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Atlas 5 rocket to fly Friday night with GPS satellite

BY SPACEFLIGHT NOW

Posted: July 30, 2014



CAPE CANAVERAL -- Continuing a surge of GPS replacement launches, the third such mission since February is due for blastoff Friday night from Florida's eastern coast. An Atlas 5 rocket will carry the GPS 2F-7 bird directly into the navigation network following launch. The evening window runs from 11:23 to 11:41 p.m. EDT. "Everyone in the room I am going to guess has been touched by GPS today in one way or another," said Air Force Space Command leader William Shelton. "Your smartphone, financial transaction, high-speed network you may have used that uses GPS timing. It literally serves the world." This will be the seventh of Boeing's dozen Block 2F spacecraft to be launched. Together, they will form the backbone of the GPS network for the next 15 years. The continuous navigation signals emitted by GPS satellites allow users to find their position in latitude, longitude and altitude and measure time. A GPS user receiver measures the time delay for the signal to reach the receiver, which is the direct measure of the apparent range to the satellite. Measurements collected simultaneously from four satellites are processed to solve for the three dimensions of position, velocity and time. Users can determine their location to within feet, speed within a fraction of a mile per hour and time to within a second. GPS 2F-7 is nicknamed Capella, the "goat star," which is the third brightest star in the northern celestial hemisphere. To symbolize the name, a ram is emblazoned on the Air Force launch crew's patch. This year has featured a pair of Delta 4 rocket successfully launching GPS satellites in February and May, deploying the satellites nicknamed Canopus and Rigel, respectively. Now, it's the Atlas 5 rocket's turn to launch GPS 2F-7 and again in October with GPS 2F-8. It has been 21 years -- back in 1993 -- since four or more GPS satellites were launched in a single year. Those were the heydays of a half-dozen launches per year to construct an operational constellation. GPS 2F-7 will take Plane F, Slot 3 of the constellation in a reshuffling plan that ultimately bolsters the network. The satellite currently in that spot -- GPS 2R-2, launched aboard Delta 245 in July 1997 -- will be freed to maneuver elsewhere within the same F Plane and replace the 22-year-old GPS 2A-14, one of the longest serving GPS spacecraft. It went up in July 1992 aboard Delta 211. "The primary purpose of launching the new GPS 2F satellites is to field increased GPS signal capabilities, more accurate clocks, and reduce overall constellation risk," according to an Air Force spokesperson. The GPS fleet features six orbital planes with at least four spacecraft in each grouping to generate the minimum 24-satellites needed for the network to function properly.

File photo of Atlas 5. Credit: ULA



The storied history of GPS to provide precision navigation through a space-based constellation of satellites dates back to the 1970s, and Atlas rockets gave the earliest craft their lift into orbit to prove the novel concept would work. Atlas boosters conducted 11 launches of the Block 1 series from February 1978 through October 1985 from Vandenberg Air Force Base in California. The operational GPS satellites that created a worldwide phenomenon and today is used by civilans across the globe relied on the Delta family of rockets for their rides into space beginning in February 1989. But Atlas got back in the game last year with the launch of GPS 2F-4, a modernized satellite made by Boeing that features improved accuracy, enhanced internal atomic clocks, better anti-jam resistance and a civil signal for commercial aviation. "As I look around at this audience, I suspect some of you may have caught the space fever, like me, in the early days of space flight. Others of you are young enough to not even recall a world without GPS chips in your cell phones," said Shelton. "Everyone in this audience knows GPS, but I'm guessing many of you did not know how this program got started. ...The Navy deployed the Transit System in the early 60's to provide two dimensional position location information to the fleet, while the Air Force worked on Project 621B to provide three dimensional position data that supported Air Force operations. "Eventually, the DoD assigned joint program responsibility for GPS to the Air Force, and it has become an amazing world-wide utility, especially after presidential directives made its highest accuracy data available to people across the globe. "From 1978, when the first GPS Block 1 satellites were launched, through 1995 when GPS Block 2 satellites became fully operational, the extraordinary precision provided by GPS navigation and timing signals has really revolutionized life as we know it. I'll be bold and say that everyone in this room has been touched by GPS today -- either through your smart phone's GPS chip or through some financial transaction -- if not both. Incredible new applications of GPS surface every day." The United Launch Alliance Atlas 5 rocket flies in its frequently used 401 configuration to carry GPS satellites, a two-stage vehicle with no strap-on solids and a standard four-meter-wide nose cone, will be used to propel the 3,400-pound payload directly into the GPS network 11,047 nautical miles up. For tips on taking pictures of the launch, see our photography guide. For details on where the best spots are to see the launch, see the viewing guide. And if you will be away from your computer but would like to receive occasional updates, sign up for our Twitter feed to get text message updates sent to your cellphone. U.S. readers can also sign up from their phone by texting "follow spaceflightnow" to 40404. (Standard text messaging charges apply.)



