All About GPS IIF
courtesy of Boeing
GPS is used to support land, sea, and airborne navigation, surveying, geophysical exploration, mapping and geodesy, vehicle location systems, aerial refueling and rendezvous, search and rescue operations, and a wide variety of additional applications. Civilian users range from commercial airlines, trucking fleets, and law enforcement agencies to farmers, fishermen and hikers. New applications are continually emerging.
These capabilities were put to the test during Operation Desert Shield and Desert Storm. Coalition forces relied heavily on GPS to navigate the featureless Saudi Arabian desert. Forward air controllers, pilots, tank drivers and even cooks used the system so successfully that several U.S. defense officials cited GPS as a key to the Desert Storm victory. Recently, during Operation Enduring Freedom in Afghanistan and Operation Iraqi Freedom, GPS proved invaluable to coalition forces navigating in difficult conditions. These operations included the use of immensely successful GPS guided munitions, such as JDAM (Joint Direct Attack Munition), allowing pinpoint accuracy with minimum collateral damage.
GPS provides the following 24-hour navigation services: extremely accurate three-dimensional location (latitude, longitude and altitude), velocity and precise time; a worldwide common grid that is easily converted to any local grid; passive all-weather operations; continuous real-time information; unlimited support to worldwide users; and civilian user support at a slightly less accurate level. The GPS signals are so accurate that time can be calculated to within a millionth of a second, velocity within a fraction of a mile per hour and location to within feet.
GPS consists of three segments: space, control and user:
The Space Segment, consists of 24 operational satellites in six circular orbits 20,200 km (10,900 nm) above the Earth at an inclination angle of 55 degrees with a 12 hour period. The satellites are spaced in orbit so that at any time a minimum of six satellites will be in view to users anywhere in the world. The satellites continuously broadcast position and time data to users throughout the world. The satellites transmit signals on two different L-band frequencies.
The Control Segment consists of a master control station operated by the 50th Space Wings 2nd Space Operations Squadron at Schriever Air Force Base, Colorado, with five monitor stations and three ground antennas located throughout the world. The monitor stations track all GPS satellites in view and collect ranging information from the satellite broadcasts. The monitor stations send the information they collect from each of the satellites back to the master control station, which computes extremely precise satellite orbits. The information is then formatted into updated navigation messages for each satellite. The updated information is transmitted to each satellite through the ground antennas, using an S-band signal. The ground antennas also transmit and receive satellite control and monitoring signals. The current Block IIF contract includes development of the Control Segment. In December 2003, a new Boeing GPS Center (BGC) was dedicated in Colorado Springs, Colorado. The center was created to develop, integrate, test and sustain the control segment hardware and software for the latest GPS IIF satellites. This facility will also have the capability to support evolutionary software development for GPS IIF and other versions of the GPS satellite.
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, velocity and precise time at any time, in any weather. The system can accommodate an unlimited number of users without revealing their positions.
The GPS concept of operation is based upon satellite ranging. Users figure their position on the Earth by measuring their distance from the group of satellites in space. The satellites act as precise reference points.
Each GPS satellite transmits an accurate position and time signal. The users 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.
GPS receivers collect signals from satellites in view. They display the users position, velocity, and time, as needed for their marine, terrestrial, or aeronautical applications. Some display additional data, such as distance and bearing to selected waypoints or digital charts.
GPS provides two levels of service a Standard Positioning Service (SPS) for general public use and an encoded Precise Positioning Service (PPS) primarily intended for use by the Department of Defense. SPS signal accuracy is intentionally degraded to protect U.S. national security interests. This process, called Selective Availability (SA), controls the availability of the systems full capabilities. The SPS accuracy specifications, given below, include the effects of SA.
SPS provides accuracies of (for position, the accuracy with respect to geographic, or geodetic coordinates of the Earth) within:
– 100 meters (2 drms) horizontal
– 156 meters (2 Sigma) vertical
– 300 meters (99.99 percent probability) horizontal
– 340 nanoseconds time (95 percent probability) time
SPS coverage is continuous and worldwide, with a position dilution of precision (PDOP) of six or less.
The Delta II expendable launch vehicle is currently used to launch GPS satellites from Cape Canaveral Air Force Station, Florida. In the future, Block IIF/III spacecraft will use the Air Forces Evolved Expendable Launch Vehicle (EELV).
