The two line orbital elements for SVN30 indicate it was placed into a
disposal orbit.

GPS IIF-3 launch is tentatively scheduled during September 2012.
Let's see what breaks during the interim.

Getting behind in the satellite count?

--- CHAS

On 2012-01-28 14:23 , HIPAR wrote:
> The two line orbital elements for SVN30 indicate it was placed into a
> disposal orbit.

I'm sure you've seen:
http://www.af.mil/news/story.asp?id=123286589

> GPS IIF-3 launch is tentatively scheduled during September 2012.
> Let's see what breaks during the interim.
>
> Getting behind in the satellite count?

31 operating birds now. Not bad at all.

Nine old (15+ years) birds up there - there is an increasing chance of
multiple sats in a failed state.

My GPS+GLONASS receiver is looking better all of the time.

--
"We demand rigidly defined areas of doubt and uncertainty."
Douglas Adams - (Could have been a GPS engineer).

On 2012-01-28 14:23 , HIPAR wrote:
> The two line orbital elements for SVN30 indicate it was placed into a
> disposal orbit.
>
> GPS IIF-3 launch is tentatively scheduled during September 2012.
> Let's see what breaks during the interim.
>
> Getting behind in the satellite count?
>
> --- CHAS

I took the satellite status from
ftp://tycho.usno.navy.mil/pub/gps/gpstd.txt and sorted by date of launch.

If you plot the days-up line as a function of the number of satellites,
the resultant line is remarkably linear. Tell me if you want the
spreadsheet with the plot.

SVN PRN YYYY.MM.DD Days up Line Years Up

23 32 1990.11.26 7,733 7,733 21.17
26 26 1992.07.07 7,144 7,484 19.56
27 27 1992.09.09 7,080 7,234 19.38
39 9 1993.06.26 6,790 6,985 18.59
35 30 1993.08.30 6,725 6,735 18.41
34 4 1993.10.26 6,668 6,486 18.26
36 6 1994.03.10 6,533 6,236 17.89
33 3 1996.03.28 5,784 5,987 15.84
40 10 1996.07.16 5,674 5,737 15.53
43 13 1997.07.23 5,302 5,488 14.52
38 8 1997.11.06 5,196 5,238 14.23
46 11 1999.10.07 4,496 4,989 12.31
51 20 2000.05.11 4,279 4,740 11.72
44 28 2000.07.16 4,213 4,490 11.53
41 14 2000.11.10 4,096 4,241 11.21
54 18 2001.01.30 4,015 3,991 10.99
56 16 2003.01.29 3,286 3,742 9.00
45 21 2003.03.31 3,225 3,492 8.83
47 22 2003.12.21 2,960 3,243 8.10
59 19 2004.03.20 2,870 2,993 7.86
60 23 2004.06.23 2,775 2,744 7.60
61 2 2004.11.06 2,639 2,495 7.23
53 17 2005.09.26 2,315 2,245 6.34
52 31 2006.09.25 1,951 1,996 5.34
58 12 2006.11.17 1,898 1,746 5.20
55 15 2007.10.17 1,564 1,497 4.28
57 29 2007.12.20 1,500 1,247 4.11
48 7 2008.03.15 1,414 998 3.87
50 5 2009.08.17 894 748 2.45
62 25 2010.05.28 610 499 1.67
63 1 2011.07.16 196 249 0.54

--
"We demand rigidly defined areas of doubt and uncertainty."
Douglas Adams - (Could have been a GPS engineer).

On Jan 28, 3:53*pm, Alan Browne <alan.bro...@FreelunchVideotron.ca>
wrote:

> I took the satellite status fromftp://tycho.usno.navy.mil/pub/gps/gpstd.txtand sorted by date of launch.
>
> If you plot the days-up line as a function of the number of satellites,
> the resultant line is remarkably linear. *Tell me if you want the
> spreadsheet with the plot.
>
> SVN * * PRN * * YYYY.MM.DD * * *Days up * * * * Line * * * * * *Years Up
>
> 23 * * *32 * * *1990.11.26 * * * 7,733 * * * * * 7,733 * * * * * 21.17
> 26 * * *26 * * *1992.07.07 * * * 7,144 * * * * * 7,484 * * * * * 19.56
> 27 * * *27 * * *1992.09.09 * * * 7,080 * * * * * 7,234 * * * * * 19.38
> 39 * * *9 * * * 1993.06.26 * * * 6,790 * * * * * 6,985 * * * * * 18.59
> 35 * * *30 * * *1993.08.30 * * * 6,725 * * * * * 6,735 * * * * * 18.41
> 34 * * *4 * * * 1993.10.26 * * * 6,668 * * * * * 6,486 * * * * * 18.26
> 36 * * *6 * * * 1994.03.10 * * * 6,533 * * * * * 6,236 * * * * * 17.89
> 33 * * *3 * * * 1996.03.28 * * * 5,784 * * * * * 5,987 * * * * * 15.84
> 40 * * *10 * * *1996.07.16 * * * 5,674 * * * * * 5,737 * * * * * 15.53
> 43 * * *13 * * *1997.07.23 * * * 5,302 * * * * * 5,488 * * * * * 14.52
> 38 * * *8 * * * 1997.11.06 * * * 5,196 * * * * * 5,238 * * * * * 14.23
> 46 * * *11 * * *1999.10.07 * * * 4,496 * * * * * 4,989 * * * * * 12.31
> 51 * * *20 * * *2000.05.11 * * * 4,279 * * * * * 4,740 * * * * * 11.72
> 44 * * *28 * * *2000.07.16 * * * 4,213 * * * * * 4,490 * * * * * 11.53
> 41 * * *14 * * *2000.11.10 * * * 4,096 * * * * * 4,241 * * * * * 11.21
> 54 * * *18 * * *2001.01.30 * * * 4,015 * * * * * 3,991 * * * * * 10.99
> 56 * * *16 * * *2003.01.29 * * * 3,286 * * * * * 3,742 * * * * * 9.00
> 45 * * *21 * * *2003.03.31 * * * 3,225 * * * * * 3,492 * * * * * 8.83
> 47 * * *22 * * *2003.12.21 * * * 2,960 * * * * * 3,243 * * * * * 8.10
> 59 * * *19 * * *2004.03.20 * * * 2,870 * * * * * 2,993 * * * * * 7.86
> 60 * * *23 * * *2004.06.23 * * * 2,775 * * * * * 2,744 * * * * * 7.60
> 61 * * *2 * * * 2004.11.06 * * * 2,639 * * * * * 2,495 * * * * * 7.23
> 53 * * *17 * * *2005.09.26 * * * 2,315 * * * * * 2,245 * * * * * 6.34
> 52 * * *31 * * *2006.09.25 * * * 1,951 * * * * * 1,996 * * * * * 5.34
> 58 * * *12 * * *2006.11.17 * * * 1,898 * * * * * 1,746 * * * * * 5.20
> 55 * * *15 * * *2007.10.17 * * * 1,564 * * * * * 1,497 * * * * * 4.28
> 57 * * *29 * * *2007.12.20 * * * 1,500 * * * * * 1,247 * * * * * 4.11
> 48 * * *7 * * * 2008.03.15 * * * 1,414 * * * * * 998 * * * * * *3.87
> 50 * * *5 * * * 2009.08.17 * * * 894 * * * * * *748 * * * * * * 2.45
> 62 * * *25 * * *2010.05.28 * * * 610 * * * * * *499 * * * * * * 1.67
> 63 * * *1 * * * 2011.07.16 * * * 196 * * * * * *249 * * * * * * *0.54
>

Your trend line probably correlates well with the usable satellite
data here:

http://adn.agi.com/SatelliteOutageCa...FCalendar.aspx

What's recently happened:

During 2010 - 2012, SVN25, SVN24, and SVN30 have gone to the
graveyard. GPSIIF-1 and GPS IIF-2 entered service and SVN35 was
recalled fromf retirement. So 31 usable satellites remain in the
constellation but there's one less spare.

The way I see it, if the system operators can maintain the 24+3
constellation, all will be well with NAVSTAR. The four remaining
satellites serve to bolster constellation robustness but don't
materially improve visibility or dilution of precision.

That's probably how the military wants the constellation managed
achieving a good balance of capability, reliability and availability.
PPS accuracy of about 2 meters is more than adequate for targeting
ordnance . It's probably even good enough for hit to kill kinetic
energy weaponry.

Going back to, Apr 30, 2009 the General Accounting Office presented
an alarming analysis (GAO-09-325) that claimed GPS was soon to be
broken. They obviously had no appreciation for the intellect behind
the system.

