Information below courtesy if the US Naval Observatory. This is an update to some material that I have published previously on the GPS constellation in my Monitoring Times Milcom column. I will be doing additional updates as time permits on other military satellite constellations in future post to this blog.
Blog Note: You can get the current status of the GPS Satellite Constellation by going to the USNO ftp site at ftp://tycho.usno.navy.mil/pub/gps/gpstd.txt
GPS OPERATIONAL SATELLITES (BLOCK II/IIA/IIR/IIR-M)
The operational GPS satellites are designated BLOCK II, BLOCK IIA, BLOCK IIR and BLOCK IIR-M.
The BLOCK II satellites, space vehicle numbers (SVN) 13 through 21, are the first full scale operational satellites developed by Rockwell International. Block II satellites were designed to provide 14 days of operation without contact from the Control Segment (CS). The Block IIs were launched from February 1989 through October 1990.
The BLOCK IIA satellites, SVNs 22 through 40, are the second series of operational satellites, also developed by Rockwell International. Block IIA satellites were designed to provide 180 days of operation without contact from the CS. During the 180 day autonomy, degraded accuracy will be evident in the navigation message. The Block IIAs were launched November 1990 through November 1997.
The design life of the Block II/IIA satellite is 7.3 years; each contain four atomic clocks: two Cesium (Cs) and two Rubidium (Rb); and have the Selective Availabity (SA) and Anti-Spoof (A-S) capabilities. The Block II/IIA satellites were launched from Cape Canaveral Air Force Station, Florida, aboard the Delta II medium launch vehicle (MLV).
The BLOCK IIR satellites, SVNs 41 through 62, are the operational replenishment satellites developed by Lockheed Martin and will carry the GPS well into the next century. Block IIR satellites are designed to provide at least 14 days of operation without contact from the CS and up to 180 days of operation when operating in the autonomous navigation (AUTONAV) mode. Full accuracy will be maintained using a technique of ranging and communication between the Block IIR satellites. The cross-link ranging will be used to estimate and update the parameters in the navigation message of each Block IIR satellite without contact from the CS. The design life of the Block IIR satellite is 7.8 years; each contains three Rb atomic clocks and have the SA and A-S capabilities. Launching of the Block IIRs began in January 1997.
LAUNCHES
GPS IIR-16M (SVN58/SVN12) was launched on 17 Nov 2006 at 1912 UT from Cape Canaveral, Florida.
CURRENT BLOCK II/IIA/IIR/IIR-M SATELLITES
LAUNCH LAUNCH FREQ
ORDER PRN SVN DATE STD PLANE SSC#**
*II-1 14 14 FEB 1989 19802
*II-2 13 10 JUN 1989 20061
*II-3 16 18 AUG 1989 20185
*II-4 19 21 OCT 1989 20302
*II-5 17 11 DEC 1989 20361
*II-6 18 24 JAN 1990 20452
*II-7 20 26 MAR 1990 20533
*II-8 21 02 AUG 1990 20724
*II-9 15 01 OCT 1990 20830
*IIA-10 23 26 NOV 1990 20959
IIA-11 24 24 04 JUL 1991 Cs D6 21552
IIA-12 25 25 23 FEB 1992 Rb A5 21890
*IIA-13 28 10 APR 1992 21930
IIA-14 26 26 07 JUL 1992 Rb F2 22014
IIA-15 27 27 09 SEP 1992 Cs A4 22108
