Jump to content

Rosetta, Philae and Comet 67P/Churyumov-Gerasimenko.

Vicomt

By Vicomt
in Science & Spaceflight

 Share

Recommended Posts

KerbMav

KerbMav

Posted
Posted
I'm intrigued by what looks like tracks on the plain in this image.

http://s29.postimg.org/fyjpbl3qv/67_P_2.png

My first thought was they were formed by boulders or concentrations of ice that while outgassing, rolled around on the surface, and I still can't get that out of my head.

Someone able to guesstimate the width of this "scar"?

Link to comment
Share on other sites
magnemoe

magnemoe

Posted
Posted
http://i.imgur.com/ehbi9e8.jpg

Ran across this image visualizing the size of this comet in comparison to the city of Los Angeles.

In related news, first mass estimates are in - it's in the neighborhood of 10 billion metric tons. Compare this to KSP asteroids... :P

Granted its closer to Gilly in size than the small asteroids we play with as in 3-4 km while the large E asteroids is perhaps 50 meter in diameter.

Link to comment
Share on other sites
sgt_flyer

sgt_flyer

Posted
Posted

http://www.esa.int/Our_Activities/Space_Science/Rosetta/Frequently_asked_questions

From what they tell about philae, it can't survive a too long 'cold' phase on it's own (ie, not enough solar power to maintain thermal systems)

For the trip, it's rosetta who was used to awaken Philae after the sleep phase. Once philae is on the comet, i don't think it will be able to awaken on it's own :)

Besides, Philae will need Rosetta to act as a relay for transmitting science, and i don't think 67P/C-G has enough gravity to allow a stable orbit without stationkeeping with RCS corrections. So once they can't control rosetta once the sun is too far away for maintaining rosetta active, it will surely drift away from the comet. They may be able to take control of rosetta afterwards, but it won't be in range of the comet anymore. (Besides, the planned probe lifetime was 12 years - just what was needed for the mission :P)

Link to comment
Share on other sites
lajoswinkler

lajoswinkler

Posted
Posted
http://www.esa.int/Our_Activities/Space_Science/Rosetta/Frequently_asked_questions

From what they tell about philae, it can't survive a too long 'cold' phase on it's own (ie, not enough solar power to maintain thermal systems)

For the trip, it's rosetta who was used to awaken Philae after the sleep phase. Once philae is on the comet, i don't think it will be able to awaken on it's own :)

Besides, Philae will need Rosetta to act as a relay for transmitting science, and i don't think 67P/C-G has enough gravity to allow a stable orbit without stationkeeping with RCS corrections. So once they can't control rosetta once the sun is too far away for maintaining rosetta active, it will surely drift away from the comet. They may be able to take control of rosetta afterwards, but it won't be in range of the comet anymore. (Besides, the planned probe lifetime was 12 years - just what was needed for the mission :P)

You mean, the lumpness of the gravity field? It might not be important because there's already a very small amount of attraction to begin with.

I'd like to see Rosetta lowered on the comet when the time comes. Surely the operators could do that. Or at least uncontrolled impact.

Link to comment
Share on other sites
Sky_walker

Sky_walker

Posted
Posted
and i don't think 67P/C-G has enough gravity to allow a stable orbit without stationkeeping with RCS corrections.

Yes, it does have "enough gravity" (whatever that means) for Rosetta to orbit the comet. However station-keeping burns will happen regardless - satellites orbiting earth need to perform them, and we're talking here about orbiting an object that constantly ejects material into space.

Link to comment
Share on other sites
Aningaaq

Aningaaq

Posted
Posted

Besides, Philae will need Rosetta to act as a relay for transmitting science

Additionally, they depend on each other for collecting subsurface data. The CONSERT instrument only functions when both Rosetta and Philae are transmitting/receiving electromagnetic wave data.

I look forward to seeing the results. Geophysical properties of this comet should provide some great information.

Link to comment
Share on other sites
sgt_flyer

sgt_flyer

Posted
Posted

well, they selected 5 potential landing sites and described what they need to check on each of them (currently, they are awaiting high resolution imaging of each site to decide).

they'll have a ranking of the 5 sites by 14th september - at this point they'll likely know their primary landing site :)

http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_Landing_site_search_narrows

Link to comment
Share on other sites
Aningaaq

Aningaaq

Posted
Posted
well, they selected 5 potential landing sites and described what they need to check on each of them (currently, they are awaiting high resolution imaging of each site to decide).

they'll have a ranking of the 5 sites by 14th september - at this point they'll likely know their primary landing site :)

http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_Landing_site_search_narrows

My only problem with them picking these landing sites is that they are using pretty low resolution photos. Wouldn't they want to narrow down the sites (before picking one) when they are in a circular orbit (20-50 km) around the comet. Maybe that information or photos that the blog is not posting but that is what I gathered from the blog posts on the ESA page. Maybe it's not a big deal. Not sure!

