Recent Development of the NASA High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP)

Fine scale wind measurements are crucial for the study of tropical cyclones and severe storms. Airborne radars have been proved to be effective tools for providing higher spatial and temporal resolution wind observation data than obtained by current spaceborne sensors. The High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP) is a solid-state transmitter-based, dual-frequency (Ka- and Ku-band), dual-beam (30o and 40o incidence angle), conical scan Doppler radar system, designed for operation on the high-altitude (20 km) Global Hawk Unmanned Aerial System (UAS). The long flight range of UAS makes it possible to collect wind data from the remote ocean regions where tropical storms are often formed.

This paper describes the update development of HIWRAP radar system. HIWRAP utilizes solid state transmitters along with novel transmit waveform and pulse compression scheme that will result in a system that is considerably more compact in size, lighter in weight, require less power, and ultimately cost significantly less than typical radars currently in use for precipitation and Doppler wind measurements. HIWRAP technology advances include the development of a compact dual-frequency, dual-beam conical scan antenna system; development of solid-state transmitter based transceivers that are capable of transmitting/receiving versatile waveforms and achieving performance comparable to high peak power tube-based systems; development high-speed digital receiver and processor to handle the complex receiving pulse sequences and high data rates resulting from solid-state transceiver and conical scan. With the operation at both Ku- and Ka-band, HIWRAP will be able to image the winds from volume backscattering from clouds and precipitation, enabling it to measure the tropospheric winds above heavy rain at high levels. In addition, HIWRAP is capable of measuring surface winds similar to QuikScat. HIWRAP is in a final system integration stage. First test flights on NASA manned aircraft WB57 have been scheduled for later of this year.