I think the Jupiter encounter deserves its own thread.

I've just been taking a first look at the Jupiter encounter geometry. You can do the same using Mark Showalter's excellent on-line ephemeris tools at the PDS rings node, which by good fortune happens to include a New Horizons ephemeris (calculated over a year ago) for our actual launch date, January 19th. We'll have an updated ephemeris soon, but this one's already good enough for planning. As Roby72 noted in the Star 48 thread, the satellites are (annoyingly) all on the opposite side of Jupiter at closest approach. We'll still get good views of all sides of Io because Io rotates in only 1.8 days and we'll be pretty close to Jupiter for that long. We'll get fairly good coverage on Europa too, for the same reason. But we won't get very close to Ganymede or Callisto. Luckily Io is our highest priority satellite target and Europa is next, so we'll do OK.

I think it does too, but couldn't it go under, well, Jupiter?

Nah, IMHO New Horizons discussions should stay under the New Horizons topic.

John.

John,

yes the day before (or after), Io must be on the right side of the planet, but I think the high speed of NH makes the distance about equal than on encounter day at the other side (about 2.5 Mio km). Resolution for LORRI (bw imager) should be about 12 km, for RALPH (color) about 50km) This would be nice for plume searching and is about 5 times more resolution in case of LORRI than Cassini had at its Jupiter encounter in Dec. 2000.

Robert

Any chance NH could image Europa well enough to see if any surface features have changed/moved since Galileo?

We'll be looking at Europa but not specifically for that purpose- our images will be far lower resolution than Voyager's and no changes were seen between Voyager and Galileo even at Voyager resolution, and over a longer timespan than between Galileo and NH. Our main goal in imaging Europa will be to look at the peculiar large, shallow, depressions that were seen by Galileo near the terminator- it's one area where we can improve over Galileo. Plus we'll be observing Europa's auroral emissions in Jupiter eclipse.

By the way, here's a table I just sent to the science team, showing the timing and geometry of various significant events during the encounter. Times are spacecraft times, and the numbers will change just a bit once we get a final ephemeris. I've only calculated the times of the eclipses of each satellite that occur closest to the spacecraft- there are many more at greater ranges. "UT" means Universal Time, "mrad" means the angular diameter in milliradians, and "Sub-S/C Lon" means the sub-spacecraft longitude. I couldn't figure out how to align the columns properly without replacing all the spaces with underscores...


---------------------------------------------------------------------------
____________________Range___Diam__Solar__Sub-
____Date_______UT___(km)___(mrad)_Phase_S/C_Lon__Event
---------------------------------------------------------------------------
February_25__09:45_6334186__0.831___11____349____Ganymede eclipse ingress
February_25__11:45_6222615__0.846___12____352____Ganymede eclipse egress
February_27__10:46_3074450__1.021___40____315____Europa eclipse ingress
February_27__13:18_3045261__1.030___45____321____Europa eclipse egress
February_27__14:20_2734370__1.331___48____303____Io Eclipse ingress
February_27__16:28_2758131__1.320___53____316____Io Eclipse egress
February_28__02:00_2957815__1.061___72____347____Europa closest approach
February_28__05:00_2304575_61.920___82___________Jupiter closest approach
February_28__06:00_3029556__1.737__102_____41____Ganymede closestapproach
February_28__06:30_4153289__1.156___81____353____Callisto closest approach
February_28__22:00_2260221__1.610__118____141____Io_closest approach
___March__1__08:48_2748816__1.324__120____231____Io_eclipse ingress
___March__1__10:58_2951842__1.233__121____248____Io_eclipse ingress
---------------------------------------------------------------------------


John.

Thank you for the information, John. Would New Horizons be able to look for any possible geysers from Europa as well? Might be good practice for similar events in the Pluto system, too.

Especially if Triton is supposed to be a lot like Pluto.

How many days/weeks before closest approach will New Horizons start imaging Jupiter?

Maybe I missed it in another thread (or website), John, but is there any possibility of getting imagery of any of the outer jovians (e.g., Himalia)?

Judging from the NH Jupiter encounter planning meeting I attended back at the 2003 DPS meeting, the most interesting piece of new information that comes out of the NH Jupiter flyby may be its near-IR spectra of the surface composition of the Galilean moons -- especially Europa. Its spectrometer has much higher spectral resolution than Galileo's and will be considerably closer to the Galilean moons that Cassini's, implying that it may be able to nail down whether that stuff mixed with Europa's ice is Mg sulfate or sulfuric acid.

We typically get a couple of pixels on Himalia, similar to Cassini, though I haven't seen the geometry for the actual trajectory yet. Anyway, don't expect anything too dramatic on any outer satellties.

On an extremely amateur basis, I did some (very) back of the envelope calculations and came up with Himalia spanning about 9.5 pixels a week after Jupiter C/A - slightly better than Cassini.

Can't wait to hear real numbers from people who actually know in a couple of weeks.

