Messenger is hitting relatively memorable locations much more often. In just over two months (65 days) it will make its first flyby of Mercury. On the other hand, you are right, that unless you like watching numbers tick by, the progress threads here can be kind of dull.

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Forming opinions as we speak

<<I can't even pretend this trip isn't boring.>>

Kind of reminds me of this stand-up routine I saw where the ventriloquist's dummy commeted on the inanity of a NASCAR race: "He's going to make a left turn! He's going to make a left turn! He's going to make another left turn!..."



No offense to any racing fans out there, of course.

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"Call me old-fashioned, but I think fire is magic. And it scares me a lot."

--The State

In a way, that makes it worse. Every flyby of Venus I keep hoping they're going to release some great scientific discovery, but it always turns into a pit stop. With a wave to Venus Express and a few cursory blob shots with the long range camera, we're off again.

65 days. I can handle that.

*crosses fingers and shuts eyes*

Giant volcanoes!
Giant volcanoes!
Giant volcanoes!

Giant active volcanoes!

*Slaps inner Hoagland*

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There is a growing tendancy to think of Man as a rational, thinking being, which is absurd.- Marvin the Martian.

It's gotten to the point where careful investigation is needed just to tell parody from reality. I think that means reality is broken.- Noclevername.

Very funny!

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I want to go back to the moon.
I don't care which rocket you use, whichever one you pick, I'll like it, I swear.
"If you think the LHC will create black holes, you might as well believe Hobbits are at the bottom of your garden."- Dr. Mike Inglis
Rovers forever! - ToSeek

JHUAPL Messenger status report, November 19, 2007:

Soon, MESSENGER Completes Fifty Percent of Cruise Phase

Already!

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Messenger has crossed the orbit of Venus for the final time. On to Mercury! 53 days to go.

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Forming opinions as we speak

OK, maybe I jumped the gun by a day. Here's today's map.

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Forming opinions as we speak

I thought you were a day or two early, but I figured what's a few hours among friends. Speaking of hours, it is only 13.5 hours until the chronological halfway point.

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Keeper of the Jabberwock

Nice. And a little over seven weeks till the first flyby.

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Forming opinions as we speak

Does anyone know at what range Messenger will start snapping shots (and doing other science) of Mercury? Based on the mission page, the probe appears to be about half the distance from Venus's orbit from Mercury and closing. What is the effective range of the equipment?

The problem is that the Sun would be in the background until at least another week. Right now, Messenger has passed Mercury slightly but has a longer path to take. It will be probably New Years before Messenger could see anything on the sunlit side.

Any pictures taken now will only be of the sun which would likely overwhelm the camera.

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Keeper of the Jabberwock

Well, Messenger has completed its fifth orbit of the sun. It's taken close to four years to do so. The next five orbits will only take about three years.

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Keeper of the Jabberwock

I'm glad someone else is following the Mercury probes. I have a few questions about the issues getting to the planet.
#1) Why does it take as much fuel to get to Mercury as it does to get to Saturn??
#2) Why so many gravity assists? Wouldn't it be faster with less? The ESA space craft is using ION propulsion so I understand why it takes forever to get there and needing the gravity assists.
#3) Wouldn't a straighter path take less fuel and save money??
The probe is treking almost 5 billion miles to get to a planet that is only about a third the Earth's distance from the Sun.
I know its close proximity to the Sun has unique challenges but.... the stats seem way out of whack......
Can someone educate me on the specifics please??

Messenger needs to enter orbit to do this it has to be slow enough, these flyby's are designed for precisely the opposite of say Voyagers flyby's, they are designed to leak excess speed that Messenger will gather being that much closer to the sun. Flying in a straight line to Mercury would crash Messenger against the sun, I believe.

My understanding of the science details are limited but I'm sure one of the other posters will fill you in far better than I did.

