__________________________________________________________________________ T H E O L E R O E M E R M E S S E N G E R _______________________________________________ JJJJ C G JJJJJJ I E JJJJ __________________________________________________________________________ Newsletter of the International Jupiter Watch Satellite Discipline E-mail issue 13 February 8 1995 Editor and Discipline Leader: John Spencer Voice: (602) 774-3358 Lowell Observatory Fax: (602) 774-6296 1400 W. Mars Hill Rd. Internet: spencer@lowell.edu Flagstaff, AZ 86001 ___________________________________________________________________________ EDITORIAL COMMENTS This is the first Ole Roemer Messenger in a while, but they will be coming more frequently during Jupiter season (opposition is June 1st), and in the buildup to the Galileo encounter in December. Please send me information on your observing plans or results, and new publications, and I'll put them in subsequent issues. Also please send corrections to any errors you find here. ___________________________________________________________________________ BETHESDA DPS IJW SATELLITE MEETING: REPORT A meeting of the IJW Satellite Discipline was held on Thursday November 3rd 1994 at the DPS meeting in Bethesda. We had perhaps 20 attendees (I didn't count). An impromptu "satellite lunch" was also held on Tuesday. The following items were discussed: 1994 Results: Lonne Lane (alane@jplal2.dnet.nasa.gov) showed UV ground-based spectra of the Galilean satellites taken in Spring 1994 which gave tantalising evidence for temporal changes since IUE observations a decade ago. Gilda Ballester (gilda@sunshine.sprl.umich.edu) showed UV images of Io's trailing hemisphere from HST, taken in June 1994, showing the darkness of SO2 regions below 3000 Angstroms more clearly than pre-repair HST images. Bob Howell (rhowell@corral.uwyo.edu) showed a remarkably successful fit to the Voyager measurements of Loki's thermal emission, and the enhanced emission during the 1991 Europa occultations, using a simple model of continuously erupting and cooling silicate flows, indicating that silicate volcanism was consistent with Loki's thermal emission at Voyager time. Coincidentally, Ashley Davies at JPL (agd@scn1.jpl.nasa.gov) has been working on a similar silicate flow model to explain the much brighter 1990 outburst at Loki. The cooling phase of these models, after the active eruptions cease, provides a good test of the models and it was agreed that it would be nice to have more observations of the characteristics of the return to "normal" flux levels after a Loki brightening or major outburst. I (spencer@lowell.edu) briefly mentioned the two infrared brightenings of Io noted in 1994- a "normal" Loki brightening seen in January, and a brighter outburst on the Jupiter-facing hemisphere seen at the end of May. Paul Schenk (schenk@lpi.jsc.nasa.gov) described his continued work on producing stereo images of Io from Voyager data, which is providing new information on Io's topography. Some of his best images were presented in an article in the Jan. 94 "Astronomy" magazine. ________________________________________________________________________________ OBSERVING PLANS FOR 1995 In 1995 we begin to address more directly one of the primary goals of the IJW: earth-based observational support of the Galileo spacecraft observations of Jupiter, which begin in December 1995. The Galileo Io encounter, which will get high-resolution observations of most of the anti-Jupiter side in sunlight, and small portions of the Jupiter-facing side at night, occurs on December 7th 1995, with Jupiter 9.5 degrees from the sun as seen from Earth. Coordination of groundbased programs in the coming year was thus a major topic of discussion at the meeting. I know of the following observational programs for monitoring Io volcanism. Dates of scheduled observations are given in UT: the IRTF is so far scheduled through July 1995. 1) The JPL group (Goguen, Matson, Johnson, Veeder, Blaney) A. 5-20 micron monitoring of Io's disk-integrated lightcurve near opposition in 1995, from the IRTF, continuing their long-term program. 6/11-6/13, and 6/16. B. Dual-wavelength measurements of Io's eclipse cooling and heating, at the IRTF, to test thermophysical models. 