Here is just a little snip from www.gao.gov.y2kr.htm that once again shows things are not "fine" or "Y2K is AOK". :

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I will now discuss the potential impact of the Year 2000 problem and the upcoming end-of-week rollover on each of the three GPS components space, control, and useras well as the status of remedial efforts.

Space Component The space component of GPS consists of 24 operational satellites in 6 orbits at approximately 11,000 miles above the earth. The satellites

transmit radio signals that permit adequately equipped users to calculate position, velocity, and time anywhere on or above the Earth's surface and in any weather condition. They are equipped with very precise clocks that keep accurate time to within 3 nanoseconds. According to the Air Force Materiel Command (AFMC), the executive agent for the Department of Defense in acquiring GPS satellites, all GPS satellites are Year 2000 compliant as well as end-of-week rollover compliant.

The space component also includes satellite support systems, which are physically located on the ground. These systems are responsible for maintaining the satellites and their proper functioning. This includes keeping the satellites in proper orbits (called station keeping) and monitoring satellite subsystem health and statuse.g., monitoring solar arrays, battery power levels, and propellant levels and activating spare satellites, if possible. While the satellite support systems are end-of-week

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rollover compliant, they are not yet Year 2000 compliant, according to AFMC. AFMC reports that these systems are in the process of being either replaced or renovated and tested. This work is expected to be done by December 1999. Workarounds have also been reportedly developed for systems being replaced.

Ground Component The GPS control, or ground, component consists of a master control station, five monitoring stations, and three ground antennas located

throughout the world. The monitoring stations track all GPS satellites in view and collect ranging 2 information from the satellite broadcasts. The stations send these data to the master control station, which computes precise satellite orbits. This information is then formatted into updated navigation messages for each satellite and transmitted to each satellite through the ground antennas, which also transmit and receive satellite control and monitoring signals. These systems are interconnected through networks and also have their own information systems and equipment that must be renovated for Year 2000 compliance. According to AFMC, the ground support systems are now both Year 2000 and end- of-week rollover compliant. Contingency plans are also in place for these systems.

User Component The user component consists of receivers, processors, and antennas that allow land, sea, or airborne operators to receive the GPS satellite

broadcasts and compute their precise position, velocity, and time. According to AFMC, many newer GPS receivers, including all designs procured for the Department of Defense by the GPS Joint Program Office, have been tested and have demonstrated that they are Year 2000 compliant and end-of-week rollover compliant. According to the U.S. Coast Guard Navigation Center, however, the accuracy of navigation on some older receivers may be severely affected by the end-of-week rollover.

2 Distance from a receiver to the satellites.

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Activities Ongoing to Raise Awareness of Problem With Older Receivers

Several activities are ongoing to raise awareness among owners of older GPS receivers of the upcoming end-of-week rollover problem. The U.S. Coast Guard Navigation Center has been assigned responsibility for being the government liaison to the civil sector for GPS. Its Internet website explains the potential rollover problem on older receivers and provides an extensive list of manufacturers and points of contact. The Air Force has provided a list, also available on the Internet, of specific receivers that have been tested and found to be compliant by the Department of Defense. Furthermore, the President's Council on Year 2000 Conversion's Internet site provides links to sources of GPS Year 2000 and end-of-week rollover information. These activities are important and should be useful to GPS users seeking to determine whether their receivers will operate correctly at the end-of-week rollover.

However, even with these awareness efforts, it is conceivable that some organizations and users may not be aware that their GPS receiver could be vulnerable to the end-of-week rollover problem. Moreover, some may not even be aware that they rely on a GPS receiver as a communications network tool. Because they contain precise clocks, GPS receivers are sometimes used to synchronize time in communications networks. Synchronization is critical to the transmission of compressed or packetized 3 voice, data, and video transmissions. Timing errors due to the lack of synchronization, in fact, can lead to data loss and degradation and eventually to network disruption or even complete failures. Because of the interconnective and interdependent nature of networks, these problems, in turn, could affect other networks and even the Internet.

