Are you travelling far on holiday this year? We thought it would be fun to look at some of the extreme journeys that spacecraft from Earth are making, which might put that 4-hour flight to Lanzarote into perspective….
The Cassini-Huygens spacecraft launched from Cape Canaveral in October 1997. It had a relatively eventful journey, involving several ‘gravity-assist swingbys’ – it picked up speed by swinging past Venus twice, then past Earth and Jupiter before finally arriving in orbit around Saturn in July 2004. And it has been there ever since, in orbit around the planet, seeing the sights and doing lots of science. Cassini has seen far more than we could ever mention here, but we did a round-up of 10 things we’ve learned from Cassini-Huygens when it celebrated 10 years in orbit last summer (Cassini did such a good job that its mission has been extended, twice!).
"This is a mission that never stops providing us surprising scientific results and showing us eye popping new vistas," said Jim Green, director of NASA's planetary science division at NASA Headquarters in Washington. "The historic traveller’s stunning discoveries and images have revolutionized our knowledge of Saturn and its moons."
(Credit: NASA Jet Propulsion Laboratory, 2012)
Do you seek out unspoiled holiday locations? When the Huygens probe landed on Titan (one of Saturn’s moons) in January 2005, it became the first spacecraft to land in the outer solar system.
It took Cassini nearly 7 years to reach Saturn, snapping pictures all the way, but when the Rosetta spacecraft set out to catch up with a comet it had a much longer journey to make. Rosetta was launched in March 2004, and travelled around the Sun five times, picking up gravitational boosts from the Earth and Mars along the way. By July 2011, Rosetta was travelling close to the orbit of Jupiter, and the solar-powered spacecraft was running low on juice. The mission controllers put Rosetta into hibernation, with an internal alarm clock to wake it when it was on its way back into the Solar System.
Rosetta woke up in January 2014, to actively pursue comet 67P/Churyumov-Gerasimenko. It caught up with the comet in in August 2014.
"After ten years, five months and four days travelling towards our destination, looping around the Sun five times and clocking up 6.4 billion kilometres, we are delighted to announce finally 'we are here'", said Jean-Jacques Dordain, ESA's Director General.
In November 2014, lander Philae completed the first ever ‘controlled touch down’ on a comet, conducting science experiments and sending back data whilst its batteries lasted. Stuck in the shade, Philae then went into hibernation until the comet got closer to the Sun. With more light reaching its solar panels, Philae woke up again in June 2015, and there’s hope it will be able to do more science in the coming months.
Meanwhile, Rosetta continues to observe comet 67P as it approaches the Sun. Rosetta has seen sinkholes forming in the surface of the comet (results published in Nature in July 2015), a process which scientists believe is very similar to that seen on Earth. ESA has confirmed that the Rosetta mission will continue until September 2016. By then, comet 67P comet will be moving far away from the Sun again, and there won’t be enough solar power to keep Rosetta’s instruments running. Rosetta’s long journey will probably end with the spacecraft being brought to rest on the comet it has chased for so long.
But even Rosetta’s epic journey isn’t the longest. In 2013, Voyager 1 became the first man-made object to leave the solar system and start exploring interstellar space. Launched in 1977, Voyager 1’s original mission was to study the outer planets. After taking a good look at Jupiter and Saturn, it continued on to the far reaches of our solar system. By 2013, with its power supplies running low and its sensors failing, Voyager 1 was almost 19 billion kilometres from Earth. Signals from the probe took 17 hours to travel back to Mission Control.
(Credit: NASA Jet Propulsion Laboratory, 2013)
It’s not easy to tell whether a spacecraft has left the solar system. NASA scientists are monitoring three different indicators, two of which you can see for yourself – they’re shown on a gauge on the Voyager homepage. After careful consideration of their plasma density readings, they confirmed that Voyager 1 crossed the heliopause on 25th August 2012. Voyager 2 is a few years behind, having taken a detour to study Uranus and Neptune. Both probes have enough power left to continue operating until at least 2020, and are sending back scientific information about their surroundings through the Deep Space Network, or DSN.
“Voyager has boldly gone where no probe has gone before, marking one of the most significant technological achievements in the annals of the history of science, and adding a new chapter in human scientific dreams and endeavours,” said John Grunsfeld, NASA’s associate administrator for science in Washington. “Perhaps some future deep space explorers will catch up with Voyager, our first interstellar envoy, and reflect on how this intrepid spacecraft helped enable their journey.”
The Voyagers aren’t our only source of information on what’s outside the solar system, as telescopes can see to the far reaches of the Universe. A lot of what’s out there is obscured by interstellar dust, which limits what we can see in visible and ultraviolet (UV) light. The VISTA telescope uses infrared (IR) light to see past the dust to what lies beyond, giving astronomers a really good view – it has been used to create a huge, nine-gigapixel, zoomable image of 84 million stars in our galaxy, the Milky Way. Handy if you’re planning your own extreme journey into space!