January 26, 2005

There are no 7-11s on Titan

Note: This entry has been updated.

So, Titan:

Photo: ESA"You can't be there -- but you are. You're seeing the pictures through an artificial eye made for humans by humans. The eye belongs to a probe called Huygens, which landed on Titan over the weekend. It took pictures in ultra-freezing temperatures and sent them 40,000 miles through space to a satellite, which relayed them across the solar system to Earth.

To give you some idea of the distance involved, we're about 93 million miles from the sun. Mars is about 140 million miles from the sun. Titan is about 900 million miles from the sun. In basketball terms, the difference between landing a rover on Mars and landing a probe on Titan is the difference between a layup and a full-court heave.

Actually, we didn't send Huygens directly to Titan. We put it on the back of the satellite, Cassini. We made Cassini fly to Saturn. We threaded it through a tiny crack in Saturn's perilous rings. We put Cassini into a perfect orbit around Saturn, passing this moon, then that, then another, taking pictures the whole time. Just before Christmas, Cassini launched Huygens on a 2.5 million-mile trip to Titan. Huygens survived atmospheric entry and opened three parachutes in sequence, ejecting its heat shields and slowing from 12,000 mph to a gentle landing.

Can you imagine that? A machine that can fly a billion miles, sneak through a hole in Saturn's rings, dance around its moons, fire a 700-pound bullseye from a distance of 2.5 million miles, and retrieve pictures from the ground? What could be more amazing?


We didn't send Cassini straight to Saturn. Given its weight, that was impossible. So we invented a shortcut: We made its route longer. Yes, longer. We sent Cassini around the sun and past Venus for a velocity-boosting "gravity assist" (derived from being slung around the planet) in 1998. Then we sent it around again for two more assists from Venus and Earth in 1999. That gave it enough speed to get to Jupiter for a final gravity assist in 2000, which propelled it to Saturn four years later. The trip required a perfect symphony of projections over seven years, so that Cassini would barely miss each orbiting planet. Total distance: 2.2 billion miles."

Excerpt from Lords of the Rings (Slate.com); Photo: ESA

I mean, damn! The ESA web site has more on Cassini-Huygens, of course -- including sound!

UPDATE: George asked about the low-res quality of the images. The ESA website actually has an impressive volume of information on the Cassini-Huygens instruments. The details there lead me to believe the images are actually that quality -- it doesn't seem that the ESA is downgrading them for any reason. The DISR imager which apparently took the images being posted on the ESA website is discussed here. If you take the table of data at face value, Huygens' highest quality imager has a 176x256 pixel format.

There's a whole website on the DISR at the Lunar and Planetary Lab at the University of Arizona, which is listed as a partner with the ESA, NASA, and the JPL for the images on the ESA website. The information on this website seems to back up the idea that these images are actually that low-res. Again, the amount of information is pretty incredible. Check out the cameras page and the test images. The LPL website does say that the images have to be processed before they'll look like they're supposed to. Obviously this won't increase the resolution, but judging by the test images, presumably there will be less noise so they'll look sharper. Also:

"Each of the cameras in the imaging system takes a picture of Titan's surface in a different direction and at a different resolution to produce a "triplet" collection of three images which may be combined with other triplets to create a mosaic of the surface."

Interestingly, according to the LPL website, "Huygens' batteries will allow DISR to collect data for twenty minutes on the surface if the probe survives impact." Talk about time being precious.

Posted by anatole at January 26, 2005 10:58 PM

Ummm, shouldn't you attribute this quote? I think it's from slate, right?

Also, I like the ESA website: http://www.esa.int
In addition to some Titan images, there are some great images from the mars Express orbiter, presented with a cute orbiting Mars map.

It's weird, the Titan images they offer are extremely low-res. I wonder if this is because Huygens had a very durable but low-res camera strapped to it, or whether the ESA for political/security reasons doesn't want to release raw data that could start a furore (not that I'm suggesting there are actual alien footprints in these images, or verdant river valleys, but it might be their policy? Because these 200K "high-res jpg's" are really poor quality compared to the amazing images available from the Mars mission (some are 7 megs). I realize the Mars Express has newer hardware on it...

Posted by: George at January 27, 2005 02:24 PM

Attribute it? No, I like to plagiarize. No, actually, I just can't cut-and-paste HTML code to save my life. Oops. It's all fixed now.

Good question about the images. I was wondering about the quality myself. I looked it up on the ESA website and will add something about it to my post.

Posted by: Anatole at January 29, 2005 06:43 PM

Yes, the shortness of battery life boggles the mind; it was the first thing I noticed when I read about the project. I suppose within twenty minutes the probe can scan all its surroundings with all its instruments. Since it's unable to move, that's about all it can do anyway. BUT it would seem obvious to me that it should stay "alive" for a few days at least, so that every hour or so it can take temperature, pressure, and atmospheric composition readings (or whatever).

I find it extremely painful to imagine the budgetary mindset that could have led to the short battery life and the limited resolution of the cameras. It seems like a situation where incremental investment would yield incrementally better data; if it is so, then once you've got all the way to Titan, wouldn't it be worth putting a few million more in the front end? And, is the difference between a .5 megapixel and a 2 megapixel CCD really more than a few thousand dollars?

Of course there are data transmission issues, and crash-resistance, and overall complexity, etc. etc. But now that Huygens landed successfully and executed almost flawlessly, are the penny-pinchers at ESA kicking themselves?

Posted by: George at January 29, 2005 08:17 PM

Actually, I'm remembering now that the main issue is really temperature. I guess Huygens used the residual warmth it picked up from flying through the atmosphere to allow it to operate at all when it landed. Perhaps the energy to reheat its equipment and then broadcast would have required a much, much larger battery.

Posted by: George at January 29, 2005 08:20 PM