After almost 20 years in space, the Cassini mission will end on September 15, 2017

After almost 20 years in space, the Cassini mission will end on September 15, 2017 at 5:07 a.m. PDT (8:07 a.m. EDT). Here’s how it will happen:

In late 2016, the Cassini spacecraft will begin a completely new type of mission at Saturn. During its final months, the intrepid spacecraft’s orbit will carry it high above the planet’s north pole and then send it plunging between the planet and the innermost edge of its dazzling rings.

Beginning on Nov. 30, 2016, Cassini will repeatedly climb high above Saturn’s north pole, then plunge to a point just outside the narrow F ring (the edge of the main rings), completing 22 such orbits. Then, on April 22, 2017, Cassini will leap over the rings to begin its final series of daring dives between the planet and the inner edge of the rings. This is the Cassini “Grand Finale.” After 22 of these orbits, each taking six days to complete, the spacecraft, will plunge into the upper atmosphere of the gas giant planet, where it will burn up like a meteor, ending the epic mission to the Saturn system.

As it plunges past Saturn during the Grand Finale, Cassini will collect some incredibly rich and valuable information that the mission’s original planners might never have imagined:

• The spacecraft will make detailed maps of Saturn’s gravity and magnetic fields, revealing how the planet is arranged on the inside, and possibly helping to solve the irksome mystery of just how fast the interior is rotating.


• It will vastly improve our knowledge of how much material is in the rings, bringing us closer to understanding their origins.


• Cassini’s particle detectors will sample icy ring particles being funneled into the atmosphere by Saturn’s magnetic field.


• Its cameras will take amazing, ultra-close images of Saturn’s rings and clouds.

This computer-generated view shows the view from the perspective of the Cassini spacecraft as it dives between the rings and Saturn’s cloud tops.

In an initial test on 10 August, ESA’s tracking station at New Norcia, Western Australia, hosting a 35 m-diameter, 630-tonne deep-space antenna, received signals transmitted by Cassini through 1.44 billion km of space.

New Norcia station Copyright ESA/S. Marti

“This was the farthest-ever reception for an ESA station, and the radio signals – travelling at the speed of light – took 80 minutes to cover this vast distance,” says Daniel Firre, responsible for supporting Cassini radio science at ESOC, ESA’s operations centre in Darmstadt, Germany.

“We had to upgrade some software at ESOC, as we discovered that one file used for pointing the antenna did not have enough digits to encode the full distance to Cassini, but the test worked and demonstrated we can catch Cassini’s transmissions.”

Tracking stations control room at ESOC

Some types of radio science observations use a ground station to detect signals transmitted from a spacecraft that have reflected off a planet or moon’s surface, or passed through the various layers of its atmosphere – or, in the case of Saturn, its rings.

Effects on the signals provide valuable information on the composition, state and structure of whatever they have passed through.

Numerous missions, including ESA’s Venus Express and Mars Express, have used this technique in the past. All three of ESA’s deep-space tracking stations (New Norcia in Australia, Cebreros in Spain and Malargüe in Argentina) were specifically designed to enable a radio science capability.

The Cassini mission has performed radio science observations many times during its time at Saturn. Previously, the mission relied solely on the antennas of NASA’s Deep Space Network for these observations.

Now, the addition of ESA tracking capability will help provide the continuous radio contact needed during Cassini radio science activities. The data received by ESA will be delivered to NASA for subsequent scientific analysis.

Grand Finale orbits

Copyright NASA/Jet Propulsion Lab

Starting in December and running into July 2017, Cassini will conduct a daring series of orbits in which the spacecraft will repeatedly climb high above Saturn’s poles, initially passing just outside its narrow F ring, and then later diving between the uppermost atmosphere and the innermost ring.

When Cassini plunges past Saturn, an ESA station will listen, recording radio signals that will be relayed to NASA.

These data will provide detailed maps of Saturn’s gravity, revealing the planet’s inner composition and possibly helping solve the mystery of just how fast the interior is rotating. They will also help scientists study the rings.

Until December, a half-dozen more test passes using ESA’s New Norcia and Malargüe stations to receive Cassini signals are planned, after which the two will be used during some two-dozen Grand Finale orbits.

After almost 20 years in space, the Cassini… ufospace