CIMR goals
The main goal of the CIMR mission is to monitor changes in the Arctic, which is dominated by the Arctic Ocean. The majority of the Arctic Ocean is covered by sea ice for most of the year but due to climate change, the extent and thickness of this ice is reducing, leaving more of the surface of the Arctic Ocean exposed to the atmosphere.
CIMR is designed to measure key sea ice and ocean parameters that will be used by Copernicus Services to provide short-range forecasts and long-term predictions for the Arctic.
A key challenge for Earth observation is the provision of microwave radiometer measurements with good spatial resolution based on measurements in the 6–10 GHz frequency (C-band and X-band), which requires a very large reflector system.
CIMR uses the largest rotating reflector in the world – 8 m in diameter – to provide such measurements at unprecedented spatial resolution for this class of mission.
As a key parameter, CIMR will determine the sea-ice concentration in the Arctic on sub-daily timescales at a spatial resolution of <5 km for the entire Arctic Ocean and adjacent seas – so without any data gap over the North Pole.
Historically, values of sea-ice concentration have been determined using microwave frequency data at K-, Ka- and W-band from a variety of satellite instruments including the US Special Sensor Microwave Imagers and the Advanced Microwave Scanning Radiometer series. However, the future continuity of these mission in an operational context is not foreseen.
CIMR will also provide high-resolution sea-surface temperature measurements in the polar regions. The inflow of warm, saline Atlantic water to the Arctic, between Iceland and the Faroe Islands, is the strongest Atlantic inflow to the Arctic in terms of volume and associated transport of heat that impacts the formation and demise of sea ice.
A challenge in this region is the persistent cloud that prohibits measurements of sea-surface temperature from thermal-infrared satellite measurements.
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Microwave frequencies at C- and X-band offer well-established measurement capabilities that are not affected by cloud cover. And CIMR will measure sea-surface temperature at a spatial resolution of <15 km (real aperture) on sub-daily timescales over the pan-Arctic region and adjacent seas.
Sea-surface salinity has been measured using L-band frequencies since 2009 by ESA’s SMOS mission and NASA’s SMAP missions. Since sea-surface salinity is a fundamental part of the ocean–cryosphere system, a third objective for CIMR is to maintain a European L-band capability at least equivalent to SMOS and SMAP in an operational context.
As well as sea-ice concentration, sea-surface temperature and sea-surface salinity data, CIMR is tasked to deliver a number of other measurements, including ocean-wind vectors, sea-ice parameters in the Arctic and the Antarctic, and measurements over land of snow extent, snow-water equivalent, soil moisture, land-surface temperature, vegetation optical depth/indices, surface-water extent. CIMR will also deliver cloud liquid water and precipitation measurements over the global ocean.
Since Copernicus requires data products to support forecasting systems, data delivery is required to be with users within three hours of sensing. In support of shipping and safe navigation in the Arctic, which is expected to significantly increase as sea-ice extent and thickness decrease in the coming decade, sea-ice concentration data are required within one hour of sensing.
Synergy is also considered with respect with other relevant satellite missions including Copernicus Sentinel-1 (C-band imaging radar), ROSE-L (L-band imaging radar), CRISTAL (Ku- and Ka-band interferometric radar altimeter), and ESA’s Arctic Weather Satellite and subsequent potential Sterna constellation (19-band microwave radiometer) that are expected to be in orbit at same time, i.e. between 2029 and 2035.
The complementary payload of other Copernicus polar missions and the European MetOp-SG-1B, carrying a wind scatterometer and multichannel microwave imagers with frequencies selected for numerical weather prediction is also of particular importance.
For example, CIMR is to be placed in the same Sun-synchronous orbit as MetOp-SG-1B, but operating in a different dawn-dusk orbit plane allowing CIMR measurements to be made within 10 minutes of MetOp-SG-1B over the polar regions, above 60 degrees latitude.