The sense of it is this. The Earth's near circular orbit has us moving around the Sun at about 19 miles a second. For us to make a probe fall in close enough to the Sun to get to Mercury's orbit, we need to shed most of that speed (I don't know the exact number, but it is probably around 12 to 14 miles per second). This is almost double the change in velocity required to get to Saturn.

If you did this direct to Mercury flight, the probe would be in an elliptical orbit taking it from Mercury's orbit back out to Earth's. If you wanted to use rockets to slow the probe down directly, you'd need to adjust the probe's velocity to enter Mercury orbit, but this time you'd need to change it much more (IIRC, you'd need to change it by about 30 miles per second).

The trip that Messenger is taking will use *much* less fuel, and require a much smaller rocket than the trip you're asking about. I don't think that a Saturn V could have had enough energy for the direct to Mercury orbit flight with a one ton probe.

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Forming opinions as we speak

Getting out of Earth's gravity well is a large energy expenditure regardless of destination. It takes very little additional fuel to get TO Mercury. It takes a LOT of energy to slow down enough to be captured by Mercury's gravity.

Again, the problem isn't getting TO the planet, it's slowing down enough to take more than a few fleeting snapshots. Those weren't gravity assists, they were gravity brakes; the opposite of outward bound probes get.

This isn't about simply flying by Mercury. Mercury is very small and close to the sun. Any probe simply pushed toward the Sun will accelerate so much that Mercury will never be able to capture it. We could go straight to Mercury and fire retro-rockets to slow the probe down, but the probe would have to be the size of the original launching rocket. Which means that the original launching rocket would have to have been something the size of the Saturn rockets that launched Apollo.

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Keeper of the Jabberwock

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Everything I need to know I learned through Googling.

The only thing close to interesting for awhile will be in March when Messenger begins falling back toward the Sun. Mercury won't be there to meet it, though.

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Keeper of the Jabberwock

Right. Mercury will orbit thrice, while Messenger orbits twice. With each pass the ratio will get larger, and the interval between meetings gets longer.

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Forming opinions as we speak

I decided to do a little bit of orbit calculation; how many orbits around the Sun that Messenger has made and how many it will make. Using this trajectory page as a guide, I've come up with:

Earth 1, 2004 Aug 3 - 53220
Earth 2, 2005 Aug 2 - 53584
Venus 1, 2006 Oct 24 - 54032
Venus 2, 2007 Jun 5 - 54256
Mercury 1, 2008 Jan 14 - 54479
Mercury 2, 2008 Oct 6 - 54745
Mercury 3, 2009 Sep 29 - 55103
Mercury 4, 2011 Mar 18 - 55638

The first one is the launch of Messenger, and the last one is insertion into Mercury orbit; all the others are flybys.

The numbers at the end are Modified Julian Dates, which are easier to compare than typical calendar representations.

Earth 1 - Earth 2: 1 Msgr orbit
Earth 2 - Venus 1: 1 2/3 Msgr orbits
Venus 1 - Venus 2: 1 Msgr orbit, 1 Venus orbit
Venus 2 - Mercury 1: 1 1/2 Msgr orbits
Mercury 1 - Mercury 2: 2 Msgr orbits, 3 Mercury orbits
Mercury 2 - Mercury 3: 3 Msgr orbits, 4 Mercury orbits
Mercury 3 - Mercury 4: 5 Msgr orbits, 6 Mercury orbits

I will now consider what Messenger will be able to see in its upcoming flybys. This will be determined by how Mercury rotates.

Mercury's rotation period is rather odd: it is 2/3 Mercury years relative to the stars, and thus 2 Mercury years relative to the Sun. So a Mercury "day" is 2 Mercury years long.

Note: 1 Mercury year is about 88 Earth days.

Mercury had been visited once before, by the Mariner 10 spacecraft, which flew by three times. But between each pair of flybys was 1 spacecraft orbit and 2 Mercury orbits, and thus 1 Mercury day. This meant that Mariner 10 saw the same half of Mercury all three times, which I will call the Mariner hemisphere. The other half of Mercury's surface is thus the anti-Mariner hemisphere.

