ESA Rosetta Spacecraft now in orbit around a comet - eventually to land on it!

[Peter Lemkin]

After a ten year journey, history and science have been made! Amazing photos coming in now...this is what the Solar System looked like about 5 Billion years ago...lots of blobs like this zooming around that mostly collided and formed planets and moons, etc....but some are still around from the 'get go' and this is one....have a look! Later, in a few months, Rosetta will attempt to land on the comet and do a variety of tests. Some astronomers believe the water on Earth came from comets; others believe life itself may have.....we may soon know. http://sci.esa.int/where_is_rosetta/

[Peter Lemkin]

SUMMARY

Rosetta is a cornerstone mission to chase, go into orbit around, and land on a comet. It will study the Jupiter-family comet 67P/Churyumov-Gerasimenko with a combination of remote sensing and in situ measurements. The spacecraft will orbit the comet and release the Philae lander, which carries a suite of instruments for imaging and sampling the comet nucleus. The mission will track the comet through perihelion, examining its behaviour before, during and after.[TABLE="width: 295, align: right"]
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[TD]Rosetta and Philae at the comet.
Credit: ESA- C. Carreau/ATG medialab
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The mission was first considered in the late 1970s and developed from a sample-return plan to the plan for a lander. It was approved in November 1993 by ESA's Science Programme Committee. The original mission target had been comet 46P/Wirtanen, but this was changed to 67P/Churyumov-Gerasimenko when it was clear that the launch would take place in 2004.
The spacecraft was launched from Kourou aboard an Ariane 5G+ on 2 March 2004. It required four gravity assists for its journey, one by Mars and three by Earth. Rosetta had already flown by the asteroids 2867 Steins (in 2008) and 21 Lutetia (in 2010), before entering deep space hibernation in June 2011.
Rosetta's main goals will be reached in 2014. Following a planned exit from hibernation on 20 January, the spacecraft's instruments were checked as it continued on its journey to 67P/Churyumov-Gerasimenko. The spacecraft arrives at the comet in August 2014, and deploys the lander in November 2014.
Here are the key dates of the Rosetta mission:

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[TD="bgcolor: #cccccc, align: center"]Event[/TD]
[TD="bgcolor: #cccccc, align: center"]Nominal date[/TD]
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[TD="bgcolor: #cccccc, align: left"]Launch[/TD]
[TD="bgcolor: #cccccc, align: right"]2 March 2004[/TD]
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[TD="bgcolor: #cccccc, align: left"]First Earth gravity assist[/TD]
[TD="bgcolor: #cccccc, align: right"]4 March 2005[/TD]
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[TR]
[TD="bgcolor: #cccccc, align: left"]Mars gravity assist[/TD]
[TD="bgcolor: #cccccc, align: right"]25 February 2007[/TD]
[/TR]
[TR]
[TD="bgcolor: #cccccc, align: left"]Second Earth gravity assist[/TD]
[TD="bgcolor: #cccccc, align: right"]13 November 2007[/TD]
[/TR]
[TR]
[TD="bgcolor: #cccccc, align: left"]Asteroid Steins flyby[/TD]
[TD="bgcolor: #cccccc, align: right"]5 September 2008[/TD]
[/TR]
[TR]
[TD="bgcolor: #cccccc, align: left"]Third Earth gravity assist[/TD]
[TD="bgcolor: #cccccc, align: right"]13 November 2009[/TD]
[/TR]
[TR]
[TD="bgcolor: #cccccc, align: left"]Asteroid Lutetia flyby[/TD]
[TD="bgcolor: #cccccc, align: right"]10 July 2010[/TD]
[/TR]
[TR]
[TD="bgcolor: #cccccc, align: left"]Enter deep space hibernation[/TD]
[TD="bgcolor: #cccccc, align: right"]8 June 2011[/TD]
[/TR]
[TR]
[TD="bgcolor: #cccccc, align: left"]Exit deep space hibernation[/TD]
[TD="bgcolor: #cccccc, align: right"]20 January 2014[/TD]
[/TR]
[TR]
[TD="bgcolor: #cccccc, align: left"]Rendezvous manoeuvres begin[/TD]
[TD="bgcolor: #cccccc, align: right"]May 2014[/TD]
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[TD="bgcolor: #cccccc, align: left"]Arrive at comet[/TD]
[TD="bgcolor: #cccccc, align: right"] 6 August 2014[/TD]
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[TR]
[TD="bgcolor: #cccccc, align: left"]Start global mapping[/TD]
[TD="bgcolor: #cccccc, align: right"]August 2014[/TD]
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[TR]
[TD="bgcolor: #cccccc, align: left"]Lander delivery[/TD]
[TD="bgcolor: #cccccc, align: right"]November 2014[/TD]
[/TR]
[TR]
[TD="bgcolor: #cccccc, align: left"]Perihelion passage[/TD]
[TD="bgcolor: #cccccc, align: right"]13 August 2015[/TD]
[/TR]
[TR]
[TD="bgcolor: #cccccc, align: left"]End of mission[/TD]
[TD="bgcolor: #cccccc, align: right"]31 December 2015