Bart

So New Horizons will take images of the Gas giant Jupiter and some of its moons?
Wondered if the lenses on the cameras are closed afterwards as some kind of protection and opened before Pluto encounter?

* ASTRONOTES: Derelict Booster to Beat Pluto Probe to Jupiter

http://www.space.com/astronotes/astronotes.html

NASA's Pluto-bound New Horizons spacecraft now speeding through the Solar System
is set to reach Jupiter on Feb. 28, 2007, but it will not be the first craft of
its mission to reach the gas giant, mission officials said this week.

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.

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 ?

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

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.

Click to view attachment

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.

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!

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.

'

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

Good luck!

Bob Shaw

Thanks for those samples!

I can't wait!!!

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

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

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?

I am sure there is a good reason for not doing this, but I have always wondered why these ejectable lens covers aren't made of lexan.

If they don't come off, camera would still work.

Must be missin' sumpthin' ?

Well - consider the MER MI cover - that's an orange filter - so even if the cover's shut, you can still see something.

I'd imagine using something like lexan or other transparant materials for a thermal cover of an instrument has potential for a lot of problems with being britle, heavier, bad thermal properties, perhaps outgassing and contaminating optics etc etc....

And as Alan's said a few times, better is the enemy of good enough.

Doug

Jupiter wouldn't be so bright that it could burn out NH's cameras, could it?

Nope, the New Horizons CCDs, like most CCDs, are very resistant to burnout.

Here is the snapshot when NH is around the closest distance from Jupiter at February 28, 2007, 05:00 am.

http://space.jpl.nasa.gov/cgi-bin/wspace?t...orbs=1&showsc=1

Jupiter: 2.306 millions km
IO : around 2.664 millions km Closer
Europe: 2.967 millions km
Ganymede: 3.020 millions km
Calixto: 4,160 millions km

These above predicted distance might change after the next TCM.

Rodolfo

what is the wavelength range for LORRI? Does it extend at all into the near-IR? would be interesting to see how active Pele (or Pillan 10 years after its big eruption) is when Io is in eclipse.

Remember John, there is no need to image any of the other moons, just focus on Io

Pfaw. The most important thing NH will do at Jupiter is get near-IR spectra of the Galilean moons' surface compositions far better than any obtained by either Galileo or Cassini -- maybe good enough to settle the question of what the non-ice component of Europa's surface really is.

LORRI extends to 1 micron wavelength so we may see some volcanic thermal emission on the nightside, as we will with MVIC, and with LEISA of course. We should get a nice data set on the hot spots! Plumes, too...

Can NH look for any plumes from Europa as well?

Funny you miss spelled Europa Io

Maybe you folks can help us...

We're now starting to lay out the timeline for the Jupiter encounter, but what we haven't done so far is look for "Kodak moments" as the Cassini imaging folks call them- times when we have scenic alignments or unusual geometries that call for a picture that's motivated by beauty more than science. Anyone want to help us find these moments?

Mark Showalter has now updated his New Horizons ephemeris tools to include the actual spacecraft trajectory through the Jupiter system. So you can download a table of satellite positions as seen from the spacecraft, and see views from the spacecraft of any body in the system at any time. It's probably most efficient to use the "Jupiter Ephemeris Generator" tool to create a table first and use that to find possible interesting alignments (e.g. times when the RA and Dec offsets of two satellites are similar), and then use the "Jupiter Viewer" to check out the view from the spacecraft at that time. The field of view of LORRI, our greyscale telephoto camera, is 5 x 5 milliradians, or 1044 arcseconds (parameters for all instruments are here). Make sure that you are using the "Official Post-Launch" trajectory option, which is the default.

If you find a specific time when you think we should press the shutter, let us know! No guarantees that we'll be able to do so, as there are numerous conflicts and constraints, but we'll give it a try. LORRI images don't take a lot of resources so we can probably spare a few for scenic purposes. MVIC color images are more "expensive", and are likely to have partial saturation except at high phase angles, so we're less likely to use MVIC for this purpose.

Thanks!
John.

The very easiest way for this is if someone can get it into celestia, and we can just run thru the flyby looking for interesting moment

You've opened a big bad can of worms here John Downlink was 2048kbps from Jupiter wasnt it

I'm sure you'll have lots of loonie ideas - but a moon rising or setting from behind Jupiter with possible refraction thru the upper atmosphere could be interesting....

Not sure of exact timing (see attached) if I have the night-side-day-side right, this would see a crecent Io set behind the dark-limb of Jupiter, so it would be squished and squashed as it set, in a way a little similar to this...
http://spaceflight.nasa.gov/gallery/images.../s103e5037.html but without a bright limb of Jupiter to get 'in the way'

Some upper atmosphere refraction has been seen by Cassini...
http://ciclops.org/media/dr/2005/1114_2631_2.png
http://ciclops.org/media/dr/2005/1191_2857_2.png
http://ciclops.org/media/dr/2005/1017_2487_1.jpg

Perhaps something to be learnt about the properties and extent of the upper jovian atmosphere by catching this little event?

