NASA spacecraft starts its final dives towards Saturn

5 Apr 2017

Saturn. Image: Aphelleon/Shutterstock

Cassini’s theatrical reconnaissance mission to Saturn is nearing an end, with the final chapter of its looping story now on the horizon.

Cassini left Earth two decades ago and arrived at Saturn 13 years ago. Now, almost out of fuel, it is set to begin the last stage of one of NASA’s most successful missions to date.

On 26 April, the spacecraft will make the first in a series of dives through the 2.4km-wide gap between Saturn and its inner rings, as part of a grand finale.


This will see five months of looping in and out of this space, up to 22 times, racking up an impressive list of scientific achievements along the way.

The mission team hopes to gain powerful insights into the Saturn’s internal structure and the origins of the rings, obtain the first-ever sampling of the planet’s atmosphere and particles coming from the main rings, and capture the closest-ever views of its clouds and inner rings.

“Based on our best models, we expect the gap to be clear of particles large enough to damage the spacecraft,” said Earl Maize, Cassini project manager at NASA’s Jet Propulsion Laboratory (JPL).

“But we’re also being cautious by using our large antenna as a shield on the first pass, as we determine whether it’s safe to expose the science instruments to that environment on future passes.

“Certainly there are some unknowns, but that’s one of the reasons we’re doing this kind of daring exploration at the end of the mission.”

Last month, Cassini’s fascinating mission around Saturn contained a big surprise, revealing that Pan, one of the giant planet’s moons, took a peculiar shape: ravioli.

Image: NASA/JPL-Caltech/Space Science Institute

Image: NASA/JPL-Caltech/Space Science Institute

The exact origin of the rings of Saturn has perplexed astronomers for centuries but, using the latest technology, the pieces of the puzzle are gradually being put together by researchers unattached to the Cassini mission.

A team from Japan analysed mid-infrared images taken by the Subaru Telescope in 2008 – the highest-resolution ground-based views ever made – to unlock new secrets behind what makes the rings tick.

Saturn rings

A three-colour composite of the mid-infrared images of Saturn on 23 January 2008 captured with COMICS on the Subaru Telescope. Colour differences reflect the temperatures; the warmer part is blue, the cooler part is red. Image: NAOJ

For Cassini, the end is nigh. In mid-September, following a distant encounter with its moon, Titan, the spacecraft’s path will be bent so that it dives into Saturn.

When Cassini makes its final plunge towards the planet on 15 September, it will send data from several instruments – most notably, data on the atmosphere’s composition – until its signal is lost.

“Cassini’s grand finale is so much more than a final plunge,” said Linda Spilker, Cassini project scientist at JPL.

“It’s a thrilling final chapter for our intrepid spacecraft, and so scientifically rich that it was the clear and obvious choice for how to end the mission.”

Gordon Hunt was a journalist with Silicon Republic