OpenSOAP

Spacecraft Operations Analysis Package

What it is

OpenSOAP is a simulator for spacecraft in LEO, with a bent for early mission design, CONOPs exploration, and technical budget analysis. When you run it, it looks like this:

The following dynamical properties are simulated:

• orbit
• attitude
• onboard power
• onboard data
• onboard operating mode (e.g. charging, science, etc.)

None of the modeled dynamics are state-of-the-art fidelity, but they are good for first-order designs.

To run it

You will need an installation of Julia.

Clone the repository into a nice place on your computer, go into the directory, and launch the Julia REPL:

$ git clone https://github.com/thanasipantazides/OpenSOAP.git
$ cd OpenSOAP
$ julia --project=.

From the REPL, hit the ] key to go into the package manager. Your prompt should change, and you should run instantiate to install required packages.

julia> ]
(OpenSOAP) pkg> instantiate

You can hit backspace to get back to the julia> prompt from the package prompt.

To launch the interactive orbit viewer, use the example called both.jl:

julia> include("examples/both.jl")

This will probably precompile for a while. This happens the first time you run something from a new REPL session, but subsequent runs are much faster. Once that's done, run the main function:

julia> main()

You should see a display like the one further up this page. Press the h key for a help menu:

Actions in the monitor

Key	Action
h	show help
v	verbose
q	quit
e	change earth texture
f	show/hide Body frame
l	show/hide labels
p	change camera projection
k	perturb attitude (check control)
spacebar	play/pause
left/right	slower/faster

To exit, press q in the viewer. Maybe also ctrl-C in the REPL.

Details

A mode is an operational state of the spacecraft. The power consumption is determined by mode. Some modes have higher priority than others. A mode may have constraints which must be satisfied to run it. A mode may have one or more targets to look at. The rules are:

• A mode can run if any of its targets are visible.
• A mode can run if all of its constraints are satisfied.

A target is a position or reference direction for the spacecraft to look at. Maybe it is a groundstation. Maybe it is the sun. Maybe it is something else. Maybe it comes with some metadata.

A constraint is a restriction of mode based on spacecraft position. This is used to enforce things like `only

As it stands now, the waters are muddy: I use constrain the usage of the B-field pointing mode, but there are no explicit constraints on groundstation communication, that info is rolled into the groundstation visibility cone. So the interface is not very pure. But I hope to change that.