Mercury Flyby 3 Options

[Greg Hullender]

We're now just one Mercury year (88 days) from flyby #3, which happens on September 29, 2009, so this seems like a good time to start a thread about it.

http://messenger.jhuapl.edu/index.php

For comparison purposes, it'd be nice if someone (probably someone on the Messenger team) put together a Mercury Map showing what areas will get better coverage from this flyby than from the previous ones. I realize it'll be very similar to flyby #1, but it won't be exactly the same.

After that, it's a long wait until MOI on March 18, 2011. Curiously, that's the same date the New Horizons crosses the orbit of Uranus.

http://pluto.jhuapl.edu/mission/passingpla...ets_current.php


--Greg

[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.