4/6; 6/16; 7/2; 7/18. C. Relatively frequent monitoring of disk-integrated thermal emission with the Goguen 4-channel IR photometer on the 48" telescope at JPL's Table Mountain Observatory, once the photometer system is working. Expected "after August". D. Global bolometric radiometry and eclipse reappearances of Io with the Goguen 4-channel photometer at the Palomar 200". 8/05; 8/12. 2) The Wyoming "group" (Howell) A. Observations of eclipses and occultations of Io by Jupiter, from WIRO, starting with single-channel photometer in February and hopefully using using a 58x62 InSb array camera starting in early summer, getting spatial resolution from Jupiter occultation photometry. Will try to observe close to the sun. Jupiter's airmass will always be high from Wyoming's, latitude, limiting observing periods. B. Seeing the relative lack of planned observations of Io's anti-Jupiter side close to the Galileo Io encounter, Bob said he'd continue to monitor Io's entire 5-micron lightcurve from WIRO, using both the single-channel and array systems. 3) The Lowell "group" (Spencer) A. Continued 1.7 -- 5 micron imaging of eclipses and occultations of Io by Jupiter at the IRTF, using direct imaging and occultation lightcurves to get spatial resolution on Io. Observations will be as frequent and close to the Galileo encounter as possible, but will only cover the Jupiter-facing hemisphere. 2/17; 2/19; 2/26; 3/5; 3/7; 3/14; 4/13; 4/15; 7/9; 7/11; 7/25; 7/27. B. Monitoring Io's entire 5-micron lightcurve from the IRTF 2/27 to 3/11, as part of an educational project. C. Frequent 1.7 - 2.3 micron imaging of Jupiter eclipses and occultations with a NICMOS camera (OSIRIS) at the Lowell 72". Jupiter occultations will provide spatial resolution. 2/12; 2/28; 3/16; 3/23. April onwards not yet scheduled. 4) The UCLA "group" (Becklin) Now that the UCLA campus 24" has been repaired after last year's earthquake, Eric Becklin hopes to begin a program of monitoring Io's 2.1 micron volcanic emission in eclipse using an IR camera there. 5) The Ad-Hoc Galileo Encounter Group (Spencer, Orton) Glenn Orton will be attempting to image Jupiter's atmosphere from 2 - 20 microns, using the NSFCAM and MIRAC cameras at the actual time of the Galileo encounter by using plastic trash bags over the IRTF primary and secondary to absorb short-wavelength radiation and allow pointing at Jupiter 9 degrees from the sun. This technique was successful beyond 4 microns in November and December 1994 (see report below), so we may use the same setup for observations of Io's volcanism, interleaved with the atmospheric observations, at the time of the Galileo encounter. This seems to be our only hope for earth-based observations simultaneous with the encounter. The table below summarizes the various proposed observations of Io's volcanism in 1995. Program numbers refer to the list above. "Spatial resolution" means better than hemispheric resolution, though even disk-integrated lightcurves can give accurate longitudes for single, bright, isolated hotspots. Likely numbers of nights and distribution through the year are often rough guesses, and assume perfect weather. Spatial Resolution? Approx. 1995 Longitude Telescope Wavelength ------------------ No. Time coverage Program Coverage Aperture Coverage Direct Indirect Nights JFMAMJJASOND ------------------------------------------------------------------------------- 1A Complete 3.2m 5 - 20 N N 4+ . 1B 300 - 60 3.2m ?? N N 4+ . .. . 1C Complete 1.2m 3.5 - 20? N N ? ... 1D ?? 5.0m 3.5 - 20? N N 2 . 2A 300 - 60 2.3m 2.2 - 4.8 N Y ? . . . . . 2B Complete 2.3m 4.8 Y?? ? ? . . . . . 3A 300 - 60 3.2m 1.7 - 4.8 Y? Y 12? ... . . . 3B Complete 3.2m 4.8 Y? N 14 . 3C 300 - 60 1.8m 1.7 - 2.3 N Y 15? ......... 4 300 - 60 0.6m 2.1 N N ? ......... 