Le 28 sept. 2013 à 14:26, Magnus Danielson a écrit : > 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.
I think the radio elescope(s) needed are much smaller. There are apparently 2 pulsar clocks installed here in europe, one in St Catherine's church Gdansk and the other in the European Parliament, Brussels. The Wiki article states "The pulsar clock consists of a radiotelescope with 16 antennas, which receive signals from six designated pulsars. Digital processing of the pulsar signals is done by an FPGA device" . I have tried to find more details without success, but the antennas must be reasonable sized to be installed in such places. I think the OP link indicates that X-ray wavelengths would be used which bring down the detector size. No use on earth though. > On a space-craft it becomes easier to handle thermal noises thought. > > Cheers, > Magnus > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
