99/11/26: Bright, hot, event (9911A) seen at
63 N, 123 W (Tvashtar Patera) by the IRTF and Galileo.
More information on the NASA Photojournal web site.
Also see Bob Howell's Io Volcano Page for lots of details on his observations (for 1998 and 1999), and John Spencer's Io Volcano Page for a brief summary of his work.
2001/01/18: John Spencer and coworkers report based on sunlit images that the new Tvashtar eruption seen by Marchis et al. on 2000/12/16 is still visible, though faint.
2001/01/16: John Spencer and coworkers report that Loki activity is continuing at roughly constant levels.
2000/12/24 + 00/12/29: John Spencer and coworkers had two successful IRTF Io runs on these dates and report that Loki is at moderate brightness (32 GW/mic/str at 3.5 microns), with nothing else unusual happening on the Jupiter-facing hemisphere.
2000/12/16: Franck Marchis has reported observations on this date showing the presence of an active hot spot (0012A) on the northern polar region of Io Here is his description: "Observations have been performed using the ADONIS Adaptive Optics and its infrared-thermal camera COMIC (L' band, 3.8 micron) . We applied a blind deconvolution method (MISTRAL) and a basic solar reflection model to better isolate the hot spot emission (see Marchis et al., ICARUS, 148, 384-396, 2000). A major emission is located at (130±15 , 63±10) with a brightening of 115±5 GW/micron/str (after applying a classical cos(theta) law). Even if its location is uncertain due to its position at the edge of the disc, it may correspond to the location of the Tvashtar (9911A event) already observed last year. It is one of the most active hot spot detected since the beginning of our survey (4 years ago). For instance, in November 1999, at its maximum of activity, Loki reached a similar brightness (see Howell et al., submitted to JGR, 2000)."
"The Solar/total ratio flux is around 86%. Additional hot spots contribute to this thermal emission, mainly several area corresponding to Volund-Zamama, Pillan,and the ring of fire hot spots (Amirani-Maui-Monan, Hi'iaka-Sigurd, Malik-Altjirra).
2000/11/15: Franck Marchis and the ESO group report observations from this date. See his web site at http://astron.berkeley.edu/~fmarchis/Science/Io_OA/Run2000/ and the above notes for 2000/12/16 for details on the results and the technique. Paraphrasing Franck's report, for the L' band data: They identify several well-known hot spots and the brightest one on the earth-facing side seems to correspond to Loki (309W, 13N). The emission is quite extended in direction of Daedalus and the center-to-limb variation do not follow a classical cos(theta) law, perhaps indicating another hot spot close to Loki. The flux estimated from images with Loki near the central meridian indicates a vertical brightness of 85 ± 10 GW/micron/str (similar the medium activity determined in September 1998). Another important active area corresponds to the Janus-Kanehikili (J-K) group which does approximately follows a cos(theta) law and is estimated to have a vertical brightness of 46 ± 10 GW/micron/str. They also isolated other possible sources of emission on their last data set of this night (taken at longitude=3°). Two eastern limb emissions correspond to Hi'Iaka and Gish Bar. Two unknown faint emissions are located on the internal disc: one at the NW (astronomical) of J-K (0011A) located at (27±10W, 20±7N) and another one (0011B?) close to the northern pole (55±15W, 58±15N). In their previous survey, this part of the Io surface had been poorly imaged because of the near-limb geometry. Therefore, it is not possible to compare and confirm the presence of such emissions. Sengen Patera area seems not to be active on their data, but this is again obtained with a close-to-the-limb position.
Mid 2000: There is a significant gap in earth-based data during this time, as most of the observing programs took a break after the intense campaign during the period of the close Galileo flyby's.
2000/02/20 - 2000/02/20: Very bright, high-temperature eruption
(0002A) near 60 N, 60 W.
99/11/26: Bright, hot, event (9911A) seen at
63 N, 123 W (Tvashtar Patera) by the IRTF and Galileo.
More information on the NASA Photojournal web site.