I think that the classic Cassini 'mutual' events of transits etc are likely to be uncommon at a range worth imaging (guessing here).

Another potential target that's perhaps half scientific, half Kodak - is a lit side of a moon, being partially occulted by the jovian ring system- not sure how it might look or if it would appear at all, but again, potential for something 'interesting' if not beautiful


Doug

I created a spreadsheet and imported the ephermis for a few weeks around closest approach, for every 20 minutes in the enounter. Best one so far is:
MJD Objects Notes
54161.44 IO & EUROPA Really close pass

Try adding a few hundredths of a MJD either way. When using the Jupiter Viewer, enter MJD as MJD 545161.44.

There are a few others from further away. I want to redo the ephermis +- a day to closest approach to see if I am missing any due to the 20 minute step size.

I'll post the spreadsheet once I'm done, promise!

OK, so there were a few additional close Io and Amalthea passes. Looking at the graphs, the majority of passes are Io & Amalthea, with a few others, mostly with Amalthea. The speedy little moon gets around!

MJD Bodies Comments
54149.68056 IO & AMALTHEA Europa is just out of view to the NW, good view of the rings
54149.8888 IO & AMALTHEA Thebe is left of Amalthea, IO is pretty far away
54150.98611 IO & EUROPA Far pass
54157.925 IO & JUPITER Io grazes the north side of jupiter, leaving J disk on dark side
54158.943 IO & JUPITER Io goes behind jupiter on the dark side
54159.365 EUROPA & JUPITER Europa grazes the southern dark side of Jupiter
54160.12 IO & JUPITER Crescent IO in front of dark side Jupiter, emerges few minutes later
54160.12 AMALTHEA & JUPITER Crescent Amalthea in front of dark side of Jupiter, emerges a few minutes later
54161.042 IO & JUPITER Io disappers behind jupiter on the dark side, with the rings visible and in shadow. Encounter with Io and Rings starts earlier
54161.43646 IO & EUROPA Really close pass!!!
54161.85 EUROPA & AMALTHEA Rings are between them
54161.97083 IO & AMALTHEA Rings are between them, with Adrastea possible
54162.85365 IO & AMALTHEA Close pass, rings and Metis visible, long encounter!
54165.125 IO & EUROPA Small crescents for both
54165.70833 IO & AMALTHEA Rings & jupiter, but distance function shows a bump, so could be interesting encounter
54168.70833 IO & EUROPA Pretty far pass, but in the same field
54170.94633 IO & EUROPA Amalthea emerges from behind Jupiter, might make an interesting appearance, all objects showing thin crescents

I had to do a manual search for Jupiter events, and gave up after a bit.

Unfortunately, the spreadsheet is over 20 MB, so I can't post the full thing. Here is a PDF of the charts, and a cut-down spreadsheet that you can enter the data in yourself. Some notes:

1. You have to modify the RA so that it is monotonic. What does that mean? When scrolling down, if you get to a set of entries that go from +~24 to ~0, then you need to change the RA(corr) column to (RA+24) to keep it linear.
2. RA is multiplied by 15, to get something vaguely representing degrees.

Any other questions, or if you want the full spreadsheet, feel free to ask.

Here's the reduced spreadsheet.

Any word yet on the possibility of imaging Himalia?

Bart

Lexan isn't a good choice due to outgassing and optical quality. It's fairly hard to make a cover that doesn't screw up optical performance, especially for a fixed-focus system.
That said, the Galileo SSI did have a transparent cover (I'm guessing it was glass). All of the systems I've worked on (MOC 1&2, THEMIS, CTX, MARCI 98&05) had no covers at all -- we were too mass-constrained.

If only they had been as thoughtful with the antenna on Galileo.

Could they have put Galileo into orbit around Europa? Or was the radiation just too much for the probe towards the end of its life?

Did you mean to say 'no covers at all' ?

As thinking back to imagery from the KSC gallery - I certainly dont remember any covers on the instruments you mention.

Doug

(PS - Galileo was basically knackered - electronics exposed to huge ammounts of radiation - and certainly not enough fuel to go into Europan orbit - the reason for crashing it into Jupiter as I understand it was that they didnt expect to have enough fuel for manouvering on board to keep control of the vehicle, and they wanted to dispose of it whilst still in control of it.)

As someone already said, unfolfing HGAs were used numerous times before, with no difficulties unfolding. It was a proven concept. What got Galileo in the end was all that trucking around the country, waiting to be launched literally for years.

That's an even worse situation than trying to put Cassini into orbit around Titan. There's just too much delta-V needed for it to be anywhere near feasible. Galileo was "running on fumes" at the end of its life with practically no propellant left.
It also wasn't really designed to stand up to prolonged heavy radiation doses a Europa orbit would guarantee so that scenario wouldn't work in real life.