As a result, it is vital that organizations make an effort to determine (1) whether the networks they operate rely on GPS equipment as a time source and (2) the potential GPS-related risks. Once the problem and its potential impact are known, organizations and individual users can (1) modify receivers, (2) replace them with newer models, or (3) contact their service providers to ensure that GPS receivers supporting their telecommunications networks are not susceptible to the upcoming end-of- week rollover. Because the rollover is less than 4 months away, however, organizations must take these measures as quickly as possible.

-- Jon Johnson (narnia4@usa.net), July 07, 1999

Answers

Jon,

Information or input to your last paragraph regarding GPS receivers supporting telecomm networks. Most wireless and wireline networks do utilize a GPS receiver to provide the Stratum 1 source for timing or synchronization (in the case of wireless it is also used as source for frequency generation within the radio base station) but all systems employ a secondary clocking source i.e., T1, etc. Additionally, the switch can if necessary use its own (internal) oscillator to clock off of - major problem arising from "free-running" mode is that intersystem handoffs become quite tricky.

Finally, an extensive effort has been underway by the operators to address all of the equipment issues raised in the aforementioned paragraph- I know from first hand experience (work for one of the telecomm equipment vendors) and reports from friends and associates at other vendors that work is progressing quite well on this front.

-- william holst (w_holst@hotmail.com), July 07, 1999.

Great news thanks for the info, Jon. You do note the one bit of "bad" news pertains to the on-board satellite health and status systems. Most of these functions can be performed prior to 1/1/00, such as station keeping and battery conditioning. This will keep the birds functioning for some time into 2000.

-- Maria (maria947@hotmail.com), July 07, 1999.

I was hoping they (the satellites) would need less "constant" care and feeding from the ground, but this at least indicates they are aware of their (the ground station) vunerabilities.

It doesn't solve them - DEC 1999 - damn! - but recognizing the problem is a start. To other readers - monitor for reports of "remediation complete" or "turnover complete" in Aug and Sept for this system. The pollies will use the fact that the GPS system (overall) is able to remain operable through the turnover to demonstrate that y2k will not contain other problems.

These same pollies (and the government overall) will ignore the impact of the turnover on individual systems. They will also claim that the GPS systems are all compliant.

-- Robert A. Cook, PE (Kennesaw, GA) (cook.r@csaatl.com), July 07, 1999.

Maria:

This is probably fruitless, but:

1. Don't you realize that if an organization (especially govt!) says it will be complete by 12/99, its extremely improbable that they'll be even close by that time? Thats not an "anti-government" fanatical statement - its the way things happen.

2. Didn't you notice the concerns about the receivers? In the agency I work for our Dept has 18 GPS receivers needing firmware and software upgrades for the rollover --- I'm the only one whos got it done so far---of course theres are a whole six weeks left. There are likely to be a significant number of receivers that won't function 8/23/99. Don't know how important that will be, but what is the reason for confidence that everything will be OK?

3. This is just one small area. Maybe it'll get fixed. What about the next, or the next, or the next? Mutiply that a few thousand (actually, probably a few million) times and you'll be a "doomer" for sure.

-- Jon Johnson (narnia4@usa.net), July 07, 1999.

How does your department use these GPS devices? I assume you need to know your location and velocity otherwise they are not critical for the EOW rollover (you stated six weeks left to convert). Maybe you should let the others know how you managed to convert your terminals.

Well, no I don't know how many will not function in August. I've read that the gov terminals are compliant and that the ones affected by the EOW rollover are mostly the commercial terminals, from pre 1995. What % that represents I have no clue, do you? If that means that my car can't be tracked, oh well. That doesn't translate into a catastophe to me.

And yes, Jon, I'm aware of the gov's track record on completing projects. But believe it or not there are some success stories but they don't make for very good copy, so they are rarely reported in the media.

-- Maria (maria947@hotmail.com), July 07, 1999.

Miss Maria - to continue our delightful conversation - are the satellites spin stabilized or "fixed" (for solar panel alignment)?

In either case, if control is interrupted, or "falsely" sent a bad guidenace signal, how (for GPS satellites) can it be regained - on other satellites (Physics Today, Sept & Oct 1999) it has taken "almost miracles" to regain control of even one satellite (Solar Max I think) that spun the out of control due to automated earthside control errors during a maintenence period for gyros.

