How GPS III is performing in orbit

May 13, 2019  - By

Plus an update on GPS III satellites in production

Editor Alan Cameron talked with Johnathon Caldwell, Lockheed Martin’s vice president of navigation systems.

Tell us about the on-orbit performance of the GPS III SV01, launched in December.

On Jan. 8 we began broadcasting navigation data across all signal chains, and the satellite has been in checkout mode since then. According to all the reports I get from various independent agencies, the vehicle has been performing outstanding, and the payload performance has been exceeding expectations.

We’ve been evaluating in depth how the payload performs, including independent agencies assessing the signal quality. Later this fall we’ll transition satellite ground control from the OCX Block 0 ground control system installed at Lockheed Martin’s Waterton Launch & Check Out facility over to the GPS Operational Control Segment (OCS) the 2SOPS is using now, and we’ll really see the performance improving from where it is today.

“We’re certainly at the top end of what
we thought we might be able to achieve
in terms of signal accuracy.”

The satellite is doing what everybody had hoped. There’s always great anticipation when a new system goes up. It’s actually been a very smooth on-orbit test campaign. We’re wrapping up on the early side; we’ll be ready to transition into the OCS this fall.

This past December we completed a major Architecture Evolution Plan (AEP) 7.5 OCS upgrade. This included both hardware and software upgrades to the legacy control system, and the Contingency Operations (COps) upgrade is coming later this fall. This is the software upgrade that will let OCS fly this first GPS III satellite and let the Air Force take advantage of great new capabilities. We will deliver the upgrade in May; it will get packaged up and delivered into the OCS in the fall. SV01 will then move from Lockheed Martin’s Waterton launch and checkout facility control to Air Force 2SOPS control and join the constellation on the OCS.

A GPS satellite doesn’t do its mission by itself. It takes an entire system to run. You’re always monitoring signal quality and tweaking things to get the optimal performance. Today, we’re flying SV01 by itself. The OCS and the 2SOPS crew will start flying it like they do the others, giving it the daily update and looking at the signal quality and maximizing the performance.

We’re certainly at the top end of what we thought we might be able to achieve in terms of signal accuracy.

And GPS III SV02 has shipped to the Cape.

We’ve wrapped up functional testing; it’s in great shape. We’re now in a quiet period prior to final review leading up to fueling decisions in May for a planned July launch.

Using the Delta IVb rocket for SV02 offers a good opportunity to demonstrate the wide range of launch vehicles that GPS III is capable of. The satellite has great compatibility across platforms, a flexibility that’s a benefit for the Air Force.

The factory was also getting pretty full so it was great to ship out SV02. When it gets to the end of the line and ready to go, you want to get it out and have it doing the mission it’s designed to do.

GPS III production line. (Photo: Lockheed Martin)

GPS III production line. (Photo: Lockheed Martin)

How about the production status of SVs 03 through 10 on the factory line?

SV03 has gone through complete environmental tests and is ready for delivery to the Air Force later this spring. SV04 is in final environmental test and will deliver later this year. SV05 is in thermal vacuum (TVAC) testing now, and doing an outstanding job. TVAC is the hardest test we go through, and it’s as if it’s flying in the environment of space. It’s the stress test. SV06 is put together, and now in its initial functional testing.

There aren’t many production lines of this size of large satellites. It’s very impressive. As you look down the line, our high bay is modeled after the best of production lines. Hardware and avionics and power systems are coming in as piece parts, getting built in. As you go down the bay, the vehicles are getting more and more complete. Now on the front end of the line we’ve got SV07 and SV08 starting. SV09 will begin later this summer, and not long after we hope to open up space for the 10th vehicle.

Last words: Progress so far on GPS IIIF?

We’re now in the full design campaign for the follow-on satellites that will lead to critical design review, the capstone of the process. The CDR will wrap up in February 2020.

About the Author: Alan Cameron

Alan Cameron is the former editor-at-large of GPS World magazine.