[time-nuts] Pulsars make a GPS for the cosmos

[Magnus Danielson]

On 09/28/2013 02:15 PM, Jim Lux wrote:
>
>>>
>>> Don't forget the Doppler and relativistic effects of the earth moving
>>> around the solar system barycenter.  But that's not much different
>>> than you do for GPS (e.g. knowing satellite orbits, etc.)
>> Naturally. You also needs to compensate for their decay-rate as you try
>> to span longer periods.
>>
>> You can use them for navigation and time, just like GPS. Even seen a
>> presentation on that.
>>
>
> The big hiccup is that you need a fairly good sized antenna to detect
> the pulsars. They're "bright" in the sense of radio astronomy, but
> remember that those folks think in terms of 1000 ft apertures at
> Arecibo and huge arrays like the VLA or ATA.
>
> http://www.radio-astronomy.org/pdf/pulsars.pdf
> http://www.k5so.com/Radio_astronomy_pulsars.html - an 8.6 meter dish
> with a UHF feed.   He's using a Rb, by the way
>
> http://www.moetronix.com/pulsar/index.htm  They used a 26 meter
> antenna.  Scrolling down, it looks like they're getting a whopping 0.5
> dB SNR on the Crab Nebula pulsar.
>
>
> So, pulsar nav seems a bit impractical for present day space vehicles.
> NCC-1701 Enterprise might be big enough to carry a suitable phased array.
On a space-craft it becomes easier to handle thermal noises thought.

Cheers,
Magnus