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Post by NorthWes on Nov 6, 2008 9:56:17 GMT -9
Your tax dollars at work helping keep the constellation of navigation satellites upgraded and in good repair. For we Alaskans, this means more accuracy for air/land/sea navigation - helping Alaska Airlines be more efficient in flight routing, assisting in navigation-related safety upgrades at sea, and of course making our current hand-held GPS units obsolete (OK - not so much obsolete as 'not capable of accessing the fullest spectrum of capabilities available on the civilian channels'). With the increase in signal capability, I wonder what new features the next generation (past the Colorado/Oregon type of units) of GPSrs will feature? Kudos to the men & women of the USAF's 50th Space Wing for their (inadvertant) support of geocaching!
Here's the press release for those of you interested in what's behind the signals our GPSrs receive:GPS Modernization Steps Forward 11/3/2008 - Los Angeles Air Force Base -- In the fall of 2009, the U.S. Air Force will achieve another milestone on the path toward GPS modernization. Operators at the 50th Space Wing and the 2nd Space Operations Squadron will upload new software to the IIR-M satellites enabling the first broadcast of a transitional Civil Navigation (CNAV) message on the already transmitted second civil signal (L2C). Once the go-ahead is given, the new message will broadcast on the L2C signal emanating from the IIR-M satellites. With the upcoming launches of the remaining two IIR-Ms, there will be a total of eight modernized GPS satellites broadcasting L2C with the new CNAV message. Additionally, the IIF satellites will be launched with the built-in capability to broadcast the new message. The first steps toward GPS modernization began with a White House press release on March 30, 1998, announcing that the United States intended to modernize its GPS Position, Navigation, and Timing (PNT) service with the addition of a second civil signal on the L2 frequency (1227.60 MHz). In 2001, the then GPS Joint Program Office at the Space and Missile Systems Center, Los Angeles AFB, CA, and the civil community began work defining the implementation of the new signal. Many expected a replication of the L1 C/A signal, however, a modernized L2C signal was designed with several significant advantages over L1 C/A. The L2C signal will provide a lower tracking threshold and better cross-correlation protection than L1 C/A. The data portion of the L2C signal is also different; instead of the current "legacy" navigation (LNAV) structure with subframes of data repeating in a fixed pattern as on L1 C/A, the CNAV structure which will be used on L2C has individual messages which can be broadcast in a flexible order with variable repeat cycles. The CNAV structure, as defined in Interface Specification (IS)-GPS-200D, 7 Dec 2004, (available online at www.navcen.uscg.gov/gps/geninfo) allows up to 63 different message types, of which 15 types have already been defined. The 15 CNAV message types will be incrementally phased in over time, with the first CNAV message to broadcast being the "default message," also known as Message Type 0. Message Type 0 consists of a twelve second, 300 bit long message including the preamble, satellite pseudorandom noise (PRN) number, message type ID (=0), GPS Time of Week, a sequence of alternating 1s and 0s, and a Cyclic Redundancy Check (CRC) parity block. The GPS Time of Week will change every 12 seconds, as will the CRC bits. The addition of the L2C signal, with the modernized CNAV messages, is only part of the larger GPS modernization program. In addition to L2C, a third civil signal will be added centered at the L5 frequency (1176.45 MHz) as well as M-Code signals on L1 and L2. L5 will also carry CNAV messages and will broadcast from the IIF satellites and the GPS III satellites. The United States continues to modernize the GPS constellation and ground segment to bring added capability to civil and military users alike. Adding the first type of CNAV message to L2C is one more step in the roll-out of the overall GPS modernization plan.
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Post by saidbystacy on Nov 6, 2008 12:05:59 GMT -9
Well, that will be about time for me to upgrade my gps anyways. Good timing. Will have to make hints to my husband for my birthday next year ;D  ;D |
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Post by NorthWes on Jan 25, 2012 8:37:33 GMT -9
The USAF continues to upgrade the GPS satellite constellation. Here's news on what they're doing about the early generation GPS satellites as they're being 'retired' from service - in this case, a satellite placed on orbit in 1996. The report is from the 50th Space Wing (managers of the GPS system, based at Schriever AFB, CO):
Cosmic Guinea Pig: Preparing to decommission a Global Positioning System Block IIA satellite later this month, operators at Schriever AFB, Colo., are testing the spacecraft to characterize how similar satellites' systems respond to shutdown. "The information we gain from testing will drive down risk in future disposal operations," said Lt. Col. Dean Holthaus, 2nd Space Operations Squadron operations director. In addition to SVN-30, "we still have 12 GPS Block IIA vehicles on orbit," noted Holthaus. Although it may be several years before another of the Block IIA satellites is retired, with limited slots on orbit, the Air Force wants to ensure it can safely swap out a retiring satellite to reuse its place on orbit. "We know if anything falls outside the norm during future operations, we'll have quantifiable data" to troubleshoot the vehicle's disposal deeper into space, said Holthaus. Operator's switched SVN-30's role to another satellite after it showed degraded function last May.
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Post by SSO JOAT on Jan 25, 2012 19:31:04 GMT -9
Ah ha! So that explains the rash of DNF's last May. I knew it wasn't me.  |
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Post by NorthWes on Jan 28, 2012 15:26:18 GMT -9
Ah ha! So that explains the rash of DNF's last May. I knew it wasn't me. I'm quite certain we experienced several 'low satellite availability' moments last summer... usually when were were caching, right? |
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;D
