Saturday, June 06, 2009

Why featured pictures is ailing

Reposted from Wikipedia's featured pictures talk page:

Picking up on the 'crap technical quality' comment in the thread above,[21] a problem in recent months has been myopic understanding of technical quality. One of the best examples to diagnose the ailment is the Titan delisting nomination.

The image is dated 2004, but of course the camera wasn't made in 2004 because the spacecraft was launched in 1997. The exact mass of all the equipment had to be known and tested years before launch in order to plot its course, which included two gravity assist flybys at Venus and Jupiter. So the camera was built with early 1990s technology. It had to perform at temperatures a few degrees above absolute zero in near-total darkness because at Saturn's orbit the sun doesn't provide much more energy than a bright star.

Titan has been visited by spacecraft only three times in human history. The first was Pioneer 11 in 1973, which returned this image. Then the Voyager missions in 1980-1981 shot this. And in order to even do that well with the technology that existed at the time, NASA scheduled Voyager I's final encounter as a close Titan flyby.

The technical challenges that arise after launch add additional layers of difficulty to these missions. Voyager I was nearly destroyed in the rings of Saturn before its Titan encounter because the best technology available when the mission was planned had been unable to detect any matter in the dark zones of its ring system. After the Jupiter encounter the craft sent back images of literally hundreds of rings in the zone of its planned course: a grain of sand would have operated like a bullet on the craft at the speeds it was traveling. Emergency course modifications were extremely difficult to execute, but the mission was saved. Without that rescue, much of the data never would have been obtained that went into planning the Cassini mission.

This is all cutting edge science and sometimes the technical team has to work around hardware failures. One famous save occurred here:

Since Galileo's high-gain antenna failed to open in 1991 the mission was forced to use the low-gain antenna for all communication to Earth. This meant that data storage to Galileo's tape recorder for later compression and playback was absolutely crucial in order to obtain any substantial information from the planned Jupiter and moon flybys. In October 1995, Galileo's 114 megabyte (914,489,344 bits[40]), four-track digital tape recorder which was manufactured by Odetics Corporation, remained stuck in rewind mode for 15 hours before engineers learned what happened and sent commands to shut it off, after recording an image of Jupiter. Though the recorder itself was still in working order the malfunction possibly damaged a length of tape at the end of the reel. This section of tape was subsequently declared "off limits" to any future data recording and was covered with 25 more turns of tape to secure the section and reduce any further stresses, which could tear it.

The software needed extensive rewrites after the antenna failure, then a second round of even more drastic rewrites after the tape recorder failure. And all of the relevant imaging had to be rescheduled and replanned because the data was moving much more slowly, but the craft was still flying at orbital speed.

It simply isn't rational to review the Titan image by the same standards one would apply to a home tripod photo of earth's moon. Of course the Titan mosaic isn't stitched: it was shot for scientific purposes, not for an art gallery. Of course it's contrasty: Titan is the only astronomical body in the solar system other than earth that has liquid at its surface--they were looking for specular reflections.

As stated before, I do have a conflict of interest regarding the Titan image and will disclose fully to anyone who emails a request. So far, no one from the featured pictures program has inquired. Most of the statements in this post are readily verifiable; a few aren't. A barnstar to the first person who detects which information wasn't published officially. Several of the regulars at featured picture candidates need to spend more time reading the articles these images illustrate.

And yet 'crap technical quality' is a comment that gets taken seriously. And the delisting nominator himself hasn't been called to task for saying FPC is not an image gallery and nobody puts quality ahead of EV. Just take a look at the page now and see for yourself. The images that are being opposed because of quality concerns have TERRIBLE quality.(original poster's emphasis)[22] That is an expression of misplaced priorities, superficial understanding, and distorted perspective. Knowledge of digital photography is not a substitute for research. The technical quality of this image is a feat of international science and engineering, and those who deny that reveal their own ignorance. It will likely be a quarter century before better images can be taken of this astronomical object. Those are the realities of science, and this website is an encyclopedia. Cross posting to my blog. DurovaCharge! 21:18, 6 June 2009 (UTC)

1 comment:

William M. Connolley said...

bizarre co-incidence

"It would be a pleasure if we can get someone to sharpen it" - why not just fake the whole thing?