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

[Jim Lux]

On 4/19/13 11:47 AM, Peter Monta wrote:
> Hi Hal,
>
>
>
>> Why are X-Ray pulsars better than radio pulsars for navigation?
>>
>
>
> My impression is that it's easier to manage all-sky coverage at x-ray with
> a small spacecraft package (I think millisecond pulsars generally emit at
> both microwave and x-ray).  Also there's some interstellar scintillation at
> microwave frequencies, which would hurt short-term timing performance
> (something like the ionosphere's effect on terrestrial GNSS).
>
>

One of the hits when you google "XNAV detector" is a AAS paper from an 
SBIR Phase 1 describing a potential system..
Note that their assumption is that the detector has:
1) 1 square meter detector area
2) Integration time of 100k seconds
3) detector eff 95%
4) detector background rate 0.1ph/s
etc

 From what I've heard casually, a detector like this is unobtanium.

http://microcosminc.com/analysis/AAS%2008-054%20XNAV.pdf


For instance, Chandra's detector is a 10x10cm Microchannel Plate, 
although the Xray telescope aperture is somewhat larger.