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[Peter Lemkin]

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[TD="width: 30%"]Objectives:[/TD]
[TD]To study the origin of comets, the relationship between cometary and interstellar material, and its implications with regard to the origin of the Solar System. The measurements to be made to achieve this are:

• Global characterisation of the nucleus, determination of dynamic properties, surface morphology and composition;
  
• Determination of the chemical, mineralogical and isotopic compositions of volatiles and refractories in a cometary nucleus;
  
• Determination of the physical properties and interrelation of volatiles and refractories in a cometary nucleus;
  
• Study of the development of cometary activity and the processes in the surface layer of the nucleus and the inner coma (dust/gas interaction);
  
• Global characterisation of asteroids, including determination of dynamic properties, surface morphology and composition.
  

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[Peter Lemkin]

ROSETTA TAKES COMET'S TEMPERATURE

01 August 2014
ESA's Rosetta spacecraft has made its first temperature measurements of its target comet, finding that it is too hot to be covered in ice and must instead have a dark, dusty crust.

[TABLE="width: 565, align: center"]
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[TD="class: caption"]Rosetta measures comet's temperature. Credit: ESA[/TD]
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The observations of comet 67P/Churyumov-Gerasimenko were made by Rosetta's visible, infrared and thermal imaging spectrometer, VIRTIS, between 13 and 21 July, when Rosetta closed in from 14 000 km to the comet to just over 5000 km.
At these distances, the comet covered only a few pixels in the field of view and so it was not possible to determine the temperatures of individual features. But, using the sensor to collect infrared light emitted by the whole comet, scientists determined that its average surface temperature is about -70°C.
The comet was roughly 555 million kilometres from the Sun at the time more than three times further away than Earth, meaning that sunlight is only about a tenth as bright.
Although -70°C may seem rather cold, importantly, it is some 2030°C warmer than predicted for a comet at that distance covered exclusively in ice.
"This result is very interesting, since it gives us the first clues on the composition and physical properties of the comet's surface," says VIRTIS principal investigator Fabrizio Capaccioni from INAF-IAPS, Rome, Italy.
Indeed, other comets such as 1P/Halley are known to have very dark surfaces owing to a covering of dust, and Rosetta's comet was already known to have a low reflectance from ground-based observations, excluding an entirely 'clean' icy surface.
The temperature measurements provide direct confirmation that much of the surface must be dusty, because darker material heats up and emits heat more readily than ice when it is exposed to sunlight.
"This doesn't exclude the presence of patches of relatively clean ice, however, and very soon, VIRTIS will be able to start generating maps showing the temperature of individual features," adds Dr Capaccioni.
In addition to global measurements, the sensor will study the variation of the daily surface temperature of specific areas of the comet, in order to understand how quickly the surface reacts to solar illumination.
In turn, this will provide insight into the thermal conductivity, density and porosity of the top tens of centimetres of the surface. This information will be important in selecting a target site for Rosetta's lander, Philae.
It will also measure the changes in temperature as the comet flies closer to the Sun along its orbit, providing substantially more heating of the surface.
"Combined with observations from the other 10 science experiments on Rosetta and those on the lander, VIRTIS will provide a thorough description of the surface physical properties and the gases in the comet's coma, watching as conditions change on a daily basis and as the comet loops around the Sun over the course of the next year," says Matt Taylor, ESA's Rosetta project scientist.
"With only a few days until we arrive at just 100 km distance from the comet, we are excited to start analysing this fascinating little world in more and more detail."

