Ground Control Readied for GPS III

September 30, 2013  - By

Raytheon Company reached several milestones recently in its development of the GPS Next -Generation Operational Control System (GPS OCX).  Lockheed Martin’s GPS III Non-flight Satellite Testbed (GNST) — a full-sized, functional satellite prototype currently residing at Cape Canaveral Air Force Station — successfully established remote connectivity and communicated with OCX during pre-flight tests.

GNST proved that it could connect with and receive commands from Raytheon’s Launch and Check Out System (LCS), a part of OCX that supports the satellite and mitigates risks prior to launch. The GNST received commands from Lockheed Martin’s Launch and Checkout Capability (LCC) node in Newtown, Pennsylvania via the OCX servers at Raytheon’s facility in Aurora, Colorado; the system then returned satellite telemetry to the control station. The tests mirror launch and early orbit testing planned for all flight vehicles.

“While we have connected OCX with ground-based simulators before, these tests were the first time that OCX and a GPS III satellite have actually communicated,” said Keoki Jackson, vice president for Lockheed Martin’s Navigation Systems mission area.

Ahead of Schedule. Raytheon received Interim Authorization to Test (IATT) security certification from the U.S. Air Force for OCX LCS four months ahead of schedule. The company received a one-year certification with no liens, meaning the government does not require any changes.

“Typically, IATT certification is given for six-month increments,” said Matthew Gilligan, Raytheon’s GPS OCX program manager and a vice president in Raytheon’s Intelligence, Information, and Services business. “The LCS one-year accreditation speaks to the quality of the information assurance design and threat protection.” The IATT not only includes the LCS, but also Lockheed Martin’s GPS III satellite support systems, Exercise and Rehearsal Training Tool, and Upload Generation Tool.

OCX is being developed in two blocks. There are seven iterations in Block 1 and one in Block 2. LCS is the fifth Iteration of Block 1; it successfully completed Critical Design Review in June 2013.

Early Orbit Exercises. Lockheed Martin and Raytheon also completed the third of five planned launch and early orbit exercises to demonstrate launch readiness of GPS III and OCX.

Exercise 3 demonstrated space-ground communications; first acquisition and transfer orbit sequences; orbit-raising maneuver planning and execution; and basic anomaly detection and resolution capabilities. In addition, the industry and Air Force GPS Directorate teams jointly executed mission planning activities, such as orbit determination and the generation of upload command files.

Two additional readiness exercises and six 24/7 launch rehearsals are planned before launch of the first GPS III satellite. The first flight GPS III space vehicle (SV-01) is expected to be available for launch in 2014, and launched by the U.S. Air Force in 2015.

Exelis Encryptors. Exelis delivered the first three of a planned 14 ground-based encryptors to Raytheon Company for OCX. Designed to automatically code and decode GPS signals, encryptors facilitate the exchange of user information by securely transmitting navigation payload data between the OCX ground station and the orbiting constellation of satellites.

Delivery followed successful thermal, electromagnetic interference and security verification testing. Exelis provides critical elements of software in the navigation processing subsystem that will enable controllers to better understand the exact position of GPS satellites. This helps ensure accurate navigation information is securely broadcast to users. In addition to encryptors, Exelis is building high-precision receivers for use in GPS ground monitoring stations and satellite signal simulators for testing purposes.

Exelis is also on contract with Lockheed Martin to provide the payloads for the GPS III satellites.

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About the Author:

Alan Cameron is editor-in-chief and publisher of GPS World magazine, where he has worked since 2000. He also writes the monthly GNSS Design & Test e-Newsletter and the Wide Awake blog.

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