99/09/08-00/01/12: Brightening at Loki. First seen Sept. 9, continuing to brighten through Oct 1, more steady thereafter. Continued bright through March 7 2000.
99/08/02-99/08/04: Very bright (outburst-class) eruption (called 9908A) observed near longitude 80 W. More detailed positional information from Bob Howell- he estimates a location near 9 N, 71 W, +/- 5 degrees. Possibly the brightest event seen on Io since 1986! Fainter but still visible on 99/08/04, gone 99/08/09.
99/07/22-99/07/29: No unusual activity on the Jupiter-facing hemisphere.
99/06/22-99/07/08: Bright, hot, event (called 9906A) near 20 W, 25 S. Still visible, but had faded by a factor of several on 99/06/29 and 99/07/01, and had faded still further, to a level comparable to other hot spots, on 99/07/08.
99/05/12-99/05/30: Loki faint, no other unusual activity seen.
99/01/23-99/02/09: Loki faint, comparable in 3.5 micron brightness to Kanehekili. No other notable activity on the Jupiter-facing hemisphere.
98/05/27-98/12/31: Brightening at Loki: Loki's 3.4 micron brightness doubled between May 20 and May 27, and continued to brighten through early July (Bob Howell): brightness was sustained through Fall 1998. Loki faded considerably between 98/12/31 and 99/01/23, on which date it was back to "background" flux levels. This is was probably the longest-running Loki brightening to have been reliably recorded.
98/12/15: New hot spot (9812A) at lon. 8 +/- 8 W, lat. 8 +/- 10 S, which contributed 1/3 of the 3.5 micron in-eclipse flux and about 2/3 of the 2.3 and 1.7 micron flux. This spot was absent on 98/11/29 and had faded considerably by 98/12/31. Unlike many of these type of events, the spot was not particularly hot on 12/15 (1.7:2.3 micron color temperature was about 900 K), suggesting that it might have been the tail end of a much brighter event that occurred sometime in the previous two weeks
98/10/23: Additional brightening at or east of Loki, observed by Bob Howell.
98/08/29: New bright hot spot (9808A) at 45 S, ~70 W, comparable to Loki in brightness. Not seen on lower-quality images of this longitude taken 98/08/31 UT, and definitely gone on 98/09/30. Position is consistent with Masubi.
98/07/28-98/08/04: Brief event SW of Loki, seen at Keck. See images.
98/04/07-98/05/20: No unusual activity on the Jupiter-facing hemisphere
97/08-97/12/06: No unusual activity seen on the Jupiter-facing hemisphere. Loki has returned to normal activity levels, at least at short wavelengths, and Kanehekili is also visible. Emission possibly from Amaterasu Patera noted on 97/10/20.
97/06/27 - 97/07/05: Large plume at Pillan Patera (245W, 12 S) seen in images by Galileo SSI and HST. Hot spot also seen here in ground-based satellite occultation lightcurves. Major new dark pyroclastic deposits centered on the plume site seen in Galileo SSI images taken on 97/09/17.
97/06/07: Bright event on the Jupiter-facing hemisphere, increasing the disk-integrated 2.3 micron brightness about tenfold, not present one week earlier or later. No positional constraints.
97/03/12 - 97/07/23: Major brightening at Loki. Mutual event observations constrained the location to the Loki Patera "lake". Galileo NIMS observations around 97/02/20 show that the brightening had not begun at that time. Increased in brightness about 20% at 3.5 microns between mid March and late April. Probably peaked (at short wavelengths) in May, and was largely back to normal 3.5 micron brightness by late July.
96/10/08 - 96/11/08: Relatively low activity on Jupiter-facing hemisphere.
96/10/06: New, very bright, hot spot in the north polar region (c. 75 N, 35 W, +/- 15), Jupiter-facing hemisphere. Temperature at least 1500 K. Faded on 96/10/08.
96/09/08 - 96/10/01: Relatively low activity levels on the Jupiter-facing hemisphere.
