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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
Phil Stooke
From a global point of view I don't think there will be any significant extension of coverage this time. The important thing will be the chance to extend the area covered by the highest resolution images shortly before and after closest approach. Things happen so fast near closest approach that only a small area can be seen in the highest resolution images. This time it will be possible to image areas not covered at highest resolution before, or to plan images to give good stereo viewing when combined with the earlier images. So, lots of opportunity to do good things, but not really any chance of increasing coverage.

Phil
Greg Hullender
Yes, I understand that. I was hoping someone might make a map that indicated which areas would get improved coverage though. That is, if one were trying to make a Mercury map, which existing areas should one expect to upgrade as a result of this flyby.

Of course, that'll all be obsoleted when Messenger goes into orbit, but that's still a long time from now.

--Greg
Phil Stooke
There's no public information on coverage yet, but it will come.

Phil
MarkG
It will also be interesting if any stereo-pair frames are shceduled.


Any further word on the search for "Vulcanoids"?



--Mark G.
Vultur
Probably a dumb question, but what are Vulcanoids - Mercury-crossing asteroids?
mps
There is an article about vulcanoids in Wikipedia.
MarkG
QUOTE (Vultur @ Jul 9 2009, 06:49 AM) *
Probably a dumb question, but what are Vulcanoids - Mercury-crossing asteroids?

There is a Wikipedia, but the short answer is that Vulcanoids are a purported group of small bodies orbiting inside Mercury's orbit. Messenger can look for them when at perigee -- looking at an angle away from the sun, but still look at space inside Mercury's orbit.
ugordan
QUOTE (MarkG @ Jul 12 2009, 06:21 PM) *
Messenger can look for them when at perigee

I think you meant perihelion.
MarkG
QUOTE (ugordan @ Jul 12 2009, 08:27 AM) *
I think you meant perihelion.

Sorry to anthropomorphise...
Paolo
By the way, this year marks the 150th anniversary of the publication of Le Verrier's first study of the "intramercurial planet" and of Lescarbault's observed transit of Vulcan across the Sun http://en.wikipedia.org/wiki/Vulcan_(hypothetical_planet)
Greg Hullender
Just half an orbit away now. (Messenger's orbit is currently 116 days). Even if the coverage largely duplicates flyby #1, the phase angle might be different enough to be useful. Does anyone remember how close to the other flybys the Messenger team started posting information for the public?

--Greg
dmuller
QUOTE (Greg Hullender @ Aug 3 2009, 03:12 PM) *
Does anyone remember how close to the other flybys the Messenger team started posting information for the public?

I dont recall for sure but if memory serves me right they published their flyby timeline very close to C/A, maybe 2 or 3 weeks in advance.

The press-kit seems to have been published on 13 Sep 08 for the 06 oct 08 flyby
QUOTE (peter59 @ Sep 13 2008, 06:56 AM) *
stevesliva
Just got an email with a 5-year milestone press release:
http://messenger.jhuapl.edu/news_room/details.php?id=127

QUOTE
The probe has completed four major deep-space maneuvers (DSMs) and 12 trajectory-correction maneuvers, and mission controllers have been able to forgo six additional planned course corrections by using MESSENGER’s solar panels creatively, harnessing solar radiation pressure to adjust the spacecraft’s trajectory.

“Because of the implementation of solar sailing, the MESSENGER team has not used propellant to correct the cruise trajectory of the spacecraft since December 19, 2007, in advance of the first Mercury flyby,” says MESSENGER Mission Systems Engineer Eric Finnegan, of APL.


Neat!
Greg Hullender
That suggests they might be able to have quite the extended mission, when the time comes. I wonder if this counts as the first successful solar sail application? :-)

--Greg
Holder of the Two Leashes
Opportunities for magnetometer - Flyby 3
Vultur
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...
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 Two Leashes
Some new diagrams showing picture plans were put up on the main website today.

