I was not following evetything so I missed posting this on Friday. A single Glonass "M" satellite was launched on a Soyuz rocket. Typically they launch 2 or 3 in a single rocket. With this single launch the Glonass constellation will shortly be full with 24 active satellites.
Three Glonass Ms are schedule for a July launch on a Proton rocket.
Also coming up on May 15 is the launch of the 4th GPS 2F. The 5th 2F is listed for an October launch.
Paul in PA
Room Made For Next GPS 2F Satellite
Today SVN 35 (PRN 30) was decommisioned giving room for this month's launch of a GPS 2F satellite. While the GPS constellation is supposed to allow 32 PRN numbers certain receivers cannot handle 32. Thus the Air Force keeps the active number at 31.
Paul in PA
Geostationary Before Geosynchronous
Three Geostationary broadcasting L1/L2/L5 would better serve North America. Actually L1/L5 is the plan.
Ashtech does very well with just L1 ranging from our WAAS, atmospheric correction would be a bonus.
Japan is farther North and narrow so highly elliptical geosynchronous is a better first choice. The US could later add 6 HEO in 2 orbits. All that after we resolve the PRN number problem.
Paul in PA
Geostationary Satellites Have A Predictable Orbit
The bonus is that it changes very slowly. So the predicted orbit is nuch less complex than the typical GPS.
In fact a broadcast orbit may be uneccessary if the position is broadcast as part of the signal.
Paul in PA
Geostationary Satellites Have A Predictable Orbit
I wouldn't take the word of someone who thinks Japan is "farther north". 😉
FWI Tokyo is on the same latitude as Oklahoma City.
My Bad On Tokyo
I overreached on reasons.
Geostationary is favorable because the coomunications satellites are there anyway and the only cost is the adding of the WAAS receiver transmitter package.
Highly elliptical geosynchronous are specifically designed for that one purpose.
However the US weather satellites could be utilized with the addition of a WAAS style package saving major expense.
Paul in PA
HEO for Other Purposes
I was unaware that Highly Elliptical Orbit satellites were being used for other purposes. Since some else has a reason to put the staellite in orbit it becomes economical to just pay for the payload space for the GPS? transmitter.
Ashtech's BLADE technology uses the WAAS signal transmitted on the L1 frequency to get an L1 ranging distance to mix in with the other L1 ranging signals to quickly resolve a position. I am unsure if they even care about a predictable orbit. For their purposes it may be acceptable to assume the WAAS fixed and just use that position to speed up the final fix for a kinematic receiver.
The future of WAAS will include broadcasting an L1 & L5 correction signall on the L1 and L5 frequencies. A receiver could use those signals to calculate more precise ranging.
Whether it is Geostationary or Geosynchronous satellites someone has to track them and provide broadcast and post process orbits to make them truly useful GNSS satellites.
Paul in PA