On Nov 5, 12:32*pm, Alan Browne
wrote:
...
Given the state of the US federal debt and deficit and the high
reliability and availability of GPS, there is no urgency to spend more
money.

While it might annoy those with an interest in the advancement of GPS,
it is not a priority. *The more advanced birds can wait for greener
times - although there are few bets that there will be greener times in
the US budget morass.

One important angle is when more SVs will be needed, beyond the 10 IIF
birds already in the pipeline, as they *could* last throughout this
decade, add 2 IIIA + 2 IIIB and I *bet* that's all GPS launches before
2020.

Assuming SVN27 is reactivated, 10 IIF birds will retire the last 10
IIA birds sustaining a 31 bird constellation. Add two IIIA plus two
IIIB, and chances are that's all that will be launched until 2020
(average three launches every two years, about a 100% launch speedup).

The fact is USAF must plan based on essentially the worse possible
scenario, even if that scenario is quite unlikely (let's say 10%
chance).

Their SV production plans are based on a quite pessimistic scenario,
of 2-3 SVs dying yearly.

All GPS production / launch planning has been done at 3 yearly
launches, but we're launching less than one yearly. That's quite a
mismatch.

If anybody on the list has any information about SVN27 (old PRN27) is
it worse now that it was before its deactivation, or just was retired
to free a PRN (while IIF-2 was undergoing checkout and PRN24 stayed
active) ? With PRN24 retired, PRN24 and 27 are unused, with no
launches on schedule, using the 31st PRN would be a good thing.

Even with 30 healthy birds plus some spares, GPS still looks better
than ok.

So one point is IIIA/B/OCX development isn't time sensitive yet.

My prediction is: With Galileo coming online, a new shiny GNSS (from a
democratic union of countries) making the geriatric (by then) GPS look
bad, but GPS will still be alright except for the 15 yr late
modernization schedule. The fact that GLONASS is on the verge of
having signal coverage comparable to GPS might also pressure GPS
modernization, and by the end of the decade they should have the
entire constellation with GLONASS K models with CDMA capability plus
atomic clocks performing on par with GPS average.

GPS is such an essential part of the modern world, and given the
creative ways in which GPS has been used for War and Peace, I contend
at least the current modernization effort (with the slow launch
schedule) should continue, just plan more realistically and the budget
forecast will come down.

Marcelo Pacheco