Space operations units assume control of new GPS satellite

by Staff Sgt. Don Branum, 50th Space Wing Public Affairs

SCHRIEVER AIR FORCE BASE, Colo. (AFNS) -- The 2nd and 19th Space Operations Squadrons here assumed control of the Air Force's newest GPS satellite shortly after its launch from Cape Canaveral Air Force Station, Fla., March 24.

The satellite, named GPS IIR-20(M), is the 34th satellite in the GPS constellation, which provides precise navigation and timing data to military and civilian customers around the world.

Space operators with 2nd SOPS and 19th SOPS took over early-orbit operations for the new satellite 68 minutes after launch, said Lt. Col. Douglas Schiess, 2nd SOPS operations officer.

"We're getting it ready to provide its combat effects to warfighters as soon as possible," Colonel Schiess said. "It's a great team effort by 2nd SOPS and 19th SOPS."

GPS IIR-M satellites provide combat capability for military applications such as Joint Direct Attack Munitions and handheld, vehicle-based and aircraft navigation aids. Civilian applications include ATMs, bank and stock market transactions and power grid management. Currently, 31 of the 34 GPS satellites in orbit transmit navigation and timing signals to users.

A Delta II launch vehicle carried GPS IIR-20(M) into low-Earth orbit. From there, a booster will lift the satellite into its operational orbit approximately 12,500 miles above the Earth.

The launch was delayed from June 2008 due to a fault in the 40-second timer that triggers separation of the third-stage booster from the satellite. Air Force and contractor engineers resolved the problems, said Lt. Col. John Wagner, mission director for the Launch and Range Systems Wing at Los Angeles Air Force Base, Calif.
The IIR-M spacecraft includes several upgrades from the earlier Block IIR model. A modernized antenna panel provides a stronger signal that is more resistant to GPS jamming and stronger encryption for military signals. It also includes two military signals and one civil signal beyond those transmitted by earlier GPS satellites.

Other Air Force Space Command agencies that supported the launch include the 22nd Space Operations Squadron here, the 45th Space Wing at Patrick AFB, Fla., and the Space and Missile Systems Center at Los Angeles AFB. Contractor partners included United Launch Alliance, the Aerospace Corporation and Lockheed Martin Corporation.

GPS upgrade will require 'complicated choreography'

by Staff Sgt. Don Branum
50th Space Wing Public Affairs

1/31/2007 - SCHRIEVER AIR FORCE BASE, Colo. -- Space professionals with the 2nd Space Operations Squadron have a daunting task ahead of them this summer: replacing the command-and-control system for GPS without any loss of "on-time, on-target" service to military or civil users.

The new system, called the Architecture Evolution Plan, will provide 2nd SOPS with the tools to command upcoming generations of GPS satellites, said 1st Lt. Robert Kaegy, who is assigned to 2nd SOPS' AEP migration program.

The upgrade consists of hardware and software to replace the original command-and-control system, which has operated since GPS' inception, said Capt. Brian O'Connell, GPS Modernization Flight commander.

"The system will be capable of commanding and controlling the GPS constellation much as we do today, but planned software drops will also allow us to control the new II-F block of satellites when they're ready to fly," Captain O'Connell said.

The system also lets operators link directly into the Air Force Satellite Control Network, more than doubling the number of sites they can use for satellite command and control.

"This provides us with a greater capability to command our satellites, reduce commanding visibility gaps and potentially reduce our anomaly response time," Captain O'Connell said.

The transition process won't be as simple as turning off one system and turning on another, however.

"The core of the system is something called the Kalman Filter," Captain O'Connell said. "This system takes in data from our monitoring stations worldwide and uses this data to predict where each of the satellites will be in the future. This model is constantly updated, and the model in turn is uploaded to each vehicle."

The Kalman Filter makes sure each GPS satellite is broadcasting a precise navigation and timing signal. The new system will have a new Kalman Filter--which means the system will have to be carefully aligned with the current system's Kalman Filter.

"If we didn't do this, and we began uploading satellites with data from the AEP Kalman Filter, those vehicles would tell you that you're in a different place than the vehicles that still contain 'legacy' uploads," Captain O'Connell explained. "Clearly you wouldn't want your GPS receiver trying to tell you that you're in two different places."

In addition, each GPS ground antenna and monitoring station must migrate to the new system.

"This is a complicated piece of choreography," the captain said.

The process of converting the constellation and ground system takes about five days.