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R.C. Woodward Jr. (U Wisc), R.J. Oliversen (NASA/GSFC), F. Scherb, A. Steffl (U Wisc), G.M. Hilton, N.E. Doane (Raytheon)
We recently initiated a synoptic broadband imaging program targeting the Io plasma torus at \rm S\,II\,\lambda 6731. These data are acquired on the west auxiliary telescope (0.81\,m primary) of the McMath-Pierce Facility on Kitt Peak, and imaged through an interference filter in a custom instrument. Our field of view of ~7' and plate scale of 0.794''/pixel captures both sides of the torus, along with Jupiter itself, in the same image. A neutral density filter attenuates Jupiter, allowing us to use it for spatial alignment and intensity calibration. Jupiter's moons are blocked as necessary with small, moveable masks. To minimize smearing from the motion of the torus (one full revolution every ~10 hours), we restrict most integrations to ten minutes. The constraints of primary aperture and integration time are severe, but allow us to obtain the long telescope access times necessary to study the complex, time-variable behavior of the plasma torus.
In September and October 1997 we acquired the first data from this program: 260 images over 20 nights. We present here these data and our initial analysis of them.
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