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Smart Solutions for Challenging Environments


C-CORE Calibration Transponder for Sentinel-1

C-CORE calibration transponder supports first successful overpass of new ESA Sentinel-1A satellite

19 April 2014 saw the first successful overpass of the calibration transponder supplied by C-CORE for the European Space Agency’s (ESA’s) new Earth-monitoring satellite, Sentinel-1A, launched on 3 April 2014. Sentinel-1 is a polar-orbiting, all-weather, day-and-night radar imaging mission supplying data for land and ocean monitoring service.

[ABOVE LEFT: Sentinel-1; image (c) ESA/ATG medialab]

[RIGHT: The target is very bright and the sidelobes can be seen in the range (East to West) and Azimouth (North to South) directions in the image. Satellite image ©ESA]

The transponder imaged on April 19th was one of three high-precision active radar calibration transponders designed and fabricated by C-CORE for external characterization of Sentinel-1’s C-Band Synthetic Aperture Radar (CSAR) sensor. These transponders receive signals from Sentinel-1A as it passes overhead at 7.7 kilometres per second. They then send back a response signal mimicking a programmed fixed target, thus enabling Sentinel-1 to self-adjust as needed. The successful April 19th overpass indicates that the transponder is operating within specified parameters and can now be used to calibrate the Sentinel-1A CSAR instrument.

[LEFT: Installing the transponder at the NLR site, March 2014. Photograph  ©ESA ]

Each transponder carries a single Potter Horn antenna with attached waveguide subsystem and associated transceiver to both send and receive radar signals. The antenna and waveguide platform is mounted on an aluminum instrumentation cabinet which houses the electronic and computer components, including the transceiver, high-speed server and digital input/output interface and uninterruptible power supply. The unit can also store the received signals from Sentinel-1A for future analysis.

All components were either developed at C-CORE’s Newfoundland & Labrador facility or assembled from commercial equipment customized to C-CORE specifications, with the project team logging well over 20,000 person-hours of painstaking design, fabrication and testing over 36 months.

[RIGHT: Testing the unit at C-CORE  before shipping to Netherlands.]



[Above: Assembling transponder units in the C-CORE Systms Lab, March 2013]

This project builds on previously demonstrated expertise: C-CORE’s Moving Object Detection Experiment (MODEX) Ground Moving Target Indicator (GMTI) Calibration Transponder mimicks the radar returns from multiple moving targets. Developed for the Defence Research and Development (DRDC) Ottawa to support MODEX, the GMTI mode of RADARSAT-2, it is a coherent calibration transponder for generating moving target returns from RADARSAT-2 transmissions. C-CORE developed all components: software; graphical user interface (GUI); signal processing package; and radio frequency (RF) front-end, transmitter, receiver and antenna turning unit.