GPS Jamming Trials in UK - GASIL
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to Keith smith
1.I know of no reason why Galileo should be superior to GPS,and anyrate it doesn't exist yet (just two demonstrators, the cheaper of which was from a UK university and saved the dayfrom losing frquency allocation to comms industry)
If the link doesn't convince you PM me for more.
Again, Gallileo its not about making a superior system (at least at first) but about strategic independence...
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DanW wrote: "GPS has a problem in that the programme of replacing satelites is behind schedule. Recently, the US Government accountability office warned that full coverage may be lost in the near future due to this.”
Does anybody know what is really happening on this? I did some searches which suggest that there is no significant risk to the basic GPS system. The following suggest something rather different - no threat to present coverage, just a hitch in launching extra functionality.
Some people who seem to know what they are talking about say the following:
“CautiousOptimist” :
“ . . . There have been 2.5 generations of GPS satellite, with the third being developed currently. There are 32 satellites in orbit, the most recent being launched in March of last year and the oldest in 1993. To provide a fix accurate to 10 meters, a receiver needs to get signals from 4 satellites concurrently. . . . The Air Force is currently launching 5 new GPS satellites in the space of one year (March was the third). Presently, there are 31 active satellites, and one spare. When the one launched in March goes active, one of the current satellites will become the second spare. The system only allows for 31 active satellites at a time. 21 are needed for full coverage for the Earth, so there is significant redundancy in the current "constellation". By November, there will be 31 active, and 4 spares.
There have been delays in the third generation GPS satellites (Block III), due to new features (such as 10X power transmission, interoperability with Galileo, and resistance to jamming). But if we suddenly started losing satellites, current levels of service would be maintained with up to 10 satellites lost.
. . . . meant to say that, once the final 2 launches of the 2nd Gen satellites this year, the constellation will be able to continue service with the loss of up to 12 satellites, without additional launches.
[Excerpts from GPS system 'close to breakdown' | Technology | guardian.co.uk ]
---------------------
And from : GPS Satellite Glitches Fuel Concern on Next Generation - WSJ.com :
By ANDY PASZTOR
[re a satellite launched in March] “ . . experiencing performance problems in orbit. It hasn't become part of the "operational constellation" of more than two dozen other GPS satellites, and is slated to undergo a battery of tests expected to stretch through October to try to resolve the problems, according to an Air Force news release.
The GPS system, which serves both military and civilian users, provides precise time and location coordinates for everything from military missile launches and "smart" bombs to automated bank-teller machines to aircraft, ships and everyday vehicles. The Lockheed satellite is the first to include a new civilian frequency -- dubbed L5 -- designed for, among other things, use by future nationwide air-traffic control systems. But that signal, part of test package, apparently is interfering with other signals from the satellite and reducing their accuracy, according to industry and Air Force officials. The degraded signals are accurate only to about 20 feet, versus about two feet for typical GPS signals, industry officials said.
The issue is significant, according to these officials, because it could complicate deployment of a new family of Boeing Co. GPS satellites currently being built that also feature the L5 signal. Already years behind schedule and hundreds of millions of dollars over budget, the 12 satellites, which are scheduled to replace satellites currently in orbit, could face further testing and delays to ensure that they are free of interference problems. The Boeing satellites have a history of quality-control and manufacturing problems unrelated to the latest concerns.
. . . . Concerns over signal quality come barely weeks after a Congressionally-ordered study raised a red flag about potential erosion of GPS accuracy in the next few years due to launch delays and other challenges. If certain launches get delayed up to two years, the General Accountability Office report predicted, the Pentagon could have trouble maintaining the desired fleet of 24 fully-functional GPS satellites in operation.
The Pentagon responded by minimizing the potential risk, arguing that significant spare capacity remains on orbit and on the ground to handle unexpected problems. Gen. Robert Kehler, head of Air Force Space Command, said in an interview earlier this month that the GAO conclusions were overly pessimistic partly because they failed to take into account strategies the Air Force could use to extend the life of existing satellites. For example, Gen Kehler said, managing power output could give solar arrays longer life.
Despite some continuing quality-control issues with Boeing's IIF versions, Gen. Kehler said, "we're not going to have an issue" maintaining the current robust constellation.”
Does anybody know what is really happening on this? I did some searches which suggest that there is no significant risk to the basic GPS system. The following suggest something rather different - no threat to present coverage, just a hitch in launching extra functionality.
Some people who seem to know what they are talking about say the following:
“CautiousOptimist” :
“ . . . There have been 2.5 generations of GPS satellite, with the third being developed currently. There are 32 satellites in orbit, the most recent being launched in March of last year and the oldest in 1993. To provide a fix accurate to 10 meters, a receiver needs to get signals from 4 satellites concurrently. . . . The Air Force is currently launching 5 new GPS satellites in the space of one year (March was the third). Presently, there are 31 active satellites, and one spare. When the one launched in March goes active, one of the current satellites will become the second spare. The system only allows for 31 active satellites at a time. 21 are needed for full coverage for the Earth, so there is significant redundancy in the current "constellation". By November, there will be 31 active, and 4 spares.