MORE ABOUT ROSETTA

Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta's Philae lander is provided by a consortium led by DLR, MPS, CNES and ASI. Rosetta will be the first mission in history to rendezvous with a comet, escort it as it orbits the Sun, and deploy a lander.
Comets are time capsules containing primitive material left over from the epoch when the Sun and its planets formed. By studying the gas, dust and structure of the nucleus and organic materials associated with the comet, via both remote and in-situ observations, the Rosetta mission should become the key to unlocking the history and evolution of our Solar System, as well as answering questions regarding the origin of Earth's water and perhaps even life.

[Peter Lemkin]

Astronomy/cosmology, as well as mineralogy/geology have always been passions of mine...both in and of themselves - and also a way of not [for a short time] thinking about all the shit we are faced with on Earth and in our polity by the Evil People in control most things down here on this little speck of dust which is important to us, but insignificant in Universal terms. ::lilgreenman::

[Magda Hassan]

I love astronomy and cosmology too but I find some things very mysterious and confusing. Like Pluto. Planet one day and not the next. What's with that? They couldn't tell? So close and in our solar system. Yet they can take photos of other galaxies in brilliant colour and detail. Le sigh...

But seriously, these posts are just amazing. The collaborative science involved over so many years. Beautiful. I hope they have moved on from NASA's 286 computers....

[Peter Lemkin]

I love astronomy and cosmology too but I find some things very mysterious and confusing. Like Pluto. Planet one day and not the next. What's with that? They couldn't tell? So close and in our solar system. Yet they can take photos of other galaxies in brilliant colour and detail. Le sigh...

But seriously, these posts are just amazing. The collaborative science involved over so many years. Beautiful. I hope they have moved on from NASA's 286 computers....

I could explain Pluto if you really want...anyway, it was there long before anyone on Earth considered it anything..and is still there. Its loss of status was by vote in the astronomical community - and was not agreed by all. It is a 'call' for the smaller bodies. Some beyond Pluto are even larger than Pluto. In fact, Pluto will long outlive the Earth, which will be swallowed up by the then expanding sun in a few billion years.

Rosetta just shows that technology and science can be used for good, for exploration, for pure knowledge - and not how it is all too often used to make more weapons of war and control. This comet to me looks like a pock marked bathtub rubber duck. In November Rosetta will send down a lander with ice screws for feet and hope to attach to the surface and do tests on many things. In the next month, it will slowly get closer and closer, with better and better photos of the surface, which to most astronomers surprise seems to NOT be ice, but dust or crust of some kind....though it is known that a large part of the object is water ice. It is also surprisingly warm. -70C can almost be found on Earth, and this object is now 3x further from the sun than the Earth ever is - and getting only 1/10th the sun's energy.

[Magda Hassan]

Rosetta just shows that technology and science can be used for good, for exploration, for pure knowledge - and not how it is all too often used to make more weapons of war and control.

Yes. Pure research is so important. I was listening to a radio programme just today actually. It was mostly abut funding universities. But the different types of research was discussed. Few want to fund pure research these days. Unless there can be a definite and immediate corporate benefit it is not attractive to private funding. Governments are not funding universities as they did. Students can't all afford fees (not that there should be fees either) to fund unis (most going to CEOs of corporate type unis rather than the uni itself). But there has been amazing out comes for some pure research and who knows what is to come yet?

[Peter Lemkin]

Rosetta just shows that technology and science can be used for good, for exploration, for pure knowledge - and not how it is all too often used to make more weapons of war and control.

Yes. Pure research is so important. I was listening to a radio programme just today actually. It was mostly abut funding universities. But the different types of research was discussed. Few want to fund pure research these days. Unless there can be a definite and immediate corporate benefit it is not attractive to private funding. Governments are not funding universities as they did. Students can't all afford fees (not that there should be fees either) to fund unis (most going to CEOs of corporate type unis rather than the uni itself). But there has been amazing out comes for some pure research and who knows what is to come yet?

I don't usually post them, because most here don't seem to have much interest in science, but just yesterday I saw a technical article on a new type of solar 'panel'...which is so thin that it lets most of the light in and is like a flexible film - so it could be put on all windows, let the light in and still generate electricity!....amazing technical achievement and how it is constructed is amazingly high-tech, but not expensive, if done in large quantities. It also could be made into many sandwiched layers and used as more normal panels on the roof or elsewhere - still only 1/50th the weight of a normal panel and cheaper - but generating as much power or more. Yeah, if it isn't for the corporate bottom line, it doesn't get funded. When I was in graduate school in the USA working on a degree in Environmental Science, graduate students couldn't get any grants - only those who were working to pollute and destroy the world could......


