Title of Presentation: Passive A-Band Wind Sounder (PAWS) for Measuring Tropospheric Wind Velocity
Primary (Corresponding) Author: Shane Roark
Organization of Primary Author: Ball Aerospace & Technologies Corp.,
Co-Authors: Robert Pierce, Grzegorz Miecznik, Philip Slaymaker, Brian Johnson,
Abstract: The Passive A-Band Wind Sounder (PAWS) is funded through NASA’s Instrument Incubator Program (IIP), and is directed at determining the feasibility of measuring tropospheric wind speed profiles from Doppler shifts in oxygen absorption features. Although this passive approach is not expected to provide the potential performance of Doppler lidar, it is being pursued as a low-cost and low-risk alternative capable of providing better wind data than is currently available. The instrument concept is adapted from heritage of the Wind Imaging Interferometer (WINDII) sensor on the Upper Atmosphere Research Satellite. The operational concept for PAWS is to view an atmospheric limb over an altitude range from the surface to 20 km with a wide-field Doppler interferometer in a sun-synchronous low-earth orbit. Two orthogonal views of the same air mass will be used to resolve horizontal winds from measured line-of-sight winds.
A breadboard instrument was developed to demonstrate the measurement approach and to optimize the design parameters for the subsequent engineering unit and future flight sensor. The breadboard instrument consists of a telescope, collimator, filter assembly, and Michelson interferometer, and functions essentially as a highly sensitive wavemeter. From interference between two tilted wavefronts, a fringe pattern is recorded on a sensitive CCD in order to determine the Doppler shift of the oxygen absorption line. This paper will describe the results to date from laboratory testing, as well as radiative transfer and instrument model development.
Keywords: Remote sensing, troposphere wind, Doppler interferometer, optical design.