HST Observations of Jupiter's Aurora Simultaneous with GALILEO Measurements

J.T. Clarke (U. Michigan), G. Ballester (U. Michigan), J. Trauger (JPL), J. Ajello (JPL), W. Pryor (U. Colorado), K. Tobiska (JPL), G.R. Gladstone (SwRI), J.H. Waite, Jr. (SwRI), L. Ben Jaffel (IAP), J.E.P. Connerney (NASA GSFC), J.C. Gerard (Univ. of Liege)

An HST observing program is underway to obtain images and spectra of Jupiter's ultraviolet aurora during key events in the GALILEO orbiter mission, including remote observations of the nightside aurora and measurements of the magnetic field and charged particle environments. We have obtained WFPC 2 images and GHRS spectra of Jupiter's aurora overlapping with GALILEO measurements during GALILEO orbits G1 (June 1996), G2 (Sept. 1996), G7 (April 1997), and G8 (May 1997), and at the time of writing we are scheduling STIS spectra for summer 1997. The WFPC 2 images appear similar to earlier reported auroral images, with the main oval at the same location observed over the last 2 years, rapidly variable emission poleward of the main oval, and the Io footprint with a similar longitudinal offset from the local magnetic field. Spectra were obtained of auroral emission features including the northern and southern main ovals, the diffuse emission poleward of the main oval, and the northern and southern Io footprints. These spectra will be presented with estimates of the overlying hydrocarbon columns, the energy of the exciting electrons, the rotational temperature of the emitting hydrogen, and the overlying column of atomic hydrogen. This work was supported by NASA under contract JPL 959122 and grants GO-5828.01-94A and GO-6743.01-95A to the University of Michigan.