The solar cell's layer system: two semiconductor layers in the middle, connected to electrodes on either side.
Credit: Image courtesy of Vienna University of Technology, TU Vienna

[Click to enlarge image]

Extremely thin, semi-transparent, flexible solar cells could soon become reality. At the Vienna University of Technology, Thomas Mueller, Marco Furchi and Andreas Pospischil have managed to create a semiconductor structure consisting of two ultra-thin layers, which appears to be excellently suited for photovoltaic energy conversion.


Several months ago, the team had already produced an ultra-thin layer of the photoactive crystal tungsten diselenide. Now, this semiconductor has successfully been combined with another layer made of molybdenum disulphide, creating a designer-material that may be used in future low-cost solar cells. With this advance, the researchers hope to establish a new kind of solar cell technology.
Two-Dimensional Structures
Ultra-thin materials, which consist only of one or a few atomic layers are currently a hot topic in materials science today. Research on two-dimensional materials started with graphene, a material made of a single layer of carbon atoms. Like other research groups all over the world, Thomas Mueller and his team acquired the necessary know-how to handle, analyse and improve ultra-thin layers by working with graphene. This know-how has now been applied to other ultra-thin materials.
"Quite often, two-dimensional crystals have electronic properties that are completely different from those of thicker layers of the same material," says Thomas Mueller. His team was the first to combine two different ultra-thin semiconductor layers and study their optoelectronic properties.
Two Layers with Different Functions
Tungsten diselenide is a semiconductor which consists of three atomic layers. One layer of tungsten is sandwiched between two layers of selenium atoms. "We had already been able to show that tungsten diselenide can be used to turn light into electric energy and vice versa," says Thomas Mueller. But a solar cell made only of tungsten diselenide would require countless tiny metal electrodes tightly spaced only a few micrometers apart. If the material is combined with molybdenium disulphide, which also consists of three atomic layers, this problem is elegantly circumvented. The heterostructure can now be used to build large-area solar cells.
When light shines on a photoactive material single electrons are removed from their original position. A positively charged hole remains, where the electron used to be. Both the electron and the hole can move freely in the material, but they only contribute to the electrical current when they are kept apart so that they cannot recombine.
To prevent recombination of electrons and holes, metallic electrodes can be used, through which the charge is sucked away -- or a second material is added. "The holes move inside the tungsten diselenide layer, the electrons, on the other hand, migrate into the molybednium disulphide," says Thomas Mueller. Thus, recombination is suppressed.
This is only possible if the energies of the electrons in both layers are tuned exactly the right way. In the experiment, this can be done using electrostatic fields. Florian Libisch and Professor Joachim Burgdörfer (TU Vienna) provided computer simulations to calculate how the energy of the electrons changes in both materials and which voltage leads to an optimum yield of electrical power.
Tightly Packed Layers
"One of the greatest challenges was to stack the two materials, creating an atomically flat structure," says Thomas Mueller. "If there are any molecules between the two layers, so that there is no direct contact, the solar cell will not work." Eventually, this feat was accomplished by heating both layers in vacuum and stacking it in ambient atmosphere. Water between the two layers was removed by heating the layer structure once again.
Part of the incoming light passes right through the material. The rest is absorbed and converted into electric energy. The material could be used for glass fronts, letting most of the light in, but still creating electricity. As it only consists of a few atomic layers, it is extremely light weight (300 square meters weigh only one gram), and very flexible. Now the team is working on stacking more than two layers -- this will reduce transparency, but increase the electrical power.

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Story Source:
The above story is based on materials provided by Vienna University of Technology, TU Vienna.

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Journal Reference:

• Marco M. Furchi, Andreas Pospischil, Florian Libisch, Joachim Burgdörfer, Thomas Mueller. Photovoltaic Effect in an Electrically Tunable van der Waals Heterojunction. Nano Letters, 2014; 140728125936002 DOI: 10.1021/nl501962c
  

[James Ruby]

Peter:

Have you seen these?

https://www.youtube.com/watch?v=tRV1e5_t...pH&index=3

The third documentary posits some intriguing ideas about comets. All of them are well produced and not in the least patronising. The one on Mars is excellent: visually stunning, a challenge to scientific orthodoxy and with all the majestic bleakness of an alien world laid out before us in glorious Google Mars quality. I even liked the music!

Regards,

J.