I’m a long-time fan of The Straight Dope question and answer website (and podcast) authored by the pseudonymous Cecil Adams. Awesomely, a recent article addressed two outdoors-related topics– GPS and sunscreen.
Question: Is it true our GPS satellites are deteriorating and there’s no good fix?
I had the same question while researching for my TTB piece on Geocaching last year. A few excerpts from Cecil’s response:
The satellites have limited life, typically seven to ten years. There’s no practical way to fix them once they break. Of the 59 GPS satellites launched to date, 31 are still operating. Of those 31, 17 are past their life expectancy — the oldest was launched in 1990.
The problem is that 24 functional GPS satellites are required for complete global coverage. With 31 still beeping we’ve got plenty of spares for the moment. However, due to a combination of schedule slips, construction problems, and cost overruns, we haven’t been launching new satellites fast enough to replace those likely to fail soon.
So what’s the possibility that military operations and, heaven forbid, consumer recreation could be interrupted? Adams cites a 2009 U.S. Government Accountability Office (GAO) report estimating that “over the next four years or so the probability that at least 24 satellites will remain operational will be less than 95 percent, at times dipping as low as 80 percent.” (gotta love that government nuance). Dropping below 24 won’t spell system-wide disaster, but it could mean reception problems in urban and mountainous areas.
The U.S. Air Force responded quickly to the GAO report, stating flat out (via Twitter, amusingly) that “going below 24 won’t happen.”
Adams is also optimistic:
The fact that GPS technology has become ubiquitous is the best guarantee that the system won’t be out of action for long, if at all. Ten years ago civilian GPS use was confined to a gaggle of geeks. Today if the system goes down, just imagine the screaming: fix this sucker now.
Thank goodness for ubiquity!
Bonus question (paraphrased): Does 2 coats of SPF 8 sunscreen equal SPF 16?
The answer? Yes! And some.
Check out the full piece here.