Technical Specifications

The HIAPER cloud radar (HCR) initiative provides an opportunity for expanding the envelope of airborne radar systems by delivering high spatial and temporal resolution observations with improved accuracy in comparison to existing radars.

A survey of current technologies indicates that it is best to optimize the radar system to study one of the highest priority missions such as cloud remote sensing. At a future date, based on the performance of the cloud radar system, we may explore the possibility of expanding its utility to include remote sensing of the ocean and land surface.

Requirements for cloud and precipitation radar remote sensing are very stringent due to the need for high sensitivity (> -25 dBZ @ 10 km) and wide dynamic range of received signal strengths (90 dB or more). The intent is to build an airborne millimeter wave radar to satisfy the observational needs of the atmospheric research community.

Desired HCR features were distilled from responses to a selectively distributed scientific community survey, a thorough examination of millimeter wave radar technologies, and input provided in discussions with engineers and scientists at JPL, NASA Goddard, and the University of Wyoming. These discussions led to a proposed millimeter wave radar system which is capable of measuring both spectral moments and the polarimetric scattering matrix with sufficient sensitivity and accuracy to be useful in the study of cloud microphysics. Given cost constraints, and to obtain the greatest spatial coverage, the vast majority of the radar system will be housed in HIAPER’s 20” wing pod, designated the NCAR pod.

EOL staff considered four designs incorporating a pod-based polarimetric scanning radar (dual-wavelength: Ka- and W-band, matched or unmatched beams, and dual-Doppler: Ka- or W-band). Based on the results of community surveys, EOL recommended building a polarimetric Doppler dual-wavelength (Ka- and W-band) radar with both matched and unmatched beam configurations in a pod.

The cost of this dual wavelength system eclipsed the available MREFC funds, and a phased development approach was adopted. The phase A system will consist of a pod mounted W-band Doppler radar. In phase B, pulse compression and polarimetric capabilities will be added. In phase C, the Ka-band radar will be added. At this point, only phase A is funded and it is this system design that this document supports; however, the phase A system will be designed so as to incorporate the electronic and mechanical requirements of phases B and C.