The Forward-Looking Interferometer (FLI) is a new instrument concept for obtaining the measurements required to alert
flight crews to potential weather hazards to safe flight. To meet the needs of the commercial fleet, such a sensor should
address multiple hazards to warrant the costs of development, certification, installation, training, and maintenance. The
FLI concept is based on high-resolution Infrared Fourier Transform Spectrometry (FTS) technologies that have been
developed for ground based, airborne, and satellite remote sensing. The FLI concept is being evaluated for its potential to
address multiple hazards including clear air turbulence (CAT), volcanic ash, wake vortices, low slant range visibility, dry
wind shear, and icing, during all phases of flight. This project has three major elements: further sensitivity studies and
applications of EOF (Empirical Orthogonal Function) Regression; development of algorithms to estimate the hazard
severity; and field measurements to provide an empirical demonstration of the FLI aviation hazard detection and display
capability. These theoretical and experimental studies will lead to a specification for a prototype airborne FLI instrument
for use in future in-flight validation. The research team includes the Georgia Tech Research Institute, Hampton
University, the University Corporation for Atmospheric Research, the Air Force Institute of Technology, and the
University of Wisconsin.
A revolutionary satellite weather forecasting instrument, called the "GIFTS" which stands for the "Geostationary
Imaging Fourier Transform Spectrometer", was recently completed and successfully tested in a space chamber at the
Utah State University's Space Dynamics Laboratory. The GIFTS was originally proposed by the NASA Langley
Research Center, the University of Wisconsin, and the Utah State University and selected for flight demonstration as
NASA's New Millennium Program (NMP) Earth Observing-3 (EO-3) mission, which was unfortunately cancelled in
2004. GIFTS is like a digital 3-d movie camera that, when mounted on a geostationary satellite, would provide from
space a revolutionary four-dimensional view of the Earth's atmosphere. GIFTS will measure the distribution, change,
and movement of atmospheric moisture, temperature, and certain pollutant gases, such as carbon monoxide and ozone.
The observation of the convergence of invisible water vapor, and the change of atmospheric temperature, provides
meteorologists with the observations needed to predict where, and when, severe thunderstorms, and possibly tornados,
would occur, before they are visible on radar or in satellite cloud imagery. The ability of GIFTS to observe the motion
of moisture and clouds at different altitudes enables atmospheric winds to be observed over vast, and otherwise data
sparse, oceanic regions of the globe. These wind observations would provide the means to greatly improve the forecast
of where tropical storms and hurricanes will move and where and when they will come ashore (i.e., their landfall
position and time). GIFTS, if flown into geostationary orbit, would provide about 80,000 vertical profiles per minute,
each one like a low vertical resolution (1-2km) weather balloon sounding, but with a spacing of 4 km. GIFTS is a
revolutionary atmospheric sensing tool. A glimpse of the science measurement capabilities of GIFTS is provided
through airborne measurements with the NPOESS Airborne Sounding Testbed - Interferometer (NAST-I).
The AERI (Atmospheric Emitted Radiance Interferometer) has served as a primary instrument for the continuous measurement of down welling infrared emission within the DOE-ARM (Department of Energy - Atmospheric Radiation Measurement) program since 1993. AERI instruments have been deployed at ARM measurement sites that include the NSA (North Slope of Alaska), the TWP (Topical Western Pacific), and the SGP (Southern Great Plains). Marine versions of the AERI instrument (M-AERIs) have also operated on board ships by the University of Miami to measure SST (Sea Surface Temperature). The UW-SSEC (University of Wisconsin - Space Science and Engineering Center) operates an AERI instrument that is housed in a mobile vehicle (Winnebago) and that has been used in support of several field campaigns for surface emissivity measurements and for satellite instrument validation. Efforts are now underway to upgrade and modify the AERI systems that will implement a rapid sampling scheme to improve temporal resolution. ARM is in the process of redeploying SGP boundary facility AERIs to additional TWP and NSA field sites. The NSA AERIs are equipped with detectors suitable for extended spectral range (3.3-25 microns) and has been be used in support of the M-PACE (Mixed Phase Cloud Experiment) in the fall of 2004. The UW-SSEC is also undertaking activities to develop an AERI to be part of the AMF (ARM Mobile Facility) and expect to upgrade this instrument to a M-AERI that will be suitable for SST and emissivity measurements during field deployments. This manuscript will summarize the AERI modifications and upgrades that are underway.
Development in the mid 80s of the High-resolution Interferometer Sounder (HIS) for the high altitude NASA ER2 aircraft demonstrated the capability for advanced atmospheric temperature and water vapor sounding and set the stage for new satellite instruments that are now becoming a reality [AIRS (2002), CrIS (2006), IASI (2006), GIFTS (2005/6)]. Follow-on developments at the University of Wisconsin-Madison that employ interferometry for a wide range of Earth observations include the ground-based Atmospheric Emitted Radiance Interferometer (AERI) and the Scanning HIS aircraft instrument (S-HIS). The AERI was developed for the US DOE Atmospheric Radiation Measurement (ARM) Program, primarily to provide highly accurate radiance spectra for improving radiative transfer models. The continuously operating AERI soon demonstrated valuable new capabilities for sensing the rapidly changing state of the boundary layer and properties of the surface and clouds. The S-HIS is a smaller version of the original HIS that uses cross-track scanning to enhance spatial coverage. S-HIS and its close cousin, the NPOESS Airborne Sounder Testbed (NAST) operated by NASA Langley, are being used for satellite instrument validation and for atmospheric research. The calibration and noise performance of these and future satellite instruments is key to optimizing their remote sensing products. Recently developed techniques for improving effective radiometric performance by removing noise in post-processing is a primary subject of this paper.
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