Cassini conducts last picture show

Engineers now have a precise expectation of when they will lose contact with the probe Cassini.

The spaceship is in the process of being abandoned in the atmosphere of Saturn, on Friday, ending a 13 extraordinary years of discovery to the ringed planet.

The team hopes to receive a signal for as long as possible, so that the satellite collapses in the giant world.

But the radio will probably be dead in about 6 seconds after 04:55 local time here at the mission control in California.

It is 11:55:06 GMT (12:55:06 BST). This is the time that the antennas on the Ground, losing contact.

Because of the finite speed of light and the 1.4 billion km from Saturn, the event in space have in fact taken place 83 minutes earlier.

“The spaceship of the final signal will be like an echo. It will radiate throughout the Solar System for nearly an hour and a half after Cassini itself has disappeared,” said Earl Maize, the us space agency (Nasa) project leader.

“Even if we know that, at Saturn, the Cassini probe has already met his fate, its mission is not really for us on Earth as long as we are still receiving his signal.”

A giant dish in Canberra, Australia, will be in an ideal position for the track of the probe. Others around the world are going to be working in support.

Cassini is taking his final pictures of the Saturnian system – a few postcards of the album, if you want to.

These include views of the moon Enceladus and Titan, which are home to enormous volumes of liquid water beneath their icy surfaces and where scientists believe simple life forms may be able to lead an existence.

“And then… we’re going to see the dark side of Saturn at a point where Cassini will plunge into the atmosphere, to the research in the near-infrared and ultraviolet, try to get a few photos from the Cassini end of the house to the inside of the planet Saturn itself,” said Nasa project scientist Linda Spilker.

NASA/JPL-CALTECH/SSI

All photos must be downloaded and the devices turned off before the death of the dive can begin.

The data rate flowing from return of Saturn will not be in charge of imaging on the way to the bottom. Instead, Cassini will be configured to run only instruments able to detect the planet’s near-space environment, such as its magnetic field, or can the example of the chemical composition of its gas.

Hunter Waite led the probe Ion and Neutral Mass Spectrometer (INMS).

“We’re going to be able to look at some of the important constituents that we know that they are there because we have been able to, but we’re going to have a better idea, for example, hydrogen to helium ratio, and it is important in terms of understanding the formation and evolution of Saturn,” he said.

In the final three hours or more before the impact on the Friday, all the data acquired by the satellite will be relayed directly to Earth, bypassing the edge of the solid state memory.

NASA/JPL-CALTECH/SSI

The end when it comes will be a bittersweet moment. The probe has dazzled all those who have followed its progress, including Jim Green, head of planetary science at Nasa.

He said Cassini has re-written the textbooks from which we may try to find life beyond the Earth.

“Nobody ever thought that we could move to the outer part of the Solar System,” said BBC News. “This is where the water, because the Sun is shining just, should be frozen and you must have liquid water to be able to have life.

“And now, we are together to find moons with oceans of liquid water that have been that way for 4.5 billion years. That has blown our minds.”

Looking towards the future, many Cassini scientists are looking forward to come back with a new, more capable spacecraft.

Mission proposals were submitted to Nasa that include instrumented boats that could float on Titan’s seas, and the life-detection probes which may be exploited by the jets of water that spout from the south pole of Enceladus.

In the short term, however, a lot of researchers are working on the American Clipper mission to Europa, a moon of Jupiter, which in many ways is just a big version of Enceladus. And in tandem, European Cassini scientists will be targeting Ganymede, another jovian moon, which is even larger than Titan, and that is also believed to hide a vast ocean of liquid water beneath its icy shell.

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453,000 images taken

2.5 million orders executed

635GB of the science data collected

3,948 scientific papers published

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The Cassini-Huygens mission is a joint project of Nasa, and the European community and the Italian space agencies.

BBC News will have live coverage of the end of the mission on TELEVISION and radio. Inside Science will be presented in avant-première at the highest point, this Thursday at 16:30 BST on Radio 4. A Horizon documentary will also review the mission and the final hours of a special programme to be broadcast on Monday 18 September at 21:00 BST on BBC Two. And you can always look at the Sky at Night programme Cassini: The Gamechanger on the iPlayer. This is repeated on Thursday on BBC four at 19:30 BST.

[email protected] and follow me on Twitter: @BBCAmos