Concerns with GPS Satellites and Future Viability

Kurt Lawton

If you’ve heard news about potential failure of satellites in the GPS constellation by 2010…the sky is not falling and it’s not time to panic.

Is there concern? Yes. A study just released by the US Government Accountability Office (GAO) shows that the Air Force (which maintains the system) and suppliers have not lived up to their promises of replacing satellites—which have an operational life of about 7.5 years.

If new satellites are not deployed on a more timely basis, there is an increased likelihood that the overall GPS constellation could fall below the number of satellites required (24) for proper function.

What does that mean for agricultural uses? Precision.AgWired.com talked to sources at Trimble who stated that there is concern, but it will likely cause only potential degradation of the free WAAS signal.

Trimble expressed confidence in the GPS satellites, and stated they are preparing for the future by incorporating signals from other systems. Their AgGPS 442 receiver (with the new AgGPS FmX Integrated display) can receive signals from the Russian version of the US GPS, known as GLONASS. This system isn’t as developed yet as the US system–currently containing 18 satellites–but it is predicted to increase to 30 satellites by 2011, according to the Russian space agency Roscosmos. While the current 18 satellites are not enough to be an effective system by itself yet (minimum of 24 needed), adding those extra satellites can make a significant difference in uptime for anyone who can reference both the US and Russian systems with one receiver, according to Trimble.

As more countries add their own navigational systems (like the Compass system being developed by the Chinese Aerospace Industry—which Trimble is a 50-50 partner), Trimble predicts there will be a shift in thinking. It will shift from exclusively US GPS to thinking GNSS (global Navigation Satellite System), which includes GPS, GLONASS, Compass and several additional satellite constellations being developed in the EU (Galileo) and Japan (QZSS).

BREAKING NEWS…
If you are a Twitter member, the Air Force (who tweets at AFSpace) conducted a tweet forum Q&A session on this issue yesterday (May 20) and just posted a transcript this morning. Bottom line from the conversation is that the Air Force “has plans to mitigate risk and prevent a gap in coverage,” and it’s very unlikely that a user will notice any difference in GPS accuracy. Currently there are 30+ satellites in orbit, and they plan to launch another in August and one in early 2010. “Going below 24 (satellites) won’t happen,” stated Col. Dave Buckman, AFSPC command lead for Position, Navigation and Timing.

What could happen if the GPS falls below the needed 24 satellites? Check out this piece by GPS World magazine.

Education, GPS, Industry News, International, Precision Ag in the News, Satellite, Trimble