As reported in this news page, Messenger has seen half of the Mariner hemisphere and half of the anti-Mariner hemisphere. So on its next two flybys and on its arrival in Mercury orbit, Messenger will see the other half of both the Mariner and the anti-Mariner hemispheres. This is because there is an odd number of Mercury days from the first to the second flyby, but even numbers of Mercury days between the second flyby, the third flyby, and orbit insertion.

Messenger will then orbit Mercury for the next Earth year, which is about 2 Mercury days; it will see both the Mariner and the anti-Mariner hemispheres from the full range of solar illumination directions.

Critical Deep-Space Maneuver Targets MESSENGER for Its Second Mercury Encounter

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Everything I need to know I learned through Googling.

Messenger is at its sixth aphelion just a few miles inside Venusian orbit (well, maybe more than just a few miles). It will be back at Mercury orbit at about this time in May and again on 6 October when Mercury will also be there.

By year's end, Messenger will be heading toward its ninth perihelion.

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Keeper of the Jabberwock

Mercury has completed its 6th orbit around the sun since launch.

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Keeper of the Jabberwock

Messenger has passed inside of Mercury's orbit. It will pass through its 7th perihelion within the next 24 hours or so.

Edit: It will pass outside Mercury orbit at 1800 UTC on 31 May.

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Keeper of the Jabberwock

1000 Days until Mercury orbit insertion.

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Keeper of the Jabberwock

Johns Hopkins University APL: NASA to Reveal New Discoveries from Mercury

Audio available at: http://www.nasa.gov/news/media/newsaudio/index.html
Related images at: http://messenger.jhuapl.edu/news_room/telecon4.html

Teleconference begins:
July 3 1100 PDT Thursday
July 3 1400 EDT Thursday
July 3 1800 UTC Thursday

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Audio available at: http://www.nasa.gov/news/media/newsaudio/index.html
Related images at: http://messenger.jhuapl.edu/news_room/telecon4.html

Press conference about to begin. Images are up.

JHU APL Press release: NASA REVEALS NEW DISCOVERIES FROM MERCURY

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about now!

and my baby's house name at school is Mercury!

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clear skies

If you want to make an apple pie from scratch, you must first create the universe. CARL SAGAN

Mak: Pass the pepperoni please.
Fazor: "Hail, Bautainia! We pledge our hearts to thee! Science and woo, some babbling too, and astron-oh-meee!"
slang: And it made ash out of yew and tree.

From a celestial mechanics standpoint, the MESSENGER spacecraft's trajectory is interesting. From the point of view of using the Sun as a frame of reference, the spacecraft had to be slowed down after it left the Earth in order to reach Mercury. In essence the spacecraft has to remove velocity in order to fall into the inner solar system. It incurs a great penalty in fuel to do this, so the navigators put in the planet flybys to help reduce the fuel usage.

I think MESSENGER, like other JHUAPL projects, gets little press because JHUAPL does not invest in public relations and press relations as much as JPL does.

The previous NEAR-Shoemaker mission got the same sparse attention for the same reason. JHUAPL needs to add a bit more to its PR budget....

MESSENGER Mission News: Sharing the Wealth: MESSENGER Team Delivers Mercury Flyby 1 Data to Planetary Data System (August 4, 2008)

It looks like it might include the navigation SPICE data, at NAIF (Navigation Ancillary Information Facility): mess-e_v_h-spice-6-v1.0, at a glance from early and late July, 2008.

This could be yet another opportunity for reluctant believers in weird gravitational physics to analyze the captured navigational data, plug it into their superior non-mainstream physics formulas, produce a more accurate analysis report that would support their ideas, and demonstrate to the world how much better off we'd be if only people would accept that the weird physics is the one true physics. Just saying they could, if they had the passion and time, maybe, and funding, if they really cared, and their ideas were actually sound and supportable, you know?

Also via PDS: MESSENGER SPICE KERNELS V1.0

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