High-resolution imaging interferometer

Abstract

The result from the feasibility study ESTEC contract no 7943/88/NLIJS on High Resolution Imaging Interferometer (HRII) are presentedThe goal of this study has been to review the technologies which are basic in a development of an imaging spectrometer using Fourier Transform Spectroscopy and to discuss the advantages and possible limitations to this technique in development of a space instrument fulfilling the basic instrument requirementThe main part of the study has been devoted to detailed studies of what was felt as critical technologies in relation to the two basic criteria that the instrument performance should only be limited by the fundamental noise limitations given by the signal photon fluctuation and that all technologies and components used will have a lifetime of4 years.With current technology we have found it possible to develop detector arrays for all three spectral ranges, design a special scanning Michelson interferometer and develop application specified integrated circuits for the on board signal processing all of which should fulfill the above two criteria.The proposed instrument has three spectral ranges, a Visible and Near Infrared (VNIR) from 0.45 to 1.0 j.un, a Short Wave Infrared (SWIR) from 1.0 to 2.5 im and one optional Thermal Infrared (TW) from 8.0 to 12.5 pm. The spatial resolution (pixel size) on ground is proposed to be 40 m for VNIR and SWIR and 200 m for TIR. The swath width will be 30km, giving an image resolution for VNIR and SWIR of 768 pixels normal to satellite scan direction. The spectral resolution will be 200 cm in the VNIR range, 50 cm in the SWIR range and 10 cm for the TW range. The instrument will have a weight of less than 150 kg, a dimension of 1750 mm x 750 mm x 500 mm and a total power consumption of less than 250 W when 100 spectral channels are to be transferred to the ground and less than 150 W for 50 spectral channels.

Birefringent laterally sheared beam splitter-Savart polariscope

“…The imaging spectrometers based on two beam interference are often called the Imaging Fourier Transform Spectrometers(IFTS) [1][2][3] . It includes temporally modulated interference imaging spectrometer based on Michelson interferometers [4][5][6][7] , spatially modulated interference imaging spectrometer based on Sagnac interferometer [2][3][8][9][10] , and Polarization Interference Imaging Spectrometer(PIIS) based on birefringent compacts, such as Savart plate, presented by zhang et al in 2000 [11][12][13][14][15] and Wollaston prism [16] .…”