Under management of a Joint Program Office at the U.S. Air Forces Space and Missile Systems Center, Los Angeles Air Force Base, California, Boeing Reusable Space Systems, Seal Beach, California, designed, built, and tested 11 developmental Navstar GPS satellites; developed and qualified a second-generation production prototype; and built 28 production Navstar GPS satellites under a $1.35 billion contract awarded in 1983. The original Air Force contract for GPS was awarded in 1974, resulting in the first Block I Navigational Development Satellite (NDS) satellite being launched in 1978 by an Atlas F rocket.
Today, the majority of the constellation consists of Boeing Block IIA satellites. The GPS Block IIR satellites, built by Lockheed Martin, are currently being launched on Boeing Delta II rockets.
Boeing is currently under Air Force contract to build 12 GPS IIF satellites. The GPS IIF satellites, with a design life of 12.7 years, will have improved anti-jam capability and substantially increased accuracy from earlier satellite versions. The first GPS IIF launch launched on May 27, 2010, from Cape Canaveral Air Force Station.
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Guarding South Africas Shipping Lanes
From a building high on the slopes of the Tygerberg, north-east of Cape Town, South Africas Centre for Sea Watch and Response (CSWR) keeps an eye on the hundreds of ships that pass around the Cape each day.
When busy, the center might be using its sophisticated satellite technology to track as many as a thousand vessels, CSWR executive head Karl Otto said. The CSWR is a division of the SA Maritime Safety Authority (Samsa).
With its Long-Range Identification and Tracking system (LRIT), launched 18 months ago, at the time the CSWR was established, his staff could see ships up to 1,850km off the South African coast.
Otto said another satellite-based system, AIS (Automatic Identification System), allowed his staff who man the center around the clock, seven days a week to access information relating to each vessel. This includes the size and type of vessel, the ships origin and destination, and what cargo was being carried.
Over 90 percent of South Africas trade is carried to and from the country by sea; it is important we know what is going on, Otto said.
Both systems rely on transponders, fitted to ships, which transmit information to orbiting satellites. This data is then transmitted to ground stations and fed through to the CSWR.
Once there, the information is displayed, via computer, on large screens. Software allows operators to forecast from the data, factoring in information such as weather, winds and currents. This is useful in the event of the center having to respond to an emergency, such as a sinking ship or an oil spill. The system can then be used to predict the likely drift of survivors, or slicks, allowing rescue or clean-up efforts to be focused on a particular area.
The maritime region South Africa monitors, in terms of its international obligations, is vast: 27.7-million square kilometers. It stretches from Antarctica in the south to the Kunene River in the north; and from 10 degrees west in the mid-Atlantic to a point well past Madagascar in the Indian Ocean.
Among the CSWRs functions is watching for ships that pollute. Ships, at night, pump out dirty oil into the water. But by the time we see the slick, we dont see the ship, Otto said.
The center was hoping to acquire more high-tech equipment, in the form of a synthetic aperture radar system, to catch the culprits. This would allow his centers operators to view, from satellite, the stretch of sea the ship was passing through and provide direct evidence of the offence. Otto said a lack of long-range maritime aircraft restricted South Africas ability to directly monitor shipping. Its a concern, yes, definitely, he said.
It is understood that the only official aircraft available for long-range marine surveillance off the Cape coast are two ageing C130s.
On illegal fishing within South Africas economic exclusion zone, which stretches to 200 nautical miles offshore, Otto said this was certainly happening, but was unable to say to what extent. Many foreign fishing vessels were not fitted with transponders. He said coastal radar had a range of about 50 nautical miles; beyond that, it was not possible to know what was happening if the area was not patrolled by ships or planes.
Samsa CEO Tsietsi Mokhele said South Africa was the only country on the continent with the capacity to monitor shipping off its coast.
The centers focus was on maritime traffic management, accidents and incidents at sea, pollution and security.
The CSWR represents a high concentration of maritime experience that can serve the nation, he said.
Article is courtesy of SouthAfrica.info, available at...
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Communicating from land to sea and air plays a vital role during joint operations in the U.S. military. Soldiers and Marines have made this communication possible in Kodiak, Alaska, for Exercise Northern Edge 11.
Signaliers attached to Charlie Company, 307th Expeditionary Signal Battalion, joined with Marines of Marine Air Control Squadron One to ensure communication needs are met during the joint training. MACS-1, from Marine Corps Air Station Yuma, Arizona, is typically an autonomous unit.
