The objectives were to address major risks with the manufacture of the large area 2d curved sensors.  These included the assessment of the viability of a 2d curving process as an evolution of Teledyne e2v’s back thinning process, the development of the basic process and packaging concept, and the evaluation of the surface form achievable.

The use of a traditional flat image sensor requires optical elements to project the image onto a flat plane.  Introducing an appropriately curved sensor removes the need for these optical elements. Thus, by eliminating one constraint on the design of the lens it becomes possible to design systems with reduced size and weight and improved performance.

The de-risk activity has verified that viable process to manufacture curved visible image sensors can be established, based on additional substrate thinning after advanced back thinning processing already in place at Teledyne e2v.  The programme has included the development of jigging and packaging concepts and the selection of appropriate adhesives. The curvature targeted and achieved was of concave spherical form with a radius of curvature of 500mm for a 6cm by 6cm back illuminated CCD.  Evaluation of a packaging concept for suitability for use with the proposed process has been undertaken successfully, and the accuracy of the surface form established. Electro-optical testing was outside the scope of this de-risk activity, although DC testing to confirm the electrical viability has been undertaken.

The number of lenses in Sentinel 5 would have been reduced from 6 to 3 with the use of a sensor of the appropriate curvature. Similar benefits should be possible for the camera systems for Copernicus next.

Currently, potential follow-up activities are being discussed with ESA. The aim of the main GSTP programme already identified in the ESA GSTP compendium would be to establish the manufacture of 2d curved sensors as a viable production process and to carry out initial validation.