NH at Jupiter, Planning the Jupiter encounter Options

[MahFL]

I think the lens cover on LORRI is designed just to open, its better to have a bit of dust on the lens than having a lens cover stick in the closed position.

[Guest_PhilCo126_*]

Don't know about covers on the NH lenses but I guess that by February 2007, the spacecraft's rotation will be stopped and will operate in 3-axis stabilisation mode.
( Remember Dr Alan Stern confirmed that NH can operate in both spin-stabilisation for cruise phase and in 3-axis stabilisation mode for encounter phases which will allow correct instrument pointing ).
Between Jupiter and Pluto, NH will probably go back into spin ?

[Decepticon]

Does anyone know what Voyager/Galileo images will be comparable to the Horizons?

I'm trying to get a idea of what to expect.

Also will we get enough Jupiter imaging to create Voyager approach type movies?

[Bob Shaw]

Does anyone know what Voyager/Galileo images will be comparable to the Horizons?

I'm trying to get a idea of what to expect.

Also will we get enough Jupiter imaging to create Voyager approach type movies?

My impression from what I've read so far is that NH isn't set up to obtain close-up imaging data from the illuminated portion of Jupiter and it's satellites, but will do well in 'Jupiter-shine' images of the satellites. Remember that NH is designed to explore a dark, dark place, rather than one that's just a bit dim!

Bob Shaw

[john_s]

My impression from what I've read so far is that NH isn't set up to obtain close-up imaging data from the illuminated portion of Jupiter and it's satellites, but will do well in 'Jupiter-shine' images of the satellites. Remember that NH is designed to explore a dark, dark place, rather than one that's just a bit dim!

Bob Shaw

Actually, we've just figured out that we can probably take unsaturated daytime images with our telephoto camera (LORRI), though we won't know for sure until we can do some tests in flight. So we hope to get some nice B/W dayside images of the satellites after all. We're still stuck with dayside saturation in our color camera, MVIC, though, so our only color images of Io will be taken in Jupiter shine, and will thus (obviously) cover only the Jupiter-facing hemisphere.

Here's a simulation of some of our best views of the four Galileans, from LORRI (highest resolution), MVIC (color, though only B/W in this simulation, and saturated on most of the daysides), and LEISA (where every pixel represents a 1.2 - 2.5 micron near-infrared spectrum). The geometry is pretty accurate. I've brightened up the nightside of Io so you can see what volcanos might be glowing in the dark there.

[icez]

Here is Celestia's view of Io and Europa--relative to Jupiter and the Sun on the time of the Jupiter encounter. It "looks" like there could be some moonshine going on from what I see.

Attached thumbnail(s)

 

[ugordan]

Actually, we've just figured out that we can probably take unsaturated daytime images with our telephoto camera (LORRI), though we won't know for sure until we can do some tests in flight.

That's very nice to hear, but I'm curious how you suddenly came to that conclusion?

Here's a simulation of some of our best views of the four Galileans, from LORRI (highest resolution), MVIC (color, though only B/W in this simulation, and saturated on most of the daysides), and LEISA (where every pixel represents a 1.2 - 2.5 micron near-infrared spectrum).  The geometry is pretty accurate.  I've brightened up the nightside of Io so you can see what volcanos might be glowing in the dark there.

That's awesome! I see the LORRI images are slightly blurred, did you actually go through the trouble of simulating the camera's PSF as well?

[john_s]

That's very nice to hear, but I'm curious how you suddenly came to that conclusion?
That's awesome! I see the LORRI images are slightly blurred, did you actually go through the trouble of simulating the camera's PSF as well?

Now the spacecraft is launched we have time to think of creative ways to use the instruments. The problem with LORRI was that it has no shutter, so light falls on the CCD during the readout phase, producing a smeared image. If the exposure is shorter than the readout time, as needed to avoid saturation on the Galileans, the "readout smear" can be brighter than the image itself, and can be difficult to remove. What we just figured out is that for the special case of a small target against black sky there's a fairly easy way to remove the readout smear, even if we can't remove the smear from, for instance, a short-exposure closeup image of Jupiter's clouds.

And yes, I included a very crude estimate of the LORRI PSF in those simulations. Well spotted!

[JRehling]

Actually, we've just figured out that we can probably take unsaturated daytime images with our telephoto camera (LORRI), though we won't know for sure until we can do some tests in flight.  So we hope to get some nice B/W dayside images of the satellites after all.  We're still stuck with dayside saturation in our color camera, MVIC, though, so our only color images of Io will be taken in Jupiter shine, and will thus (obviously) cover only the Jupiter-facing hemisphere.

Is moonshine bright enough to help you out there? Io will experience a pretty full Europa late on Feb 27 and into Feb 28 (UTC), which by my crude math would be as bright as a magnitude -11 in the ionian sky. During that interval, Io would wane from gibbous as seen from NH, leaving a crescent in europashine; to crescent in the sunshine leaving a gibbous swath in europashine. During the same interval, Jupiter would go from a sliver to a full disk as seen from Io, so Europa may end up illuminating a small segment only for NH's benefit, but that's something? If having too much light is a problem, does europashine result in not enough?

[john_s]

Is moonshine bright enough to help you out there? Io will experience a pretty full Europa late on Feb 27 and into Feb 28 (UTC), which by my crude math would be as bright as a magnitude -11 in the ionian sky. During that interval, Io would wane from gibbous as seen from NH, leaving a crescent in europashine; to crescent in the sunshine leaving a gibbous swath in europashine. During the same interval, Jupiter would go from a sliver to a full disk as seen from Io, so Europa may end up illuminating a small segment only for NH's benefit, but that's something? If having too much light is a problem, does europashine result in not enough?

Interesting thought- we'll check into it, though my gut feeling is that moonshine won't be bright enough to be useful. Galileo took some cool images of Jupiter's clouds in Io-shine, but they were very long exposures and fairly smeared.

'

[Bob Shaw]

Interesting thought- we'll check into it, though my gut feeling is that moonshine won't be bright enough to be useful.  Galileo took some cool images of Jupiter's clouds in Io-shine, but they were very long exposures and fairly smeared.

'

Perhaps the combination of the two light sources may be a winner - Jupitershine and light reflected by the moons.

Good luck!

Bob Shaw

[Decepticon]

Thanks for those samples!

I can't wait!!!

[JRehling]

Perhaps the combination of the two light sources may be a winner - Jupitershine and light reflected by the moons.

Good luck!

Bob Shaw

There'll also be a pretty full Callisto in the ionian sky, but that would contribute much less light than Europa.

[tty]

Is there any plans for imaging the night side of Jupiter? There might be some interesting things to see there for a high-sensitivity camera (auroras, thunderstorms, meteorite impacts....).

tty

[Comga]

I think the lens cover on LORRI is designed just to open, its better to have a bit of dust on the lens than having a lens cover stick in the closed position.

The doors on LORRI and Ralph both open with one-time, spring loaded mechanisms. These devices are well proven and have high reliability, as almost anything is better than having the door stick in the closed position, as you said.

We will know for sure in a few months. Does anyone know when they plan to open the doors and take test images?