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Mercury Flyby 3
Holder of the Tw...
post Aug 20 2009, 04:03 PM
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Opportunities for magnetometer - Flyby 3
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Vultur
post Aug 30 2009, 08:55 PM
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QUOTE (Greg Hullender @ Aug 3 2009, 07:52 PM) *
That suggests they might be able to have quite the extended mission, when the time comes.


It does sound very promising (and it's really a quite amazing thing that they can correct the course using just radiation pressure! That must take very precise calculations...) Imagine what an inner-system probe with actual sails could do...
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MarkG
post Sep 8 2009, 01:15 AM
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Does anyone know of a detailed diagram of the flyby (#3). I actually want not just the inner stuff, but the stuff from a couple million KM out, to show the interactive dance of the 3-body problem to my son.

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Hungry4info
post Sep 8 2009, 02:39 PM
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You could download Celestia and the MESSENGER add-on with it. It's a wonderful tool for visualising such things.


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gndonald
post Sep 9 2009, 01:42 AM
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The page outlining the plans for the third flyby is up.

Mercury Flyby 3
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dmuller
post Sep 9 2009, 04:03 AM
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Haven't been able to find much information yet. According to the site, closest approach is 29Sep2009 17:54:58 EDT, presumably that translates to 29Sep2009 22:54:58 UTC but it doesn't state if it's Earth received time (ERT) or spacecraft event time (SCET). Does anybody know the answer to this?

The latest SPICE kernel I could find was updated on 30 Mar 09 and implies closest approach on 29Sep09 22:53:00 SCET ET at 199.7km altitude and a relative speed of 19,094km/h. That time translates to 29Sep09 22:58:32 ERT UTC. (66 leap seconds and one-way light time of 6min38sec)


EDIT: Assumed that time given is ERT and have updated MESSENGER realtime simulation (http://www.dmuller.net/messenger) accordingly


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MarkG
post Sep 10 2009, 04:21 PM
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Thanks for the tip on Celestia -- I'm working with it now.

At 8 million km distance today, the crescent of Mercury would be barely resolved by a human eye traveling with Messenger (~2 arc minutes).
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Holder of the Tw...
post Sep 15 2009, 02:45 PM
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Some new diagrams showing picture plans were put up on the main website today.

Link
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stevesliva
post Sep 15 2009, 03:46 PM
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QUOTE (Holder of the Two Leashes @ Sep 15 2009, 09:45 AM) *

Which links here -- easy to miss if you focus on diagrams and not text:
http://messenger.jhuapl.edu/target_observ.html

They're doing 30-second stares for spectra and full color filter coverage of some targets they found extra interesting in previous data. Gives a little perspective on what makes this encounter a unique one rather than a repeat.
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tanjent
post Sep 15 2009, 04:01 PM
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In the related link, showing the simulated position of Messenger relative to Mercury and the sun

http://messenger.jhuapl.edu/whereis/index.php#current_orbit

Messenger seems to be cruising almost "parallel" with the planet while approaching from the night side.
It's hard to tell the relative sizes of things from the sim diagrams, but in the fourth picture it looks like
even now the planet is directly between the spacecraft and the sun. I'd be curious to know - about how
much total time will the spacecraft be spending in Mercury's eclipse during this approach?
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dmuller
post Sep 16 2009, 12:14 AM
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QUOTE (tanjent @ Sep 16 2009, 02:01 AM) *
Messenger seems to be cruising almost "parallel" with the planet while approaching from the night side.


Yes MESSENGER is cruising more or less directly behind Mercury at the moment (as seen from the Sun). See also the sim images on my site http://www.dmuller.net/messenger (apologies for the "advertisement"), in particular how close the Sun and Mercury are as seen from MESSENGER and the all-dark Mercury enlargement. That can also be seen on the solar system maps on my site: http://www.dmuller.net/realtime/map.php?mt=aboveinner and http://www.dmuller.net/realtime/map.php?mt=eclipticinner. You can also see that the relative speed between MESSENGER and Mercury is now down to less than 22,000km/h. Still too much for an orbit insertion burn, hence this is a flyby and not (yet) the orbit capture.

Mercury will move to the right of the Sun as seen from MESSENGER. View from above and over time (sorry didnt have the time to make an animated gif):
16Sep: http://space.jpl.nasa.gov/cgi-bin/wspace?t...=1&showsc=1
19Sep: http://space.jpl.nasa.gov/cgi-bin/wspace?t...=1&showsc=1
22Sep: http://space.jpl.nasa.gov/cgi-bin/wspace?t...=1&showsc=1
25Sep: http://space.jpl.nasa.gov/cgi-bin/wspace?t...=1&showsc=1
28Sep: http://space.jpl.nasa.gov/cgi-bin/wspace?t...=1&showsc=1
Flyby: http://space.jpl.nasa.gov/cgi-bin/wspace?t...=1&showsc=1


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tanjent
post Sep 16 2009, 09:30 AM
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Well then it seems like for the moment I should put aside my hopes of an eclipse picture taken at some point
from which the angular diameter of the planet just about matches that of the Sun. I don't know what the science
value of such a shot would be, but it would definitely be a memorable sight to see. Perhaps the orbital phase
will present opportunities for this kind of a photograph.
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djellison
post Sep 16 2009, 10:21 AM
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Hmm - I wouldn't fancy that observation too much - being THAT close to the sun and then you're pointing the entire instrument deck sunward? No thanks.
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dmuller
post Sep 16 2009, 01:20 PM
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That would be the shot:

Attached Image

Source: http://space.jpl.nasa.gov/cgi-bin/wspace?t...=1&showsc=1

Mercury about dead-center in the sun on 16 Sep at 12noon UTC. The Sun's apparent size is about 15 times larger than that of Mercury.


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gndonald
post Sep 17 2009, 12:15 AM
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Preparations for the third flyby

They still have not released a press kit for this. It looks like it won't be released until the 23rd when they have the teleconference.
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