IIA-16 01 32 22 NOV 1992 Cs F6 22231
*IIA-17 29 29 18 DEC 1992 Rb F5 22275
*IIA-18 22 03 FEB 1993 22446
*IIA-19 31 30 MAR 1993 22581
IIA-20 07 37 13 MAY 1993 Rb C5 22657
IIA-21 09 39 26 JUN 1993 Rb A1 22700
IIA-22 05 35 30 AUG 1993 Rb B4 22779
IIA-23 04 34 26 OCT 1993 Rb D4 22877
IIA-24 06 36 10 MAR 1994 Rb C1 23027
IIA-25 03 33 28 MAR 1996 Rb C2 23833
IIA-26 10 40 16 JUL 1996 Cs E3 23953
IIA-27 30 30 12 SEP 1996 Cs B2 24320
IIA-28 08 38 06 NOV 1997 Cs A3 25030
***IIR-1 42 17 JAN 1997
IIR-2 13 43 23 JUL 1997 Rb F3 24876
IIR-3 11 46 07 OCT 1999 Rb D2 25933
IIR-4 20 51 11 MAY 2000 Rb E1 26360
IIR-5 28 44 16 JUL 2000 Rb B3 26407
IIR-6 14 41 10 NOV 2000 Rb F1 26605
IIR-7 18 54 30 JAN 2001 Rb E4 26690
IIR-8 16 56 29 JAN 2003 Rb B1 27663
IIR-9 21 45 31 MAR 2003 Rb D3 27704
IIR-10 22 47 21 DEC 2003 Rb E2 28129
IIR-11 19 59 20 MAR 2004 Rb C3 28190
IIR-12 23 60 23 JUN 2004 Rb F4 28361
IIR-13 02 61 06 NOV 2004 Rb D1 28474
IIR-14M 17 53 26 SEP 2005 Rb C4 28874
IIR-15M 31 52 25 SEP 2006 Rb A2 29486
IIR-16M 12 58 17 NOV 2006 Rb B5 29601
* Satellite is no longer in service.
** US SPACE COMMAND, previously known as the NORAD object number; also referred to as the NASA Catalog number. Assigned atsuccessful launch.
*** Unsuccessful launch.
HISTORY OF BLOCK II/IIA/IIR/IIR-M SATELLITES AND STATUS
SVN/PRN
13/02 Launched 10 JUN 1989; usable 10 AUG 1989; decommissioned 12 MAY 2004. Set unusable 22 Feb 2004 at 1037 UT (NANU 2004025). Decommissioned from active service 12 MAY 2004 at 1701 UT.
14/14 Launched 14 FEB 1989; usable 15 APR 1989; decommissioned 14 APR 2000. Unusable 29 AUG 1992 2030 UT to 01 SEP 1992 1425 UT due to the failure of its operational frequency standard and change to its second Cs frequency standard. Unusable 26 JAN 2000 0130 UT to 03 FEB 2000 1816 UT due to change in operational frequency standard from Cs to Rb. Set unusable 26 MAR 2000 at 2348 UT. Decommissioned from active service 14 APR 2000 at 1347 UT.
15/15 Launched 01 OCT 1990; usable 15 OCT 1990; decommissioned 15 MAR 2007. Unusable 10 NOV 1992 1604 UT to 13 NOV 1992 1910 UT due to change in operational Cs frequency standards. Set as a test vehicle on 17 NOV 2006. Decommissioned from active service 14 MAR 2007.
16/16 Launched 18 AUG 1989; usable 14 OCT 1989; decommissioned 13 OCT 2000. Unusable 07 JAN 1991 1200 UT to 09 JAN 1991 1639 UT due to change in operational frequency standard from Rb to Cs. Unusable 06 FEB 1996 0556 UT to 21 FEB 1996 1648 UT due to change in operational Cs frequency standards. Unusable 04 MAR 2000 0955 UT to 07 APR 2000 2112 UT due to change in operational frequency standard from Cs to Rb. Decommissioned from active service 13 Oct 2000 at 0045 UT.
17/17 Launched 11 DEC 1989; usable 06 JAN 1990; decommissioned 23 FEB 2005. Unusable 06 APR 2001 1848 UT to 16 APR 2001 2253 UT due to change in operational frequency standard from Cs to Rb. Unusable 07 OCT 2002 0110 UT to 15 OCT 2002 1626 UT due to change in operational frequency standard from Rb to Cs. Unusable 26 JUN 2003 1942 UT to 22 JUL 2003 1600 UT due to change in operational frequency standard from Cs to Rb. Decommissioned from active service 23 Feb 2005 at 2200 UT.
