19, April 2019

ESA Open Invitation to Tender AO9782
Open Date: 12/04/2019
Closing Date: 07/06/2019 13:00:00

Status: ISSUED
Reference Nr.: 19.1ET.05
Prog. Ref.: Technology Developme
Budget Ref.: E/0901-01 – Technology Developme
Tender Type: C
Price Range: 200-500 KEURO
Products: Satellites & Probes / Payloads / Instruments / RF and microwave Instruments / Imaging Radars
Techology Domains: Electromagnetic Technologies and Techniques / Antennas / Measurement, Characterisation and Calibration Techniques for Radiative Payloads and Antennas
Establishment: ESTEC
Directorate: Directorate of Tech, Eng. & Quality
Department: Electrical Department
Division: RF Payloads & Technology Division
Contract Officer: Hertzog, Hendriline
Industrial Policy Measure: N/A – Not apply
Last Update Date: 12/04/2019
Update Reason: Tender issue

The M5 future science candidate mission EnVision foresees an S-Band interferometric synthetic aperture radar (InSAR) instrument. Aninternal calibration loop as used in the heritage EO mission NOVASAR-S is current baseline. However, an additional external calibration loop, i.e. including the SAR antenna, is currently not foreseen. An external calibration requires reference objects in the antenna field-of-view. Earth observation SAR instruments use reference objects such as corner reflectors and/or active signal sources forthis purpose. Such devices are not available on Venus. However, the absence of an external calibration would be a major mission risk as for once the internal calibration could then not be verified. Second, a degradation of antenna characteristics during the mission lifetime cannot be detected. At the beginning of this activity, calibration reference objects on Venus shall be investigated suchas the Veneras, Vegas, Pioneer Venus Large Probe landers as well as potential natural reference objects which are sufficiently stable in S-Band throughout all six EnVision mission cycles. VenSAR-specific InSAR end-to-end error sources over lifetime shall be determined. Based on this, an external calibration method for antenna correction based on delta-measurements shall be developed. In thisrespect, a comparison of measurements in mission cycles two to six to a reference measurement in the first mission cycle shall be used for characterisation of antenna degradation. A corresponding antenna calibration error model shall be developed. An optimum VenSARsignalling for this calibration shall be identified considering optimum SAR modes, potential phase centre sequencing, signalling,etc. A final model considering propagation effects (affecting calibration uncertainty) shall be developed. The capability of the developed method shall be proven in a final demonstration.

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