5 Complete 3.2m 5 - 20 N? Y? ? . OTHER (NON-VOLCANIC) GROUNDBASED OBSERVATIONS Wendy Calvin and I are planning to look for Ganymede O2 near 1 micron from Lowell in May or June, and I'm planning more CCD spectrscopy of Io and Ganymede around the same time. What else are people planning? ________________________________________________________________________________ REPORT ON NEAR-SUN IR OBSERVATIONS OF JUPITER IN NOVEMBER AND DECEMBER 1994: This from the IJW Atmospheres newsletter. Hopefully we can use similar techniques to check on Io's volcanism near the Galileo encounter next December: Yanamandra-Fisher, Orton and Shure at IRTF, used NSFCAM to image Jupiter, Nov. 28, 29 between 6 to 9 AM when Jupiter was 7 degrees from the sun, post-conjunction, in practice for Galileo real-time support in late 1995. A polypropylene cover (supplied by Drake Deming at NASA GSFC) over the primary allowed these near-solar observations by preventing the primary from focusing potentially lethal levels of visual sunlight. Seeing was 2 - 3 arcsec. Nothing short of 4 microns wavelength was transmitted through the cover, so we did not detect 2-micron or shorter-wavelength signatures of high-altitude dust as reported recently by Herbst et al. at Calar Alto (see below). Useful observations were made at 4.6, 5.05 and 5.30 microns. Friedson, Spitale, Orton, Hoffmann, Hora, Dayal used MIRAC2 at the IRTF to image Jupiter in mid-ir, 6 AM - noon, with good weather (finally) on Dec. 8. Jupiter was 14 deg. from the sun. Seeing was a remarkable 1 - 2 arcsec under the circumstances. Observations at 2 and 3 microns were impossible, and those at 7.85 microns (2% spectral resolution) were difficult. Other wavelengths observed included: 5, 8.57, 10.2, 10.5, 10.74, 11.7, 12.2, 13.0, 13.6, 17.8, 20.3, and 20.8 microns. We're sorting through the data for evidence of the impacts (which we don't consider likely). We do see probable C2H6 emission from the south polar hot spot at 12.2 microns, however, at a appropriate System-III longitude. _______________________________________________________________________________ HST CYCLE 5 GALILEAN SATELLITE OBSERVATIONS The Hubble Space Telescope Cycle 5 (July 1995 - June 1996) time allocations have now been published. The Galilean satellites will be getting attention. The following Jovian satellite programs got time: PI Program ------------------------------------------------------------------------------- Ballester The atmosphere of Io and its interaction with the plasma torus Noll UV imaging and spectroscopy of the icy Galilean satellites Schneider HST/Galileo Io torus observations Spencer Composition of surface units on Io Spencer Distribution of O2 on Ganymede There are also GTO observations of Io in the UV by John Clarke et al., and perhaps others. It's not clear which of these programs will be done in 1995 and which in 1996: Jupiter is favorably placed only near the beginning and end of Cycle 5. ________________________________________________________________________________ IO PLASMA TORUS WORKSHOP Just got word from the Torus discipline newsletter that an Io Plasma Torus workshop is planned for 27-28 April at New Mexico State University, Las Cruces, New Mexico. Contact discipline leader Nick Thomas (thomas@linmpi.mpae.gwdg.de) or Nick Schneider (nschneid@nmsu.edu) for more details. _________________________________________________________________________________ PUBLICATIONS Note the special issue of Icarus partially devoted to results from the San Juan Capistrano Io conference, September 1994, volume 111. As mentioned above, the January 1995 issue of "Astronomy" magazine has Paul Schenk's article on stereo images of Io and elsewhere. SA Sandford, TR Geballe, F Salama, D Goorvitch New Narrow Infrared Absorption Features in the Spectrum of Io Between 3600 and 3100 cm(-1) (2.8-3.2-mu m). Icarus 110 292-302 P Descamps. Astrometric analysis of Europa-Io occultations observed in 1991 Astronomy and Astrophysics 291: 664-667 NA Solovaya, EM Pittich. Orbital evolution of Jupiter's 8th satellite Planetary and Space Science 42, 685-689 From Jody Wilson: If you did not receive a copy of "Io's Fast Sodium: Implications for Molecular and Atomic Atmospheric Escape" (Wilson and Schneider 1994), and you would like a copy, please e-mail your address to wilson@surt.colorado.edu. Let me know if you have other recently published or submitted Jovian satellite publications that you want to publicise, and I'll include them in the next newsletter. ___________________________________________________________________________