Optical design of the stratosphere-troposphere exchange and climate monitor radiometer (STEAMR) instrument

In this paper we present details of the design and optimisation for the optics for the STEAMR multi-beam limb sounder instrument. This optimisation process was required to achieve the simultaneous goals of beam amplitude circularisation and phase shift matching and was conducted using a combination of analytical methods. These goals were subsequently achieved optically with the use of `astigmatic´ reflectors. The results of this optimisation have been verified through a combination of first order Gaussian beam analysis coupled with Physical Optics calculations. Additionally the concept and design of a focal plane array element which will couple the individual beams to the corresponding feed horns is presented.