The Cassini spacecraft arrived in orbit around Saturn on July 1, 2004. In just one month, its mission will end forever with a suicidal plunge into the giant planet’s vast atmosphere. The periapse of Orbit 288 was completed Sunday evening (JPL time; Monday morning UTC), marking the start of the final five orbits.
This periapse was just 1,060 miles above what is arbitrarily described as Saturn’s “surface” — the altitude where the atmospheric pressure is similar to that of Earth at sea level (1 bar). This is low enough that the spacecraft has now tasted Saturn’s atmosphere directly, using its Ion and Neutral Mass Spectrometer to make the first ever direct measurements of Saturn’s atmosphere. It’s also low enough the spacecraft may have had to tweak its course with its reaction control thrusters. Also planned for this orbit are observations of the mysterious streaks in the rings, spectroscopic measurements of the atmosphere, and passive radar observations of Saturn’s atmosphere (observing changes in the carrier signal sent from Earth).
Not long now….