Coarse Earth Sun Sensor (CESS)

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

Spacetech offers a thermo-optical Coarse Earth and Sun Sensor (CESS) for this purpose. 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 editedCoarse Earth and Sun Sensor (CESS)

Key features of the CESS

  • Attitude information during de-spin and earth-oriented safe-mode
  • Robust, lightweight, easy to accommodate
  • Zero power consumption
  • Excessive flight heritage

CESS SpecificationsTable 03 2018CESS specifications

CESS 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

CESS deliverables

(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.