The fourth international meeting of the Multifrequency Imaging Microwave Radiometer (MIMR) Science Advisory Group (SAG) was held at the European Space Research Institute (ESRIN), at Frascati, Italy, July 5-7, 1995.

Johnny Johannessen (MIMR SAG Coordinator, and Head of the Ocean/Sea-Ice Unit, Earth Science Division, ESA) opened the meeting by going over the last meeting minutes. He then expressed his gratitude to the U.S. scientists for attending the SAG despite ESA's not providing a MIMR instrument for the PM platform.

The agenda for the meeting listed several presentations to be made to the entire group before the subgroups would finalize the draft of the MIMR Interim Report. On the last day the mid-term results of the project studies were presented, and the meeting closed with planning for the next SAG.

Yvon Menard's (ESA, MIMR Program Manager) presentation included MIMR hardware status, polarimetry, spectral response, calibration/validation, preprocessing, and products. Evert Attema completed the presentation with a ground-processing discussion. Currently, the plan is to build 3 instruments: the first is an engineering model (not spaceworthy), and the others are radiometers for the Meteorological Operational Satellite (METOP) 1 and 2.

METOP phase B kick-off occurred July 12, 1995. The MIMR demonstrator work is on schedule with the final review planned for the end of May 1996. On-going work includes breadboarding receivers, calibration targets, scan/balance mechanism, and electrical and mechanical ground equipment. Remaining work is EMI/EMC testing, scan-mechanism life test and sensor calibration test.

The polarimetry discussion was shortened because of the revelation that ASCAT (Advanced Scatterometer) will fly on METOP (precluding the need for polarimetry), and that METOP is an operational program where an experimental add-on (such as polarimetry) is not warranted.

The resampling presentation led to a recommended scan speed of 30 rpm for precipitation measurements.

Finally, Menard showed an outline for the data preprocessing program. The Level 1b data (data available to scientists) will be corrected for all the instrument-induced errors (antenna pattern, spill over, polarization correction, incidence-angle bias, local oscillator (LO) leakage), and thus they are not reversible (for scientists that want to work with raw data).

E. Attema discussed the ground processing and data flow concepts. The European Meteorological Satellites (EUMETSAT) representative, Graeme Mason, gave a brief presentation on the EUMETSAT/NOAA joint polar system. Both METOP and NOAA satellites would directly transmit all data to their own and to each other's ground stations at all times. He also delineated ESA's responsibilities: develop ASCAT and MIMR Level 1b data, maintain algorithms and databases for the lifetime of METOP-1, and transfer working algorithms for database production and services to EUMETSAT when they are qualified for operational use with succeeding METOPs.

Short presentations on various research topics concluded the first day. L. Eymard (Centre Universitaire de Velizy, Velizy, France, eymard@piano.velizy.cnet.fr) presented work showing the need for algorithm validation, especially the sensitivity to the choice of radiative transfer model (RTM) used in parameter retrieval. She is also involved in the design of the Fronts and Atlantic Storm Track Experiment (FASTEX) campaign (occurring in early 1997) where she will be able to test some of the candidate RTMs. The scientific objectives of this campaign are: feasibility of "adaptive observational system," analysis and forecast of cyclone activity in Eastern oceanic basins, air-sea interaction and its role in cyclogenesis, and embedded mesoscale substructures.

Data will be taken by aircraft (NOAA Gulfstream, University of Washington Convair, USAF C-130, NASA DC-8, NCAR Electra), ships (Ukrainian, French Navy, NOAA oceanographic), satellites (NOAA and DMSP), and radiosondes along the U.S., Canadian, Greenland, and European coasts.

C. Mätzler (University of Bern, Institute of Applied Physics, Bern, Switzerland, fax 41-31-631-3765) found good agreement between different soil emissivities measured with a non-scanning, land-based radiometer and with the Special Sensor Microwave/Imager (SSM/I). P. Gudmansen (Electromagnetics Institute, Technical University of Denmark, Lyngby, Denmark, pg@emi.dth.dk) reported on a comparison between data from the Scanning Multichannel Microwave Radiometer (SMMR) and the Scatterometer on ERS-1 over the Greenland Ice Sheet. In comparing these data an anisotropy was detected, ascribed to sastrugies influenced by the dominant wind.

M. Hallikainen (Laboratory of Space Technology, Helsinki University of Technology) described a study conducted to design a MIMR airborne instrument simulator (called MAMR). This simulator would fly onboard a Skyvan aircraft, have four fixed channels (between 6.8 and 23.8 Ghz) and two conically scanning channels (36.5 and 89 Ghz), with a 55 degrees incidence angle, each channel having a 3.3 degrees beamwidth. The challenging specification, the pointing- and attitude-determination accuracy, was achieved with active stabilization of the instrument mounting platform.

The final presentation of the day was a study on the use of cloud-radiation models for passive microwave precipitation retrieval given by G. Panegrossi (student of A. Mugnai, Instituto di Fisica dell'Atmosfera, Frascati, Italy, mugnai@hp.ifsi.fra.cnr.it). The main conclusion of this study is that microphysics changes affect the resulting precipitation rate. Thus, there is a need for more-accurate modeling of microphysical properties of hydrometeors and for more-accurate radiation transfer models.

The second day was dedicated to finalizing the Interim Report. The sub-group findings were then presented to the entire group at the end of the day. Most of the comments were directed to making the document uniform over all four disciplines. Regarding the need for polarimetry for the METOP mission, the consensus was that polarimetry is a good scientific experiment, but it does not belong on an operational satellite, especially when the satellite is flying a scatterometer. The Oceans and Marine Atmospheres sub-group discussed at length an algorithm conceptual model and a pre-launch validation plan to improve the radiative transfer model used. A work plan was developed to: a) do a direct intercomparison of RTMs, b) compare measurements with software simulations, and c) adapt the SSM/I and TRMM algorithms. It was also decided to append the earlier San Miniato report, which led to the MIMR concept, to this final MIMR Interim Report. Johannessen will incorporate all comments and send the report (as Draft 1.0) to the MIMR SAG members for a final review.

On the final day of the meeting, there were presentations on the mid-term results of different ongoing project studies. S. English (U.K. Met Office) reported on a variational analysis of MIMR sea surface temperature (SST) information content and some aircraft measurements of sea surface emissivities. M. Fischer discussed the impact of MIMR wind data on the El Niño/Southern Oscillation analysis and predictions. Preliminary results of the intercomparison of the Florida State University and SSM/I wind speed data indicate the need for more-accurate wind measurements from space. L. Phalippou (European Center for Medium-range Weather Forecasts [ECMWF], Reading, U.K.) reported on his work on the use of microwave imagery in numerical weather prediction. He concluded that the variational approach extension method for forecasting has more advantages than the regression methods. L. Eymard reported on her work in the laboratory measuring the dielectric constant of different salinity water, and Josef Noll [ESTEC], (Noordwijk, Netherlands, josef@estec. esa.nl) briefly discussed his collaboration with P. Schlüssel on studies of sea ice and atmospheres.

In closing, the logistics of membership, short presentation topics for next meeting, and time and place for the next meeting were discussed. John Foote (U.K. Met Office) is withdrawing from the SAG. The members agreed to have S. English as a replacement, and also have L. Phillapou become a member, as a representative of ECMWF. The presentation topics for the next meeting will be informational talks on the other METOP and EOS PM instruments, as well as the status of the PM platform and the potential PM radiometer, Advanced Microwave Scanning Radiometer (AMSR). It was tentatively decided that the next MIMR SAG will take place in New Orleans, LA, February 5-7, 1996.

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