Oldest GPS Satellite To Be Retired

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jimh
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Oldest GPS Satellite To Be Retired

Postby jimh » Tue Jan 26, 2016 5:33 pm

The oldest currently operational GPS satellite is being retired from service next month. The Air Force has indicated that SVN-23, presently signaling as PRN-32, will be taken out of service after over 25-years in operation. The design life of the satellite was only seven years. The Air Force, taxpayers, and global users, got an extra 18-years of service from the GPS-IIA-10 spacecraft. It was launched in late November of 1990. (Heck--it is older than my classic Boston Whaler boat, a 1992 model.)

The phasing out of SVN-23 will occur following the launch of the last in the series of 12 GPS IIF satellites, GPS IIF-12; that launch is scheduled for February 3, 2016, or about seven days from now.

See:

http://www.gps.gov/systems/gps/space/#IIF

http://www.ulalaunch.com/atlas-v-to-lau ... GPS+IIF-12

http://gpsworld.com/last-block-iif-to-r ... satellite/

for more details. A great way to keep track of all GNSS satellites in service is from The Almanac, at http://gpsworld.com/the-almanac/

jimh
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Re: Oldest GPS Satellite To Be Retired

Postby jimh » Sun Jan 31, 2016 1:22 pm

As mentioned above, when GPS IIF-12 is launched it will mark the end of the IIF series of improved GPS space vehicles. The next generation of GPS satellites is already in production and is called the GPS III series. It is anticipated the first of the GPS III space vehicles will be ready for launching in 2017. The GPS III is being built by Lockheed-Martin Space Systems. Their website has more information about the GPS III satellite hardware:

http://www.lockheedmartin.com/us/products/gps.html

If you visit the above resource, be sure to study the pictures showing the partially assembled GPS III space vehicle with human workers in view. This will impart a good sense of the size of these devices. These GPS satellites are larger than the early manned spacecraft and are launched into orbits with over 12,000-miles heights, whereas the usual manned mission orbits are only at altitudes of a few hundred miles.

jimh
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Re: Oldest GPS Satellite To Be Retired

Postby jimh » Fri Feb 05, 2016 11:28 am

The GPS IIF-12 launch this morning was a success. I missed the real-time coverage. I am waiting for the replay to be posted. This is more great work by our United States military in the form of the U.S. Air Force and our fantastic aerospace contractors. Their record of successful deployments is amazing.

jimh
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Re: Oldest GPS Satellite To Be Retired

Postby jimh » Sat Feb 06, 2016 10:05 am

With this successful launch, we will enter a long period of no GPS satellite launches while we await SVN-1 of the GPS III series to be prepared for launch, which won't be until sometime next year, 2017.

The GPS IIF satellite was carried into orbit on an Atlas V 401 configuration, that is, with a 4-meter payload fairing, 0-external boosters, and 1-upper-stage-main engine. The first stage rocket engine is the Russian-made RD-180, which has become the center of a controversy regarding USA-Russian geo-political relations. (More on that in a follow-up article.) The launch is provided by United Launch Alliance (ULA) which is a 50-50 joint venture of the Boeing and Lockheed-Martin companies.

Interest in space vehicle launches is a global phenomenon. I found a very interesting animated presentation created by a fellow named Lukas, who is not a native speaker of English. I don't know where he is from, but Lukas runs a blog that documents many space vehicle launches. He produced an excellent animation with a very well done and extremely concise and informative narration track for the GPS IIF-12 launch. This 3-minute 40-second presentation is highly recommended for viewing. You can find it at

https://www.youtube.com/watch?v=IdU5n7nqHVY

Also on youTube.com I found several replays of the GPS IIF-12 launch webcast from ULA. The longest one is I found is available at

https://www.youtube.com/watch?v=UdqpmfgfwhI

The above is watermarked twice, once with the original ULA watermark and then a second watermark from the media outlet providing the replay. I watched it via the youTube app on my Apple TV on my HD display. The pictures sent from the rocket itself are the most interesting. Some day I must get to Florida to see one of these Atlas V launches. It looks like it would make a good show.

The webcast usually only covers the launch for about 30-minutes into the flight, to the point of Centaur main engine cut-off (MECO). The spacecraft goes into a coasting phase for several hours until its elliptical transfer orbit reaches apogee. At that point the Centaur main engine is ignited for a second burn to sustain the spacecraft in a circular orbit at that altitude, about 12,300-miles.

A shorter version of just the liftoff and initial ascent up to booster engine cut-off (BECO) is found at

https://www.youtube.com/watch?v=F8fssipuwm4

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Re: Oldest GPS Satellite To Be Retired

Postby jimh » Thu Mar 17, 2016 1:49 pm

The recently launched GPS IIF-12 satellite was put into active service in mid-February 2016. It should now be received as PRN32 by your GPS L-1 C/A receiver. Look for it to be in range by checking at http://www.nstb.tc.faa.gov/rt_waassatellitestatus.htm

The launch of this final GPS IIF satellite concludes a very active period of GPS satellite launches; there were six launches in just 18-months. A rather long period of no new launches is anticipated as we await the delivery of the first space vehicle in the GPS III series, as well as a determination of which contractor will provide the launch services.

The oldest satellite in service, SVN23, caused quite a stir in the GPS timing community on January 26, 2016. As Dylan Thomas wrote many years ago, maybe SVN 23 decided to "not go gentile into that good night."

When SVN23 was removed from the GPS constellation, a timing error of 13-microseconds was very curiously broadcast by 15 GPS satellites. The 13-microsecond error is said to have triggered thousands of warnings across the globe on systems that use high-precision time-keeping based on GPS time data. The cause of the error was traced to a problem in the ground software used to control legacy satellite's L-band signals.

CHRONOS TECHNOLOGY is reporting that some 100 users of its timing equipment in more than 50 countries continued to have problems for two days after the brief time error transmission occurred. More at

http://www.chronos.co.uk/index.php/en/r ... 6-jan-2016

This minor incident is a good example of the extraordinary influence of GPS technology on global time keeping. An error of 13-microseconds is astonishing small yet its effects were similarly astonishing in their wide ranging influence. While boaters tend to use GPS for navigation and position finding, time-keeping is another major global use for the signals.