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View Full Version : Don't Get Rid of That Sextant Just Yet



AJZimm
11-06-2011, 02:16 PM
I just stumbled across this US GAO report from 2009 on the maintenance of the GPS satellite system:
http://www.gao.gov/new.items/d09670t.pdf

Some quotes from the report:
"It is uncertain whether the Air Force will be able to acquire new satellites in time to maintain current GPS service without interruption. If not, some military operations and some civilian users could be adversely affected."

"If the Air Force does not meet its schedule goals for development of GPS IIIA satellites, there will be an increased likelihood that in 2010, as old satellites begin to fail, the overall GPS constellation will fall below the number of satellites required to provide the level of GPS service that the U.S. government commits to."

http://i368.photobucket.com/albums/oo123/AJZimmerman/Misc/GPSReliabilityProbability.jpg

"Such a gap in capability could have wide-ranging impacts on GPS users, though the exact impact is hard to precisely define, as it would depend on which satellites stop operating. To illustrate, however, the military could see a decrease in the accuracy of precision-guided munitions that rely on GPS to strike their targets. Disruptions in service could require military forces to either use larger munitions or to use more munitions on the same target to achieve the same level of success. Intercontinental commercial flights use predicted satellite geometry over their planned navigation route, and may have to delay, cancel, or reroute flights. Enhanced 911 services, which rely on GPS to precisely locate callers, could lose accuracy particularly when operating in urban canyons or mountainous terrain."

Not good news for mariners either

PS: I haven;t looked into what has happened since this report came out in 2009. Anyone know?

S.V. Airlie
11-06-2011, 02:33 PM
I have not used a sextant in years. I may have to dig it up and polish it a bit..:)

John E Hardiman
11-06-2011, 04:48 PM
I think your data is a little dated. The chicken little sceaniaro did not come to pass. Currently there are 30 birds up, the lowest number up since that report was 28. Since 2003 there have always been at least 24 up. http://adn.agi.com/SatelliteOutageCalendar/SOFCalendar.aspx

I does no one any good to grab a false alarmist piece of data and publish it just to see if it gets a rise. It wastes bandwith and shows your ignorance that you posted it without checking. Even the most jaded of observers would question the data after reading only the title page. FWIW, the relevent data on the title page of the report you listed is "Statement of Cristina T. Chaplain, Director Acquisition and Sourcing Management". No director of "Acquisition and Sourcing" is going to say that they have enough in front of Congress...that puts themselves out of a job. If the US constellation is not good enough, go to the Euro (Galileo) or Russian (GLONASS-K) ones.

wizbang 13
11-06-2011, 06:14 PM
wastes bandwidth? ouch!

AJZimm
11-06-2011, 08:03 PM
I think your data is a little dated.
Agreed, I pointed out it was from 2009


The chicken little scenario did not come to pass.
Good to hear


I does no one any good to grab a false alarmist piece of data and publish it just to see if it gets a rise.
That was certainly not my intention although the title of the post could be seen to be provocative


shows your ignorance that you posted it without checking.
Fair criticism, I should have done more work, however, I had no idea that the excellent information in the link you provided even existed and wouldn't have known where to look


Even the most jaded of observers would question the data after reading only the title page. FWIW, the relevent data on the title page of the report you listed is "Statement of Cristina T. Chaplain, Director Acquisition and Sourcing Management". No director of "Acquisition and Sourcing" is going to say that they have enough in front of Congress...that puts themselves out of a job.
I'm not sure that's entirely accurate. Under the "Why GAO Did This Study" on the title page, it also says GAO was asked to do the study - presumably by the US Congress.

John E Hardiman
11-07-2011, 08:49 AM
Agreed, I pointed out it was from 2009

Then why, for God's sake, bring it up now! Do you tweet "I burped once when I was a baby"?


I'm not sure that's entirely accurate. Under the "Why GAO Did This Study" on the title page, it also says GAO was asked to do the study - presumably by the US Congress.

You obviously have never worked with either a government orgnization or consultants hired to find problems. They always find problems wether there are any or not. That's thier job, especially the GAO. If the GAO isn't telling the US congress that they paid too much, or that there was risk, congress wouldn't believe them. Looking for budget problems in US aqusitions is a self fulfilling job because: 1) some company is is overcharging for something easy, or 2) some agency is overbudget because it was a difficult task. If it was easy a company would have lobbied their congressman to outsource it to them so that they could make a ton of money. The fact alone that the USAF ended up doing it is an indication that there was risk. If you believe this report then you MUST believe that there were WMD in Iraq.

Colin Burt
11-07-2011, 09:49 AM
Why are you so worked up?

A: yeah it is outdated but only by a couple years.

B: You seem to be familiar with US government organizations and consultants. Most people are not. Alex did end the post asking if anyone knows what happened. It is also worth pointing out that the report does not claim that the sky is falling. It deals with possibilities that the maintenance schedule will fall behind. The chart included shows no more then a 20% chance of falling below 24 satellites, that of course means they were predicting a 80% chance of things being fine.

C: Even if this report (as the intervening years have shown) was not accurate it does help to remind people that GPS is a complex and fragile system that requires constant maintenance. Those general points are important and should be understood by all and while it is important that the details of the report be criticized if they are wrong, it is a good topic to bring up.