Link to comment
Share on other sites
Sky_walker

Sky_walker

Posted
Posted (edited)

Live Google Hangout with Philae/Rosetta scientists streams now: https://plus.google.com/u/0/events/c9gb2sk457gharo9tr2m85bsnng

Questions can be asked on twitter at #AskRosetta.

Highlights:

  • They're still unable to precisely position center of mass for the comet, there are just rough estimations.
  • Tomorrow morning Rosetta approaches closer to the comet - on Wed. next week they'll be 29km away from the center of a comet.
  • So far operations are going very well, C&C (command and control) chain also performs excellent.
    1. Two big questions:
      What they will find when approaching more closely to the comet? They need to be ready for higher activity on a coment. Right now they have 3 emergency pans to contain that in case something would go wrong.
    2. Preparations for the landing - where Philae will end up?

    [*]There are "hundreds of people" supporting the mission.

    [*]Rosetta is right now on the "edge" of some of the instruments

    [*]This is probably the most operationally intensive mission that ESA have ever flown

    [*]Comet shape was the biggest surprise for a scientists

    [*]In 2 days they begin last testing phase of the Philae - communications test, battery recharging, first pictures from Philae camera, etc.

    [*]Selecting an optimal landing site proved to be more complicated than initially expected during the detailed analysis.

    [*]Landing site confirmation will be announced in mid-October.

    [*]They pulled 10 runners-up in Rosetta "Are We There Yet?" competition during the stream - first time ever ESA awarded rewards during live stream.

    [*]They still cannot tell the exact altitude at which Philae will be released, but it'll be around 25km

    [*]Spacecraft will be kept no further than 60km away from the lander

    [*]Frequency of communication between Philae and Rosetta is as important as keeping safe altitude for the spacecraft, as lander got a limited amount of memory and uploading the data regularly is essential, otherwise some might be lost.

    [*]Lifetime of lander is limited by the temperatures on a comet. Best scenario estimates end of March for the Philae lifetime.

    [*]Comets are very unpredictable, so it's hard to say what exactly will happen or if comet will fall apart / split into two.

    [*]Rosetta/Philae will provide us with the best and most detailed informations on the comet ever collected.

    [*]They're still work on a naming convention for the features on a comet, but it's probably going to be something in Egyptian theme. They need to look into international standards, they cannot just name stuff like they'd want to.

    [*]Temperature and solar balance are two major problems to solve when choosing the landing site.

    [*]There are different spots that "perform different science" but everything needs to be balanced for an optimal science return.

    [*]Surface is, and will be, probed in a number of wavelenghts giving the team indications on what they might expect on each of the landing site.

    [*]One of the objectives is to study how comet interacts with a solar wind and how does it shape magnetic charges on a comet.

    [*]They don't have any good methods of proving if comet is covered with dust or not, they can get some estimations and guesses, but that's all. One of the worries was that Philae will be covered in dust upon landing, though solar arrays got a power overhead, so this problem can be easily migrated.

    [*]Philae will drill down to 20cm into the comet and "cook samples in an oven" to perform a spectral analysis.

    [*]Real color of a comet is black. It's blacker than a blackest T-shirt you can buy in a shop, reflecting only 2% of light. Images on a web are overexposed to show it in a black and white.

    [*]Images from the NavCam are only B&W. OSIRIS camera got numerous color filters.

    [*]Philae got 5 cameras, one of each side, and can take full 360 degree panorama. One of the objectives is to take a full picture of a comet horizon.

    [*]Rosetta is most likely not a contact binary, though more studies still need to be done. Knowing the precise center of mass will help to determine uniformity of a comet. The closer Rosetta gets the more data they'll get to explain the origin of 67P.

    [*]Dust is not affecting spacecraft much, there is no mechanical stress, the only problem are perturbations on a trajectory caused by a huge area of solar panels.

    [*]Dust won't affect performance of solar panels, however scientists need to be careful about damage to the optics.

    [*]Core team supporting lander is made of around 15 people though there are many teams supporting different aspects of a mission and there are separate teams for each of the instruments.

    [*]Landing is fairly automated - they upload commands with emergency plans and Rosetta/Philae performs descent autonomously.

    [*]15 September - 2 landing sides are selected. Major and a back-up one.

ESA plans live stream during the Philae landing streaming from 3 different centres at the same time.

ps. Seems like they answered well over a half of questions asked by people on twitter. Impressive.

pps. Stream will be available on ESA Youtube channel.

Edited by Sky_walker
Link to comment
Share on other sites
SuperFastJellyfish

SuperFastJellyfish

Posted
Posted
Its year last for 6.45 of Earth years. It has been in its perihelion a lot of times. Why would it suddenly break apart? It's not a sungrazer.

It loses material just like any other comet when it nears the sun. Sungrazer or not, it will eventually turn into an asteroid-like object or break apart depending on concentration of ices and rock.

