using SwingBy to create trajectorys for Celestia

[ncc1701d]

In a message posted somewhere else in the forums, it was mentioned
"One utility which can produce trajectory files that only have to be modified slightly for use with Celestia is SwingBy by JAQAR."
It outputs .jsb files.
Is there a tutorial anywhere covering how to convert these .jsbs file types to xyz files?

thanks

[selden]

SwingBy's SB.tf trajectory file is what you want, not its .jsb file.

run the Astrodynamics package
select the menu item Tools/SBC
select SwingBy's menu item Options/Write Trajectory Files of best solutions
use the various tabs to specify appropriate start, flyby and destination parameters
select File/Run-stop optimization

copy (or rename) and edit SB.tf to have filetype xyz or xyzv.
Delete the header and the last three (velocity) columns if you're creating an xyz file.
Delete just the header if you want an xyzv file (requires Celestia to have been built from current svn code).

In your SSC file specify something like

Code: Select all

       SampledOrbit "mytrajectory.xyz"
       OrbitFrame { EquatorJ2000 { Center "Sol" } }

since SwingBy's trajectories are referenced to the Earth's equator, not to Celestia's default ecliptic coordinate system.

[chris]

Selden,

Do you know what the units for velocity are in JAQAR's tf files? Celestia uses km/s; I'm hoping that's enough of a standard that I don't have to add a Units property to SampledTrajectory.

--Chris

[selden]

Chris,

Yes, they're km/sec. Here's an example.

Code: Select all

                    ORBIMAT TRAJECTORY FILE
                    =======================

                    CENTRAL BODY:   10

          REFERENCE FRAME: MEAN EARTH EQUATOR 2000

       MJD2000            X(KM)            Y(KM)           Z(KM)           VX(KM/S)         VY(KM/S)         VZ(KM/S)
--------------------------------------------------------------------------------------------------------------------------
  3573.5000000000000 139985958.9810613100 47478540.8982628435 20576627.9800624177   -11.9776447748    28.2987297786    12.1960554125
  3576.7500000000000 136403938.4362850190 55345876.5602022856 23967075.4436893463   -13.5291452049    27.7215127817    11.9460041123
  3580.0000000000000 132391848.7341325581 63038707.1216657534 27281954.9207083918   -15.0394433513    27.0563398945    11.6580488340


I'd forgotten that they use MJD, so that'll require some modification.