Match Your Orbiter Sim Live to the Shuttle STS-118 Mission

The Orbiter Space Flight Simulator is a piece of completely free software by the very generous Martin Schweiger.

Apart from being able to simulate all sorts of launches and missions both historical and future, even fantasy, my interest at the moment is in it’s ability to make the Shuttle and ISS missions more understandable. With the right tools and add ons it’s possible to follow along a mission “side by side”, right from launch to landing. This is an excellent way to learn about the missions, as things that would normally be confusing immediately become obvious with a simulation to check.

orbiter_live.jpg

nasatv_2007-08-11_14-51-11-87.jpg

You can see that the view is close to the one showing in mission control.

orbiter_live_tracking1.jpg

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The telemetry also matches the actual mission. You can see here that the ISS, visible on the NASA TV feed over the Pacific, just coming into the left hand side of the display, matches the virtual tracking simulation.

How is this achieved ?

Realword TLE‘s —> Orbiter Scenario Config File.

1. Use eq_to_ecl to convert elements into a format suitable for Orbiter.

2. Convert elements available at http://celestrak.com/NORAD/elements/

3. Only copy 2 lines of elements, plus the title !

4. Remove RPOS & RVEL entries from the scenario file and add the TLE. Copy it in without the title.

5. Put in the Julian Date using this convertor … http://aa.usno.navy.mil/data/docs/JulianDate.html.

6. Make sure you put in a Julian Date ( JD ) not a Modified Julian Date ( MJD ) ! The Orbiter date prefix should equal JD.

7. In the Scenario file that I am using I have STS-118 docked to the ISS (just add it to the dock list). Don’t remove the STS-118 entry though, it has all the status of the vessel in there. You don’t have to remove things like RPOS right now as it does’nt seem to effect anything, as long as the craft is docked.

Use other Scenario files to check things if you are unsure. One thing I’m not sure about is the ISS rotation ( AROT) setting. This is the only thing that does not match in my simulation. I’ll add something here when I find this out, or leave me a comment.

Just as an aside, there’s a way to update the Orbiter Scenario file automatically. Here’s something I’m working on. I’m using Lynx (for my OS it’s the Win32 version ), and Sed (I’m using the Dos version ).

This command line will give only the element lines you need (between the two search terms ISS and SOYUZ).

> lynx -dump http://celestrak.com/NORAD/elements/stations.txt | sed -n ‘/ISS/,/SOYUZ/p’ > file_to_give_to_eq_to_ecl.txt

I just need to write something that will edit the Orbiter Scenario file.

On another Blog I will discuss how to do this for other missions and solar system bodies, like the Cassini mission. I have not done this yet, but I think it involves taking elements from the Horizons project. I also need to cover how to do a live launch using the PEG Autopilot add on.

DJ Barney

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