09.04
IR Photometry and Spectra of Io Occultations in 1997
J.D. Goguen, D.L. Blaney, G.J. Veeder, D.L. Matson, T.V. Johnson (JPL), P.D. Nicholson, T.H. Hayward, J.E. Van Cleve (Cornell U.), D. Toomey, L. Bergknut, C. Kaminski, W. Golisch, D. Griep (NASA IRTF, U. Hawaii)
We report results of IR measurements of occultations of Io by Europa
made at the NASA IRTF and Palomar, observations that we use to map the
thermal emission from Io's volcanos at high spatial resolution. The
figure illustrates one result from 
=8.7 
m photometry of
the 4/18/97 UT occultation. The graph plots the combined flux from
both satellites, normalized to the unocculted flux, versus UT with 4
times labelled. A bright hot spot containing 
50% of the total
flux disappears behind Europa's limb between times 1 & 2 and reappears
between times 3 & 4. The image shows a map of Io and the outline of
Europa's limb at these 4 times based on the Galileo navigation
ephemeris (courtesy W. Owen). The eruption lies within the region of
overlap of the 4 limb projections, squarely centered on Loki Patera.
The lightcurve shows that no other comparably bright hot spots were
occulted. The data set we are analyzing includes 8.2-11.2 m spectra
of the 3/28/97 UT occultation acquired with SpectroCAM-10 on the
Palomar 5-m.
