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Star Trackers

Star Trackers provided by Terma secure focus on fully autonomous attitude determination with high accuracy. Different versions support missions ranging from satellites with short mission lifetimes to satellites having long lifetimes and stringent requirements for radiation tolerance.


Introduction

The Terma HE-5AS Star Tracker is a new and fully qualified design, offering a favorable combination of arc-second performance at an affordable price. Robust algorithms provide full autonomy in initial attitude acquisition and attitude update. Terma quality standards, documentation, and component screening meet the requirements of discerning customers including the European Space Agency and the U.S. Department of Defense (DOD).

The HE-5AS Star Tracker is used on satellites owned by:

The European Space Agency:

Terma's Star Tracker
  • Cryosat 1 and 2
  • Aeolus
  • LISA Pathfinder

The U.S. Naval Research Laboratory (NRL):

  • Nemo
  • Tacsat-1/Mitex
  • Tacsat-4
  • Joint Milli-Arcsecond Pathfinder Survey (JMAPS)

The U.S. Air Force Research Laboratory (AFRL): 

  • Tacsat-2/Roadrunner

The U.S. Missile Defense Agency: 

  • ORS Trailblazer

National Reconnaissance Office:

  • USA-225 (or NROL-66)

SSTL:

  • Kanopus-V

Benefits

Terma's Star Tracker

The camera is separate to make it easier to place on the satellite and to minimize heat dissipation (1.6W) near the sensor. The camera is a very compact unit, weighing less than 1,000 g. 

Standard baffles are available providing a Sun exclusion half-angle as low as to 30º. Where the mission calls for a custom designed baffle, Terma has the know-how to optimize baffle design in dialog with the customer.

Independent test and validation of the Star Tracker have been jointly performed by the NRL and the AFRL under the DOD.


Functionality

CryoSat (image courtesy: ESA)

The compact optics of the camera provides a 22º field of view and - although compact - provides enough light to track across the entire celestial vault. A cable provides digital data-link (LVDS) and power supply from the processor unit. The camera can be supplied with a thermo-mechanically stable bracket. 

The processing unit houses the star catalog and the software algorithms for initial attitude determination and continuing attitude update. Also, the unit provides power to the camera. The interface towards the spacecraft is redundant RS-422 or MIL-STD-1553 and a power supply voltage from 22 V to 34 V. Dissipation is 5.2 W. 

The Star Tracker may be delivered with ground support equipment, developed for ease of use and with comprehensive user manuals. The options are:

  • Optical Stimulus: A light-weight optical stimulator reproducing the star field for a fixed attitude. Requires only a power interface and mounts without tools directly onto the baffle.
  • Electrical Stimulus: Provides a stimulus reproducing the starfield at any attitude. May be used stand-alone or to close the loop for avionics testing. The equipment is delivered as a PC with interface cards, and provides both a user interface for the definition of attitude maneuvers and an RS-422 interface for commanding from higher-level test equipment.
  • EGSE: Provides TM/TC interface to the Star Tracker for unit testing. Delivered as a PC with software and interface cards.