On the Design of Fourier Transform Spectrometers for Space-based Remote Sensing

After some four decades of development, Fourier transform spectrometers have become the premier high resolution, broadband passive spectometer for laboratory and remote sensing applications. Following the four flights of the ATMOS instrument onboard the space shuttle, and with the development of emission sounders such as MIPAS (limb) and TES (nadir and limb), geostationary mesoscale sounders (GHIS), and polar meteorological sounders (IASI), the scientific role of FTS for remote sensing is indisputable. However, in general they remain less than ideal for space-based applications as a consequence of their size, mass, power, and telemetry requirements. A new concept for high resolution Fourier transform spectrometers suitable for space applications is described that reexamines each of the historical assumptions that have led to massive, large interferometers. The result will deliver the optical and radiometric performance of a high performance FTS such as ATMOS in a small (<0.25 m3), lightweight (20-25 kg) instrument with modest power requirements (<50 W), and with onboard data processing will have modest telemetry rates. Central to the concept is the realization that many of the historic assumptions about interferometer design are unnecessary, especially in a zero gravity environment.