It stands for Tactical Arms and Security Council - so, as you can guess, their business is military intelligence.

[There's a thoughtful pause before he adds:]

I owe their engineers my life.

[After the accident, it had meant all the world to have been approached during his rehabilitation leave and to have gotten that second chance at life. And he'd been all too glad to set aside lingering personal problems to take on the perilous rescue mission they'd assigned him. God, it had been good to move again, to feel independent and free and stronger than he'd ever been.]