The EarthCARE Cloud Profiling Radar (CPR) instrument is a 94 GHz pulse radar, which measures altitude and Doppler velocity from the received echo. It is the world’s first space-borne cloud radar that estimates vertical profiles of clouds and their vertical motion.

Its minimum sensitivity is better than -35 dBZ with a Doppler velocity measurement accuracy of better than 1.3 m/s for specification and also 1.0 m/s for target performance. To achieve those performances, the CPR is equipped with a large reflector with a diameter of 2.5 m.

The instrument has three observation modes: Low (16 km), Middle (18 km), and High (20 km).

The instrument is jointly developed by Japan Aerospace Exploration Agency (JAXA) and National Institute of Information and Communications Technology (NICT).

The reflector size of 2.5 m aperture diameter is derived from the Radar performance requirements (sensitivity, Doppler, Field of view). All of the radar active sub-systems are enclosed within the arrow-shape platform visible under the antenna.

A Transmit-Receive Subsystem encompasses the radar transmitter with its power supply and the receiver electronics. A quasi-optical feeder is used to emit the transmitter Radar Frequency (RF) pulses towards the reflector and to collect the return signal for further on-board processing.

After down-conversion to Intermediate Frequency (IF), the received signal is sent to the Signal Processing Unit (SPU). The SPU is also used as the main CPR control unit and interface towards the spacecraft. Besides its high sensitivity, the CPR implements a unique Doppler capability that will allow it to retrieve the vertical velocity of the cloud’s particles.