GAO Report: The Long Form; my thoughts

GS world reports that The 61-page long version of the GAO report is
available. The PDF can be found here.
http://gao.gov/products/GAO-09-325

I read this report and decided to do my own analysis.

The active GPS constellation (see for example
ftp://tycho.usno.navy.mil/pub/gps/gpsb2.txt
) consists of:
IIA        12
IIR        12
IIRM         7
---------------
Total 31


The Boeing IIF Launch Schedule
http://www.boeing.com/defense-space/space/bss/launch/launch_sched.html

shows eight IIF's will be launched by the end of 2010, followed by the
remaining 4 by 2012.

If 9 IIA birds have failed over to a critical backup subsystem (and
therefore are a single failure away from death) then by the end of
next year, eight of these 9 will be replaced. By 2012 all 12 will
have been replaced leaving the remaining IIA satellites as spares.

[Aside: Even if the bump of the launch of the first IIF to 2010
results in only 7 IIF replacements by the end of 2010 instead of 8,
this will not alter the basic conclusion.]

Thus by 2014 just before the first IIIA is scheduled to be launched,
the GPS constellation will consist of:
IIF        12
IIR        12
IIRM         7
__________
31

Plus some number of IIA birds as spares.

---

GPS Block IIR Rubidium Clocks "have proved to be the best performers
in the current GPS".

http://www.stormingmedia.us/96/9687/A968724.html

"The superior performance and lifetimes of the GPS IIR Rb clocks" will
lead to the set of three clocks outliving the satellite.

The specified life span of the IIR is 10 years
http://articles.gpsfaq.com/details.aspx?item=41

The first successful IIR was launched on July 22nd 1997. The 12th and
last IIR was launched on November 6, 2004. So by the scheduled launch
of the first IIIA in 2014, all 12 of the Block IIR satellites will be
at or past their design lifespan. Not too bad; these satellites will
exceed their design lifespans.

---

Lockheed-Martin knows how to build satellites. The same group that
built the IIR(M) is building the IIIA. If the program office
cooperates by keeping change activity in check, there is every reason
to think that the IIIA will arrive on or near schedule.

--Mike Jr

GPS world reports that The 61-page long version of the GAO report is
5
b/gps/gpsb2.txt
ss/launch/launch_sched.html
I forgot to add the 8th Block IIRM satellite, scheduled for launch in
August 2009, to the mix.

Thus by 2014 just before the first IIIA is scheduled to be launched,
the GPS constellation will consist of:
IIF =A0 =A0 12
IIR =A0 =A0 12
IIRM =A0 8
__________
=A0 =A0 =A0 =A0 32
details.aspx?item=3D41

325
pub/gps/gpsb2.txt
/bss/launch/launch_sched.html
m/details.aspx?item=3D41
d
h

It's about maintaining parity. The recent constellation hstory goes
something like this:

PRN/SVN Plane Std # Block
---------+-------+-----+----------+--------------------------- Recent-
Activities--------------------------------

Mar 2009 Spare
Mar 2008 Spare
20 Dec 2007 Spare
23 Oct 2007
14 Mar 2007

2008
2008
2008
2007
2006
2006


##/50 E3? Rb? IIR-21/M8 Scheduled launch: NET Aug 2009
##/62 C2? Rb? IIF-1 Scheduled launch: TBD
2009/2010

The Air Force has easily maintained parity despite a nine month Delta
II booster delay
and delinquent delivery of the IIF series.

Remarkably, as of May, three IIA satellites are not on the 'watch
list' with all twelve
still functioning well. Many IIA satellites exhibit errors that do
not often exceed
1.5 meters.

As of May, there are no IIR satellites on the 'watch list'. All
nineteen IIR series, including
the currently unusable new one, routinely exhibit errors less than
one meter.

With due deference to IIA exceeding design life, three or four of
those satellites might fail within
the next year but it's quite possible those of most importance to the
constellation value can be
replaced before they actually fail.

Of course, much depends upon launching a IIF within the next year
months.

So, I won't argue with the GAO analysis on it's technical merits. I'm
thinking
it's overly pessimistic with respect to the historical evidence.

--- CHAS