Link
stevesliva
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.
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
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
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:

Click to view attachment
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.
tanjent
The mission website discussion of the orbital phase does not say much about how the mission will end.

http://messenger.jhuapl.edu/the_mission/orbit.html

Maintaining the orbit will require continued fuel consumption.
The page does not reveal if, after 12 months or 2 solar days they expect to simply run the tank dry and
lose contact with the spacecraft, or what other sort of ending will follow. I have heard no
proposals for extending the mission, but somewhere near the end - after completion of all the major objectives
a moment may come when otherwise unacceptable risks can be considered. My little suggestion represents just one
possibility - maybe not a very strong candidate, but if the mission can end with an attention-grabbing "goodbye" shot,
there would be some value in that.

Dmuller, thanks for pointing out the big advantage in apparent size still enjoyed by the sun at the present time.
tedstryk
While we are waiting, I have added my Mariner 10 set to my blog http://planetimages.blogspot.com/2009/09/m...at-mercury.html
4th rock from the sun
ExcellentMariner 10 images! And a very nice job of bringing out the subtle color differences from a very limited dataset. They match very well with the Messenger global views.
tedstryk
Thanks. I made them just before the first Messenger flyby. The correlation isn't perfect, but the filter combinations here are much more blue-shifted. The south pole view is just a rough overlay based on the color seen in the first two images.
Greg Hullender
James Leary has discussed a possible extended mission:

http://www.nasa.gov/missions/highlights/we...transcript.html

However, all he said was that they mght get the spacecraft into a slightly lower orbit so as to get slightly better pictures. He didn't suggest that Messenger would ultimately impact Mercury.

Solomon's "Mercury After Messenger" is a very cool read all by itself, and he suggets an XM for Messenger might be just a single Earth year:

http://www.spacepolicyonline.com/pages/ima...n_MESSENGER.pdf

Despite the title, it's mostly about what Messenger will do at Mercury, but it suggests that after Messenger and Bepi-Colombo, there won't be a lot gained by another orbiter. The next step would have to be a lander or sample-return mission.

--Greg
Greg Hullender
The Messenger team will be doing a press conference tomorrow to discuss next week's flyby:

http://messenger.jhuapl.edu/news_room/details.php?id=130

QUOTE
WASHINGTON -- NASA will host a media teleconference at 1 p.m. EDT on Wednesday, Sept. 23, to preview MESSENGER's third and final flyby of Mercury.


This appears to be limited to press, but perhaps someone like Emily will be able to report back to us. :-)

--Greg
Greg Hullender
There is a nice map, just posted today, showing the planned imaging coverage:

http://messenger.jhuapl.edu/gallery/scienc...mp;image_id=326

Note that this suggests that Flyby #3 will cover more than half of the never-seen terrain.

I also note that the areas marked for Flyby #1 and Flyby #2 are backwards. Flyby #1 coverage is actually the area outlined in red on the image and Flyby #2 is outlined in blue, as we can see from the Flyby #2 coverage plan:

http://messenger.jhuapl.edu/gallery/scienc...erage_Sep08.jpg

We knew that this flyby would be very similar to Flyby #1 -- so much that some of us had worried there would be nothing new to see at all. What's surprising (to me, anyway) is that the coverage on approach is much larger and significantly shifted compared to flyby #1 (and this is where almost all the new coverage comes from) but the coverage on departure is almost the same as for Flyby #1. Wonder why so much difference between the two?

--Greg
elakdawalla
QUOTE (Greg Hullender @ Sep 22 2009, 07:48 AM) *
This appears to be limited to press, but perhaps someone like Emily will be able to report back to us. :-)

Gosh, I'd missed the fact it was a telecon, not TV briefing. I'm glad you mentioned it -- got my request for the phone number in in time! I'll certainly be reporting on it. Today I'm working on my usual preview timeline.

--Emily
elakdawalla
QUOTE (Greg Hullender @ Sep 22 2009, 07:56 AM) *
I also note that the areas marked for Flyby #1 and Flyby #2 are backwards. ...
I don't think so. According to my notes, it's flyby 2 and 3 that had the same geometry:

QUOTE
Flyby 1: January 14, 2008
» Sun illuminates 95 to 275°E
Flyby 2: October 6, 2008
» Sun illuminates 273 to 93°E
Flyby 3: September 29, 2009
» Sun illuminates 270 to 90°E


The two maps you point to are just centered on different longitudes.