96/08/28 - 96/09/06: A very hot event (1.7:2.3 micron color temperature of 1100 K) was seen on 8/28 at or near the dark feature at 15 W, 2 N. It was visible in sunlight at 3.8 and 4.8 microns, but did not dominate the reflected sunlight. In eclipse, it was even visible at J (1.26 microns). It was not apparent in disk-integrated 4.8 micron sunlit photometry in the following few days. On 9/06 this hot spot had faded by a factor of 3 at 2.3 microns, but was still prominent in Jupiter eclipse.
96/06/04 - 96/08/12: Io continued faint in eclipse, perhaps fading even further on 6/20 compared to earlier in June. WIRO 4.8 micron data and IRTF 3.8 and 4.8 micron images show no major activity at any longitude near the G1 encounter in late June, but the IRTF 8.7 micron lightcurve showed somewhat enhanced activity at the longitude of Pele.
96/05/29 -96/06/04: IRTF 3.8 micron images of all Io longitudes shows no bright activity anywhere, including Loki and Pele.
96/06/02: Unusually good conditions at the IRTF allowed tentative identification of eleven faint hot spots on the Jupiter-facing hemisphere, including Loki, Kanehekili, Surt (which was not active in late April), and the relatively bright spot S. of Loki which was seen in April. See here for more details.
96/02/06 - 96/05/28: Low-level activity on Jupiter-facing hemisphere: Loki (or a combination of Loki and another spot at the same longitude in the southern hemisphere) provided 60% of the total 3.5 micron volcanic flux and was at "intermediate" activity levels in February, but had probably faded by late March and early April, contributing less than 50% of the total 3.5 micron flux on April 24th. April 8th and 24th images show non-Loki activity concentrated near Kanehekili and at the spot south of Loki, but with many other faint sources.
96/01/23: 11-micron in-eclipse flux "within typical range"
95/10/03 - 95/10/05: Brightening near 25 N, 220 W (+/- 15 degrees).
95/09/27: Major outburst on leading hemisphere, possibly at same location as March 1995 event (45 S, 95 W).
95/08/26 - 95/11/12: Brightening at Loki.
95/08/19 - 95/09/20: Brightening near 28 N, 12 W, fainter but still visible on 09/04 and 9/20.
95/08/17 - 95/08/24: Low-level activity on anti-Jupiter hemisphere, Jupiter-facing hemisphere brighter at 5 microns than in June.
95/07/20 - 95/09/20: Brightening at unnamed caldera on Jupiter-facing hemisphere, brightest in July (22 N, 351 W)
95/06/11 - 95/06/16: Low-level activity at all longitudes
95/04/15 - 95/07/18: Low-level activity on Jupiter-facing hemisphere
95/03/23 - 95/04/08: Bright high-temperature event on Jupiter-facing hemisphere, location consistent with Surt (45 N, 339 W)
95/02/28 - 95/03/11: Major outburst near 45 S, 95 W (+/- 10 degrees), much brighter 3/02 (and 2/28?) than on 3/09 or 3/11
95/02/17 - 95/03/16: Low-level activity on Jupiter-facing hemisphere
Jay Goguen, Glenn Veeder, Diana Blaney, Torrence Johnson, Dennis Matson, IRTF. 5-20 micron sunlit and Jupiter eclipse photometry.
Jay Goguen, Phil Nicholson, Palomar 200". 10-micron spectroscopy of Io, including satellite occultations of Io. Jay Goguen, IRTF. 3-10 micron photometry of satellite occultations of Io.
Bob Howell, John Spencer, John Stansberry, Lowell 72" telescope. 2-5 micron imaging of Io in sunlight, Jupiter eclipse, and during Jupiter occultations.
Bruce McIntosh, Claire Max, Seran Gibbard, D. Gavel, and Imke de Pater, Keck. Speckle imaging of Io in eclipse.
Murray Silverstone and Eric Becklin, UCLA 24" telescope. 2.1 micron eclipse photometry with IR camera (1995 only).