18/18 Launched 24 JAN 1990; usable 14 FEB 1990; decommissioned 18 AUG 2000. Unusable 07 MAY 1996 0406 UT to 09 MAY 1996 1737 UT due to change in operational Cs frequency standards. Decommissioned from active service 18 Aug 2000 at 0742 UT.
19/19 Launched 21 OCT 1989; usable 23 NOV 1989; decommissioned 11 SEP 2001. Unusable 16 OCT 1994 0545 UT to 19 OCT 1994 1354 UT due to change in operational frequency standard from Cs to Rb. The course acquisition (C/A) code deficiency problem on PRN19 was corrected effective 04 JAN 1994 at 0000 UT; performance no longer degraded. Unusable 30 DEC 1994 0536 UT to 04 JAN 1995 1740 UT due to change in operational Rb frequency standards. Unusable 22 SEP 1999 1715 UT to 04 OCT 1999 1727 UT due to change in operational frequency standard from Rb to Cs. Unusable beginning 16 MAR 2001 at 0126 UT and will remain unusable until further notice. Decommissioned from active service 11 SEP 2001 at 2200 UT.
20/20 Launched 26 MAR 1990; usable 18 APR 1990; decommissioned 13 DEC 1996. Unusable 06 AUG 1994 0000 UT to 17 AUG 1994 1908 UT due to change in operational frequency standard from Cs to Rb. Unusable 13 JAN 1996 0937 to 1355 UT due to change in operational frequency standard from Rb to Cs. Set unusable 21 MAY 1996 at 2242 UT and will not return to service. Boosted out of the GPS constellation 13 Dec 1996.
21/21 Launched 02 AUG 1990; usable 22 AUG 1990; decommissioned 27 JAN 2003. Unusable 07 OCT 1996 1430 UT to 10 OCT 1996 2152 UT due to change in operational Cs frequency standards. Set unusable 25 SEP 2002 at 1830 UT and decommissioned from active service 27 JAN 03 at 2200 UT.
22/22 Launched 03 FEB 1993; usable 04 APR 1993; decommissioned 06 AUG 2003. Unusable 07 OCT 1998 1102 UT to 14 OCT 1998 2229 UT due to change in operational frequency standard from Cs to Rb. Unusable 28 JUL 2001 2358 UT to 11 AUG 2001 0413 UT due to change in operational Rb frequency standards. Unusable 05 NOV 2002 1756 UT to 18 NOV 2002 1403 UT due to change in operational frequency standard from Rb to Cs. Set unusable 03 DEC 2002 at 1402 UT and decomissioned from active service 06 AUG 2003 at 2200 UT.
23/23 Launched 26 NOV 1990; usable 10 DEC 1990; decommissioned 13 FEB 2004. Unusable 04 JAN 1991 1600 UT to 06 JAN 1991 2049 UT due to change in operational Cs frequency standards. Unusable 13 NOV 2003 0121 UT to 25 NOV 2003 2104 UT due to change in operational frequency standard from Cs to Rb. Set unusable 05 FEB 2004 at 2030 UT and decommissioned from active service 13 FEB 2004 at 2200 UT. An initial assessment period for SVN23 utilizing PRN32 was accomplished 01 DEC to 06 DEC 2006; SVN23 is no longer transmitting L-band. During this assessment period SVN23 was broadcasting L-band and set unhealthy. SVN23 was not included in the operational constellation almanac.
24/24 Launched 04 JUL 1991; usable 30 AUG 1991; Operates on Cs std.
Unusable 23 JAN 1994 1745 UT to 01 FEB 1994 1516 UT due to change in operational frequency standard from Cs to Rb. Unusable 01 JUL 1995 0750 UT to 07 JUL 1995 2223 UT due to change in operational Rb frequency standards. Unusable 07 SEP 2000 1742 UT to 11 SEP 2000 2020 UT due to change in operational frequency standard from Rb to Cs.
