[time-nuts] OT: Far-out space navigation from sideways satnav signals

[Jim Lux]

On 4/18/13 12:15 PM, Peter Monta wrote:

> I wonder if there's any advantage in combining far-away GPS with X-ray
> pulsar navigation (XNAV), which is said to be good to a few kilometers,
> though long integration times are needed.  For example, the rough system
> time from XNAV could enable very long (arbitrarily long?) coherent
> integration for very faint GPS signals obtained with a gain antenna pointed
> at the Earth.
>

Of course, building an X-ray detector for XNAV is an unsolved problem, 
at least for spacecraft practical systems.