Millennium’s GNC system protects itself, the vehicle and the mission

Every satellite’s mission critically depends on the Guidance,Navigation and Control, or GNC, system. GNC keeps the satellite powered, oriented and on the right track.  

“Millennium builds and codes its own high-performance, cost-efficient GNC hardware and software for a wide array of spacecraft and missions,” said Andrew Walsh, principal Guidance, Navigation & Control engineer at Millennium Space Systems, a Boeing Company. “And our GNC system works. We’ve had 100% mission success to date.”

Part of the team’s success is its inclusion and participation from the start of a satellite’s design.

“Early on, we determine what kind of hardware the GNC needs, such as star trackers to orient the spacecraft, reaction wheels for attitude control, thrusters for orbit maintenance and the required capabilities of the components,”said Walsh. “One of our advantages is that we build the majority of the necessary components in-house.”

And many of these components are built from the latest commercial tech.

“Building our GNC hardware in-house with space-qualified commercial parts not only saves our customers time and money, and we can also integrate the components seamlessly with our GNC software,” said Walsh.

Once hardware needs are set, engineers tailor the software to each component and to the overall system. Millennium satellites use a common GNC software platform configurable to specific missions.

“We don’t have to reinvent the wheel over and over, we simply configure the GNC algorithms to support the selected components and import the updated software to the vehicle,” said Reid Reynolds, principal Guidance Navigation & Control engineer. “Our cutting-edge estimation and control algorithms ensure stability and global convergence.”

Thanks to these algorithms, Millennium’s systems reliably meet mission objectives under all operating conditions.

For imaging and intelligence, surveillance and reconnaissance missions, GNC points the payload at its objective. For missile warning and tracking missions, GNC keeps the payload pointing at Earth and, should it detect a missile, keeps track of the threat. Other times, the system points the satellite to another for communication.

“Our missions vary widely, from national security to scientific explorations that probe the boundaries of human knowledge,” said Reynolds.“For some missions, we use single or dual-spin stabilization to provide inertial stiffness and maintain a steady orientation while collecting valuable scientific measurements.”

For all missions, GNC ensures solar arrays get enough sun to power instruments and maintain the thermal environment.

“Unintended rotation of an Earth-observing satellite by fractional degrees in space equals miles on Earth,” said Reynolds. “A vehicle that cannot maintain its orbit may not be able to perform its mission or may interfere with other spacecraft on orbit. Plus, a vehicle that cannot maintain power dies.”

Operators who issue commands on the ground need precise GNC systems to maintain orbital position, point various imaging and communications instruments at their objectives, and receive accurate, timely data.

“We build systems that can monitor and maintain themselves, safeguarding the vehicle and the mission,” said Walsh. “Our GNC responds to the plan set by the ground team, but it also autonomously monitors the entire system, checking for anomalies and taking corrective action when needed.”

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