25/25 Launched 23 FEB 1992; usable 24 MAR 1992; Operates on Rb std. Unusable 01 DEC 1993 1904 UT to 05 DEC 1993 1941 UT due to change in operational frequency standard from Rb to Cs on 02 DEC 1993. Unusable 07 JAN 1995 1938 UT to 12 JAN 1995 1821 UT due to change in operational Cs frequency standards. Unusable 22 Mar 2006 0149 UT to 28 Mar 2006 0144 UT due to change in operational frequency standard from Cs to Rb.
26/26 Launched 07 JUL 1992; usable 23 JUL 1992; Operates on Rb std. Unusable 10 Mar 1998 1541 UT to 16 Mar 1998 1818 UT due to change in operational frequency standard from Cs to Rb.
27/27 Launched 09 SEP 1992; usable 30 SEP 1992; Operates on Cs std. Unusable 10 Jun 2002 1516 UT to 20 Jun 2002 1402 UT due to change in operational frequency standard from Cs to Rb. Unusable 14 MAY 2005 1955 UT to 31 MAY 2005 1749 UT due to change in operational frequency standard from Rb to Cs.
28/28 Launched 10 APR 1992; usable 25 APR 1992; decommissioned 15 AUG 1997. Unusable beginning 04 NOV 1996 1634 UT and will remain unusable until further notice (NANU 179-96309). Removed from broadcast almanac of all GPS satellites 15 AUG 1997.
29/29 Launched 18 DEC 1992; usable 05 JAN 1993; Operates on Rb std.
Unusable 21 MAY 1997 1504 UT to 31 MAY 1997 0355 UT due to change in operational frequency standard from Cs to Rb.
30/30 Launched 12 SEP 1996; usable 01 OCT 1996; Operates on Cs std. Unusable 29 Aug 2001 2102 UT to 04 Sep 2001 2055 UT due to change in operational frequency standard from Cs to Rb. Unusable 02 JUN 2006 to 07 JUN 2006 due to change in operational frequency standard from Rb to Cs.
31/31 Launched 30 MAR 1993; usable 13 APR 1993; decommissioned 24 OCT 2005. Unusable 17 JAN 1995 1705 UT to 25 JAN 1995 2013 UT due to change in operational frequency standard from Cs to Rb on 18 JAN 1995. The MCS and P-code users experienced intermittent lock on the L2 navigation signal of PRN31 from 13 Apr 1993 2053 UT to 16 Jun 1993 0824 UT. Since corrective maintenance was performed on 16 Jun 1993, the MCS has not experienced lock problems on PRN31's L2 navigation signal. Change in operational frequency standard from Rb to Cs on 23 JUL 1997. Unusable 15 APR 2002 1431 UT to 23 APR 2002 2018 UT due to change in operational frequency standard from Cs to Rb. Unusable 28 DEC 2004 0042 UT to 04 APR 2005 0913 UT, during the outage a change in operational frequency standard from Rb to Cs.
32/01 Launched 22 NOV 1992; usable 11 DEC 1992; Operates on Cs std. Unusable 28 JAN 1993 2000 to 2200 UT for maintenance and changed the Pseudo Range Number (PRN) from 32 to 01. Unusable 03 MAY 1995 0604 UT to 12 MAY 1995 1528 UT due to change in operational frequency standard from Cs to Rb. Unusable 16 AUG 1996 1655 UT to 22 AUG 1996 1620 UT due to change in operational frequency standard from Rb to Cs.
33/03 Launched 28 MAR 1996; usable 09 APR 1996; Operates on Rb std. Unusable 18 JUN 2006 to 29 JUN 2006 due to change in operational frequency standard from Cs to Rb.
34/04 Launched 26 OCT 1993; usable 22 NOV 1993; Operates on Rb std. Unusable 13 Sep 1998 1728 UT to 21 Sep 1998 2214 UT due to change in operational frequency standard from Cs to Rb.
35/05 Launched 30 AUG 1993; usable 28 SEP 1993; Operates on Rb std. Unusable 02 Jun 2003 1518 UT to 09 Jun 2003 1417 UT due to change in operational frequency standard from Cs to Rb. Unusable 26 Sep 2003 0745 UT to 14 Oct 2003 1633 UT due to change in operational frequency standard from Rb to Cs. Unusable 08 SEP 2005 0032 UT to 16 SEP 2005 1945 UT due to change in operational frequency standard from Cs to Rb.
