broader concept

Change note

  • 2018-07-04 08:32:27.0 [mmorahan] Insert Concept add broader relation (Star Tracker [2380ecc6-b5ae-4ad8-a56a-9740166465aa,367735] - Radar Altimeters [92ddaaca-40b2-4936-bc1a-28cc5743e8b8,347963]);
  • 2018-07-04 08:41:28.0 [mmorahan] insert Definition (id: null text: the star tracker calculates a coarse attitude by matching triangle patterns of stars with patterns stored in its catalog. Subsequently, in attitude update mode it calculates precise attitude at a rate of 1.7 Hz. The star tracker attitude serves also as reference for determining the orientation of the SIRAL interferometric baseline. The orientation of the interferometric baseline needs to be very accurately measured in-flight: small errors in knowledge of the roll-angle translate into substantial errors in the elevation of off-nadir points. The HE-5AS star tracker of Terma A/S, originally developed and qualified for the NEMO (Navy EarthMap Observer) and FCT (Foreign Comparative Test) projects, is selected for CryoSat. It is a fully autonomous star tracker capable of delivering high-accuracy inertial attitude measurements from a lost-in-space condition with no external attitude information. The EOL performance of the star tracker is < 3.2 arcsec in the lateral axes and < 16 arcsec about the roll axis under worst-case conditions. 13) The star tracker baffle has been designed to meet the required sun exclusion angle of 30º and the moon exclusion angle of 25º. These exclusion angles ensure together with the star tracker accommodation on the antenna bench that during the whole mission sun and moon can only blind one star tracker head at any time. language code: en);
  • 2019-02-12 14:55:45.0 [mmorahan] insert WeightedRelation (id: null related concept uuid: e377ef25-1612-4b8d-ac98-54e3977d7e31 relationship type: null relationship value: null generated by: null);
  • 2019-02-13 08:30:48.0 [mmorahan] insert WeightedRelation (id: null related concept uuid: a915ab2f-46c5-493b-9f18-aeb3383ee72b relationship type: null relationship value: null generated by: null);
  • 2019-02-22 17:26:18.0 [mmorahan] insert WeightedRelation (id: null related concept uuid: 054787a6-0c47-43af-a4ee-05c572dd1705 relationship type: null relationship value: null generated by: null); insert WeightedRelation (id: null related concept uuid: ab7f9a64-ca5d-4795-94ff-fd5367d39f9f relationship type: null relationship value: null generated by: null); insert WeightedRelation (id: null related concept uuid: 769a52d4-7db1-4b8e-8d39-6fee4e74d34f relationship type: null relationship value: null generated by: null);
  • 2021-08-04 17:03:23.0 [sritz] insert AltLabel (id: null category: primary text: Star Tracker language code: en);

URI

https://gcmd.earthdata.nasa.gov/kms/concept/2380ecc6-b5ae-4ad8-a56a-9740166465aa

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