I got a reply from the HRSC data processing manager, Dr. Thomas Roatsch, about some of the map-projected PDS/PSA tag issues, which seemed appropriate to share here.

As to the duplicate RADIANCE_OFFSET and RADIANCE_SCALING_FACTOR tags, the second ones are correct to the map projected images. For anyone particularly interested in the reflectance data, there is a necessary tag which is missing (REFLECTANCE_OFFSET). Dr. Roatsch has suggested to the PDS/PSA that they deliver a new version soon to fix both of these problems.

When considering the radiance information recoverable by applying the offset and scaling factors, a third tag becomes important as well. The radiance values are in units of Watts/m^2/sr, and is not spectral radiance (Watts/m^2/sr/nm). This means that the calibrated radiance values in the images are a summation across the whole bandwidth of the filter+ccd. This is important because bandwidths of the HRSC color filters differ significantly. The red filter is 48 nm wide, green is 88 nm wide, and blue is 76 nm wide. In other words, if one didn't take this into consideration, the green filter would appear almost twice as 'bright' as the red filter, since its radiance is considered across a spectrum twice as wide.

So, to recover spectral radiance from the HRSC map-projected images, one must apply the offset and scaling factors, then divide that value by the bandwidth of the filter.

Nice and simple then

Doug

Dont forget to throw salt thrice over your left shoulder on a full moon night...

Here's a recent Phobos image from Mars Express.

Phil

Click to view attachment

I'm still looking for a good, perhaps even iconic, Phobos image for my avatar. The search continues...

My fav Phobos image...but I guess you're looking for something a bit better than that

D

Gotta have Stickney.

http://solarsystem.nasa.gov/planets/profil...ject=Mar_Phobos

Here's the most recent Deimos image in the PSA. It's a composite of two SR frames.

Phil

Click to view attachment

Here's one for you Phil,

Deimos has, to me at least, looked to be a much smoother almost 'softer' looking body than Phobos. Is that a symptom of the common images we see being of lower resolution, or an actual property difference between the two.

Doug

It's not a resolution effect. The best Viking images of Deimos have higher resolution that the best Viking images of Phobos. Deimos is smoother because it's almost completely covered by a thick debris layer. Peter Thomas (Cornell) has argued, and I agree, that the debris is ejecta from a crater with a diameter almost as large as Deimos's longest dimension, which is visible to us as the south polar "saddle" of Deimos. Most debris from a crater like that is ejected at very low velocity (forming the heaped-up rim of a lunar crater, plus lots of that never gets outside the crater at all) and coated Deimos at once. The rest was probably re-accreted from Mars orbit. Phobos lacks a "giant" crater of the same relative scale.

Phil

Here's the saddle:

Click to view attachment

Phil

PS one of the most amazing views in the solar system would be had from the righthand hill here, looking across the 10 km wide saddle to the other hill, with Mars in the background surrounding that hill like a halo.

I'm getting closer but not quite there yet. Maybe I should change my avatar to Deimos

Here's another image of Phobos from the PSA. It's not so hard to use once you get into it. I was misled slightly by the image size in the label, as I had to open this as a raw image in Photoshop, but once you remember to add the line prefix pixels to the width of the image it's OK.

Phil

Click to view attachment

If you compare this with the last one, it's a mirror image. This is the ND2 image and it's reversed. The previous Phobos post was SR2, and it's right-reading.

I was going to use the latest Deimos image but I really prefer Phobos. Luckily, ugordan made a nice PNG image for me based on my favorite MOC image of Phobos. Hopefully, this should alleviate the bandwidth issues some were having loading my previous Phobos avatar, which was an offsite image at MSSS.

Uh, oh. I hate to point it out but I can see a face in that image! Not so much on the thumbnail version as on the fullsize one. It kind of pops out there. (It's on the righthand side looking toward the right: two eyes--one round, the other sort of orientalish--a flat nose, and the lefthand cheek, a kind of sneer or grimace for a mouth.)

Maybe you shouldn't have shown us that pic! Now we'll be hearing about The Face on Deimos and how NASA tried to hide it from us.

======
Stephen

I'll bet ESA PAO never used this one on the kooks: "Pardon moi. One of our scientists accidentally included one of his wife's ultrasound images."

There are probably faces all over it. The first one I noticed is facing to the left and down. Big white lips at bottom of image, teardrop-shaped eye above, nose in profile flush with upper lip. In fact the whole thing seems to be a giant head sculpture obviously made by the Roswell people (who also influenced the Olmecs) . . .

Check out this abstract from the new EGU meeting: Greg Michaels on a new HRSC data viewer. Very promising. Also news of the release of HRSC-derived topography data.

Phil

http://www.cosis.net/abstracts/EGU2007/075...88baf6c8092ff18

(or go to:

http://www.cosis.net/members/meetings/sess...88baf6c8092ff18

and find his abstract in the middle of the page, or failing that go to:

http://www.cosis.net/members/meetings/prog...88baf6c8092ff18

and find the mars session in the middle of that page.

Hey, come on people, give us some simple URLs! All that search stuff is unnecessary or should be hidden.

Phil

This is great to see Phil. I think NASA and the various PI's (notably MSSS, THEMIS, the MER/Athena teams and the HiRISE team, Cassini to a lesser extent) have really set a high standard for outreach and no doubt the ESA is feeling some heat for keeping its data so close. But that is not to in any way discourage them from this generous initiative.