The issues involved in the project
The project needs to model the stray light generated in the SPICA instrument and design mechanical components which will allow the specified maximal level to be reached.
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The optics centre came up with a design for mechanical parts (known as “baffles”) and the optical properties of the various components of the instrument required in order to achieve the specified level of stray light. Amongst other things, this study included the following:
- The use of ASAP to model the stray, specular and diffused light reaching the focal plane and generated by the mechanical components in a thermal infrared band (baffles, structures, spider bars, radiator) and by the natural sources in the field (zodiacal light, the Moon, the Earth, etc.)
- The dimensioning of the various baffles (outer baffle, primary mirror baffle, secondary mirror baffle) in order to eliminate as many of the stray rays reaching the focal plane as possible
- Deciding upon the coverings for each mechanical component and the characterisation of their emissivity, their specular reflection coefficients and their TIS
- The identification of the major elements seen by the detector
- The client was provided with a design adhering to the specifications given.