Space Payload
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Concept
The payload design follows that of the prototype without the CCD imager but with three frequencies (90, 150, and 270 GHz). The first two (90 and 150 GHz) are optimal for observing the CMB from the ground, and the third (270 GHz) is optimal for observing the foreground interstellar dust emission.
The COSMOCal source is 100% polarized. The signal is beamed towards ground-based telescopes in northern Chile and southern Europe with long horns.
Two main requirements determine the design of the payload. (i) The angle must be known with respect to the celestial reference frame to an accuracy of 0.1° (3σ). (ii) The flux received on Earth must be comparable to that of the astronomical sources used today to calibrate microwave instruments.
At 90 and 150 GHz, the user requirement is that the flux from the COSMOCal source be comparable to that of Uranus in total intensity. At 270 GHz, the requirement is that the COSMOCal flux be comparable to that of the Crab Nebula in polarization.
Development plan
Our present goal is to build a payload prototype with a microwave source at 90 and 270 GHz that meets the required power specifications. The source will be combined with two horns and a polarizer. This demonstrator will allow us to complete the payload definition and demonstrate the project feasibility.
At the same time, we are working with ground-based observatory teams to develop the calibration strategy needed to achieve the scientific objective of the mission.
We are also working with EUTELSAT engineers to define the electromagnetic, mechanical, and thermal interfaces between the COSMOCal instrument and the satellite and its equipment, and develop the test plan that will validate its integration and proper functioning in space.
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