It's usually helpful to post the relevant part of the log along with your bug report. Although, the "invalid character" thing coupled with the fact you're using Linux tells me that it may be some IDs being capitalized in some parts of the mod, but not in others.
If that's the case, you can fix it on your end while the author returns to do it themselves. It's fairly easy and quick to do, especially in a simple ship pack like this.
Sorry about that, dunno why it slipped my mind. For the mod author here is the relevant snippet in the log:
1063 [Thread-3] INFO com.fs.graphics.TextureLoader - Cleaned buffer for texture graphics/fonts/orbitron12_0.png (using cast)
2886 [Thread-3] INFO com.fs.starfarer.launcher.ModManager - Error loading mod from [./mods/Asteroid ship pack 1.4b]
2886 [Thread-3] INFO com.fs.starfarer.launcher.ModManager - /home/whitestar60/Downloads/Starsector Mod Test/./mods/Asteroid ship pack 1.4b/mod_info.json
A JSONObject text must begin with '{' at 1 [character 2 line 1]
org.json.JSONException: /home/whitestar60/Downloads/Starsector Mod Test/./mods/Asteroid ship pack 1.4b/mod_info.json
A JSONObject text must begin with '{' at 1 [character 2 line 1]
at com.fs.starfarer.loading.LoadingUtils.return(Unknown Source)
at com.fs.starfarer.launcher.ModManager.loadModSpec(Unknown Source)
at com.fs.starfarer.launcher.ModManager.access$1(Unknown Source)
at com.fs.starfarer.launcher.ModManager$1.accept(Unknown Source)
at java.io.File.listFiles(Unknown Source)
at com.fs.starfarer.launcher.ModManager.updateList(Unknown Source)
at com.fs.starfarer.launcher.opengl.GLModPickerV2.<init>(Unknown Source)
at com.fs.starfarer.launcher.opengl.GLLauncher.showModsDialog(Unknown Source)
at com.fs.starfarer.launcher.opengl.GLLauncher.actionPerformed(Unknown Source)
at com.fs.starfarer.ui.o0O0OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO
OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO.buttonPressed(Unknown Source)
at com.fs.starfarer.ui.I.Ò00000(Unknown Source)
at com.fs.starfarer.ui.I.processInput(Unknown Source)
at com.fs.starfarer.ui.W.o00000(Unknown Source)
at com.fs.starfarer.BaseGameState.traverse(Unknown Source)
at com.fs.starfarer.launcher.opengl.GLLauncher$2.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
