OK, so my poll is over and folks want Io science. One way I study Io is by using the IRTF (InfraRed Telescope Facility) to watch Io as it either disappears or reappears from behind Jupiter. I've been doing this for over 20 years now. #teamIo

Here's a (really old) false color sequence of images of Io reappearing from behind Jupiter. Since Io is in eclipse all of the light you see is from the volcanoes. We observe in the infrared to see heat.

We take dozens of images during this occultation and, for each image, determine the total brightness of Io. The resulting plot looks like a flight of stairs where each step is another volcano (or volcanoes) coming out from behind Jupiter.

The timing of when the step happens tells us where the volcano is (in one dimension only) and the height of the step tells us the brightness of the volcano. We've taken data like this more than 100 times over the past >20 years.

One of the volcanoes we see during nearly every observation is Loki, which is generally the brightest volcano on Io and can, when it's bright, account for 15% of Io's total volcanic output. That's a lot, considering that Io is like 100X for volcanically active than the earth.

So, each time we observe, we get a measure of Loki's brightness. Here's a plot of Loki's brightness over more than 30 years. This includes IRTF data plus data from other telescopes and spacecraft. It shows that Loki's brightness varies dramatically.

I first noticed the periodicity in Loki's brightness about 20 years ago. We found that Loki had an eruption periodicity of 510 days with an average brightness (During the eruption) of 60 GW/mic/str.

We published a paper on this and, nearly immediately after, Loki's periodicity STOPPED. This is what we get for naming a volcano after a trickster god.

The periodicity started again around 2013, this time with a 475 day period and brightness of 90 GW/mic/str. In several presentations last year I predicted, based on that period, that Loki would erupt in September/October 2019.

Of course, since I publicized that prediction, Loki decided to be contrary. We had observations in fall and saw no eruption. We had to stop observing for a while due to Jupiter's location and, when we started back up about a month ago, it was already erupting.

We've only had one successful observing run this year, so far. And, unfortunately, the telescope is currently closed. But, I'm really glad we got that one point, because it's the best constraint on the eruption start date.

One of the major projects I'm currently wrapping up is to get all of these data (the occultation curves themselves) into the PDS (Planetary Data System - a depository for planetary data, particularly spacecraft data).