OPENSATKIT (OSK):
UNDERSTANDING SATELLITE FLIGHT SOFTWARE

Software controls the entire existence of satellites.

You cannot download real satellite firmware. You cannot experiment on an active spacecraft. You cannot “try things and see what happens” once something is in orbit.

Space systems are inaccessible, expensive, and unforgiving by design.

Mistakes in space aren’t educational. They’re permanent.

That learning gap is exactly why OpenSatKit exists.

OpenSatKit (OSK) is an open-source platform built to run real satellite-style flight software on normal computers.

It is built around NASA’s core Flight System (cFS), the same architectural foundation used in real missions.

OSK does not simulate concepts — it runs real structured flight software.

It doesn’t teach you about satellites. It places you inside their software architecture.

Most people misunderstand OSK’s value. It’s not just about “running satellite code.”

OSK solves three problems that are otherwise almost impossible for beginners.

On real satellites, you cannot attach a debugger. In OSK, you can.

Satellite flight software is structured, not monolithic.

At the center is the core Flight Executive (cFE), which handles scheduling and coordination.

On top of that are applications (apps), each responsible for specific tasks.

Apps communicate over a software bus using structured messages.

From a security perspective, controlling that message bus can influence system behavior.

OSK follows the same architecture used in real missions.

It includes a cFS-based core, multiple flight style applications, and a full command-and-telemetry pipeline.

When you send a command, it is parsed, routed, validated, and executed just like in actual missions.

This is real software architecture not simplified demo logic.

OSK does not focus on security by default — and that’s important.

Many real satellites prioritize functionality first and assume trusted environments.

OSK shows how design assumptions become attack surfaces.

It teaches why satellites are hackable not just how.

OSK does not automatically make systems secure.

It does not protect you from attacks.

It does not magically teach hacking.

It is a learning environment.

If you assume something is secure just because it’s based on NASA software, you’ve already failed at security thinking. Security is designed intentionally. It’s never inherited automatically.

At this point, you should have a solid mental model of what satellite flight software actually looks like in practice, what OpenSatKit represents beyond just “another simulator,” and why it’s the right environment to start learning how real spacecraft are built, operated, and eventually tested from a security perspective.

So far, everything has been software-only and conceptual.

That changes next when this moves from simulations to real hardware. And that’s where things start getting interesting.