On-board Processing to Advance the PanFTS Imaging System for GEO-CAPE

The Panchromatic Fourier Transform Spectrometer (PanFTS) is an imaging instrument designed to record atmospheric spectra of the Earth from the vantage point of a geosynchronous orbit. Each observation covers a scene of 128x128 pixels. In order to retrieve multiple chemical families and perform passive vertical profiling, the recorded spectra will cover a wide wavelength range, from the thermal infrared to the near ultraviolet. The small size of the nadir ground-sampling distance and the desire to re-visit each scene hourly result in a PanFTS design that challenges the downlink capabilities of current radio communication. The PanFTS on-board processing will reduce downlink rates by converting time-domain interferograms to band-limited spectra, hence achieving a factor 20 in data reduction. In this paper, we report on the first year progress of this NASA AIST-11 task and on the adaptation of existing Virtex-5 FPGA designs to support the PanFTS Focal Plane Array control and data interfaces. We have produced a software demonstration of the current PanFTS data reduction algorithms. The real-time processing of the interferometer metrology laser signal is the first step required for the conversion of time-domain interferograms to path difference. This laser processing is now performed entirely as digital signal processing inside the Virtex-5 FPGA and also allows for tip/tilt correction of the interferometer mirrors, a task that was previously performed only with complicated and inflexible analog electronics.