434 
the estimation of the HH/VV ratio. The results reveal the presence of thawed lakes in the midst 
of the facies, and areas of wetter snow in local surface depressions, which are all fact confirmed by 
examination of the video imagery. The estimated values of snow wetness in these depressions are 
consistent with in-situ measurements conducted at the Swiss Camp by glaciologists. In the future, 
radar maps of snow wetness will be combined with maps of snow albedo derived from AVHRR data 
for estimating regional surface fluxes in the soaked-snow facies. 
Acknowledgements: We thank Dr. R. Thomas, Head of the Polar Research Program at NASA 
Headquarters, for supporting this research. This work was carried out at the Jet Propulsion Labo 
ratory, California Institute of Technology, under contract with the National Aeronautics and Space 
Administration. 
REFERENCES 
[1] van Zyl J. J., R. Carande, Y. Lou, T. Miller, and K. Wheeler, The NASA/JPL three-frequency 
polarimetric AIRSAR system, Proc. Int. Geosc. and Rem. Sens. Symp., Houston, Texas, May 
26-29, 1992, IEEE New York Pub., 649-651, 1992. 
[2] E. Rignot, S. Ostro, J. van Zyl, and K. Jezek, Unusual radar echoes from the Greenland Ice 
Sheet, Science 261, 1710 (1993). 
[3] K. C. Jezek and S. P. Gogineni, Microwave remote sensing of the Greenland ice sheet, IEEE 
Geosc. Rem. Sens. Soc. Newsletter 85, 6 (1992). 
[4] C. S. Benson, Stratigraphic studies of the snow and firn of the Greenland ice sheet, US Army 
Snow Ice Permafrost Res. Estab. Res. Rep. 70 (Hanover, NH, 1962). 
[5] S. J. Ostro et al., Europa, Ganymede, and Callisto: New radar results from Arecibo and Gold- 
stone, J. Geophys. Res. 97, 18277 (1992). 
[6] H. J. Zwally, Microwave emissivity and accumulation rates of polar firn, J. Glaciol. 18, 195 
(1977). 
[7] C. T. Swift, P. S. Hays, J. S. Herd, W. L. Jones, and V. E. Delmore, Airborne microwave 
measurements of the southern Greenland ice sheet, J. Geophys. Res. 90, 1983 (1985). 
[8] B. Hapke, Coherent backscatter and the radar characteristics of outer planet satellites, Icarus Figure 1. M 
88, 407 (1990). track of AIRS 
[9] M. P. van Albada, M. B. van der Mark and A. Lagendijk, in Scattering and Localization of GISP jj ¿ ee p. 
Classical Waves in Random Media , P. Sheng, Ed. (World Scientific, Singapore, 1990), p. 97. 
[101 K. J. Peters, Coherent-backscatter effect: A vector formulation accounting for polarization and 
absorption effects and small or large scatterers, Phys. Rev. B 46, 801 (1992). 
[11] M. I. Mishchenko, Polarization characteristics of the coherent backscatter opposition effect. 
Earth, Moon, and Planets 58, 127 (1992). 
[12] S. J. Ostro and E. M. Shoemaker, Icarus 85, 335 (1990).