ISMAR: A new Submillimeter Airborne Radiometer

ISMAR (International SubMillimeter Airborne Radiometer) is a new passive remote-sensing radiometer which has been jointly funded by the UK Met Office and the European Space Agency (ESA). It contains a number of heterodyne receivers operating at frequencies between 118 and 664 GHz, some with dual polarisation. The design is modular and will allow further channels to be added in future, including 874 GHz. Submillimeter waves are very sensitive to scattering by ice particles, and the channels have been selected to allow the direct retrieval of various ice-cloud properties, including Ice Water Path (IWP) which is an important parameter in General Circulation Models (GCMs). ISMAR can also be used for surface emissivity and radiative transfer studies as it can view in multiple nadir and zenith directions. ISMAR has been developed as a satellite demonstrator for ICI (Ice Cloud Imager) due for launch in 2022 on the EUMETSAT Polar System - Second Generation satellites (EPS-SG). It can be used for testing and developing retrieval algorithms prior to launch, as well as for calibration/validation post-launch and specific scientific case studies. It is designed to operate on board the FAAM BAe-146 atmospheric research aircraft, which also carries a wide range of complementary remote-sensing and in-situ instrumentation including microwave radiometers, infra-red and visible spectrometers and cloud physics probes. The instrument is self-contained, allowing simple ground-based operation as well as the potential for installation on other aircraft. ISMAR is currently undergoing integration testing, and flight testing will take place from April 2014. An ISMAR science campaign is currently planned to take place in Goose Bay, Canada in 2015 to study the submillimeter signature of cirrus cloud.