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ULA set to complete Block IIF GPS constellation

The Air Force's twelfth Global Positioning System (GPS) IIF satellite is encapsulated inside an Atlas V 4-meter payload fairing.

The U.S. Air Force’s twelfth Global Positioning System (GPS) IIF satellite about to be encapsulated inside an Atlas V 4-meter payload fairing. Photo Credit: ULA

CAPE CANAVERAL, Fla. — For United Launch Alliance’s (ULA) first mission of 2016, the firm is also looking to conduct their 60th operational GPS launch mission. The Colorado-based company will use the 401 configuration of their Atlas V booster to deliver the 12th GPS IIF satellite to orbit on Feb. 5, 2016. This mission should mark the final installment of the Block IIF GPS satellites to be sent aloft for the United States Air Force.

The Air Force's twelfth Global Positioning System (GPS) IIF satellite is encapsulated inside an Atlas V 4-meter payload fairing.

The U.S. Air Force’s twelfth Global Positioning System (GPS) IIF satellite is encapsulated inside an Atlas V 4-meter payload fairing. Photo Credit: ULA

The launch window for the mission will begin at 8:38 a.m. EST (13:28 GMT) and remain open for nineteen minutes. Currently, there is a 40 percent chance that weather conditions will be favorable for the launch.

The payload for this mission measures some 251 cm by 206 cm by 180 cm and weighs 1,633 kg. The GPS IIF satellites were designed to replace the Navstar satellites that were launched into orbit from 1990 to 1997.

These new satellites should have a lifespan of about 12 years and will be able to operate autonomously for 60-day periods. In many ways, Friday’s launch has been in the making for a long time.

“GPS II processing at the Cape started while the Shuttle program was here, when the Air Force was still launching Delta IIs and the Cold War was still going on,” said Capt. Trung Nguyen, field program manager for GPS-IIF at the 45th Launch Support Squadron. “The GPS processing program has been a staple at the Cape. There are engineers and technicians here who worked on the first GPS II block satellite. Some have launched over 20 satellites. Some have been with the program since 1989.”

GPS IIF-12 is slated to be placed in a semi-synchronous circular orbit which will allow the satellite to orbit the Earth in slightly under twelve hours.

This satellite would be the newest edition to the Navstar Global Positioning System constellation that consists of twenty-four satellites total, with the twelve satellites from the IIF block eventually replacing the original twenty-four satellites. While the older Block IIFs might appear similar or the same as early additions to the fleet – each satellite has its own unique personality.

“Just because it looks like the final one, it is not exactly the same; each spacecraft is built by hand and thus is a little different from every previous unit,” said Scott Chappie, lead Air Force Responsible Engineer for GPS IIF-12.

These spacecraft orbit the Earth on six different planes with a minimum of four satellites per plane and are all controlled from the 50th Space Wing located at Schriever Air Force Base in Colorado.

Even though these spacecraft are used and paid for by the United States Air Force, the contractor, and developer of the Block IIFs is Boeing. Boeing designed these satellites to be precise and accurate regarding their perception of time, velocity, and three-dimensional position.

The satellites use atomic clocks to transmit digital radio signals in exact time, and they are capable of receiving signals in order to calculate its own time, location, and velocity. These signals are so accurate that they can measure up to a micro-second of time which is which allows them to be efficient enough for multiple purposes.

GPS IIF-12 lift and mate to Atlas V booster at Pad 41.

The GPS IIF-12 satellite, encapsulated inside a 4-meter diameter payload fairing, is mated to an Atlas V booster inside the Vertical Integration Facility or VIF at Space Launch Complex-41. Photo Credit: ULA

The GPS IIF satellites are used by the United States military, for commercial purposes, and are specifically developed for use with aircraft, land vehicles, ships, as well as personal devices.

The GPS IIF block contains updates that were incorporated into them, specifically for commercial use. The Block IIF satellites will have a signal accuracy that is two times greater than the original system.

These new satellites also have new L5 legacy signals. The L5 signals are used for civilian broadcasting for safety, rescue, and other purposes. The spacecrafts’ capabilities are superior to their predecessors because of their enhanced performance, higher transmitting power, and a wider broadband.

GPS Block IIF also has improved M-code signals for the military. M-code signals are used through the L1 and L2 frequencies to allow a large and global communication range within the United States military. The IIF satellites were designed to prevent the jamming of M-code signals within hostile environments. Along with the ability to transmit strong signals, these satellites also have the capability to be reprogrammed on-orbit which will allow uploads for improved system operation.

For this mission, ULA’s Atlas V 401 rocket will be used to deliver the payload into orbit. This version of the Atlas V booster has been used to deliver five of the GPS IIF satellites (4, 7, 8, 10, and 11) in the past while the other six satellites were delivered into orbit using ULA’s Delta IV Medium+(4.2) boosters.

Out of the Atlas V rocket family, the 401 model is the smallest launch vehicle due to the lack of solid rocket boosters and its smaller payload fairing. The rocket has more than enough capability for this light payload mission, however. The Atlas V utilizes a Russian-built RD-180 engine in its first stage. The RD-180 engine consumes liquid oxygen and highly purified kerosene (RP-1) for fuel and produces approximately 860,200 lbf (3,826.4 kN) of thrust at sea level.

In terms of the second stage, it is powered by the Centaur upper stage with a single RL-10C engine. This engine if fueled by liquid hydrogen and liquid oxygen, and creates some 22,900 lbf (101.9 kN) of thrust. This will be the last launch of GPS IIF satellites for the United States Air Force, and should secure the full range of navigational improvements these new satellites will provide.

“That [spacecraft] is going to touch the lives of hundreds of millions if not billions of people on a daily basis,” Chappie said. “It not only vastly increases our military’s position, navigation and timing capabilities all over the world, but so many people and business activities have also come to depend on GPS. This is a [stunningly successful] program – the way the Air Force conceived it and the way they continue to manage and implement the program.”

Video Courtesy of United Launch Alliance


Amoree Hodges Florida Institute of Technology image posted on SpaceFlight InsiderAmoree Hodges is a SpaceFlight Insider Launch Correspondence intern from the Florida Institute of Technology, where she is currently working on obtaining her Bachelors degree in Astronomy & Astrophysics. Amoree loves telescopes and all things that are related to space, and NASA.

Hodges is planning a career in public science communications, and will be using her internship with SpaceFlight Insider to get great science and engineering communications experience while she works on completing her studies. In her capacity as a volunteer, Ms. Hodges has not only produced written content for SpaceFlight Insider but has also served as the co-host for one of our live webcasts.



Founded at the very dawn of the Space Race in 1958, the Florida Institute of Technology is the only independent, technological university located in the Southeast. Times Higher Education ranks Florida Tech in the Top 200 Universities in the World. The university has been designated a Tier One Best National University in U.S. News & World Report, and is one of just nine schools in Florida lauded by the 2014 Fiske Guide to Colleges. The university offers undergraduate, graduate and doctoral programs. Fields of study include science, engineering, aeronautics, business, humanities, mathematics, psychology, communication and education.

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