There have been delays in the third generation GPS satellites (Block III), due to new features (such as 10X power transmission, interoperability with Galileo, and resistance to jamming). But if we suddenly started losing satellites, current levels of service would be maintained with up to 10 satellites lost.
. . . . meant to say that, once the final 2 launches of the 2nd Gen satellites this year, the constellation will be able to continue service with the loss of up to 12 satellites, without additional launches.
[Excerpts from GPS system 'close to breakdown' | Technology | guardian.co.uk ]
---------------------
And from : GPS Satellite Glitches Fuel Concern on Next Generation - WSJ.com :
By ANDY PASZTOR
[re a satellite launched in March] “ . . experiencing performance problems in orbit. It hasn't become part of the "operational constellation" of more than two dozen other GPS satellites, and is slated to undergo a battery of tests expected to stretch through October to try to resolve the problems, according to an Air Force news release.
The GPS system, which serves both military and civilian users, provides precise time and location coordinates for everything from military missile launches and "smart" bombs to automated bank-teller machines to aircraft, ships and everyday vehicles. The Lockheed satellite is the first to include a new civilian frequency -- dubbed L5 -- designed for, among other things, use by future nationwide air-traffic control systems. But that signal, part of test package, apparently is interfering with other signals from the satellite and reducing their accuracy, according to industry and Air Force officials. The degraded signals are accurate only to about 20 feet, versus about two feet for typical GPS signals, industry officials said.
The issue is significant, according to these officials, because it could complicate deployment of a new family of Boeing Co. GPS satellites currently being built that also feature the L5 signal. Already years behind schedule and hundreds of millions of dollars over budget, the 12 satellites, which are scheduled to replace satellites currently in orbit, could face further testing and delays to ensure that they are free of interference problems. The Boeing satellites have a history of quality-control and manufacturing problems unrelated to the latest concerns.
. . . . Concerns over signal quality come barely weeks after a Congressionally-ordered study raised a red flag about potential erosion of GPS accuracy in the next few years due to launch delays and other challenges. If certain launches get delayed up to two years, the General Accountability Office report predicted, the Pentagon could have trouble maintaining the desired fleet of 24 fully-functional GPS satellites in operation.
The Pentagon responded by minimizing the potential risk, arguing that significant spare capacity remains on orbit and on the ground to handle unexpected problems. Gen. Robert Kehler, head of Air Force Space Command, said in an interview earlier this month that the GAO conclusions were overly pessimistic partly because they failed to take into account strategies the Air Force could use to extend the life of existing satellites. For example, Gen Kehler said, managing power output could give solar arrays longer life.
Despite some continuing quality-control issues with Boeing's IIF versions, Gen. Kehler said, "we're not going to have an issue" maintaining the current robust constellation.”
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Anthony
Quote"There's also too much willingness to trust GPS for approaches (in theory or in practice), as a substitute for ILS. But ordinary GPS cannot come close to ILS for accuracy, especially for precision approaches. Using GPS in place of ILS requires LAAS (which is not GPS at all, but merely a supplementary technology), and even that is delicate. And no, things like WAAS or RAIM do not make GPS anywhere close to foolproof."
Not totally true. In the USA there are now more LPV approaches than ILS approaches. LPV approaches use WAAS technology to give ILS like indications in the cockpit to help you fly down to CAT I limits. They currently go down to 200 feet and 1/2 mile RVR (Depending on the runway / approach lighting).
WAAS is a form of SBAS (Satelite Based Augmentation System). The Australians are leading the way with GBAS (Ground Based Augmentation System)at airports such as Sydney. GBAS is a much improved form of LAAS which never really got fully developed.
Quote"There's also too much willingness to trust GPS for approaches (in theory or in practice), as a substitute for ILS. But ordinary GPS cannot come close to ILS for accuracy, especially for precision approaches. Using GPS in place of ILS requires LAAS (which is not GPS at all, but merely a supplementary technology), and even that is delicate. And no, things like WAAS or RAIM do not make GPS anywhere close to foolproof."
Not totally true. In the USA there are now more LPV approaches than ILS approaches. LPV approaches use WAAS technology to give ILS like indications in the cockpit to help you fly down to CAT I limits. They currently go down to 200 feet and 1/2 mile RVR (Depending on the runway / approach lighting).
WAAS is a form of SBAS (Satelite Based Augmentation System). The Australians are leading the way with GBAS (Ground Based Augmentation System)at airports such as Sydney. GBAS is a much improved form of LAAS which never really got fully developed.
