While in safe-mode, preservation of a spacecraft is the number one priority. Essential AOCS input needs to be provided by high reliable sensors.

For this purpose, Spacetech offers a thermo-optical Coarse Earth and Sun Sensor (CESS). The CESS is a passive sensor that provides spacecraft orientation at any time, crucial for SC deployment, de-spin and survival in safe mode. It has been used in numerous successful LEO space missions e.g. CHAMP, GRACE, TerraSAR-X, TanDEM-X, Paz, Cryosat, SWARM.

CESS frei edited

Key Features
  • Attitude Information during De-spin and Earth-oriented Safe-Mode
  • Robust, lightweight, easy to accommodate
  • Zero Power Consumption
  • Excessive Flight Heritage

CESS SpecificationsTable 03 2018

Working Principle

A set of 6 orthogonal accommodated CESS heads is used to determine the relative earth and sun vector in the following way.

  1. Perform a continuous measurement of the temperatures of all black and mirror reference surfaces
  2. Extrapolate temperatures to steady-state
  3. Estimate the irradiated infra-red and solar flux, for both black and mirror OSR via their respective values for α and ε
  4. Deduce IR (solar) flux imbalance for opposing CESS heads and construct earth (solar) vector

CESS Working Principle Illustration

Illustration of different Heat Sources from Earth and Sun on 6 CESS Heads accommodated to Spacecraft


(Standard HW)

  • 6 FM + 2 Spare CESS Heads incl. Protective Caps
  • Flight S/W Algorithm


  • Customer Specific Acceptance Testing
  • Mission specific Mechanical Interfaces
  • AIT Support
  • Performance / Thermal In-Orbit Simulator

If you are interested in our existing components or are in need of a new development or modification, please do not hesitate to contact us.