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First landing on comet today

Started by Hardy Heinlin, Wed, 12 Nov 2014 04:35

Hardy Heinlin

The spacecraft has been launched 10 years ago, and today is the big day:

Exciting moment ...


Hardy Heinlin

Amazing how the acceleration segments are calculated so precisely in order to "hit" that little comet after 10 years after several orbits around the sun:

(Zoom out with the mouse wheel to see Jupiter and the comet approaching. Drag the mouse to change the 3D perspective.)


To give an idea of the scale in the fantastic images sent from the comet, someone copied a 744(!) in. Amazing.


Hardy Heinlin

Now waiting for confirmation of separation ...

... and ... yes! Applause :-)

I'm wondering if Torrence is there in that room :-)


The thruster which was supposed to counter the harpoon action (recoil) isn't working, but they went ahead anyway.
So, perhaps Bounce instead of Landing?

Very exciting...



In the discussions so far I've not heard them talk about thruster failure. They're waiting for touchdown confirmation, and whether the harpoons worked.


< 8 minutes to touchdown, then 30 mins delay before they'll see it in mission control.  8)


Philea made it to the surface intact, but it is not anchored to the surface (the harpoons that were to be fired to anchor it, failed to do so). They are currently assessing the situation, and trying to determine if they need to re-attempt to anchor it to the surface.

Phil Bunch

They look bored in the control room, but there's not much they can do now anyway since the speed of light probably means it takes quite a few minutes for comms to be sent from the satellite and then for earth to send correctional instructions back.  It's must be an automated landing, preprogrammed for various situations.  The ultimate LAND3, CATIII situation!
Best wishes,

Phil Bunch

Phil Bunch

As best I can follow various sites, the thing appears to have landed successfully.  It takes 28 minutes for comms to reach the earth due to the limited speed of light and the distance to the comet.

"Rosetta's lander Philae landed on Comet 67P/Churyumov-Gerasimenko on 12 November 2014."
Best wishes,

Phil Bunch


From the live feed, the scientists weren't so definite. :(

Phil Bunch

This web page features an interesting tour of the control room.  If you hover the cursor over each monitor and each chair, a popup describes the responsibilities in some detail of a specific manager or assistant manager for the project.  It's interesting to read how they coordinate the instructions to actually be sent to the satellite.  The software management and coordination must be very complex and yet requires freedom from bugs as well as the ability to adapt to unpredictable circumstances.

I can't imagine how stressful it would be to mostly just watch as the lander tries to hook up to the comet after a 10-year process of intercepting the comet.  Somewhere in the background is a large team of scientists who would like to use their instrumentation and analyze many aspects of the comet.  

I suppose the Cassini Project to photograph and analyze Jupiter and its moons would be a somewhat similar project, lasting many years and taking a small army to operate and maintain, and with a long lead time.

As best I can follow, it seems that the lander has harpooned the comet and they *seem* to think it will be able to stick in spite of not having a functioning thruster that was supposed to hold it against the comet.  It may take some time to figure out what is really going on.

I just noticed that a USA cable TV channel, the "Science Channel", has an hour-long show on Rosetta.  It's on tonight on Time-Warner Cable TV at 9pm (NYC time; US east coast).  I suspect that there isn't much if any real-time imaging yet, so it will probably mostly be a review of its capabilities and purposes.
Best wishes,

Phil Bunch

Phil Bunch

More info is given here, indicating that there are problems regarding the landing, especially with respect to getting the thing to anchor itself to the comet.  Unless this can be accomplished, I suspect most of the most interesting tasks can't be attempted.


"Rosetta probe has bounced away from landing site and lost contact, admit scientists.  Although scientists celebrated landing probe Philae on comet this afternoon, the lander is not securely attached and has already bounced away from its landing site."

Also see:

I'm finding that it's unusually hard to find authoritative information about the probe.  At the moment I suspect that the ESA spokesmen are necessarily holding back further updates until they can reassess and learn much more information than they have now about the probe's status and prospects.  I read that the project's cost was 1.3 billion UK pounds.
Best wishes,

Phil Bunch

Garry Richards

By the time you read this you will probably know that it landed successfully and is now sending pictures back. What an achievement!


Jeroen D

Quote from: martinTo give an idea of the scale in the fantastic images sent from the comet, someone copied a 744(!) in. Amazing.

Looks like KLM has opened a new route. Certainly gives new meaning to long haul!




Quote from: PhilI'm finding that it's unusually hard to find authoritative information about the probe.
Indeed. Partly it's the usual impatience of the Press, and also this new-fangled habit (even of official bodies) to spread information on channels such as "blogs" and "social media" with their often chaotic structure and very low signal-to-noise ratio...

So as to add to the confusion on this forum, too, here's what I have heard read:

¤ The thruster supposed to counter the harpoons' recoil didn't work.
But that was discovered before separation already, and discussed when they had to make the go/no-go decision for landing. Which is perhaps why it wasn't much of an issue (i.e. mentioned) any more during the landing phase itself.

¤ Contrary to what ESA themselves initially had stated, the harpoons to anchor the lander did not fire. The stability of the situation was (is?) therefore somewhat unclear.

¤ Radio signals were successfully received, indicating that [some sort of] landing had indeed been achieved.

¤ However, the signal strength (and the solar panel output) fluctuated somewhat (also gaps?) which it shouldn't have. Apparently signals then stabilized, after about two hours.
One explanation may be that this indicates the lander is/was actually not sitting firmly on the ground but floating. (Last night when I read this, it was still speculation, but interesting speculation, methinks.)

¤ At 20 h (probably CET = GMT+1, or possibly GMT, not clear) radio signals were lost, but that was according to plan (Rosetta, the "mothership" on the "wrong" side of the comet.)

¤ The team always needs a lot of time to evaluate the situation from the signals they receive*, hence the delay of clear info (and the obnoxiousness of the Press's impatience: better to tell something wrong quickly than to tell something correct later).
* not to mention the 28 min signal travel time. This is all happening about half a light hour away! We will never again be "in touch" with the lander, only with its history...

¤ Batteries will last for 68 hours. What contribution the solar panels can make is so far unknown, as it depends on the amount of dust etc.

¤ Newest info: The lander has (or still: may have?) indeed bounced twice, once for ca. two hours, and then again for ca. four minutes.
Pending further evaluation, it seems however now to be in a stable position (perhaps secured by the "drilling feet", if the ground allows it?).

¤ Next press conference seems to be scheduled for today (Nov 13) at 14h (again, probably CET = GMT+1 but may be GMT. I am unable to find this information directly on the ESA pages...).

In my personal opinion, whatever happens next, I think this enterprise can already be declared a success. At the very least for Good Entertainment!  8)

Main Sources:
Der Spiegel (in German)
The Register

The ESA website itself seems to be somewhat sluggish with updates.
(May be my own fault: It is entirely possible that there is an abundance of up-to-date ESA stuff, but which I am simply unable to find because it is sprinkled across blogs, Twitter, Facebook, Flickr, whatever, the utilization of which I have never quite grasped.)


Hardy Heinlin

Does anybody know what weight on the comet corresponds to 1 kg on the Earth?

I can't imagine how one wants to shoot harpoons into the ground without those opposite thrusters -- or how to drill holes without being anchored.




About 10^-3 m/s² says wiki:

I think if they just need to fit a 8km string around the comet, they should be fine  :D

Jeroen Hoppenbrouwers

Escape velocity estimated at one meter per second ... You can jump into space off that rock!