However, with their communications detachment currently deployed overseas, they looked to the 59th Signal Battalion at Joint Base Elmendorf-Richardson, Alaska, for the connection they needed.
We normally work with our own assets; it is a new and rewarding experience working with the Army com guys, said Marine Master Sgt. Brad Barber, MACS-1 senior air director, from Atlanta. At home, we dont get the opportunity to work with joint contingencies.
The Marines and soldiers are working in the same capacity here as they do during combat deployments.
Were learning how they work; theyre learning how we work, said Army Spc. James Havens, a native of Gulfport, Mississippi. We all have one main goal, to accomplish the mission.
Their mission for Northern Edge is to ensure land, air and sea units are able to communicate effectively to accomplish their respective missions. The Army signaliers install, operate, maintain and protect communication systems, to enable MACS-1 to receive information instantaneously via secured and unsecured communications and relay messages between military services.
Its a good experience for [the soldiers] to work with the Marines before they deploy overseas, said Army 2nd Lt. Rose Munroe, the 307th ESB Heavy Signal Platoon leader.
NE11 was Alaskas largest joint military training exercise and ran through June 24th in various locations throughout the state and the Gulf of Alaska. It prepares U.S. forces to respond to crises throughout the Asian-Pacific region. The exercise affords Army, Navy, Marine, Air Force and National Guard members active duty and reserve highly flexible, tactical real life experiences.
(article is courtesy of Alaskan Command Public Affairs via DVIDS)
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Smart Phones Have U.S. Armys Attention
The Army is finding the use of smart-phone devices such as an Android or iPhone leads to an increase in SPOT reports, wherein Soldiers share tactically relevant information across the force in real-time.
Through a series of ongoing evaluations called Connecting Soldiers to Digital Apps an initiative which places smart phones and PDA-like devices in the hands of Soldiers in mock combat operational scenarios Army officials are learning that sharing data, images and even video instantaneously can potentially provide a tactical advantage on the battlefield.
Think of mission command, said Rickey Smith, director of the Army Capabilities Integration Center - Forward. Part of what we have to have shared is understanding. This is another way for the individual Soldier to send something back to his squad leader or fellow squad members.
Soldiers that went through mock-combat exercises with mobile smart devices achieved as much as a 40-percent increase in SPOT reporting, which included taking photographs and sharing data within their formation.
As much as possible, this ability to get information in real-time horizontally and vertically is important, Smith said. A smart phone is a camera. It is a voice communication device, and it provides chat text. You can send or receive photos, graphics and videos.
During evaluations, Soldiers have been able to take pictures and send them back to headquarters, or speed up the pace of a MEDEVAC by providing location information quickly, he added.
In addition, the Army has had success running situational awareness Battle Command applications on smart phones such as Joint Battle Command - Platform, a next-generation force-tracking program able to show locations of friendly forces.
The Army is now conducting cost-benefit analysis of the use of various smart phones and applications. Some of the applications involve the use of icons and maps with key location-related information, Smith said. At the same time, there are information assurance challenges with the use of smart phones, Smith explained. You dont want to use a device that might give away your locations to a potential enemy.
The Armys Connecting Soldiers to Digital Apps, or CSDA, initiative is considering various types of encryption-and other methods, designed to mitigate these concerns, Smith said.
With this in mind, the Defense Advanced Research Projects Agency has Soldiers in Afghanistan using a smart phone/PDA-type device which translates Pashtu into English and vice versa. However, the phone function on this device is turned off, for now, so as to mitigate security risks, Smith explained. Another option being explored is the use of portable cell-towers able to establish a mobile, ad-hoc cell network for deployed forces. This technique creates a mobile hot spot which can be extended by adding nodes to the network.
As part of these evaluations, the Army is assessing whether ad-hoc mobile cell networks can successfully integrate with an existing tactical network, which includes satellites, software-programmable radios, and other communications technology. The CSDA initiative is also having success in using smart devices for training materials, which can be pulled down and used by students at the place and time of the students choice, Smith said.
Documents such as the Army Blue Book instruction manual for new Soldiers, military police basic officer courses, and Patriot missile launcher crewmen courses, are using smart phone applications.
We can postulate a future where smart devices are with every Soldier, Smith said. We are thinking in terms of capability. The real key is whether the benefit outweighs the cost.