IT was a bittersweet farewell for Oxford and Harwell scientists who spent decades working on the first spacecraft to ever plunge between Saturn and its innermost rings.

The Cassini spacecraft will have come closer to the planet than any probe before it and the historic manoeuvre last week marked the beginning of its end.

Over the next five months, the satellite will make 22 orbits around Saturn, delivering data before burning into oblivion as it runs out of fuel.

The landmark mission started more than 20 years ago and the department of physics at Oxford University and the RAL Space at the Rutherford Appleton Laboratory (RAL) based at Harwell Campus was involved with the satellite's creation.

The joint US and European Cassini-Huygens mission is the most ambitious unmanned space expedition and has helped scientists understand the planet's make-up, including the realisation it has 62 moons.

Scientists from Oxford provided significant components to one of the mission's main instruments, the Composite Infrared Spectrometer (CIRS).

The CIRS measures the heat emitted by a planet's atmosphere or surface and produces a spectrum showing the characteristics of the different gas molecules or minerals present.

Although the Cassini instrument was led by NASA's Goddard Space Flight Centre, the Oxford team provided the radiative cooler and the mid-infrared focal plane assembly – which holds the infrared detectors.

Led by Dr Simon Calcutt from the university's department of atmospheric physics, the Oxford team included: Dr Patrick Irwin, Dr Neil Bowles and Dr Jane Hurley.

The team said: "Cassini has been the bedrock of our scientific exploration of the solar system for the last 20 years and has come close to Saturn than anything before it.

"For some of us, who got married around the same time of the launch in 1997, the mission has particular personal resonance and we will be very, very sad to see it finally finish.

"The instrument has been an amazing success and worked pretty much flawlessly since arriving at Saturn in 2004."

But the team says the project has not been without its challenges as the instrument is programmed using software in Oxford but commands are sent to NASA, who up-links them to the spacecraft.

They added: "The ring-dodging was an occupational hazard that none of us imagined when starting to work on this.

"None the less we are all tremendously proud of the mission's accomplishment and to have played a part in such a monumental piece of planetary research."

As the mission draws to a close the technology has allowed the team to use CIRS data to analyse the atmospheres of Saturn and Saturn's giant moon Titan.

CIRS has also been involved with mapping the temperature variations on Saturn's moons and identifying the heat pouring out of Enceladus' (the planets' sixth largest moon) south polar region.

The mission is due to self destruct in September.