Celestia Forums

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messenger.ssc et messenger.XYZ et messenger.3ds


demande merci rechercher

Let's wish this mission every success, it's great that they are going back to Mercury after a gap of over 30 years.

It seems that they are taking a very similar approach to the Mariner 10 mission, using the Earth and Venus for gravity assists, before reaching Mercury for 3 fly-bys in 2008/2009.
Only this time they will eventually place the spacecraft in orbit around the planet....in 2011.

At least most of the planet will have been photographed by then.

symaski62 wrote:
messenger.ssc et messenger.XYZ et messenger.3ds

demande merci rechercher

Maybe a 3ds model could be a possibility

I don't get why it takes 7 years to get to Mercury... can they not send it there direct instead of via Venus and Earth a zillion times?!

Evil Dr Ganymede wrote:I don't get why it takes 7 years to get to Mercury... can they not send it there direct instead of via Venus and Earth a zillion times?!

I don't think that getting it to Mercury is the problem. For that, a direct route probably would suffice. The real issue is that Messenger is an orbiter, and in order to enter orbit around a planet without burning a massive amount of fuel, a spacecraft needs to have a heliocentric velocity similar to the planet's. This is no easy feat given that Mercury circles the Sun much faster than Earth.

--Chris

Delta II "messenger"

until Launch
||
\/
paris => 2h20 3/8/2004

USA => 21h20 2/8/2004

I know!!

je sais!!

http://scorpio711.chez.tiscali.fr/mercure/messenger.htm

http://www.spaceref.com/news/viewsr.html?pid=13187

Is is possible to make a xyz-file out of the given data.
How would such a sampling method look like - I'm not familiar with xyz data files.

maxim

A preliminary trajectory is available from Horizons:



Somebody just needs to download it and convert it to Celestia's format.

Is Jack around?

ok bon!!

Seems that I'm not sure what to download and how to convert it.
My guesses are

Selecting: vectors
Coord. Center: geo
Ref. Plane: ecliptic
Starting and Ending are obvious, and sampling interval is one day.

Now the first three of the result are xyz coordinates. And now?
It's only that I'm simply not an expert in space navigation.

maxim.

Maxim,

You should consider using the e'mail template that is available at http://www.lepp.cornell.edu/~seb/celestia/horizons-template.txt
to get the trajectory mailed to you.

You then need to edit the returned file so that each line consists of four numeric values:

juliandate xvalue yvalue zvalue

When I've done such things in the past, I've usually defined a macro-command within my favorite text editor to reformat the data.

selden,

IF I would know that my above guesses are good, and IF the resulting xyz data would be the data that celestia expects, the rest would be quite easy.

It`s only that I don't know if what I get is what I need.

maxim

I've a little suite of programs I use to process and resample this stuff to minimize the file size (points closer together during flybys, farther apart during interplanetary coasting) - if people are prepared to wait for a couple of days until I have the time to get into it, I should be able to produce a fairly compact xyz trajectory.

Grant

Fine with the xyz trajectory, but what about the model ?

I still would like to learn how to do it myself.

maxim

Maxim,

I'm sorry, but I don't know how to be very much clearer than what I wrote above.

Celestia wants a file containing a list of locations in space time. Each line must contain the julian date, x, y, and z values in floating point format. For bodies orbiting the sun, the corrdinates need to be heliocentric and in the ecliptic coordinate system.

1. You need to ask Horizons to send you the xyz information in Horizon's format. You can use my e'mail template, which requests heliocentric, ecliptic coordinates. Also, Horizons has limits on how big a message it'll send, so you may need to ask for several different segments of the trajectory.

Horizon's format is very simple. Each entry is on two lines: one line with the Julian time on it in two formats (one floating point, one textual) and one line with the three floating point values for x, y and z.

2. You need to reformat that file into Celestia's format, which is very simple. Each line must have the four floating point values (separated by spaces) for the Julian date, x, y and z.

That's all there is to it.

The Messenger trajectory is now available for download - thanks as ever to Selden for hosting it. In the absence of a Messenger model, I've used the Celestia distribution Galileo model as a placeholder:
http://www.lepp.cornell.edu/~seb/celestia/hutchison/messenger.html

If you haven't done so already, you might care to replace Celestia's current orange Mercury texture with a grey-brown revision I've committed to the CVS tree recently:
medres
lores
lok-mask

Grant

selden wrote:... the corrdinates need to be heliocentric and in the ecliptic coordinate system ...

That was the information I wanted to know. It's simple if you're familiar, but you stay very uncertain if not.

maxim

merci beaucoup.

apr?s messenger.3ds quand? bient?t.


cool
-------------------------------------------

thank you very much.

after messenger.3ds when? soon.

cool

symaski62 wrote:

http://scorpio711.chez.tiscali.fr/mercure/messenger.htm

http://www.spaceref.com/news/viewsr.html?pid=13187

charge XYZ nouveau !!!!

3/10/2004 6h26 GMT launch!

merci