Temperature Measurements of the Jovian Planets and Titan by CCD Spectroscopy
E. Karkoschka (U. Ariz.)
I present a new method to measure temperatures. The method uses the fact that the width of the 890-nm methane band varies with temperature. I used spectra of the jovian planets and Titan obtained on La Silla in 1993 and 1995 to measure the width of the 890-nm methane band at absorption coefficients of 2, 5, and 15/km-am. Measurements on Jupiter and Saturn are spatially resolved. Temperature maps of their disks show a number of expected and unexpected features with amplitudes of 2-10 K.
The three selected absorption coefficients probe different altitudes near the tropopause which allows the detection of spatial features in the temperature gradient.
Some methane absorptions near the 890-nm band display little dependence on temperature. They show the penetration depths. Thus, it is possible to distinguish horizontal temperature features from measured temperature variations due to different penetration depths. This is an advantage over measurements in the thermal infrared which do not contain temperature invariant data.
This work is supported by NSF grant AST 9417368.