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The Planetary Society Weblog

By Emily Lakdawalla

Welcome to The Planetary Society's Weblog, a guide to interesting stuff going on in space science, space exploration, and space advocacy. Have any comments?

Weblog Archive

Aug. 27, 2008 | 11:30 PDT | 18:30 UTC

Ustream chat with Lou Friedman -- sadly, no recording

Permalink: http://www.planetary.org/blog/article/00001621/

Despite some initial technical difficulties I got today's Ustream chat running, pulling our esteemed leader Lou Friedman in to the broadcast from his own Webcam as a Ustream "cohost." Sadly, though, the "record" feature on Ustream did not appear to record any of Lou's signal -- it just recorded half an hour of my webcam, that is, video of me sitting quietly and typing messages to Lou. So I am very sorry to report that his broadcast is not archived in anyway that you can see or hear. I am contacting Ustream to see if the failure to record the cohost signal is a bug or a feature.

Aug. 27, 2008 | 10:56 PDT | 17:56 UTC

Pictures from the past: Viking 2 approaches Mars

Permalink: http://www.planetary.org/blog/article/00001620/

On Monday I pointed to the awesome new website for the VMC instrument on Mars Express and mentioned that the camera can get views of Mars in a crescent phase. I thought it might be the first spacecraft to do so, but a couple of readers wrote in to tell me that they remembered crescent views of Mars from Viking 2. A Google search quickly yielded an image on Astronomy Picture of the Day from 1999, showing a tiny, garishly colored view of a crescent Mars.

Crescent Mars
This Viking Orbiter 2 image of a crescent Mars, a version posted on Astronomy Picture of the Day in 1999. Credit: NASA / JPL

So, yes, Viking 2 did take such a photo -- but boy, is that an ugly picture. I thought I might be able to do a little better than that. The Viking 2 data set is pretty easy to get to, on the Imaging Node of the Planetary Data System. I located the original files taken by Viking 2 as it approached (~~Viking 1 did not take any approach images~~ I am told that it did; I'm looking for them.). The set includes 11 three-color views of a crescent Mars. For the first six, the whole disk of Mars fit in one photo. The last five were mosaics, where Mars was too big to fit into one image.

Raw Viking images contain a lot of speckly noise, random missing lines, and reseau markings, black dots painted onto the camera optics to help the imaging team remove distortion from the images. Thankfully, there is a piece of software that you can download from Peter Masek's website that copes with the first two of these problems. (His site also contains a lot of background information on how the Viking cameras worked.) I used his software to despeckle and convert the original files to a format that Photoshop could read. Then I took the images into Photoshop, combined red, green, and violet filter images into a color composite, and used the Photoshop clone stamp tool to remove the reseau markings by painting over them with bits of color from elsewhere in the image. Voila, a spectacular set of Viking 2 images of Mars' looming crescent.

Click to enlarge >

Viking 2 approaches Mars
As Viking Orbiter 2 approached to orbit Mars on August 6, 1976, it snapped many images of Mars' approaching crescent, the first such images ever taken of the red planet. Credit: NASA / JPL / color composites by Emily Lakdawalla

Those six are all the non-mosaic ones. Ken Edgett (one of the people who originally emailed me about the existence of these photos) helpfully pointed out some surface features on the biggest one.

Click to enlarge >

Viking Orbiter approaches Mars
Credit: NASA / JPL / color composite by Emily Lakdawalla / labels by Ken Edgett

I did take a crack at one of the mosaics, the last one Viking 2 took on approach. The mosaics are not hard to jigsaw together but getting the color to match between the frames was beastly difficult and I'm still not happy with the result. Still, it is a breathtaking view, with the Sun rising on Valles Marineris at the center of the disk. And, near the bottom, there's a great view of Galle, otherwise known as the Happy Face Crater.

Click to enlarge >

Viking Orbiter approaches Mars
This is the final image of Mars captured by Viking Orbiter 2 as it approached for its orbit insertion on August 6, 1976. It is a two-image mosaic. Valles Marineris is clearly visible at the center of the disk, crossing the terminator. In the south, frost extends up into the Argyre basin; on its edge, with a dark outline, is the crater Galle, famous for the eroded remnants of a central ring that makes it look like a happy face. Credit: NASA / JPL / color composite by Emily Lakdawalla

I am sure there are many people out there who can do a better job than I can with these color images. Here is a Zip file containing all of the approach images, already despeckled, in PNG format (22 MB); I hope some of you will take a crack at building some of those other mosaics!

Aug. 26, 2008 | 16:51 PDT | 23:51 UTC

GLAST has a new name: Fermi

Permalink: http://www.planetary.org/blog/article/00001619/

The erstwhile Gamma-Ray Large Area Telescope (GLAST) has today received a new name: Fermi. More officially, it is the Fermi Gamma-Ray Space Telescope, one of the flagship orbiting observatories like the Hubble Space Telescope and Spitzer Space Telescope. Fermi studies the sky at very high energies, an area of science that I don't know much about. It is therefore quite fortunate that I can point you to Phil Plait for a more knowledgeable explanation than I can provide! He also has one of the Fermi images that were unveiled at a press conference today, a view of the entire sky at gamma-ray wavelengths.

Aug. 26, 2008 | 09:06 PDT | 16:06 UTC

Asteroids and comets to scale, as a single image for printing or Powerpoint

Permalink: http://www.planetary.org/blog/article/00001618/

After posting the montage of asteroids and comets to scale last week I got a lot of requests for a single-image version of the montage. Your wish is my command! Here is a single image of all of the asteroids and comets that have been visited by spacecraft, sized to be dropped in to a Powerpoint presentation, or even used as a desktop image, at 1600 by 1200 pixels. In the caption I've provided links to a much larger version of the image, a whopping 6000 by 4500 pixels -- that's handily large enough to print as a 16 by 20 inch (40 by 50 cm) poster or even larger. Of course, I'm just going to have to update this in two weeks once Rosetta has returned photos of Steins! Steins, by the way, is supposed to be about 5 kilometers in diameter, roughly the size of Annefrank or Wild 2, so I shouldn't have any trouble fitting it in. But once Rosetta visits Lutetia in July 2010, I'll have to redo the layout -- Lutetia is expected to be about double the diameter of Mathilde. Thanks very much to Joel Parker for correcting some of my numbers on the body diameters.

Click to enlarge >

All asteroids and comets visited by spacecraft as of early 2008
The total of four comets and seven asteroid systems (including eight separate bodies) that have been examined up close by spacecraft are shown here to scale with each other (75 meters per pixel, in the fully enlarged version). Most of these were visited only briefly, in flyby missions, so we have only one point of view on each; only Eros and Itokawa were orbited and mapped completely. This image is also available without text. There is also a larger version at 20 meters per pixel (6000x4500 pixels, 4.2 MB), with or without text (3.9 MB).

Credits: Ida, Dactyl, Gaspra, Annefrank, Braille, Borrelly: NASA / JPL / Ted Stryk. Mathilde: NASA / JHUAPL / Ted Stryk. Eros: NASA / JHUAPL. Itokawa: ISAS / JAXA / Emily Lakdawalla. Halley: Russian Academy of Sciences / Ted Stryk. Tempel 1: NASA / JPL / UMD. Wild 2: NASA / JPL.

While I'm talking about asteroids and comets, I want to remind all of you amateur astronomers out there that the deadline for the next round of The Planetary Society's Gene Shoemaker NEO Grants is in a month, September 30. Get your proposals in!

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