Rosetta space mission - Philae probe due to land on comet on 12th Nov 2014
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TheHoodedClaw
acknowledging ur soup leg
They are going to be measuring deviations of Rosetta's trajectory to estimate the mass of the comet. Some tricky burns looking at the survey plan, here:
http://www.newscientist.com/data/images/ns/cms/dn25995/dn25995-2_850.jpg
(It's a fairly big image)
Crispy
The following psytrance is baṉned: All
Very very weak. About 1/10,000th of a G. They're not even in an actual orbit yet, just floating around nearby, using the spacecraft's thrusters to make a triangular path around it. It will eventually come in for an orbit, but very very low - just 30km away.
Limejuice
Well-Known Member
2hats
Dust.
It's going to be something of the order 10^-6 g. The approach via the tightening triangular trajectory (technically arcs not an orbit as such) will permit them to map out the highly irregular (and very weak) gravitational equipotential field. This provides an overall mass estimate - an idea of mass distribution and variation of density. This will be important in establishing a final safe orbit close to the comet nucleus (and maintaining that) and in steering the lander down to the surface. At the same time the trajectory provides variation in lighting angles during the survey phase so as to facilitate elevation estimates and help characterise the surface nature at potential landing sites. It's also designed to avoid the outflow (tail formation) as the comet closes towards perihelion; you don't want to clobber the various instruments. Approaching along the Sun radius vector at this stage in the comet's orbit also maximises the communications window with the Earth.
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2hats
Dust.
That's low enough to give an apple options.
If one were able to stand on the surface, providing it were sufficiently hard, it would be easy to jump and reach escape velocity; never to return again. The gravitational field is essentially similar to that found in the microgravity environment of the International Space Station (commonly, but technically incorrectly, referred to as zero-g). You can see how readily material can boil off a comet as it approaches the Sun - there is next to no self-gravity to overcome.
However initial indications are that it might be softer, much more dusty than they originally thought (ie not just, or even, a surface of solid ice). It would be a struggle to 'leap' off a thick dusty surface. One key issue that will affect the landing is how deep might a dusty regolith be - the lander needs to grip on to something to operate successfully! It has screws and harpoons but of course they need something substantial to bite in to.
Great photos. Looks like it was two original bodies that stuck with just enough energy to melt the ore, but not quite enough to rebound from an elastic collision before the melted material froze again. That would explain the relatively smooth junction between the bodies. It's an unexpectedly great comet to meet because it hints at some of the collision mechanisms in the primordial solar systems. The collisions suggested by this comet would have been typical of the impacts that initially created the planets before they accrued sufficient mass to round off the irregularities. I'm really looking forwards to the results from the lander.
editor
hiraethified
editor
hiraethified
Another amazing image:
http://www.nasa.gov/jpl/rosetta-selflessly-beams-back-comet-selfie/index.html#.VD2qRqhdWuB
http://www.nasa.gov/jpl/rosetta-selflessly-beams-back-comet-selfie/index.html#.VD2qRqhdWuB
Definitely an OMG! it's full of stars moment.
2hats
Dust.
Getting closer. 7.8km above the surface now. 3 weeks till landing...
NAVCAM montages - pixel resolution of these is 66.5cm:
Hi-res version here.
Hi-res version here.
Note the rotation of the nucleus and movement of the spacecraft between images composing the montage result in a mismatch between the frames and duplication of features from different angles.
NAVCAM montages - pixel resolution of these is 66.5cm:
Hi-res version here.
Hi-res version here.
Note the rotation of the nucleus and movement of the spacecraft between images composing the montage result in a mismatch between the frames and duplication of features from different angles.
2hats
Dust.
Yes, I suspect it's probably surface material - in the smooth areas you see repeated between frames (near the edges) the "grainy" patterns also tend to repeat which would suggest it isn't noise that we are looking at.
2hats
Dust.
The ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) has been sniffing the comet and has found that:
This is surprising as it was thought that only the more volatile molecules (CO, CO2) would tend to be picked up this far (3 AU) from the sun.
More from the science team concerned here.
This is surprising as it was thought that only the more volatile molecules (CO, CO2) would tend to be picked up this far (3 AU) from the sun.
More from the science team concerned here.
2hats
Dust.
Last month jets were first seen from the neck region of the nucleus but now activity is increasing and being observed from most of the surface. Landing site J is (fortunately) largely quiescent however there are signs of activity starting to pick up around 1km away which should provide some science targets for lander instruments.
Below are two exposures of a set of jets (left hand 18.45s exposure, right hand 1s exposure) taken from a distance of 7.2km last week:
(click each image for the hi-res version).
Another montage of the surface (taken Friday, 66cm/pixel):
Hi-res version.
