Galileo (the spacecraft, not the scientist) is going to plunge into Jupiter's atmosphere tomorrow, ending its many-year exploration of that planet and its many moons. NASA is deliberately dropping it into the Jovian atmosphere in order to prevent it from accidentally hitting one of the moons, such as Europa, which may harbor life, and thereby contaminate that body with earth life that may have somehow survived the many years in deep space and Jupiter's intense radiation fields.

This weblog has a warm feeling for the spacecraft, which had a very hard life. The picture of the earth and moon in the banner was taken by it on one of its gravity-sling encounters, in which it stole a little momentum from the earth-moon system to augment its trip to the gas giant. In its honor, I'm displaying it in this post in more detail.

I don't like to anthropomorphize spacecraft, but it was a doughty explorer, and despite the rocky start to the mission, delivered a wealth of new information about our system's largest planet and its satellites. May it rest in peace.

[Thanks to my web designer Bill Simon for the heads up]

It's worth noting that Galileo was able to extend its mission to four times its design length, even though the high-gain antenna never deployed. There are many reasons for this, but I would point to three of them as critical:

1. Galileo is powered by Radioisotope Thermoelectric Generators (RTGs). Photoelectric systems (which could have worked only with some means of concentrating the low light levels at Jupiter) would have long ago been fried by the jovian radiation belts.

2. The spacecraft's systems were generously overbuilt, so they were robust and could tolerate (for example) the 4X radiation overload they experienced. Contrast this with the typical Soviet probe, which died around the end of its scheduled mission life.
3. When the high-gain antenna was lost, some very bright and motivated people reconfigured Galileo's software and hardware on the fly. They developed new encoding methods to enhance available bandwidth through the low-gain antenna, and repurposed the onboard tape recorder (intended only for data from the atmospheric probe) to store all the spacecraft's data, for leisurely transmission between fly-bys.

All this is not to slight the effort that went into merely getting it to Jupiter to begin with -- this involved inventing a new category of repeated Venus-Earth gravity whips, almost tripling its cruise time.

Rand is right: Galileo has been a real trooper, and a tribute to the now-gone class of expensive probes. As much as I loved being part of the faster-better-cheaper Mars Pathfinder effort, I can't help but think that we've lost something grand with the new model...

Here's a roundup of many good articles about Galileo the Mission and its End:
Galileo Roundup. And, in case the hyperlink didn't work, here's the URL:
*http://www.aoe.vt.edu/~cdhall/Space/archives/2003_09.html#000272*

Chris

Last night on CNN I saw the following in the crawl line relating to Galileo:

"Jupiter not likely to explode"

I wasn't sure whether to laugh or cry.

The New Yorker had an excellent review of the mission.

The political path this ship when through was just as torturous as its actual flight - at one point all that stopped the cancellation was the plaintive cries of Trekkies to Congress.

Of course there is the real value of this mission, after all the images have become pop cliches: 882 scientific publications by GEOREF's count (with more to come).

My favorite Galileo memory was discovering the discovery of the fire fountains of Tvashtar at my first American Geophysical Union conference - everybody crowding around those posters of awesome things being revealed for the first time. Good stuff.

Godspeed Galileo and bring on JIMO!

Where's the Kaboom? There's supposed to be a Jupiter-shattering Kaboom!