Title of Paper: Imaging Sensor for the Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS)
Principal Author: Mr. James Stobie
Abstract: Accurate high resolution temperature sounding through our atmosphere is paramount to improving our weather forecasting ability. From the vantage point of earth Orbit, remote temperature sounding is becoming a reality and its accuracy is bolstered by recent advances in infrared hyper-spectral sensor capability. One promising approach takes advantage of two dimensional Fourier transforms to obtain a data cube with the field of view along one plane and the IR spectrum along the orthogonal axis. The spatial resolution is limited only by the pixel pitch in the imaging focal plane and the optics used to collect the data. The number of path-length interferograms obtained per cube dictates the spectral resolution.
This paper shall discuss the unique challenges placed on the focal plane by the Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) approach and how the advanced focal plane technology satisfies these challenges. Of the two focal planes required to satisfy the spectral coverage from 4.4 to 6.1um and 8.85-14.6um the LWIR focal plane is the most stressful. In fact, the GIFTS's LWIR focal plane is the longest wavelength two-dimension PV HgCdTe array of this size (128 square on 60 um centers) to be deployed in space. Even with a charge capacity of about 100 million electrons, the LW focal plane must be over-sampled by a factor of 4 to avoid saturation. This over-sampling drives the average sample time to 150 us, and an astonishing data rate of 160 Mega-samples-per-second for the LW focal plane with a signal dynamic range exceeding 13 bits.
The paper shall present performance data of LPE fabricated HgCdTe detectors and design details of the advance readout integrated circuit necessary to meet the demanding requirements of the imaging sensor for the GIFTS instrument.