Link to comment
Share on other sites
Aethon

Aethon

Posted
Posted

Nice notes Sky_walker. Thanks.

Its year last for 6.45 of Earth years. It has been in its perihelion a lot of times. Why would it suddenly break apart? It's not a sungrazer.

Sorry, I have no documentation for this, but I read somewhere comet Cherry Gerry (easier to spell, used in the biz) had an encounter with Jupiter in the 1950's that altered it's orbit. This is the first time it's come this close to the sun.

Link to comment
Share on other sites
lajoswinkler

lajoswinkler

Posted
Posted
It loses material just like any other comet when it nears the sun. Sungrazer or not, it will eventually turn into an asteroid-like object or break apart depending on concentration of ices and rock.

There's absolutely no reason for it to happen this time. It's old as the Solar system, having orbited the Sun several billions times.

OK, done updating my ling list of highlights from the stream. Hope you'll enjoy reading it (yep, I just saved you 1 hour of your life. ;):P ).

Thanks.

Sorry, I have no documentation for this, but I read somewhere comet Cherry Gerry (easier to spell, used in the biz) had an encounter with Jupiter in the 1950's that altered it's orbit. This is the first time it's come this close to the sun.

Cherry Gerry, LOL.

From 2.7 AU to 1.24 AU, that's not a great difference. It happened in 1959, so it would be unlikely that all of the sudden right now it spectacularly breaks apart. It would be cool, though.

Link to comment
Share on other sites
SuperFastJellyfish

SuperFastJellyfish

Posted
Posted
There's absolutely no reason for it to happen this time. It's old as the Solar system, having orbited the Sun several billions times.

Cherry Gerry, LOL.

From 2.7 AU to 1.24 AU, that's not a great difference. It happened in 1959, so it would be unlikely that all of the sudden right now it spectacularly breaks apart. It would be cool, though.

I'm going to assume English isn't your first language, but when you use the word 'absolutely' you can't also use the word 'unlikely' to mean the same thing.

Link to comment
Share on other sites
Sky_walker

Sky_walker

Posted
Posted

Update on a comet.

OSIRIS camera captured jets spewing matter from the comet - full story here: http://www.planetary.org/blogs/emily-lakdawalla/2014/09040955-latest-rosetta-navcam-images.html

20140904_ESA_ROSETTA_NAVCAM_20140902A_16bit_destriped_stitch_f840.png

ESA Published very nice video with more details on the instruments onboard Rosetta, including field of view comparison: http://blogs.esa.int/rosetta/2014/09/05/alice-obtains-first-far-ultraviolet-spectra-of-comet-67pc-g/

Rosetta_instruments_fov-350x200.png

From data collected over the last month, the Alice team discovered that the comet is unusually dark in the ultraviolet and that the comet’s surface – so far – shows no large water-ice patches. Alice is also already detecting both hydrogen and oxygen in the comet’s coma, or atmosphere.

“We’re a bit surprised at just how unreflective the comet’s surface is and how little evidence of exposed water-ice it shows,â€Â

Link to comment
Share on other sites
Sky_walker

Sky_walker

Posted
Posted (edited)

European Southern Observatory VLT made the photograph of 67/P with the comet tail:

Rosetta_comet_observed_with_Very_Large_Telescope_node_full_image_2.jpg

http://www.esa.int/spaceinimages/Images/2014/09/Rosetta_comet_observed_with_Very_Large_Telescope

Since early August 2014, Rosetta has been enjoying a close-up view of comet 67P/Churyumov–Gerasimenko. Meanwhile, astronomers on Earth have been busy following the comet with ground-based telescopes. As Rosetta is deep inside the ‘atmosphere’ coma – it was 100 km from the nucleus on 6 August, and has been getting much closer since then – the only way to view the whole comet is to ‘stand back’ and observe it from Earth.

This image was recorded on 11 August 2014 using one of the 8 m-diameter telescopes of the European Southern Observatory’s Very Large Telescope in Chile.

Although faint, the comet is clearly active, revealing a dusty coma extending at least 19 000 km from the nucleus. The comet's dusty veil is not symmetrical as the dust is swept away from the Sun – located beyond the lower-right corner of the image – to begin forming a tail.

At the moment, the comet is visible only from the southern hemisphere and, at more than 500 million km from the Sun, it is still very faint. In addition, it currently sits in a patch of the sky where it is camouflaged against the crowded starry background of the Milky Way. For these reasons, the image was compiled by superimposing 40 individual exposures, each lasting about 50 seconds, and removing background stars.

A large collaboration of astronomers across the world has been working to make the most of the unique opportunity to observe the comet from the ground while Rosetta is performing measurements at the comet. The Very Large Telescope is taking images every two nights on average. These short exposures monitor the comet’s activity by studying how its brightness changes. The results are used by the Rosetta team to help plan spacecraft operations.

Edited by Sky_walker
Link to comment
Share on other sites
This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
 Share
Go to topic listing
×
×
  • Create New...