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Commercial Satellites
MIRROR: JPL's MSL - A Briefing on Worldwide Satellites
Intelligence Missions for Satellites
Constellation of 24 (48?) satellites used by military and civilians to determine a precise location anywhere on Earth. A small receiver takes signals from two to four GPS satellites and calculates a very precise position. The satellites transmit a highly precise signal to authorized users, permitting accurate navigation to within a few meters (16-20 for "normal" users). DoD has deployed more than 110,000 GPS receivers to US government and allied users, with terminals becoming much more widely available since the 1991 Persian Gulf War. Civilians use a commercial version of the terminals, with a degraded signal with an accuracy to 100 meters. Receivers are priced as low as $200. The less accurate signal prevents adversaries from using GPS for precision weapons targeting. Civilian users are working to obtain a much better signal through auxiliary equipment known as differential GPS, that corrects the degradation. DoD has become increasingly concerned about enemy use of GPS during a conflict and has begun an effort called NAVWAR (navigation warfare) to protect its advantage while preventing adversary use of GPS. GPS III is an overarching requirements process to develop a document that encompasses civil, military, scientific, and commercial use of GPS. It is also referred to as positioning, navigation, and timing. The current constellation is 25 operational Block II/IIA series and one test-and-checkout satellite. The GPS office has procured 21 Block IIR replenishment satellites. GPS IIR-1 was destroyed in the January 1997 Delta rocket explosion. GPS IIR-2 was being readied for a July 12, 1997, launch. Five IIR launches are scheduled for Fiscal 1998.
Update: All birds in the 6 operational constellations are on orbit, the orginal 6 constellations of the demo system are in an unknown status. By mid 1999, the induced error feature was turned off giving commerical users the ability to get the higher accuracy and allowing for use in commercial aircraft navigation. Rumor has it that Block III birds will transmit a signal that allows positioning at 1-2 meters accuracy, and with differential GPS, near perfect. No funding for block III is anticipated, however.
During times of conflict, U.S. reserves the right to modify the error for commercial usage in the conflict area (turns on the error induction).
Constellation of five primary spacecraft in geostationary orbit provides voice, data, digital, and television transmissions between major military terminals and national command authoritie. Secure voice and high-data-rate communications, operating at superhigh frequency, primarily for high-capacity fixed users.Five DSCS satellites remain to be launched it 1997-2002. The Air Force has funded a program that will allow more tactical users access on DSCS. The Pentagon is developing the architecture to replace the capacity in the next decade.
Update: All ten birds are now on orbit and the next generation is nearly ready for launch.
The first two Mistars of an intended constellation of four that would provide coverage between 65 north and 65 south latitude are it orbit. The first $1 billion Milstar was launched February 7, 1994, and the second November 5,1995. Originally conceived as a communications system that could survive a nuclear conflict and connect national command authorities to commanders of ships, aircraft, and missiles during a war, the system's design and application have been altered in the aftermath of the Cold War. Milstar currently serves tactical forces as well as strategic, and the last four Milstars (Milstar IIs) will include medium-data-rate payloads able to transmit larger volumes of data up to 1.45 mbps. The four are scheduled for launch in 1998-2002. All satellites have low-data-rate payloads providing communications at five bps to 2.4 kbps The system can handle a data stream equal to 50,000 fax pages an hour and 1,000 simultaneous users. The satellites are designed to be jam-proof and use sophisticated techniques to provide secure communications.
Update: All birds in orbit, third generation delayed due to funding
Infrared detectors aboard these satellites have provided early warning of ballistic missile attack to NORAD since the 1970s. During Operation Desert Storm, operators at Space Command used DSP data to provide warnings of Scud attacks to theater commanders, though DSP was not designed to spot and track smaller missiles. Information on procurement situation, number of satellites launched, and number to be launched is classified. DoD intends to replace the system with a new spacecraft, the Spacebased Infrared System, designed to spot and track the smaller, faster-burning theater missiles that have proliferated it recent years. It will be fielded in three increments; Increment 1, Fiscal 1999; Increment 2, Fiscal 2002; and Increment 3, Fiscal 2006.
Military weather satellites operating it LEO that collect and disseminate global weather information directly to the warfighter and government agencies. Operating in a two satellite constellation, each spacecraft collects high-resolution cloud imagery (visible and infrared) from a 1,800-mile-wide area beneath it. Satellites collect other specialized data, such as atmospheric temperature and moisture, snow cover, precipitation intensity and area, and oceanographic and solar-geophysical information for DoD air, sea, land, and space operations. Five satellites remain to be launched (USAF launched its last on April 4, 1997). Joint satellites will be procured with NOAA for the follow-on system, with the first to be launched in the 2007-10 time frame. It will be called the National Polar-Orbiting Gynrational Environmental Satellite System (NPOESS).
Constellation of four satellites operated by USN, USAF, and the Presidential command network. A secure link among the three, providing ultrahigh-frequency (UHF) communications. Satellites carry 23 channels for communications with naval forces, nuclear forces, and national command authorities. The last two FLTSATCOM satellites (Flights 7 and 8) carry extremely high-frequency (EHF) payloads. In operation since 1978 in geostationary orbit, with a minimum of four satellites needed for worldwide coverage.
New generation of satellites providing UHF communications to replace FLTSATCOM satellites. UFO satellites have 29 channels-compared to the FLTSATCOM's 23 ) -are bigger and have higher power. Compatible with the same terminals used by the earlier systems, UFO-4 was first in the series to include an EHF communications payload with enhanced antijam telemetry, command, broadcast, and fleet interconnectivity. EHF channels provide at additional 11 channels. Ten UF0 satellites were ordered, six are operational.
Spacecraft that have been providing Navy UHF satellite communications since first launch in 1984 to augment FLTSATCOM. Leasesat was decommissioned at the end of 1996.
GBS is projected to be a high-speed, one-way broadcast communications system that provides high-volume information worldwide directly to in-theater warfighters. GBS will provide data to large populations of dispersed users with small, mobile receive terminals. These terminals will allow data to be disseminated directly to lower-echelon forces, providing current weather, intelligence, news, imagery, and other mission essential information. GBS will be implemented in three phases. Phase 1 will consist of leased commercial transponders. Phase 2 will consist of GBS packages aboard three UFO satellites. Phase 3 will be an objective system consisting of military assets, a commercial leased system. or a combination of two.
An undisclosed number and type of intelligence satellites are operated by intelligence agencies in cooperation with the military Satellites, which monitor Earth with radar, optical sensors and electronic intercept capability, have been treated as closely guarded secrets since the start of the space age. Even the names of satellites, like LaCrosse (radar imaging), Keyhole (optical imaging), White Cloud (ocean reconnaissance)., and Aquacade (electronic ferret), are secret and cannot be confirmed by the intelligence agencies. However, the move to declassify space systems has begun, leading large release of extensive information about one-an obsolete spy satellite called Corona. The Intelligence Community also will release selected archival images obtained by older spy satellites for scientific use. Some observers believe more military space secrets will be disclosed as the Cold War fades.
Taken from Air Force Magazine, August,1997, pg. 24.
Updated, April, 2002.