![]() ![]() Block IIF spacecraft will use the Air Force’s planned Evolved Expendable Launch Vehicle (EELV). The Delta II expendable launch vehicle is used to launch GPS satellites from Cape Canaveral Air Force Station, Fl. The system can accommodate an unlimited number of users without revealing their positions. The User Segment consists of the signal receivers/processors, antennas and control/display units that allow land, sea, or airborne operators to receive the GPS satellite broadcasts and compute their precise latitude, longitude, altitude, precise time and velocity at any time, in any weather. ![]() Boeing GPS Block IIF’s partner Computer Sciences Corporation began assuming responsibility for the operational control segment in 2000. The ground antennas also transmit and receive satellite control and monitoring signals. The updated information is transmitted to each satellite through the ground antennas, using an S-band signal. The information is then formatted into updated navigation messages for each satellite. The monitor stations send the information they collect from each of the satellites back to the master control station, which computes precise satellite orbits. The monitor stations track all GPS satellites in view and collect information from their broadcasts. The Control Segment consists of a master control station operated by the 2nd Satellite Control Squadron at Falcon Air Force Base, Colorado, with five monitor stations and three ground antennas dispersed globally. The Block IIF satellites broadcast on 2 L-band frequencies. Position and time data are continuously broadcasted to users all over the world. The satellites are positioned so that at any one point in time, six of them will be in view to users anywhere in the world. The space segment of the GPS programme consists of 24 operational satellites in six circular orbits at an altitude of 20,200km (10,900nm), with a 12 hour period, at an inclination of 54.8°. ![]() The military capabilities of GPS were demonstrated in the Gulf conflict, cited by US defence officials as a key factor in the successes of operations Desert Storm and Desert Shield. Hikers, farmers and fishermen also benefit from GPS. There are also numerous civilian users, such as trucking fleets, commercial airlines and law enforcement agencies. GPS uses GPS is used to aid land, sea and airborne navigation, geographical exploration, cartography and geodesy, surveying, vehicle location systems, search and rescue operations, aerial refuelling and rendezvous and a wide range of additional applications. The system achieved full operational capability in July 1995. It consists of a constellation of orbiting satellites, a ground control system and thousands of GPS information receiver units in aircraft, ships, land vehicles and hand-held manpacks. GPS allows land, sea, and airborne users to immediately determine their three-dimensional position, speed and time, 24 hours a day, under all weather conditions, anywhere in the world. Navstar GPS is a satellite-based radio navigation system developed and operated by the US Department of Defense (DOD). ![]()
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