-- Robert A. Cook, PE (Kennesaw, GA) (cook.r@csaatl.com), July 07, 1999.

Robert, I thought you believed the earth stations would not be remediated in time. Now you think the on-board processors can't make it also. To answer your first question, I don't recall the design of the spacecraft but I guess I could look it up. But as you point out it doesn't matter to your point. Yes, it has taken "almost a miracle" to recover birds that go out of control and sometimes they are lost forever. But in GPS's case, there are backups in orbit. Because of the cost, designers build a lot of redundancy in their systems.

BTW, how often do you think control needs to contact the bird? Every minute, five minutes, day?

-- Maria (maria947@hotmail.com), July 07, 1999.

No, no - the story above clearly indicates that the earth-side stations require remediation (as I expected), but that these repairs are scheduled to complete in Dec 1999. That's late, as I said above, but they might finish in time. Space side, the satellites themselves are, and always were, felt to be okay. Regardless, they can only be launched again - you can't schedule a shuttle mission to replace parts and pieces of different controllers - these are not built nor accessible for space-based repairs.

What I was asking was in reference to the need for periodic 'station keeping" maintenance signals: in the article, it is in this section:

<< also includes satellite support systems, which are physically located on the ground. These systems are responsible for maintaining the satellites and their proper functioning. This includes keeping the satellites in proper orbits (called station keeping) and monitoring satellite subsystem health and statuse.g., monitoring solar arrays, battery power levels, and propellant levels and activating spare satellites, if possible. While the satellite support systems are end-of-week rollover compliant, they are not yet Year 2000 compliant, according to AFMC. AFMC reports that these systems are in the process of being either replaced or renovated and tested. This work is expected to be done by December 1999. Workarounds have also been reportedly developed for systems being replaced.....

Ground Component The GPS control, or ground, component consists of a master control station, five monitoring stations, and three ground antennas .... The stations send these data to the master control station, which computes precise satellite orbits. This information is then formatted into updated navigation messages for each satellite and transmitted to each satellite ... >>

____

So - how are these control signals transmitted here (earth-side) between stations, computers, and antennas? - how often are navigation and orbit correction signals needed? (on average) - for a low earth orbit, what happens if a signal is "late" or missed, and how long can one "miss" a needed signal before the orbit decays so far that on-board thrusters can no longer regain control?

The Solar Max question was prompted by the efforts to regain control of one satellite after automated control caused it to spin uncontrollably - obviously, the GPS system has several dozen satellites (so losing one isn't like loosing the single experimental platform) but the same automated error that caused one to fail could cause all to fail - right?

I agree, even if several (most ?) were "lost" the array of the remaining GPS satellites can still be used, though at reduced accuracy and at longer times to get a ground-based fix.

-- Robert A. Cook, PE (Kennesaw, GA) (cook.r@csaatl.com), July 07, 1999.

Robert, the article seems to contradict itself. The space component has its mission system and its support system. In that paragraph, it said, "space component also includes satellite support systems, which are physically located on the ground". That confuses the issue. I interpreted this as the on-board systems because the following paragraph goes into the ground control segment. And according to that paragraph, "the ground support systems are now both Year 2000 and end- of-week rollover compliant".

True, even though there won't be a shuttle launch to fix any on-board processing systems, ground control can transmit (upload) software fixes, if needed. After re-reading maybe they are referring to ground stations but the following on ground segment says they're compliant. The ground segment is responsible for health and status as well as mission systems on the bird.

If a transmission can't be made during one fly over, it can easily be made during the next. The trouble comes when the view period lapses during the transmission and the bird receives only part of the message. I can't recall the satellite period (maybe 12 hours) but they're in an orbit where station keeping (not year dependent) is not as difficult as in lower orbits. (Meaning their velocity is slower and their "in-view" period is longer so corrections aren't as critical). And as I mentioned the health functions can be performed during Dec, to lower the risk on 1/1/00. Did I answer your question?

-- Maria (maria947@hotmail.com), July 07, 1999.