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Comet-Chasing Probe Wakes Up On Monday
Hugh Pickens DOT Com writes "Jason Major reports that after nearly a decade of soaring through the inner solar system, flying past Mars and Earth several times and even briefly visiting a couple of asteroids for a gravity assist, the European Space Agency's comet-chasing spacecraft, Rosetta, is due to 'wake up' on January 20 after 957 days of hibernation. The probe is awakening to prepare for its upcoming and highly-anticipated rendezvous with comet 67P/Churyumov-Gerasimenko in August. The spacecraft was designed to be put in hibernation for the coldest part of the journey that took it close to the orbit of Jupiter, because even with massive solar panels the size of a basketball court, Rosetta would not have enough power to complete its mission without this energy-saving strategy. Once Rosetta enters orbit around the comet — the first time a spacecraft has ever done so — it will map its surface and, three months later in November, deploy the 220-lb (100-kg) Philae lander that will intimately investigate the surface of the nucleus using a suite of advanced science instruments. 'It's the first time we've made a rendezvous with a comet — that's never been done before — and it's going to be the first time we've escorted a comet past its closest approach to the Sun,' says ESA project scientist Matt Taylor."
"massive solar panels the size of a basketball court,"
can we please have proper units for measuring things in space?
is due to 'wake up' on January 20 after 957 days of hibernation
If successful, this will be a new record for the onboard Windows XP.
You know that ice that's in the corner of the parking lot covered in black dirt and is the last piece of ice to melt? That's what's that probe is going to find.
Take the cheese to sickbay, the doctor should see it as soon as possible - B'Elanna Torres, "Learning Curve"
For the curious, here's a video showing Rosetta's path: Rosetta's Twelve-Year Journey to Land on a Comet - ESA Space Science HD Video
Saying a probe wakes up on Monday assumes no glitches. Wouldn't it be best to say "should/expected to/might" wake up Monday?
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Poor space probe, I sympathise with it. What a day to wake up on!
I remember staying up late to watch Giotto's close approach to Halley. That we're now planning to *land* on a comet, is very impressive.
I presume because a large solar array with some battery backup meets their power needs over the mission for less money than an RTG, and they only need to operate for a short period out near the outer limits of what is feasible for photovoltaics (roughly the orbit of Jupiter).
The solar panels will produce 850 watts at the rendezvous point -- roughly the same as the Cassini probe's RTG at launch. Those panels will produce prodigious amounts of power at the spacecraft's action-packed perihelion, which may be useful. For example a huge power budget would allow faster transmission of data.
The drawback I see is reliability. The spacecraft's systems have to be kept dormant for a long time when it's out near its aphelion.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
All These Worlds are Yours Except 67P Churyumov-Gerasimenko.
Attempt No Landings There.
http://www.nasa.gov/images/content/468180main_2_Lutetia_and_Saturn_946-710.jpg
With Saturn hanging in the background. Stunning. It's worth it already!
Time flies like an arrow. Fruit flies like a banana.
Wow, I don't remember seeing that pic before (must be from the 2010 flyby) but it's just about to become my desktop wallpaper. Thanks!
On a side note, for anyone who's not looked at the night sky before through a telescope, you can see Saturn somewhat like it is in that image, with an entry level (ish) telescope from your back yard. I first saw Saturn through an old TAL-1 newtonian that can be bought for as little as £100 here in the UK and on a good night you'll get a sharper view of Saturn than shown in that image. Or you could pop along to your local astro meet (there's bound to be one near you) and have a look at some of these objects through varying sizes and designs of telescopes.
Seeing Saturn for the first time through a telescope is, in my experience and from what others frequently say too, jaw dropping amazing. Then take a look at Jupiter with the same telescope and you should be able to make out Jupiter's bands and some of its moons, maybe even the great red spot if you time it right. We've all seen them in photos but there's nothing quite like the knowledge that your eye is at the receiving end of actual photons being reflected by the planets, or being emitted from galaxies.
I dug around ESA's pages and finally found details on the orbital parameters: on Comet Rendezvous, under "Comet mapping and characterisation (August 2014)" (halfway down) it says: "...the spacecraft is inserted into orbit around the nucleus at a distance of about 25 kilometres. Their [sic] relative speed is now down to a few centimetres per second. "
That slow orbital speed (OK, slow compared to what we're used to dealing with) is due to the small mass of the comet (again, compared to things like the Earth or Moon), which Wikipedia gives as about 3e12 kg. Checking the math, the equation for circular orbital velocity v[circ] = sqrt(GM/R) ~= sqrt( (7e-11)(3e12) / 25e3 ) = 0.09 m/s = 9 cm/s, cool. (Even if the quoted 25 km is to the surface rather than the centre, using that figure for R is OK since the comet's radius is only about 2 km.)
FWIW, at the surface, escape velocity sqrt(2)*v[circ] = sqrt( 2(7e-11)(3e12) / 2e3 ) = 0.5 m/s. You could easily jump off of that comet!
I was following the webcast, a few minutes ago they received the signal from Rosetta, so the wakeup has succeeded, if a bit behind schedule.
(unfortunately I can't see a way to rewind, so you'll have to wait for the video to become available on the archive section of the webcast page)