36/06 Launched 10 MAR 1994; usable 28 MAR 1994; Operates on Rb std. Unusable 27 Apr 1995 1447 UT to 03 May 1995 0541 UT due to change in operational frequency standard from Rb to Cs. Unusable 17 Mar 2004 1531 UT to 29 Mar 2004 1558 UT due to change in operational frequency standard from Cs to Rb.
37/07 Launched 13 MAY 1993; usable 12 JUN 1993; Operates on Rb std. Unusable 20 Apr 1999 0437 UT to 26 Apr 1999 1533 UT due to change in operational frequency standard from Cs to Rb. Unusable 30 MAR 1994 0730 UT to 04 APR 1994 1330 UT due to change in operational Cs frequency standards. Unusable 20 Apr 1999 0437 UT to 26 Apr 1999 1533 UT due to change in operational frequency standard from Cs to Rb.
38/08 Launched 06 NOV 1997; usable 18 DEC 1997; Operates on Cs std. Unusable 05 May 2004 0906 UT to 18 May 2004 0142 UT due to change in operational frequency standard from Rb to Cs.
39/09 Launched 26 JUN 1993; usable 21 JUL 1993; Operates on Rb std. Unusable 15 Oct 1993 1200 UT to 07 Dec 1993 1940 UT due to testing.
40/10 Launched 16 JUL 1996; usable 15 AUG 1996; Operates on Cs std. Unusable 28 Nov 1996 2018 UT to 01 Dec 1996 2325 UT due to change in operational frequency standard from Rb to Cs.
41/14 Launched 10 NOV 2000; usable 10 Dec 2000; Operates on Rb std
43/13 Launched 23 JUL 1997; usable 31 Jan 1998; Operates on Rb std
44/28 Launched 16 JUL 2000; usable 17 Aug 2000; Operates on Rb std
45/21 Launched 31 MAR 2003; usable 12 Apr 2003; Operates on Rb std
46/11 Launched 07 OCT 1999; usable 03 Jan 2000; Operates on Rb std
47/22 Launched 21 DEC 2003; usable 12 Jan 2004; Operates on Rb std
51/20 Launched 11 MAY 2000; usable 01 Jun 2000; Operates on Rb std
52/31 Launched 25 SEP 2006; usable 12 OCT 2006; Operates on Rb std
53/17 Launched 26 SEP 2005; usable 16 Dec 2005; Operates on Rb std
54/18 Launched 30 JAN 2001; usable 15 Feb 2001; Operates on Rb std
56/16 Launched 29 JAN 2003; usable 19 Feb 2003; Operates on Rb std
58/12 Launched 17 NOV 2006; usable 13 Dec 2006; Operates on Rb std
59/19 Launched 20 MAR 2004; usable 05 Apr 2004; Operates on Rb std
60/23 Launched 23 JUN 2004; usable 09 Jul 2004; Operates on Rb std
61/02 Launched 06 JUN 2004; usable 22 Nov 2004; Operates on Rb std
PERIODIC MAINTENANCE AND MANEUVERS
The backup cesiums on-board each Block II/IIA satellite require periodic, approximately twice per year, pumping of the beam tube to maintain working order. This maintenance requires, on average, 18 hours of unusable time for each satellite.
Once per year each satellite requires a stationkeeping maneuver, also referred to as repositioning or Delta-V, to move the satellite back to its original orbital position. The satellites have a tendency to "drift" from their assigned orbital positions, one reason being the earth's gravitational pull. These maneuvers require, on average, 12 hours of unusable time for each satellite.
CURRENT GPS CONSTELLATION
The current GPS constellation consists of 30 Block II/IIA/IIR/IIR-M satellites. The first operational, Block II, satellite was launched in February 1989.
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File gpsb2.txt
Last updated: Wed Mar 14 13:28:51 UTC 2007