If patience and risk are hallmarks of scientific exploration, the multinational Cassini project now visiting Saturn and its moons is a textbook example.

Cassini braked into its distant orbit right on schedule Thursday, nearly seven years and 2.2 billion miles after being launched into space from Cape Canaveral. But the ambitious enterprise was eight years in the planning before that — and it has another four years of scientific business to do before its mission will be complete. Children born in 1989, the year the project got under way, will be 19 and out of high school by the time Cassini and its space probe known as Huygens are finished.

So much for patience. As for risk, if a $3.4 billion investment doesn’t make that case, the 1997 liftoff was accompanied by intense protest over 72 pounds of highly toxic Plutonium 238 that Cassini was carrying for fuel, more radioactive material than had ever been sent into space before. Protesters warned that any mishap on launch — or when Cassini’s circuitous route brought it back past Earth two years later — risked broad human exposure to the highly toxic isotope. NASA officials said the fuel was needed to power Cassini’s instruments in the recesses of the solar system where sunlight was only 1/100th of that received on Earth and thus inadequate for solar panels. NASA said any danger posed by the marshmallow-sized pellets of Plutonium-238 was minimal, but they had a small army of technicians on the ground with equipment to measure radioactivity.

At the time the Cassini project entered serious planning, Chinese dissidents were demonstrating for freedom in Tiananmen Square, and the scandal that toppled House Speaker Jim Wright of Texas was opening the door for Spokane’s Tom Foley as his successor. When the Titan-IV rocket blasted off from the Florida coast in October 1997, Attorney General Janet Reno was defending herself against accusations of improper fund-raising activity, and the music world was mourning singer John Denver’s death in a recent plane crash.

Considerable history has piled up while scientists were steadfastly tracking their project and monitoring the meticulous route that let Cassini hitchhike on the gravitational energy supplied by Earth, Jupiter and Venus twice.

Now, though, the craft has reached its destination and is busily into its demanding agenda. Initial pictures of Saturn’s fabled rings have floored scientists with their crisp detail. Cassini will circle Saturn 40 times in the next four years and will have 52 close encounters with seven of the planet’s 31 moons. Just before Christmas, it will drop the Huygens probe to the surface of Saturn’s planet-sized moon Titan, with its nitrogen atmosphere that scientists say could offer clues about atmospheric conditions that preceded the origin of life on Earth. The probe will have to work fast; it will last only minutes in the frigid temperatures of Titan’s surface. It will be the most distant surface ever reached by a man-made object.

The expansion of human knowledge rarely comes in Eureka-like moments of instant discovery. It takes painstaking dedication and excruciating patience. If you wish you’d followed the Cassini project from the beginning, make a notation on your calendar for July. That’s when NASA will receive industry proposals for a vehicle to lift the 80-metric-ton Jupiter Icy Moons Orbiter into orbit. Launch date: 2015.