Forty-three minutes. (ducks)




Ganymede transit with crescent brought out:

Exploitcorporations, you cheater!

Great job on the Io/Europa conjunction, EC!

John.

EC, that's one of the coolest space images I've ever seen! It's amazing what a bit of color can add.

Emily's blog post is a marvelous alternate of the same concept, as is VP's in the NH at Io thread. I'm curious as to whether the colors in the MVIC product are too bold or on the mark (note the greenish tint of Io's nightside and the bright yellow of Europa in the official release)...I tend to go with muted in my color experiments as of late. John or VP, do you have any insights as to what the human eye would see in this scene?

I tend to prefer not to mess with the colors if I can, even if it makes the colors not appear as it would to human eye...

The greenish hue is the result of using a filter centered in a methane band for red. Jupiter absorbs much of the sunlight that hits at this wavelength (889 nm iirc), so very is reflected so that it can then be reflected off Io's surface and strike the camera.

Well, an excerpt from PIA09256 says this about color filters used in the MVIC image:
The colors are stretched and this has 2 important consequences: Europa and Io have a comparatively similar color and Io's nightside is greenish because the "red" in the composite is actually MVIC's narrowband methane absorption filter so Jupitershine is much weaker in that channel, leaving only the green channel prominent. In blue light Io's spectrum drops off rapidly, leading to its (un)usual color.

This release shows what the nightside of Io would probably look like in natural color.
While Io's sunlit crescent would still look yellow-greenish, I'd imagine Europa would look a much duller shade of grey. Tvashtar's plume would probably also be a bit less saturated shade of blue than PIA09256 shows. Something like the blue-gray color of smoke particles here on Earth. It would still contrast strongly with the color of the moon, however.

Note that the colors aren't "stretched" (i.e. we haven't increased the saturation), but as has been said, they aren't natural either because the wavelengths differ from the human eye's sensitivity. And in all cases the color balance results not from precise calibration, but from me tweaking the relative brightness of each channel till the color conforms to my mental picture of what Io should look like, based on previous more exactly calibrated images from Galileo. Definitely more art than science...

John.

According to Emily's chart (posted on this thread January 18, 2007), the NH Jupiter gravity boost was expected to add ~5,200"MPH" to NH's net helocentric velocity. According to Alan Stern in the Planetary Society webcast, the Jupiter encounter netted a 9,000"MPH" boost. Alan did not specify the vector (Emily's is helocentric). The current location on the NH website are consistent with a ~ 5,000 "MPH" gravity boost. My eyeball says the vector only shifted ~15% so I am wondering: Are the numbers the same?

John: What's the schedule for the release of the Jupiter encounter data to the PDS? Is there one?

--Emily

who says it hasn't already been released...

Okay, I won't be evil:

http://pdssbn.astro.umd.edu/missions/newhorizons/index.html

Wow, these are big files...

Holy cow!! That was fast!!! I'll have to see if I can get Wget to work on this...maybe I can pump this data out in a way that the rest of you guys can access it...it'll take me a few days, most likely, but I'm emptying some space on my hard drive to start now...

Whee! How I wish there were going to be more goodies that New Horizons would be flying by on the way to Pluto...I wish all missions could be run like this!

--Emily

We definitely need a "We love John, Alan, Jeff, Hal, and all the other New Horizons folks Day" here

I think a "thank you" poster, signed by the collective members of UMSF, would be a great gift for the New Horizons team. It could be decorated with some of the images from the Jupiter encounter, such as Exploitcorporation's great colour composite of Io and Europa.