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An enhanced spatial resolution brightness temperature product is proposed for future conical scan microwave radiometers. The technique is developed for Copernicus Imaging Microwave Radiometer (CIMR) measurements that are simulated using the CIMR antenna pattern at the L-band and the measurement geometry proposed in the Phase A study led by Airbus. An inverse antenna pattern reconstruction method is proposed. Reconstructions are obtained using two CIMR configurations, namely, using measurements collected at L-band by the forward (FWD) scans only, and combining forward and backward (FWD+BWD) scans. Two spatial grids are adopted, namely, 3km × 3 km and 36km × 36km. Simulation results, referred to synthetic and realistic reference brightness fields, demonstrate the soundness of the proposed scheme that provides brightness temperature fields reconstructed at a spatial resolution up to ~1.9 times finer than the measured field when using the FWD+BWD combination., This work has been produced for the European Space Agency (ESA) in the frame of the Copernicus programme as a partnership between ESA and the European Commission.

13 pages, 7 figures, 1 table, the Aquarius L2 V3.0 data are available at oceandata.sci.gsfc.nasa.gov/Aquarius/V3/V3.0/L2, the Antarctic data sets from the Bedpmap2 project are available at https://secure.antarctica.ac.uk/data/bedmap2/, the subglacial lakes inventory is available at https://doi.org/10.1017/S095410201200048X, The Dome-C region, in the East Antarctic Plateau, is regarded as an ideal natural laboratory for calibration/validation of space-borne microwave radiometers. At L-band, the thermal stability of this region has been confirmed by several experimental campaigns. However, its use as an independent external calibration target has recently been questioned due to some spatial inhomogeneities and seasonal effects revealed in the brightness temperatures (TB) acquired in this area. This paper shows the observed relationship, from exploratory research, between the Antarctic ice thickness spatial variations and the measured Aquarius TB changes. A 3-months no-daylight period during the Austral winter has been analyzed. Four transects have been defined over East Antarctica covering areas with different ice thickness variations and ranges. The theoretical L-band penetration depth has been estimated to understand the possible contributions to the measured signal. A good agreement has been observed between Aquarius TB and ice thickness variations over the whole Antarctica, with correlations of ∼0.6-0.7. The two variables show a linear trend with slopes of ∼8.3-9.5 K/km. No correlation has been observed with the subglacial bedrock. The maximum L-band penetration depth has been estimated to be ∼1-1.5 km. Results are therefore consistent: the spatial variations found on Aquarius TB are not related to the emissivity of the bedrock, which lies deeper. This study provides evidence that new L-band satellite observations could contribute to further our understanding of Antarctic geophysical processes. Key Points: Relationship between Antarctic ice thickness and observed Aquarius TB. Maximum L-band penetration depth over Antarctic ice.Possible influence of subglacial lakes on Aquarius TB © 2015. American Geophysical Union. All Rights Reserved, The work presented in this paper was supported by the Spanish National R1D Program on Space of the Ministry of Economy and Competitiveness, through a Formación de Personal Investigador (FPI) grant with reference BES-2011-043322 and the project MIDAS 7: AYA2012-39356-C05-01

End-to-end calibration of the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS) radiometer refers to processing the measured raw data up to dual-polarization brightness temperature maps over the earth's surface, which is the level 1 product of the Soil Moisture and Ocean Salinity (SMOS) mission. The process starts with a self-correction of comparators offset and quadrature error and is followed by the calibration procedure itself. This one is based on periodically injecting correlated and uncorrelated noise to all receivers in order to measure their relevant parameters, which are then used to correct the raw data. This can deal with most of the errors associated with the receivers but does not correct for antenna errors, which must be included in the image reconstruction algorithm. Relative S-parameters of the noise injection network and of the input switch are needed as additional data, whereas the whole process is independent of the exact value of the noise source power and of the distribution network physical temperature. On the other hand, the approach relies on having at least one very well-calibrated reference receiver, which is implemented as a noise injection radiometer. The result is the calibrated visibility function, which is inverted by the image reconstruction algorithm to get the brightness temperature as a function of the director cosines at the antenna reference plane. The final step is a coordinate rotation to obtain the horizontal and vertical brightness temperature maps over the earth. The procedures presented are validated using a complete SMOS simulator previously developed by the authors.