Radar Definition Experiment (RADEX) for ACE Mission

The ER-2 X-Band Doppler Radar (EXRAD) is a dual-beam, X-band radar that operates on NASA’s ER-2 aircraft. It was originally designed to fly on the Global Hawk but instead was developed for ER-2 to replace the ER-2 Doppler Radar (EDOP). EXRAD measures backscatter to determine radar reflectivity, Doppler velocity, and linear depolarization ratio. These measurements can be used to derive details about the phase, orientation, size, and other properties of precipitation particles. EXRAD operates at the 9.6 GHz frequency and has a range resolution of 37.5 to 300 meters. It has a swath width of 28 km at an altitude of 20 km in scanning mode and has a typical sampling frequency of 0.25 seconds.

The High-Altitude Wind and Rain Airborne Profiler (HIWRAP) is an airborne Ka- and Ku-band, dual-beam Doppler radar system. It measures radar reflectivity and 3-D wind fields within clouds and precipitation making it ideal for research missions into hurricanes and severe storms. It was designed to operate at higher altitudes (~ 20 km) than previous airborne wind profilers allowing for a better vertical profile of the troposphere. HIWRAP has a range resolution of 150 m and operates at the following frequencies: 13.5 GHz, 13.9 GHz, 33.7 GHz, and 35.6 GHz.

The Advanced Microwave Precipitation Radiometer (AMPR) is an airborne passive microwave radiometer. AMPR provides calibrated brightness temperature, which can be used to derive cloud and precipitation properties. It operates across four microwave channels: 10.7, 19.35, 37.1, and 85.5 GHz. These frequencies are sensitive to precipitation, thus making AMPR well-suited for rain event studies.

The Cloud Radar System (CRS) is an airborne W-band polarimetric Doppler radar. CRS provides radar observations of clouds and precipitation from the surface up to the lower stratosphere. It has an operating frequency of 94 GHz and has a 150m range resolution. CRS has a typical vertical resolution of 100m and a gate spacing of 37.5m.

The Conical Scanning Millimeter-wave Imaging Radiometer (CoSMIR) is an airborne imaging radiometer that was developed to validate the Special Sensor Microwave Imager/Sounder (SSMIS) instrument. CoSMIR operates across 9 spectral channels in the 50-183 GHz range to measure microwave brightness temperature. CoSMIR has a surface footprint resolution of 1.4 km x 1.4 km at an altitude of 20 km at nadir. It can perform both conical and cross-tracking scanning.

The Airborne Multiangle SpectroPolarimetric Imager (AirMSPI) is a passive remote, airborne pushbroom camera developed by the Jet Propulsion Laboratory (JPL) and engineers from the University of Arizona and the University of Texas. AirMSPI operates across 8 spectral bands (355, 380, 445, 470, 555, 660, 865, 935 nm) to provide multiangle radiance and linear polarization imagery which can be used to retrieve aerosol and cloud microphysical properties. AirMSPI has a spatial resolution of 10-25 m depending on the scan mode and typically provides image frames at a rate of 23 Hz. AirMSPI was designed to fly on the nose of NASA’s ER-2 aircraft and has been utilized in several aerosol and cloud investigations.

The Cloud Physics Lidar (CPL) is an airborne lidar system designed specifically to provide multi-wavelength measurements of cirrus clouds, sub-visual cirrus clouds, and aerosols. It measures lidar backscatter across three wavelengths: 355 nm, 532 nm, and 1064 nm. These measurements can be used to derive cloud optical depth, particle size distribution, extinction profiles, aerosol layers, and other properties. CPL has a vertical resolution of 30 m and a typical horizontal resolution of 200 m.

The Enhanced MODIS Airborne Simulator (eMAS) is an airborne cross-track scanning spectrometer operated by the Airborne Sensor Facility (ASF) at NASA Ames Research Center. eMAS collects high-resolution imagery of cloud and surface features which can be used to help develop and test algorithms for MODIS satellite observations. It operates across 38 spectral channels at 0.445-14.1 µm wavelengths and has a scan rate of 6.25 Hz. eMAS has a spatial resolution of 50 m and a swath width of 37.25 km at an altitude of 20 km.

The ER-2 X-Band Doppler Radar (EXRAD) is a dual-beam, X-band radar that operates on NASA’s ER-2 aircraft. It was originally designed to fly on the Global Hawk but instead was developed for ER-2 to replace the ER-2 Doppler Radar (EDOP). EXRAD measures backscatter to determine radar reflectivity, Doppler velocity, and linear depolarization ratio. These measurements can be used to derive details about the phase, orientation, size, and other properties of precipitation particles. EXRAD operates at the 9.6 GHz frequency and has a range resolution of 37.5 to 300 meters. It has a swath width of 28 km at an altitude of 20 km in scanning mode and has a typical sampling frequency of 0.25 seconds.

The High-Altitude Wind and Rain Airborne Profiler (HIWRAP) is an airborne Ka- and Ku-band, dual-beam Doppler radar system. It measures radar reflectivity and 3-D wind fields within clouds and precipitation making it ideal for research missions into hurricanes and severe storms. It was designed to operate at higher altitudes (~ 20 km) than previous airborne wind profilers allowing for a better vertical profile of the troposphere. HIWRAP has a range resolution of 150 m and operates at the following frequencies: 13.5 GHz, 13.9 GHz, 33.7 GHz, and 35.6 GHz.

The Advanced Microwave Precipitation Radiometer (AMPR) is an airborne passive microwave radiometer. AMPR provides calibrated brightness temperature, which can be used to derive cloud and precipitation properties. It operates across four microwave channels: 10.7, 19.35, 37.1, and 85.5 GHz. These frequencies are sensitive to precipitation, thus making AMPR well-suited for rain event studies.

The Cloud Radar System (CRS) is an airborne W-band polarimetric Doppler radar. CRS provides radar observations of clouds and precipitation from the surface up to the lower stratosphere. It has an operating frequency of 94 GHz and has a 150m range resolution. CRS has a typical vertical resolution of 100m and a gate spacing of 37.5m.

A dropsondes or dropwindsondes are in situ instruments designed to be released from aircraft. They are equipped with Global Positioning System (GPS) receivers and sensors to collect profile measurements of pressure, temperature, humidity, wind speed, and direction. Dropsondes are important during field investigations because they allow researchers to collect vertical profiles in remote locations and during severe weather events. Dropsondes typically have a vertical resolution of 5 m and provide measurements of wind speed/direction every 0.25 seconds and temperature, pressure, and humidity every 0.5 seconds.

The Airborne Third Generation Precipitation Radar (APR-3) is an airborne Doppler, dual-polarization radar. It provides measurements of Doppler velocity and radar reflectivity across three frequencies: 13.4 GHz, 35.6 GHz, and 94 GHz. These measurements can be used to derive vertical structures of clouds and precipitation properties. APR-3 has a horizontal resolution of 700-800 m at an altitude of 10 km and a vertical resolution of 60 m. The APR-3 was developed by NASA Jet Propulsion Laboratory (JPL) and replaced the APR-2.

The Conical Scanning Millimeter-wave Imaging Radiometer (CoSMIR) is an airborne imaging radiometer that was developed to validate the Special Sensor Microwave Imager/Sounder (SSMIS) instrument. CoSMIR operates across 9 spectral channels in the 50-183 GHz range to measure microwave brightness temperature. CoSMIR has a surface footprint resolution of 1.4 km x 1.4 km at an altitude of 20 km at nadir. It can perform both conical and cross-tracking scanning.