I think maybe the reason the approach crescents are different is because on flyby 2 MESSENGER was coming in from a direction farther from the Sun -- its orbit has shrunk since then. But I don't have the best instinct for orbital geometry. If I don't think of a better question to ask, I may ask this one tomorrow.

--Emily
Greg Hullender
QUOTE (elakdawalla @ Sep 22 2009, 10:51 AM) *
I don't think so. According to my notes, it's flyby 2 and 3 that had the same geometry:

The two maps you point to are just centered on different longitudes.


Oops!

QUOTE (elakdawalla @ Sep 22 2009, 10:51 AM) *
I think maybe the reason the approach crescents are different is because on flyby 2 MESSENGER was coming in from a direction farther from the Sun -- its orbit has shrunk since then. But I don't have the best instinct for orbital geometry. If I don't think of a better question to ask, I may ask this one tomorrow.


Actually, taking a look at the plots of the orbit, I think I can see it now:

This was flyby #2

http://messenger.jhuapl.edu/the_mission/ME...rthPoleFull.jpg

And this is flyby #3

http://messenger.jhuapl.edu/the_mission/ME...rthPoleFull.jpg

The orbit "bends" a good bit more this time -- which makes sense, as Messenger is losing energy with each flyby. It's probably just a coincidence that the outbound path seems to be more or less the same (with respect to the planet surface) as it was for flyby #2. Especially since this flyby seems to be about 25 degrees further around Mercury's orbit than the last two were.

http://messenger.jhuapl.edu/the_mission/trajectory.html

Shoot. Just as I typed all this, the Messenger folks released this:

QUOTE
Because the spacecraft velocity relative to Mercury is about one-third slower at Mercury flyby 2 than at Mercury flyby 2, the gravity-assist turn angle to the spacecraft’s trajectory increases from about 27° to nearly 50°,” explains Jim McAdams, the MESSENGER mission design lead engineer. “This greater bend in the trajectory provided by the gravity of Mercury offers the spacecraft its first opportunity to view a small portion of Mercury’s surface twice with different vantage points and nearly identical lighting conditions just a few hours apart.


So I guess that's the answer. I'd still like to know exactly what percentage of Mercury will remain unimaged after this flyby . . .

--Greg
dmuller
Does anybody have the flyby timeline in spreadsheet form? Going through the encounter sim just drives me nuts, plus it doesn't match with any other info i have :-(
Greg Hullender
Another press release today:

http://messenger.jhuapl.edu/news_room/details.php?id=132

A couple of things I hadn't realized before:

1) This is their last chance to study the magneto tail in the equatorial plane.
2) The flyby images are higher-resolution near the equator than any pictures Messenger will take later.
3) They are still looking for possible moons, down to radius 100m.

--Greg
Greg Hullender
Another Messenger update, this one has a new photo.

http://messenger.jhuapl.edu/mer_flyby3.html

Given the approach image we saw before, I think that means the lighted part of this crescent is mostly terrain that has never been imaged before, so that's kind of cool. Interesting-looking bright crater near the top.

--Greg
kohare
QUOTE (gndonald @ Sep 17 2009, 01:15 AM) *
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.

MESSENGER Mercury Flyby 3 Press Kit (PDF) now available. File title seems to indicate it's draft 3 from 23 September, so maybe it will be updated in a a final release??
dmuller
I have uploaded Emily's flyby blog onto my realtime simulation at http://www.dmuller.net/messenger. Less than 4 days to go.
Phil Stooke
This is the first Mercury 3 image release enlarged and with the terminator brightened. The bright crater was seen last time too.

Phil

Click to view attachment
Phil Stooke
The latest image, enlarged, terminator brightened and sharpened.

Phil

Click to view attachment
Hungry4info
Latest image from the website, showing essentially the same thing as Phil Stooke was able to get by sharpening the image before.

http://messenger.jhuapl.edu/gallery/scienc...4M_RA_3_web.png
Phil Stooke
And here's what he gets by enlarging, selectively brightening and sharpening this new image:

Click to view attachment

Phil
Ant103
My own sharpenning of the last picture of Messenger.
Just a wavelett sharpen wink.gif
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