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Old 01-21-2014, 08:06 AM   #61
Urwumpe
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...as black as a 3K background...
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Old 01-21-2014, 09:56 AM   #62
Unstung
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Does anybody know why Rosetta will approach the comet in an unusual way?

It seems like getting closer and preforming one longer burn would be more efficient than a looping pattern. I think Rosetta may do this for safety, to avoid entering any potential coma or tail.
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Old 01-21-2014, 10:04 AM   #63
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Quote:
Originally Posted by Unstung View Post
 Does anybody know why Rosetta will approach the comet in an unusual way?
Rosetta's orbit around the comet
It seems like getting closer and preforming one longer burn would be more efficient than a looping pattern. I think Rosetta may do this for safety, to avoid entering any potential coma or tail.
That, but also remember that the gravity of the comet has almost no effect on Rosetta. The perturbations of the planets will constantly distort the very weak gravity field and require constant corrections to prevent drifting away or crashing into the comet.
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Old 01-21-2014, 11:49 PM   #64
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Quote:
Originally Posted by Unstung View Post
 Does anybody know why Rosetta will approach the comet in an unusual way?
It seems like getting closer and preforming one longer burn would be more efficient than a looping pattern. I think Rosetta may do this for safety, to avoid entering any potential coma or tail.
It needs to first map the details of the comet and hazard zones. The imagery of the comet right now is rather coarse.

Also, keep in mind that the animation is much faster than the actual motion. The energy to make these trajectory changes is miniscule as it really is not "fighting" the comet's gravity in any meaningful way. Even when it finally settles into "orbit" the period will be very long and perturbations from other cosmic bodies will necessitate frequent small corrections to stay in orbit.
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Old 01-22-2014, 02:17 AM   #65
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Quote:
Originally Posted by Unstung View Post
 Does anybody know why Rosetta will approach the comet in an unusual way?
That approach makes perfect sense. The initial part is not an orbit at all. The craft is so far away that it can fly a triangle path using 3 small burns. This is a good way to get imagery of possible hazards and measuring the gravitational forces.
Notice the position of the comets tail. The craft is kept as far away from it as possible.

Quote:
This animation is not to scale; Rosetta's solar arrays span 32 m, and the comet is approximately 4 km wide.
The initial distance is 100 km, and the close 'periapsis' is 2.5 km. The displayed maneuvers stretch from August to November.

Last edited by C3PO; 01-22-2014 at 02:22 AM.
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Old 01-22-2014, 05:31 AM   #66
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What sort of propulsion Rosetta have?
Ion engine?

Surprisingly, neither wiki, nor ESA site seem to say.
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Old 01-22-2014, 06:37 AM   #67
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Quote:
Originally Posted by Artlav View Post
 What sort of propulsion Rosetta have?
Ion engine?

Surprisingly, neither wiki, nor ESA site seem to say.
"Bipropellant"

http://www.esa.int/Our_Activities/Sp...osetta_orbiter

---------- Post added at 12:37 AM ---------- Previous post was at 12:35 AM ----------

"The Rosetta thruster are bipropellants units which use monomethylhydrazine fuel and mixed oxides of nitrogen as oxidizer."
http://space.unibe.ch/fileadmin/imag...g_AIAA_rev.pdf
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Old 01-22-2014, 07:17 AM   #68
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I can't wait until the data start to come! It is not the wheezing by as all the previous missions!
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Old 01-22-2014, 07:34 AM   #69
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 I can't wait until the data start to come!
It's been a decade, can as well wait another 6 months.
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Old 01-22-2014, 08:54 AM   #70
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Quote:
Originally Posted by Artlav View Post
 It's been a decade, can as well wait another 6 months.
When it was designed, I was still apprentice at the German aerospace agency, and had the team designing the lander structure in my institute.
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Old 02-06-2014, 01:19 PM   #71
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Some comparisons

http://what-if.xkcd.com/82/
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Old 02-06-2014, 08:32 PM   #72
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Anyone know what he meant with the mouseover text of picture #2? Practical joke or even more flyby anomalies.
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Old 02-07-2014, 06:53 AM   #73
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Quote:
Originally Posted by MattBaker View Post
 Anyone know what he meant with the mouseover text of picture #2? Practical joke or even more flyby anomalies.
Possibly this?
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Old 03-29-2014, 09:46 AM   #74
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Rosetta recently captured the first two photos of its target, 5 million km away, since hibernation using the wide-angle (top image) and narrow-angle (bottom) cameras:


The globular cluster M107 is in the above image.

JPL: "Rosetta Sets Sights on Destination Comet"
The Planetary Society: "Comet spotted! Rosetta's first sight of Churymov-Gerasimenko since wakeup"


This is what 67P/Churyumov-Gerasimenko will look like in the coming months from the spacecraft's perspective:


Philae has also been successfully reactivated.
Universe Today: "ESA Awakens Rosetta’s Comet Lander"
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Old 05-09-2014, 07:42 AM   #75
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Rosetta performed the first small deceleration manoeuvre to test the thruster system. Over the next weeks, a number of burns will be performed to slow the spacecraft to less than 8 m/s relative to the comet. Rosetta is now 2 million kilometres away from the target and approaching it with 775 m/s relative velocity.

Here is the table of the burns from the blog article:

DateDelta-vMidpoint of burn (UTC)ROS/67P distROS/67P rel-v
Wed 07/05/1420 m/s16:451,918,449775.1
Wed 21/05/14290.89 m/s19:081,005,056754.1
Wed 04/06/14270.98 m/s17:48425,250463.0
Wed 18/06/1490.76 m/s14:31194,846192.1
Wed 02/07/1458.80 m/s12:5751,707101.3
Wed 09/07/1424.91 m/s11:5722,31443.0
Wed 16/07/1410.65 m/s11:129,59018.4
Wed 23/07/144.62 m/s10:304,1267.9


http://blogs.esa.int/rosetta/2014/05...of-manoeuvres/


Also, what might be interesting for the German forum members: The magazine c't has a longer article about Rosetta in its current issue.

http://www.heise.de/ct/inhalt/2014/11/82/
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