Monday, June 14, 2004
It's been popping up on the news only occasionally, but the Cassini-Huygens space probe is days away from arriving at Saturn, and has already began taking pictures of Phoebe, an outer satellite of the ringed planet.
I find this mission noteworthy and fascinating not only for the simple fact that it is the first spacecraft that will orbit Saturn, but more of the strange anachronistic nature of the mission.
Cassini, in a sense, is the last of a long line of grand US interplanetary missions, the successor to the major NASA missions of the late 1970s. As some might recall, this was a stagnant era in US manned spaceflight: the last Skylab mission was in 1974, and the Space Shuttle was seven years away. Meanwhile, NASA launched some of its most ambitious unmanned exploration probes to date: the Viking Mars missions in 1975 and the Voyager outer planets "Grand Tour" in 1977. There was also the Pioneer Venus mission of 1978.
In some sense, the missions set a standard for "big" interplanetary missions. When the Space Shuttle arrived in 1981, and with space station plans on the works and an emphasis on defense research in space, planetary exploration moved to the back burner. But there were still plans being made for a few missions, such as the Galileo Jupiter probe. Those plans, though, were stopped dead in their tracks by the Challenger accident of 1986.
So it was not until 1989 that NASA's planetary missions revved up again, with the launch in that year of the Magellan mission to Venus, and the Galileo mission to Jupiter. Incidentally, the delay in NASA's return to space was a factor in the failure of the deployment of Galileo's high-gain antenna, designed to communicate with Earth; the spacecraft was forced to use a weaker low-gain antenna instead.
It was in this atmosphere that the Cassini mission was born: the idea of large space probes crammed with instruments, the way NASA has designed these missions since the 1970s. But politics and science would have other plans.
In the 1990s, much of the wrangling that NASA found itself doing against Congress and the President was over the Space Station (remember the name Freedom?), an idea that was conceived at the same time as the Shuttle itself. It was imagined that the Shuttle would serve as a cheap and reliable transportation system to and from a permanent US presence in space. As things would turn out, the Shuttle was anything but cheap, and after Challenger, not all that reliable as well. Cost estimates for the station shocked Congress, but the pork barrel that it served for several important regions helped it stay alive, despite the close shave of June 1993. Eventually, Russian participation saved the project, but what we now know as the International Space Station became the central policy-deciding issue in NASA in the 90s: everything else was planned with the massive budget drain of the Space Station in mind.
So with the budget for interplanetary missions squeezed, NASA looked to different, cheaper ways of studying the Solar System. The first attempt was the Mars Observer, which maintained the "big probe" philosophy but seeked to cut costs by adapting commerical satellite construction techniques. The attempt failed: the mission costed $1 billion, and the probe was lost days before reaching Mars, precisely because commercial satellite were not designed for the long transit that the Mars Observer took.
So we arrive at what we have today, summarized by former NASA head Dan Goldin's principle of "faster, better, cheaper." Probes are smaller and less ambitious, with an emphasis on smaller, specific objectives instead of broad goals. Results are mixed: early successes with Mars Pathfinder and the Near Earth Asteroid Rendezvous on one hand, lost probes like the Mars Polar Lander and the Mars Climate Orbiter on the other. But overall, the steady stream of planetary/cometary/asteroidary missions seem to have been sucessful in captivating public interest and the success rate is increasing.
Meanwhile, after some delay, Cassini was launched in 1997. Even by then, Mars Pathfinder was already on its way to the Red Planet to herald a new era in planetary expedition.
To put things in perspective, Cassini (below left) is approximately the size of a school bus and cost $3.4 billion.
On the other hand, Stardust (above right) is about the size of an office desk and cost $166 million.
Besides the anachronism of the design of the Cassini mission and spacecraft, its objective is also somewhat behind the times.
The Huygens probe, built by the European Space Agency, is hitching a ride off NASA's Cassini and is to parachute into the atmosphere of Titan, the largest satellite of Saturn. Back when I was younger, Titan was considered to be one of the most likely places in the Solar System where life may exist (besides Earth): its atmosphere, rich in nitrogen, methane, and other organic compounds, was considered to be similar in some ways to Earth's early atmosphere, and some hypothesized that oceans of liquid nitrogen covered its surface where a primordial soup may be mixing. Since then, though, the idea has been eclipsed by the prospect of liquid water oceans under the surface of Europa, one of Jupiter's Galilean satellites (although I haven't heard of any literature definitively refuting the Titan life hypotheses; it's just that people seem to care less about it).
Speaking of Huygens, with ESA's Mars Express mission, a slew of other interplanetary missions being planned, and a locally developed heavy lift booster in the Ariane 5, I feel that the European Space Agency will probably pursue its own path in space exploration independent of NASA in the future: co-operation on the level of Cassini-Huygens will probably come by less often with time.So, as we see Cassini arrive at its destination and the possible launch of the first private manned spacecraft this year, it is certainly a unique and special time in mankind's journey out of the cradle.