The ``Spatially Modulated Interferometer" (SMI) is a proposed design concept for a miniaturised atmospheric remote sensing instrument. It is a Fourier transform spectrometer with no moving parts and uses a rigid optical system to shear an input beam into two halves that are tilted and recombined to form a spatially modulated interference pattern. The interference pattern is fixed in space and can be sampled instantaneously by a detector array. When a broad spectrum of colours are present the interference pattern is modulated into more complex standing wave patterns called interferograms. A two dimensional detector array can be used to record multiple interferograms simultaneously, with each interferogram representing a different image pixel. The ``snap shot" sampling of each interferogram in its entirety makes the interferometer time-invariant with respect to a fluctuating target scene or an unstable observation platform. The SMI spectrometer is unique in that it can generate high étendue interferograms that are spectrally and radiometrically pure. It is easy to calibrate and can generate spectra that are very easy to incorporate into retrieval models. The inherent advantages of using the SMI method are-1. Instantaneous Interferogram: a complete interferogram is generated instantaneously which ensures that temporal or spatial shifts in the scene or path radiance do not alter the generated spectrum. 2. Pupil Plane Sampling: The pupil plane distributes the scene radiance across all pixels so that accurate measurements are always made, regardless of the scene contrast. 3. Spectral Resolution is Independent of Slit Width: The spectral resolution is independent of the width of the entrance slit that defines the instruments instantaneous field of view (IFOV), so the interferometer can achieve very high throughput without sacrificing spectral resolution. 4. Perfect Spectral Registration: The calibration of the SMI is simplified as the colours are perfectly spaced along the spectrum at equal wavenumber intervals.
AAS/Division for Planetary Sciences Meeting Abstracts #37
- Pub Date:
- December 2005