588
J. Noll
microwave radiometers. The order of magnitude can be correctly retrieved for snow height and
snow water content, the differences to ground observed data are in the order of a factor 2-3. The
difficulty in the validation of the retrieved snow properties are mainly due to the comparison
of 25 x 25 km SSM/I data with ground truth at selected points. The major limitation here is
the footprint size, which for land applications should be in the order of 10-15 km.
With respect to MIMR, the increase of the antenna size of 1.6 m compared to 0.65 m for the
SSM/I will improve the spatial resolution of the corresponding channels by about the factor
three for MIMR. The radiometric accuracy is, despite the antenna size, kept very similar to
the SSM/I. With a sampling distance of 15.5 km for the 6.8 to 23.8 GHz channels and even
smaller for the 36.5 and 90 GHz channels, the use of MIMR data will provide not only snow
extent and melt-onset, but also snow water equivalent and snow depth.
The simulations have shown also, that atmospheric parameters affect significantly the measured
emittance, thus combined models for atmosphere and surface parameter retrieval are required.
The advantages of microwave remote sensing compared to optical remote sensing is the all
weather, day and night remote data retrieval. This advantage has to be further evaluated in
models describing the change of geophysical parameters (change detection) rather than performing singular event calculations.
Acknowledgment
The authors would like to thank Frank Wentz (Remote Sensing Systems in California), the
University of Colorado in Boulder (World Data Center A) and ESA-ESRIN in Frascati for
providing us with SSM/I data. Thanks to our colleagues Johnny Johannessen and Paul Ingmann at ESA ESTEC for information and comments. All those, who were involved in ESA
contracts during the last years and delivered various direct and inverse algorithm are gratefully
acknowledged.
21.4 References
Alishouse JC, Snider JB, Westwater ER, Swift CT, Ruf CS, Snyder SA, Vongsathorn J, Ferraro RR (1990) Determination of Cloud Liquid Water Content Using the SSM/I.
IEEE Trans Geosci Rem Sms 28(5): 817-822
CEOS (1994) CEOS Dossier; Volume A: Satellite Missions. ESA ESTEC, Noordwijk (NL)
ESA (1995a) New Views of the Earth, Scientific Achievements of ERS-1. ESA SP-1176/IESA
ESTEC, Noordwijk (NL)
ESA (1995b) Land and Sea, ERS-1 Applications. ESA BR-l09 ESA ESTEC, Noordwijk (NL)
Goodberlet MA, Swift CT, Wilkerson JC (1990) Ocean Surface Wind Speed Measurements of the SSM/I. IEEE Trans Geosci Rem Sens 28(5): 823-828
Gudmandsen P, Skou N (1991) User Wishlist for future Spaceborne Microwave Radiometry.
ESTEC Contract No 8968/90/NL/US(SC) Vol 2, ESA ESTEC, Noordwijk (NL)
Hallikainen MT, Jaaskeliiinen VI (1988) Microwave Emission behaviour of Snow.
IGARSS'88 Edinburgh, Scotland
Hollinger JP (1990) Introduction. IEEE Trans Geosci Rem Sms 28(5): 779-780
Hollinger JP, Peirce JL, Poe GA (1990) SSM/I Instrument Evaluation, IEEE Trans Geosci
Rem Sens 28(5): 781-790
J. Noll
microwave radiometers. The order of magnitude can be correctly retrieved for snow height and
snow water content, the differences to ground observed data are in the order of a factor 2-3. The
difficulty in the validation of the retrieved snow properties are mainly due to the comparison
of 25 x 25 km SSM/I data with ground truth at selected points. The major limitation here is
the footprint size, which for land applications should be in the order of 10-15 km.
With respect to MIMR, the increase of the antenna size of 1.6 m compared to 0.65 m for the
SSM/I will improve the spatial resolution of the corresponding channels by about the factor
three for MIMR. The radiometric accuracy is, despite the antenna size, kept very similar to
the SSM/I. With a sampling distance of 15.5 km for the 6.8 to 23.8 GHz channels and even
smaller for the 36.5 and 90 GHz channels, the use of MIMR data will provide not only snow
extent and melt-onset, but also snow water equivalent and snow depth.
The simulations have shown also, that atmospheric parameters affect significantly the measured
emittance, thus combined models for atmosphere and surface parameter retrieval are required.
The advantages of microwave remote sensing compared to optical remote sensing is the all
weather, day and night remote data retrieval. This advantage has to be further evaluated in
models describing the change of geophysical parameters (change detection) rather than performing singular event calculations.
Acknowledgment
The authors would like to thank Frank Wentz (Remote Sensing Systems in California), the
University of Colorado in Boulder (World Data Center A) and ESA-ESRIN in Frascati for
providing us with SSM/I data. Thanks to our colleagues Johnny Johannessen and Paul Ingmann at ESA ESTEC for information and comments. All those, who were involved in ESA
contracts during the last years and delivered various direct and inverse algorithm are gratefully
acknowledged.
21.4 References
Alishouse JC, Snider JB, Westwater ER, Swift CT, Ruf CS, Snyder SA, Vongsathorn J, Ferraro RR (1990) Determination of Cloud Liquid Water Content Using the SSM/I.
IEEE Trans Geosci Rem Sms 28(5): 817-822
CEOS (1994) CEOS Dossier; Volume A: Satellite Missions. ESA ESTEC, Noordwijk (NL)
ESA (1995a) New Views of the Earth, Scientific Achievements of ERS-1. ESA SP-1176/IESA
ESTEC, Noordwijk (NL)
ESA (1995b) Land and Sea, ERS-1 Applications. ESA BR-l09 ESA ESTEC, Noordwijk (NL)
Goodberlet MA, Swift CT, Wilkerson JC (1990) Ocean Surface Wind Speed Measurements of the SSM/I. IEEE Trans Geosci Rem Sens 28(5): 823-828
Gudmandsen P, Skou N (1991) User Wishlist for future Spaceborne Microwave Radiometry.
ESTEC Contract No 8968/90/NL/US(SC) Vol 2, ESA ESTEC, Noordwijk (NL)
Hallikainen MT, Jaaskeliiinen VI (1988) Microwave Emission behaviour of Snow.
IGARSS'88 Edinburgh, Scotland
Hollinger JP (1990) Introduction. IEEE Trans Geosci Rem Sms 28(5): 779-780
Hollinger JP, Peirce JL, Poe GA (1990) SSM/I Instrument Evaluation, IEEE Trans Geosci
Rem Sens 28(5): 781-790