GPS Block IIF - AbsoluteAstronomy.com

GPS Block IIF, or GPS IIF is an interim class of GPS satellite

GPS satellite

A GPS satellite is a satellite used by the NAVSTAR Global Positioning System . The first satellite in the system, Navstar 1, was launched February 22, 1978. The GPS satellite constellation is operated by the 50th Space Wing of the United States Air Force....

, which will be used to keep the Navstar Global Positioning System

Global Positioning System

The Global Positioning System is a space-based global navigation satellite system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites...

operational until the Block IIIA

GPS modernization

The United States' Global Positioning System , having reached Fully Operational Capability on July 17, 1995, has completed its original design goals. However, additional advances in technology and new demands on the existing system led to the effort to modernize the GPS system. Announcements from...

satellites become operational. They are being built by Boeing

Boeing

The Boeing Company is an American multinational aerospace and defense corporation, founded in 1916 by William E. Boeing in Seattle, Washington. Boeing has expanded over the years, merging with McDonnell Douglas in 1997. Boeing Corporate headquarters has been in Chicago, Illinois since 2001...

, and will be operated by the United States Air Force

United States Air Force

The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...

following their launch by United Launch Alliance

United Launch Alliance

United Launch Alliance is a joint venture of Lockheed Martin and Boeing. ULA was formed in December 2006 by combining the teams at these companies which provide spacecraft launch services to the government of the United States. U.S...

, using Evolved Expendable Launch Vehicles. They will be the final component of the Block II GPS constellation to be launched.
The spacecraft have a mass of 1630 kilograms (3,593.5 lb) and a design life of 12 years. Like earlier GPS satellites, Block IIF spacecraft operate in semi-synchronous

Semi-synchronous Orbit

Semi-Synchronous Orbit: An orbit with approximately a 12-hour period. A circular Semi-Synchronous Orbit is at an altitude of approximately 20,200 km....

medium Earth orbit

Medium Earth Orbit

Medium Earth orbit , sometimes called intermediate circular orbit , is the region of space around the Earth above low Earth orbit and below geostationary orbit ....

s, with an altitude of approximately 20460 kilometres (12,713.3 mi), and an orbital period

Orbital period

The orbital period is the time taken for a given object to make one complete orbit about another object.When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars.There are several kinds of...

of twelve hours.

The satellites will replace the GPS Block IIA satellites which were launched between 1990 and 1997 and were designed to last 7.5 years. Eleven of those satellites are still in use, including four that were launched in 1992.

Because the Evolved Expendable Launch Vehicles are more powerful than the Delta II

Delta II

Delta II was an American space launch system, originally designed and built by McDonnell Douglas. Delta II is part of the Delta rocket family and was in service from 1989 until November 1, 2011...

, which was used to orbit earlier Block II GPS satellites, they can place the satellites directly into their operational orbits. As a result, Block IIF satellites do not carry apogee motors. The original contract for Block IIF, signed in 1996, called for 33 spacecraft. This was later reduced to 12, and programme delays and technical problems pushed the first launch from 2006 to 2010.

New characteristics

Broadcasting L5 "safety of life" navigation signal demonstrated on USA-203
Broadcasting a new M-code
GPS signals
The satellites of the Global Positioning System broadcast radio signals to enable GPS receivers on or near the Earth's surface to determine location and synchronized time. The GPS system itself is operated by the U.S...

signal
Doubling in the predicted accuracy
Better resistance to jamming
Radio jamming
Radio jamming is the transmission of radio signals that disrupt communications by decreasing the signal to noise ratio. Unintentional jamming occurs when an operator transmits on a busy frequency without first checking whether it is in use, or without being able to hear stations using the frequency...
Reprogrammable processors that can receive software uploads
The first GPS satellites not to have hardware Selective Availability installed which could degrade civilian accuracy

Launches

The first GPS IIF satellite, Space Vehicle 1, was launched by a Delta IV-M+(4,2) rocket at 03:00 UTC on 28 May 2010. The launch took place from Space Launch Complex 37B at the Cape Canaveral Air Force Station

Cape Canaveral Air Force Station

Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...

. It was the 61st U.S. GPS satellite to launch and the 50th GPS launched on a Delta.

The second GPS IIF satellite, GPS IIF-2 was launched on July 16, 2011 at 2:41am ET from Space Launch Complex 37B at the Cape Canaveral Air Force Station

Cape Canaveral Air Force Station

New characteristics

Launches

See also