2019-2020•Systems Engineering

GPS Next-Gen Control System

Modernizing satellite control with OCX, the next-generation GPS ground system

Systems EngineeringAerospaceSecurityEmbedded SystemsC++

Project Overview

Contributed to the development of the Next Generation Operational Control System (OCX) for GPS satellites, a critical modernization effort for the Global Positioning System. The project involves replacing the legacy ground control systems with a modern, secure architecture capable of controlling both legacy and new GPS satellites.

This massive aerospace engineering project represents one of the most complex software systems ever developed for the U.S. Department of Defense, with stringent requirements for security, reliability, and performance. The new control system enables advanced GPS functionality, improved accuracy, and enhanced cybersecurity protections.

GPS Triangulation Principle
GPS Triangulation Principle

Key Responsibilities

Satellite Telemetry Processing

Designed and implemented high-performance algorithms for processing and analyzing satellite telemetry data in real-time, ensuring accurate health monitoring of GPS constellation assets.

Command Verification Systems

Developed robust command verification protocols to ensure that all commands sent to GPS satellites are properly authorized, formatted, and validated before transmission.

System Integration Testing

Led integration testing efforts for multiple system components, designing comprehensive test scenarios to verify functionality across component boundaries and ensure end-to-end operation.

Security Architecture

Contributed to the design and implementation of the system's security architecture, ensuring compliance with DoD Information Assurance requirements and protecting against cyber threats.

GPS OCX System Overview
High-level architecture diagram of the GPS OCX system

Technical Architecture

Signal Structure

The GPS signal structure follows a complex modulation scheme that combines several components:
  • A: Signal amplitude
  • d(t): Navigation data bits
  • c(t): PRN spreading code
  • f_c: Carrier frequency
  • φ: Initial phase offset

Signal Processing

The Phase-Locked Loop (PLL) is fundamental to GPS signal tracking. The second-order PLL transfer function is given by:
The noise bandwidth of the PLL is characterized by:
  • ω_n: Natural frequency
  • ζ: Damping ratio
  • B_n: Noise bandwidth
My contributions to the signal processing component included optimizing the tracking algorithms to maintain lock under challenging conditions and implementing enhanced filters for precision timing.

Signal Processing Subsystem

  • Advanced PLL design for signal tracking
  • Multi-frequency reception (L1, L2, L5)
  • Enhanced anti-jamming capabilities
  • Robust carrier recovery algorithms

Navigation Message Processing

  • Error correction improvements
  • Enhanced CNAV message handling
  • Real-time integrity monitoring
  • Optimized update rate handling

Development Challenges

The development of the GPS OCX system faced several challenges, including:

  • Integrating multiple system components and ensuring end-to-end operation
  • Maintaining high levels of security and reliability
  • Handling the complexity of a large-scale aerospace project

Impact & Results

The GPS OCX system has significantly improved the capabilities of the Global Positioning System. It enables advanced GPS functionality, improved accuracy, and enhanced cybersecurity protections.

The system's impact is felt globally, as it serves billions of users worldwide, providing critical services for:

Aviation Navigation

Maritime Operations

Transportation & Logistics

Personal Navigation

Precise Timing Services

Financial Operations

The improvements in signal quality and additional civilian signals are particularly valuable for emerging applications like autonomous vehicles and precision agriculture.

Additional Resources

To learn more about the GPS OCX program, visit theofficial RTX page.