Disposal of SVN30

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:

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


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:

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).

wrote:

xtand sorted by date of launch.
e =A0 =A0 =A0 =A0 =A0 =A0Years Up
=A0 7,733 =A0 =A0 =A0 =A0 =A0 21.17
=A0 7,484 =A0 =A0 =A0 =A0 =A0 19.56
=A0 7,234 =A0 =A0 =A0 =A0 =A0 19.38
=A0 6,985 =A0 =A0 =A0 =A0 =A0 18.59
=A0 6,735 =A0 =A0 =A0 =A0 =A0 18.41
=A0 6,486 =A0 =A0 =A0 =A0 =A0 18.26
=A0 6,236 =A0 =A0 =A0 =A0 =A0 17.89
=A0 5,987 =A0 =A0 =A0 =A0 =A0 15.84
=A0 5,737 =A0 =A0 =A0 =A0 =A0 15.53
=A0 5,488 =A0 =A0 =A0 =A0 =A0 14.52
=A0 5,238 =A0 =A0 =A0 =A0 =A0 14.23
=A0 4,989 =A0 =A0 =A0 =A0 =A0 12.31
=A0 4,740 =A0 =A0 =A0 =A0 =A0 11.72
=A0 4,490 =A0 =A0 =A0 =A0 =A0 11.53
=A0 4,241 =A0 =A0 =A0 =A0 =A0 11.21
=A0 3,991 =A0 =A0 =A0 =A0 =A0 10.99
=A0 3,742 =A0 =A0 =A0 =A0 =A0 9.00
=A0 3,492 =A0 =A0 =A0 =A0 =A0 8.83
=A0 3,243 =A0 =A0 =A0 =A0 =A0 8.10
=A0 2,993 =A0 =A0 =A0 =A0 =A0 7.86
=A0 2,744 =A0 =A0 =A0 =A0 =A0 7.60
=A0 2,495 =A0 =A0 =A0 =A0 =A0 7.23
=A0 2,245 =A0 =A0 =A0 =A0 =A0 6.34
=A0 1,996 =A0 =A0 =A0 =A0 =A0 5.34
=A0 1,746 =A0 =A0 =A0 =A0 =A0 5.20
=A0 1,497 =A0 =A0 =A0 =A0 =A0 4.28
=A0 1,247 =A0 =A0 =A0 =A0 =A0 4.11
=A0 998 =A0 =A0 =A0 =A0 =A0 =A03.87
=A0 =A0748 =A0 =A0 =A0 =A0 =A0 =A0 2.45
=A0 =A0499 =A0 =A0 =A0 =A0 =A0 =A0 1.67
=A0 =A0249 =A0 =A0 =A0 =A0 =A0 =A0 =A00.54

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

http://adn.agi.com/SatelliteOutageCalendar/SOFCalendar.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:
fromftp://tycho.usno.navy.mil/pub/gps/gpstd.txtand sorted by date of launch.

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.


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.


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).