Below are two exposures of a set of jets (left hand 18.45s exposure, right hand 1s exposure) taken from a distance of 7.2km last week:
(click each image for the hi-res version).
Another montage of the surface (taken Friday, 66cm/pixel):
Hi-res version.
2hats
Dust.
Earlier today (around lunch, UK time) Rosetta backed away from the comet in a pre-planned manoeuver. It is now orbiting roughly 30 km from the nucleus in the pre-delivery orbit - in other words this is part of the process of positioning Rosetta so it can both release (0835 UTC, 12 November) and deliver the lander, Philae, to site J on the surface of the nucleus and then be in an optimum location to conduct some science experiments in conjunction with Philae and also relay the lander data to Earth.
The 10 km orbit that Rosetta has been in the last ~10 days was to permit close up study and surveying of landing site J (hence the orbit was known as the close observation phase orbit).
Subsequent to the lander phase of the mission, Rosetta will be parked in an orbit around 20 km from the nucleus in December, from where it will accompany and observe the comet as it heads to perihelion and activity peaks.
There's a nice ESA graphic illustrating the orbit sequencing around the nucleus here:
The 10 km orbit that Rosetta has been in the last ~10 days was to permit close up study and surveying of landing site J (hence the orbit was known as the close observation phase orbit).
Subsequent to the lander phase of the mission, Rosetta will be parked in an orbit around 20 km from the nucleus in December, from where it will accompany and observe the comet as it heads to perihelion and activity peaks.
There's a nice ESA graphic illustrating the orbit sequencing around the nucleus here:
TheHoodedClaw
acknowledging ur soup leg
It's not even the comet they were originally going for. Kerbal with limited fuel, but god-like improvisation. It's an amazing mission "Gonna have to shut you down for a couple of years on this long sling out Jupiter way, save power and that, hope to hear from you when you get back. Good luck, little probe!"
farmerbarleymow
I'm Petee's spirit animal
Someone has carved a pumpkin in honour. 
(from Twitter @willgater)
(from Twitter @willgater)
2hats
Dust.
Rosetta carried out another burn this morning which has set it up for the final lander delivery position (a week today). Separation is still planned for 0835UTC on 12 November (due to the distance from Earth the signal confirming this won't arrive until 0903UTC). Landing should occur 7 hours later:
Obligatory moody shot of the comet (taken from 33.4km on 2 November, resolution is 2.68 metres per pixel):
Hi-res version here.
Obligatory moody shot of the comet (taken from 33.4km on 2 November, resolution is 2.68 metres per pixel):
Hi-res version here.
2hats
Dust.
There's a briefing on the landing on Google hangouts at 1500UTC today.
A run down of the landing sequence complete with animations:
A run down of the landing sequence complete with animations:
2hats
Dust.
A few interesting nuggets from the ESA briefing a few hours ago...
It's easy to look at many of the images above of the nucleus in the inky darkness of space and not realise that Rosetta and Philae are 'orbiting' in the 'atmosphere' of the comet - the coma. To illustrate this here's an image of the comet taken 11 August this year at the VLT (ESO, Chile) that clearly shows the coma and the beginnings of a tail. The tail is some 19000km long. The nucleus, about 4km in greatest extent and Rosetta orbiting it are both contained in a single pixel at the centre of the bright nucleus on this scale:
There was also a fun slide illustrating the scale on the surface of the nucleus. The rock nicknamed Cheops is some 45m across at the base and 20m or so high. Below is its location with the actual pyramid of Cheops (~230x140m) photoshopped alongside for scale:
Also - Rosetta should be able to image Philae at times during the descent and after landing there it is possible that it will be able to distinguish it on the surface (though it will only appear to be a couple of pixels wide).
PS For those who can't resist going all a bit Blue Peter, a cut out and keep model of the key players.
It's easy to look at many of the images above of the nucleus in the inky darkness of space and not realise that Rosetta and Philae are 'orbiting' in the 'atmosphere' of the comet - the coma. To illustrate this here's an image of the comet taken 11 August this year at the VLT (ESO, Chile) that clearly shows the coma and the beginnings of a tail. The tail is some 19000km long. The nucleus, about 4km in greatest extent and Rosetta orbiting it are both contained in a single pixel at the centre of the bright nucleus on this scale:
There was also a fun slide illustrating the scale on the surface of the nucleus. The rock nicknamed Cheops is some 45m across at the base and 20m or so high. Below is its location with the actual pyramid of Cheops (~230x140m) photoshopped alongside for scale:
Also - Rosetta should be able to image Philae at times during the descent and after landing there it is possible that it will be able to distinguish it on the surface (though it will only appear to be a couple of pixels wide).
PS For those who can't resist going all a bit Blue Peter, a cut out and keep model of the key players.
editor
hiraethified
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