--- CHAS

On 2012-01-28 17:53 , HIPAR wrote:
> On Jan 28, 3:53 pm, Alan Browne<alan.bro...@FreelunchVideotron.ca>
> wrote:
>
>> I took the satellite status fromftp://tycho.usno.navy.mil/pub/gps/gpstd.txtand sorted by date of launch.
>>
>> If you plot the days-up line as a function of the number of satellites,
>> the resultant line is remarkably linear. Tell me if you want the
>> spreadsheet with the plot.
>>
>> SVN PRN YYYY.MM.DD Days up Line Years Up
>>
>> 23 32 1990.11.26 7,733 7,733 21.17
>> 26 26 1992.07.07 7,144 7,484 19.56
>> 27 27 1992.09.09 7,080 7,234 19.38
>> 39 9 1993.06.26 6,790 6,985 18.59
>> 35 30 1993.08.30 6,725 6,735 18.41
>> 34 4 1993.10.26 6,668 6,486 18.26
>> 36 6 1994.03.10 6,533 6,236 17.89
>> 33 3 1996.03.28 5,784 5,987 15.84
>> 40 10 1996.07.16 5,674 5,737 15.53
>> 43 13 1997.07.23 5,302 5,488 14.52
>> 38 8 1997.11.06 5,196 5,238 14.23
>> 46 11 1999.10.07 4,496 4,989 12.31
>> 51 20 2000.05.11 4,279 4,740 11.72
>> 44 28 2000.07.16 4,213 4,490 11.53
>> 41 14 2000.11.10 4,096 4,241 11.21
>> 54 18 2001.01.30 4,015 3,991 10.99
>> 56 16 2003.01.29 3,286 3,742 9.00
>> 45 21 2003.03.31 3,225 3,492 8.83
>> 47 22 2003.12.21 2,960 3,243 8.10
>> 59 19 2004.03.20 2,870 2,993 7.86
>> 60 23 2004.06.23 2,775 2,744 7.60
>> 61 2 2004.11.06 2,639 2,495 7.23
>> 53 17 2005.09.26 2,315 2,245 6.34
>> 52 31 2006.09.25 1,951 1,996 5.34
>> 58 12 2006.11.17 1,898 1,746 5.20
>> 55 15 2007.10.17 1,564 1,497 4.28
>> 57 29 2007.12.20 1,500 1,247 4.11
>> 48 7 2008.03.15 1,414 998 3.87
>> 50 5 2009.08.17 894 748 2.45
>> 62 25 2010.05.28 610 499 1.67
>> 63 1 2011.07.16 196 249 0.54
>>
>
> Your trend line probably correlates well with the usable satellite
> data here:
>
> http://adn.agi.com/SatelliteOutageCa...FCalendar.aspx

The snapshot above is for a single point in time, so it doesn't account
for other satellites that have dropped off. That said, the "Healthy
Satellites Graph" there is pretty straight line over the long period.

If you set that same graph to the 365 day view, it shows a pretty poor
average for 2011.

> What's recently happened:
>
> During 2010 - 2012, SVN25, SVN24, and SVN30 have gone to the
> graveyard. GPSIIF-1 and GPS IIF-2 entered service and SVN35 was
> recalled fromf retirement. So 31 usable satellites remain in the
> constellation but there's one less spare.
>
> The way I see it, if the system operators can maintain the 24+3
> constellation, all will be well with NAVSTAR. The four remaining
> satellites serve to bolster constellation robustness but don't
> materially improve visibility or dilution of precision.
>
> That's probably how the military wants the constellation managed
> achieving a good balance of capability, reliability and availability.
> PPS accuracy of about 2 meters is more than adequate for targeting
> ordnance . It's probably even good enough for hit to kill kinetic
> energy weaponry.

There are other ways to aim and guide munitions. Complete dependency on
GPS is not a healthy system attitude IAC.

eg: Laser designators are esp. accurate if the munitions guidance system
is agile enough.

> Going back to, Apr 30, 2009 the General Accounting Office presented
> an alarming analysis (GAO-09-325) that claimed GPS was soon to be
> broken. They obviously had no appreciation for the intellect behind
> the system.

http://www.gao.gov/new.items/d09325.pdf

In reading the executive summary I see little to suggest that the
general risks have not abated. (not as specifically stated, but as such
risks tend to never be completely manageable).

--
"We demand rigidly defined areas of doubt and uncertainty."
Douglas Adams - (Could have been a GPS engineer).