H
ISO-SWS Observations of Uranus: the Stratospheric Distribution of C H
Th. Encrenaz, B. Bézard (Obs. Paris), H.Feuchtgruber (MPI Garching), E. Lellouch (Obs. Paris), Th. de Graauw (SRON, Groningen), M. F. Kessler (ISO SOC, Villafranca), M. J. Griffin (QMWC, London), S. K. Atreya (U. Michigan)
The infrared spectrum of Uranus has been recorded between 7 and 16.5 
m
with the grating mode of the Short-Wavelength Spectrometer of the Infrared
Space Observatory, with a resolving power of 1500.
The spectrum shows no signal
except in the C H band centered at 13.7 m. From the absence
of emission in the region of the CH 
band at 7.7 m,
where the flux is lower than 0.5 Jy, an
upper limit of 10 
can be estimated for the
stratospheric mixing ratio of methane. The C H band can be
fitted with a stratospheric mixing ratio of
3 10 
. The CH and C H estimates mostly refer to the
1 - 100 bar region.
Our calculations assume a thermal profile based upon Voyager UVS
and radio data (Atreya et al, in "Uranus", U. Arizona, 1991).
It should be noted that these results are very preliminary, and strongly
depend upon the stratospheric thermal profile.