Cassini on course into Saturn's atmosphere

After a 20-year voyage, NASA's Cassini spacecraft is poised to dive into Saturn this week careening through the atmosphere and burning up like a meteor in the sky over the ringed planet.

From the early attempts to explore Saturn and its moons to the Cassini-Huygens mission, there have been trials and tribulations along the way. NASA expects to lose contact with Cassini just as at it approaches Saturn's cloud tops, an altitude of approximately 930 miles.

When it launched, Cassini-Huygens was the biggest, most complex interplanetary spacecraft ever flown. Project scientist Linda Spilker said if she could change one thing about Cassini, it would have been to add life-detecting sensors to sample these plumes.

In addition it has identified natural radio waves from inside the planet whose origin remains a mystery, and by studying the famous rings - made from dust, rock and ice - shed new light on how planets and moons form. The spectrometer will attempt to investigate what material is from the rings and what material is part of the atmosphere.

Cassini is firmly set on its crash course into Saturn, so it shouldn't need any help reaching its final destination. Ensuring that Cassini burns up in Saturn's atmosphere means that NASA is assured all Earthly life has been annihilated and the Saturnian system left pristine.

By 3:30 a.m., Cassini will be gone.

"There's no doubt about it, we'll be sad at the loss of such an incredible machine", said Earl Maize, program manager for the Cassini mission at the Jet Propulsion Laboratory in La Canada Flintridge. It arrived six years later, having navigated the unsafe asteroid-belt that lies between us and Saturn, but with only basic instrumentation on board it wasn't able to gather much scientific data. In order to protect potentially habitable moons orbiting Saturn from being contaminated with terrestrial microbes, NASA has ordered Cassini to destroy itself.

Mission planners decided that vaporising the spacecraft in Saturn's atmosphere was the best way to keep it from accidentally contaminating Enceladus and Titan - two of the solar system's most promising candidates for hosting extraterrestrial life. For the scientists who began working on the project in the 1980s, it is the end of decades of work culminating in scientific progress and never-before-seen images of Saturn's rings, moons and surface.

Moving closer to Titan, the spacecraft took advantage of the massive moon's gravitational push to make the first of 22 weekly dives between Saturn and its rings - venturing for the first time into the uncharted 1,700-mile (2,700-kilometer) space.

Once Cassini came back online, Staab said, the data could stream alongside the real-time observations, though the process would consume more bandwidth.

But Friday's dive will be like no other.

Right up until it beams its final signals to Earth eight of the spacecraft's 12 scientific instruments will be gathering data from the top of Saturn's atmosphere and transmitting information about its structure and composition. Four years became thirteen, as Cassini continuously exceeded expectations and NASA kept discovering new tasks for the probe. Hence, on 1997 NASA launched its robotic spacecraft, Cassini for an ambitious mission to Saturn.

What was the goal of the Cassini mission? The resulting information has contributed to almost 4,000 published scientific papers and some 5,000 people have worked on the mission over the years, according to NASA.

Cassini took thousands of photos of Saturn's dazzling rings and, in its final orbits, flew between the small gap between the planet and its rings.

  • Joe Gonzales