Originally Posted by
ORAC
KenV - Speak to the Japanese - they have one in service......
You're being fairly disingenuous here. I read back on post 22, it's interesting. It matches some of what I said in my rantpost, that with an altitude of 400km you basically have a 10 minute window during which the satellite will be visible and the ephemeris value will be valid.
You want to piggyback off the existing GPS constellation and use codeless p(y) dual frequency receivers on the cubesats so they can self-update their ephemeris. That works just fine. Many satellites in orbit today have GPS receivers.
Your derived system's error will be its own 'native' error (from the cubesats to the ground receiver) multiplied by the cubesats own GPS position error from when they self-located. The improved accuracies shown in the post 22 links can only be achieved when the cubesat ephemeris data is updated directly with reference to known fixed points i.e. using ground stations, the same way the GPS ephemeris is updated.
You are in reality totally dependent on the navigation message provided by the other system.
You gain only a perceived immunity from jamming which lasts only until your adversaries work out what frequency your cubesats are using and jam it.