COnformal Retro Reflectors for Earth Observation (CORREO)

University of Cranfield with University of Nottingham

Project Funded in the CEOI-ST 7th Call for EO Technologies.

Pathfinder Project

Ground-segment calibration and validation activities in support of a satellite mission are a vital and continuous component of the mission, and ultimately upon which successful exploitation of the data depends. Time has seen increasing sophistication in SAR functionality and the emergence of new application areas with a clear trend towards higher resolution and increased radiometric and geometric performance. In addition, future systems, featuring digital beam forming techniques based on multi-channel architectures, will require further sophistication of calibration techniques and procedures. In contrast to these advances, the use of trihedral retro reflectors in calibration strategies has remained largely static. Trihedrals are an effective but blunt tool;- they have fixed, broad beam patterns and operate across wide bandwidths.

The dimensions of a corner reflectors are chosen to give a large signal-to-noise (SNR) to allow them be seen and located precisely amongst background clutter in a radar image. Unfortunately, this usually results in the corner reflector being large and cumbersome which can;

  • make it difficult transporting the reflector to and around the site
  • make the reflector difficult to secure to a structure such as a bridge or side of a building
  • cause problems with stability in the presence of high winds and extreme weather conditions
  • become an eyesore in an urban environment, meaning planning applications may be resisted
  • require regular maintenance as reflectors often fill with flotsam and jetsam borne by the wind, in addition to water and snow
  • make them likely to be the subject of theft and vandalism.

To address these issues, the team is developing a new form of passive retro-reflector. A meta-reflector (M-R) is conformal, thin, lightweight, easily attached, and possesses a highly stable reflection phase property.

Electromagnetic Band Gap (EBG) polarisation transformer