Mercury Flyby 3 Options

[Holder of the Tw...]

Opportunities for magnetometer - Flyby 3

[Vultur]

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...

[MarkG]

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.

[Hungry4info]

You could download Celestia and the MESSENGER add-on with it. It's a wonderful tool for visualising such things.

[gndonald]

The page outlining the plans for the third flyby is up.

Mercury Flyby 3

[dmuller]

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

[MarkG]

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).

[Holder of the Tw...]

Some new diagrams showing picture plans were put up on the main website today.

Link

[stevesliva]

Link

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.

[tanjent]

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?

[dmuller]

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

[tanjent]

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.

[djellison]

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.

[dmuller]

That would be the shot:


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.

[gndonald]

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.