Survey Perspectives – Early January 2008

January 11, 2008  - By 0 Comments

GPS

On the GPS front, I’m going to paraphrase, plagiarize, and otherwise copy from my fellow newsletter editor Don Jewell, who writes the Military & Government PNT newsletter. He spent decades on the inside looking out (think Lt. Col. Jewell) and offers interesting perspectives.

First off, after a relatively quiet period since launching the first new modernized satellite, the Block IIR-M (offering the new L2C signal), in September 2005, there has been a flurry of activity and announced activity in the past 13 months.

First — Sept. 25, 2005. PRN 25/SVN 53 . Slot C4.
Second — Sept. 26, 2006. PRN 31/SVN 52. Slot A2.
Third — Nov. 19, 2006. PRN 12/SVN 58. Slot B4.
Fourth — Oct. 17, 2007. PRN 15/SVN 55. Slot F2.
Fifth — Dec. 20, 2007. PRN /SVN 37. Slot C1.

Remember, a total of eight IIR-M satellites were built; the GPS Wing says the remaining three will be launched in 2008. One of the remaining Block IIR-M satellites has been modified by Lockheed Martin, with the capability of broadcasting an L5 non-operational test signal. The L5 operational signal is planned for the next-generation GPS satellite, the Block II-F. The first II-F was due to launch in 2008, but this doesn’t seem likely…and it seems less urgent since the IIR-M modified to broadcast an L5 test signal will secure the signal spectrum. Securing a signal frequency, especially with the competing satellite systems from other countries is not a simple task — but we’ll save that discussion for another time.

So, from all public sources of information available, the current IIR-M launch schedule looks something like this:

Sixth — Mar. 13, 2008.
Seventh — June 2008.
Eighth — October 2008.

This is the flurry of activity I was referring to. Essentially, five launches within a twelve-month period.

And this is where I bring in some of Don’s valuable info:
“In the current constellation there are indeed 32 satellites, and normally that would be nearly the perfect constellation configuration, but a few of the older satellites and payloads are ‘single string’ in space parlance or on their last legs and require substantial care and feeding, including power management, by the very talented personnel/crews at the 50SW (Space Wing), 2SOPS (Space Operations Squadron) at Schriever AFB in Colorado, and the intrepid engineers at the GPS Wing at Los Angeles Air Force Base in California.

“Each GPS satellite is designed with an ‘A’ and a ‘B’ side that approaches 100% redundancy for critical systems. Several of the satellites were switched to the ‘B’ side years ago and have significantly outlived their design life, which differs with each series of satellites launched.

“Therefore, don’t be surprised that as we launch more and more GPS satellites (IIRM+s), the number of active satellites in the constellation stays the same. Since we have 32 satellites on orbit, remember that is almost the optimum number, we are in a replenishment mode, and attempting to maintain the constellation at the optimum number while still adding new capabilities, or modernization; a good thing for war fighters when we are involved in several hot conflicts/wars around the globe.

“Now, what about the nine possible failures of the IIA series GPS satellites? The satellites in question are all at or beyond their design life and have critical failures; they are being kept alive by heroic means that require exceptional amounts of time and money. If the worst should happen and all nine IIA birds fail, then we would be down to 23 satellites which is far from the optimum number — but remember we will be launching the rest of the IIRM satellites at the same time and that should put the number of on-orbit GPS satellites at about 29. Colonel Dave Madden says the goal is to stay as near the optimum number as possible but to certainly never go below 27 satellites if possible.”

So, I think the conclusion to be drawn here is that those of you who are experiencing “PDOP spikes” during the day that prevent you from being productive when using RTK will continue to experience those, even with the new GPS satellite launches. I mention RTK because that is the technology that relies most heavily on having a consistent number of observables (6+). Static post-processing users are affected, but to a lesser extent.

The bottom line, and I’ve made this point many times in the past, is that if you want more satellites observable, the solution in GLONASS. That subject transitions nicely into my next discussion.

GLONASS

Why is it that we always seem to hear about GLONASS satellite launches, but the number of operational GLONASS satellites never seems to increase significantly (and even decreases)? The answer is that legacy GLONASS satellites had a poor operating life span — well under four years. The good news is that the new GLONASS-M satellites they’ve been launching have a “guaranteed” operating life of seven years.

Since I touched on this subject last fall, six more GLONASS-M satellites have been launched: three on October 26, 2007, and another three on December 25, 2007 (Russia’s Christmas gift to GNSS users). Two of the October 26 satellites are operational, so there are four left in orbit and pending operational status. There are twelve operational GLONASS satellites as of December 29, 2007. This could increase to sixteen in the next couple of months as the four satellites already in orbit are made operational. That would be, by far, the most operational GLONASS satellites we’ve seen in recent years.

This is great news for GPS/GLONASS users. Actually, GPS/GLONASS users gain more marginal benefit from GLONASS satellites than from GPS satellites because GLONASS satellites are on different orbital planes than GPS, and therefore, offer a better opportunity to increase the quality of the satellite geometry (e.g., decrease your PDOP).

As in 2007, six GLONASS satellites are scheduled to launch in 2008. This is good, but we’ll probably see some legacy GLONASS satellites fail also. There are two that are past their fourth birthday, and three that just turned three years old last month. In the best-case scenario, we could see 22 operational GLONASS satellites a year from now. In the worst-case scenario, I can’t imagine having less than 14 or so available to us. Not bad considering we had as few as nine available during certain times in 2007.

Although it’s been a rough ride at times, I continue to be a passenger on the GLONASS bandwagon. You can keep up with the GLONASS constellation status by visiting

this Russian Space Agency website.

Topcon/Sokkia Merger

 

Switching gears a bit, we move on to December 10, 2007, when the Japanese Fair Trade Commission (JFTC) approved the Topcon/Sokkia merger. JFTC approval was needed because both companies are headquartered in Japan. The only constraint is that “non motor-driven total stations” sold in the Japanese market must be sold through a third party “in order to clear antitrust concerns posed by the JFTC,” according to the Topcon press release. You can view the entire press release here.

I think this is a boon for both Topcon and Sokkia. It gives Topcon another distribution channel to push its GNSS technology. It gives Sokkia access to a broader range of GNSS technology than they have with Point, Inc., their joint venture with NovAtel. Also, Leica recently bought NovAtel. Since Leica is a direct Sokkia competitor, it put Sokkia in a difficult position if the Topcon merger didn’t go through.

I don’t think this particular merger is a bad thing for the user community. My guess is that you’ll see some dual branding, like you did when Trimble acquired Spectra Precision. Even though it’s all Trimble technology, it markets the EPOCH GPS system under the Spectra name for the budget-minded user while still maintaining higher selling prices for its technology under the Trimble brand name. I could be wrong, but I bet Topcon/Sokkia does something like this.

This article is tagged with and posted in Newsletter Editorials, Opinions, Survey, Survey Scene
GPS World staff

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