RAL Space has delivered four engineering qualification model (EQM) front-end receivers (FERXs) for the Microwave Sounder (MWS) and Microwave Imager (MWI) on-board the MetOp Second Generation (MetOp-SG) satellites. This mission will provide the European and wider global communities with weather forecasting services from 2022 to 2043. The two EQM FERXs developed by RAL for the MWS operate in the 183 and 229 GHz frequency ranges, featuring average double sideband (DSB) noise figures (NFs) of 5.3 and 6.2 dB, respectively. This paper presents the design and main characterisation results of these two state-of-the-art FERXs for the MWS and compares their performance with other in-orbit microwave sounding instruments, including those on-board MetOp.

Rutherford Appleton Laboratory Space Department (RAL Space) and Radiometer Physics GmbH are responsible for the provision of millimetre-wave front-end receivers operating from 165 GHz to 664 GHz for three instruments on board the MetOp Second Generation (MetOp-SG) satellites. Qualification of the Engineering Qualification Models (EQMs) is recently completed. This paper presents the results of the EQM qualification for receivers operating at 165 GHz, 183 GHz and 229 GHz for the MWS and MWI instruments.

RAL Space and its project partner PRG are tasked with providing space-qualified heterodyne receiver front-ends operating between 165.5 GHz and 325 GHz for the Microwave Sounder (MWS), the Microwave Imager (MWI) and the Ice Cloud Imager (ICI) of the MetOp Second Generation (MetOp-SG) series of satellites. The preliminary design of the receiver front-ends is now complete. Extensive tests on performance of the individual components, as well as of the assembled breadboard versions of the receiver front-ends, have been performed. The results and conclusions derived from these tests will be presented.

Millimetre wave radar has been successfully applied in cloud research for a number of decades. The Rutherford Appleton Laboratory (RAL) has developed a 94 GHz radar based on solid state components and operated in Frequency Modulated Continuous Wave (FMCW) mode. The approach for improving the RF design — including the implementation of Doppler capability — and the results of this activity will be presented.

The activities for upgrading the Rutherford Appleton Laboratory millimetre wave radar cloud profiler are presented. The motivation for these activities and the approach are introduced. First results of these activities are presented.

Two portable mono-static FM-CW Doppler radar profiler systems have been calibrated using a continuously rotating corner reflector. The front-ends of both radars apply semiconductors for the generation of the transmitted power. The portable 24 GHz profiler's aim is to record and investigate precipitation close to the ground. The 94 GHz profiler was developed for cloud investigation from the ground and from a research aircraft. The calibrations showed that the 24 GHz rain profiler is sensitive enough to fulfill its purpose. The 94 GHz profiler lacks the required sensitivity to date. Both radar systems will undergo major design revisions to gain higher system sensitivities.

The Institute for Tropospheric Research (IfT) in Leipzig, Germany, operates a number of airborne in situ probes for cloud microphysical properties, and ground based and airborne radiation measurement tools. To enhance information about clouds for radiative transfer calculation and research, IfT decided to add a cloud radar to its equipment. In the final state, this radar system will be applicable for dual purpose operation in ground based and airborne modes. This requirement defined a number of constraints concerning size, weight, and power supply.

Continental clouds consisting of small droplets partly reveal systematic discrepancies between the calculated and measured radiative properties that need to be resolved. One possible explanation is the horizontal inhomogeneities of microphysical cloud properties. A tool to characterize these is the radar technique. For clouds dominated by larger droplets, the ability of the millimeter wave radar technique to retrieve multi-dimensional microphysical cloud properties has been proven. Here it is shown that a special design of an airborne millimeter wave radar system is capable to detect clouds dominated by small droplets

A 94 GHz FM-CW Doppler radar with a solid state transmitter is described. The radar front end was designed and constructed at the Technical University in Hamburg-Harburg. The transmitted power of approximately 1.6 W is provided by five IMPATT diodes phase locked by a GUNN Voltage Controlled Oscillator (VCO). Four of the diode outputs are joined in a power combiner, which is the heart of the power generating system. The signal analyzing system contains a TI320C30 digital signal processor and uses a 10 MHz 12 bit ADC. The radar will be used to verify or improve cloud models. In addition to the vertical cloud distribution, the radar is expected to provide the vertical wind component in clouds using cloud droplets as tracers. Monitoring entrainment processes through cloud tops is the main goal. First measurements showed that the receiver noise was far above the level expected theoretically from the specifications of the mixer and other components in the receiver. Nevertheless, first Doppler spectra of rain and snowfall have been recorded; examples are presented. In the meantime some progress in reducing the noise power has been made; Doppler spectra proving this are shown. Some options for the future are also discussed.

Describes a millimetre radar system for the measurement of clouds. The 94 GHz cloud profiler is a bistatic system with an average transmitted power of 1.6 W and it is built up using only semiconductor devices. Due to the modular design power upgrade is possible. It's size without antenna is approx. 65cm/spl times/42cm/spl times/22cm. The weight of the system is about 25 kg. The initial signal is generated by a voltage controlled CW Gunn oscillator. This signal synchronizes a 500 mW IMPATT oscillator by injection locking. The heart of the system is a power combiner consisting of four 500 mW IMPATT oscillators. A fraction ofthe transmitted signal is used as a local oscillator of the mixer which converts the received signal to IF-level. The mixer used for deriving the IF signal from transmitted and received signals has a noise temperature of T=625K at a operation temperature of 300K. The diameter of the antenna used for the first tests is 157 mm.<>