From spencer Mon Apr 11 12:30:22 1994 From spencer Mon Apr 11 12:30:22 1994 Return-Path: Date: Mon, 11 Apr 94 12:29:43 MST From: spencer (John R. Spencer) To: spencer@sunkng Subject: Ole Roemer Messenger Addendum Content-Length: 8096 X-Lines: 178 Status: RO __________________________________________________________________________ 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 8-addendum April 11, 1994 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 --------------------------------------------------------------------------- Here are a few items resulting from feedback from last week's newsletter, plus a couple of additional items. BILL SINTON It's Bill Sinton's birthday today! He was the first IJW Satellite Discipline Leader and originator of this newsletter, and is now retired here in Flagstaff. If you send birthday greetings to me by e-mail I can pass them on to him. OBSERVING PLANS John Clarke gives more details on his upcoming HST imaging of Io: The ST ScI is now scheduling the WFPC 2 science team imaging of Io and the torus for the week of 15 May 1994. We do not yet know the exact days. This will include far-UV (1150-2000 A) imaging of Io and its atmosphere, 2000-4000 A imaging of Io, and visible narrow-band imaging of the torus and structure near Io. Ground-based data in the same week of the volcanic activity, i.e. thermal IR data, would be particularly helpful for comparison with the WFPC 2images. ASTROMETRY My apologies to Bill Owen (wmo@muon.jpl.nasa.gov) of JPL for quoting from a talk he just gave in Flagstaff without checking with him first. He offers the following clarification and elaboration on the astrometric effort: Jay Lieske's E-3 ephemeris doesn't contain any observations later than 1983, and what's obviously happened is that small errors in the mean motion have built up over the last 11 years to a sizeable downtrack (longitude) error. Nevertheless, the observations NOFS [U.S. Naval Observatory Flagstaff Station] has been making are only one data set out of several. We've got mutual event observations from K. Aksnes and others that in principle are at least as good, plus a long series of photographic observations made by Dan Pascu at the USNO's 26-inch refractor in Washington, plus lots of eclipse timings, plus the Voyager optical navigation pictures in 1979. It remains to be seen how well these various data sets will agree with one another and what their relative weights should be. These considerations will determine the level to which we'll trust the next ephemeris. Jay is supposed to have something out by the end of the year. The bottom line is that 60-km RMS residuals [in the NOFS astrometry] don't necessarily imply an ephemeris that's good to 60 km, because there could be as-yet-undetected systematic errors in the NOFS observations. FTP AVAILABILITY I have put all Ole Roemer Messengers in our anonymous ftp directory so you can access them. Do anonymous ftp to "sunkng.lowell.edu" (192.103.11.2), and look in directory "pub/ijw". COMET IMPACT SATELLITE REFLECTIONS Prompted by Kelly Beatty, here's an updated table of satellite reflector availability, based on the latest (1994/02/23) Chodas and Yeomans ephemerides. Times haven't changed much but uncertainties have gone down. No impact times are yet available for P1=8a and Q2=7b. In the table, a "+" next to the orbital longitude means that the impact will be visible from the satellite. Longitudes greater than 90 degrees will be less useful as the phase angle of the reflected light (to first order, equal to the longitude) will be high and its brightness will be greatly reduced. An "e" means the satellite will be visible in eclipse, allowing higher sensitivity observations, and an "o" means it will be occulted by Jupiter. I've included Callisto (J4) for completeness but it's likely to be too far out to be useful- the same may be true for Ganymede (J3). --------------------------------------------------------- UT Satellite Orbital Longitudes date of Bright (degrees past superior conj.) impact -ness --------------------------------- Nucleus (July) Index J5 J1 J2 J3 J4 --------------------------------------------------------- A=21 16.81 1 193 340 103+ 75+ 35+ B=20 17.11 1 50+ 41+ 133+ 90+ 42+ C=19 17.27 1 165 74+ 149+ 98+ 45+ D=18 17.48 1 317 116+ 171 109+ 50+ E=17 17.61 2 51+ 143+ 184 116+ 52+ F=16 18.02 2 347o 226 225 136+ 61+ G=15 18.30 3 190 283 254 150+ 67+ H=14 18.78 3 177 21+ 302 174 78+ K=12 19.42 3 279 151+ 7e 207 91+ L=11 19.89 3 259 246 55+ 230 101+ N=9 20.41 1 274 352o 107+ 256 113+ P2=8b 20.61 2 59+ 33+ 128+ 266 117+ P1=8a 1 Q2=7b 2 Q1=7a 20.80 3 196 72+ 147+ 276 121+ R=6 21.28 2 183 169+ 196 300 131+ S=5 21.61 3 61+ 236 229 317 138+ T=4 21.75 1 162 265 243 324 141+ U=3 21.88 1 256 291 256 330 144+ V=2 22.18 2 113+ 352o 287 345 151+ W=1 22.32 2 214 21+ 301 352+ 154+ Uncertainties (1-sigma): 0.03 1 22 6 3 1.5 1 --------------------------------------------------------- As before, the "brightness index" subjectively rates comet fragment brightnesses, 3 being brightest. Brightnesses are eyeballed from the press-released HST image where possible and are different from those in previous versions of the table. There's a good chance that reflections from the impact of the large fragment K=12 will be visible off Europa in eclipse, very close to Jupiter: this impact can be seen in a dark sky from Australia, New Zealand, and Hawaii. Given the uncertainties, there's nearly a 50% chance that the impact of either H=14 (a large fragment) or W=1 will be seen reflected off Io in eclipse. The H=14 impact will be visible in darkness from East and South Africa, and the middle East, the W=1 impact from New Zealand and Hawaii. The table below gives the orbital longitudes (in degrees) of satellites when in Jupiter eclipse and occultation (used to annotate the above table). Values should be good to about one degree. ------------------------------------- Satellite Occulted Eclipsed ------------------------------------- J5: Amalthea 337 - 023 023 - 034 J1: Io 351 - 009 009 - 020 J2: Europa 355 - 005 005 - 016 J3: Ganymede 358 - 002 009 - 013 J4: Callisto No occultations or eclipses ------------------------------------ COMET IMPACT ANIMATION If you caught the NBC Evening News on Wednesday April 6th, or the "Today" show the following morning, you may have seen a feature on the comet crash featuring MIT astronomers (Joe Harrington and Tim Dowling), and several computer animations. The "scenic" simulation of the collisions as seen from one of the fragments in the chain was an animation I generated, with help from several people. I MAY be able to make copies of this animation for interested people, possibly for a small charge to cover costs, but would like some idea of the likely demand. Let me know if you might be interested in this videotape. PUBLICATIONS Here's another paper that was just published: Harmon, J. K., S. J. Ostro, J. F. Chandler, and R. S. Hudson (1994). Radar ranging to Ganymede and Callisto. Astron. J. 107, 1175-1181.