New Horizons: Approach Phase, OpsNav - 25 January 15 to 28 June 15 Options

[MahFL]

The LORRI image release for today is up at :

http://pluto.jhuapl.edu/News-Center/News-A...p?page=20150204

[JTN]

The LORRI image release for today is up at :
http://pluto.jhuapl.edu/News-Center/News-A...p?page=20150204

Are we seeing a terminator here, or is that an artifact?

Looking at Solar System Simulator (one, two) I think the terminator's in the wrong place to match the "flat side", but I might be driving SSS wrong (e.g. not attempted to check for SCET/ERT). In any case phase is only 14.1°. And "Pluto and Charon subtended 2 pixels and 1 pixel, respectively" (I guess the larger 'discs' are due to lack of deconvolution). So I guess it's just an artifact of some kind.

[MarsInMyLifetime]

We need a lot more pixels in order to differentiate a gibbous shape from a true circle. This shape is pretty much an artifact of making a very few points try to approximate a circle. On the other hand, the two are separated by enough pixels that the barycenter of their dance is truly a point in space between them, about 1/3 the distance from Pluto, now very easy to imagine in this gif.

[john_s]

The apparent shapes of Pluto and Charon at this resolution are still dominated by the LORRI point-spread function, which is slightly teardrop-shaped, giving that gibbous appearance. It will be another month or two before we see the true shape of Pluto, and then Charon a little later. Can't wait!

John

[Bjorn Jonsson]

Even though the resolution is far too low to reveal anything like phase angle or surface markings I decided to check the viewing geometry. At first the results were confusing to me; the reason is Pluto's axial tilt. For the OPNAV on 2015-01-27 03:21:00 it was like this:



Pluto's north is down since its axial tilt is ~120°. This is a bit confusing (should one display future images that show some details with Pluto's north up or down?).

The orientation of the 2015-01-27 03:21:00 OPNAV isn't like this. Here is a view from the Solar System Simulator at the time of the OPNAV. Here north is also down:

[jgoldader]

Pluto's north is down since its axial tilt is ~120°. This is a bit confusing (should one display future images that show some details with Pluto's north up or down?).

Right-hand rule or bust!

[elakdawalla]

For painful detail on the issue of Pluto cartography, read my blog entry about Amanda Zangari's work on this or her recently published paper (which is open-access).

Short version: there is much confusion in the literature about whether north is north or south of the ecliptic, and whether longitude increases east or west; the recommendation is to use right-hand rule going forward, but beware that the New Horizons planning software does *not* use this convention, although JPL Horizons does.

[Bjorn Jonsson]

I had forgotten about this blog entry - thanks for pointing it out. I'm a bit relieved to know that I'm not the only one that is confused!

[alk3997]

It's just too soon to see any detail. In the original non-enhanced image, Pluto is only 2 pixels in size and Charon is 1 pixel wide. Luckily time will fix that.

Looking forward to the 4x4 binned images. Hopefully those will be released this week or next. Resolution won't be better but sensitivity will be. It will be interesting to see Nix & Hydra orbiting Pluto/Charon.

Andy

[alk3997]

New Pluto/Charon animation available from end of January:
http://www.nasa.gov/content/the-view-from-...ml#.VN0cuvnF98H

[jasedm]

For those members (and I include myself) who are not entirely au-fait with celestial mechanics, I found these animations very useful in making sense of the Pluto/Charon orbital dance in the latest opnav campaign images. (Scroll up).....

Jase

[john_s]

ILooking forward to the 4x4 binned images. Hopefully those will be released this week or next. Resolution won't be better but sensitivity will be. It will be interesting to see Nix & Hydra orbiting Pluto/Charon.

And here they are: Nix and Hydra movie release

John

[alk3997]

And here they are: Nix and Hydra movie release

John

Thank you, John! Changing the attitude of the spacecraft to prevent a digital artifact from obscuring a moon may be a first in the space program. One of many firsts for New Horizons.

Probably a bit too early to analyze Nix and Hydra's surface features, eh?

Andy

[algorimancer]

And here they are...

What is the object that appears on frames 4-6 (circled in the clipped version of the animation below)? There's a similar object that appears once in frame 7 (circled, with question mark), but in a slightly different location. The object in frames 4-6 clearly seems to be an object moving downwards. Camera artifact? Other known satellite? Random KBO drifting past?

[john_s]

We noticed that bright spot and looked into it- it turns out that it’s a hot pixel on the CCD that was not corrected by the rather quick-and-dirty processing that went into making that movie. When we go back to the original images, it’s always in the same place on the camera frame regardless of where the camera is pointing, so we know it’s not real. We'll have better processing in future releases.

John