Antenna for receiving pulsar signals

"GD" == George Dishman writes:

GD "Joseph Lazio" wrote in message
GD ...
"GD" == George Dishman writes:

GD Given a quiet local environment and several hours of integration
GD time, what rough size of antenna would be needed to receive
GD millisecond pulsar signals?
I may have missed it in some of the discussion, but it's not clear
to me if you want to detect individual pulses or just take an FFT
and see the spike in the power spectrum.

GD I have to admit I am an armchair astronomer (so far) and my
GD interest is theoretical. I had an idea but thought I might try to
GD learn enough to understand why it won't work before making a fool
GD of myself.

GD The aim is to extract a time reference from a long period of
GD integration on the order of days to weeks given continuous
GD visibility but very limited antenna size (...).

So you need to know the pulsar's period, DM, and maybe its period
derivative, though for millisecond pulsars, period derivatives are
usually fairly small.

So, I approached this question from a slightly different angle.
What should one's target be? I went to the ATNF pulsar database,
URL:http://www.atnf.csiro.au/research/pulsar/psrcat/, and
searched for all pulsars with periods less than 25 ms (by
specifying the condition P0 0.025). [...]

GD There seems to be a break around 10ms with quite a few in the
GD 4-8ms range. Of those only 3 are above 45mJy and the majority are
GD around 15mJy to 30mJy so I guess that would be the target
GD threshold.

GD Do you have a rough comparable figure for the background noise in
GD that band?

Take a look at URL:http://adil.ncsa.uiuc.edu/document/95.CH.01.01.
This is an all-sky map by Haslam et al. at 408 MHz. Pick your
favorite line of sight. You can scale to any other frequency by
scaling by (frequency)^{-2.55}.

Note that this map gives the sky brightness in units of "brightness
temperature."

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"Joseph Lazio" wrote in message
...
"GD" == George Dishman writes:
...
GD The aim is to extract a time reference from a long period of
GD integration on the order of days to weeks given continuous
GD visibility but very limited antenna size (...).

So you need to know the pulsar's period, DM, and maybe its period
derivative, though for millisecond pulsars, period derivatives are
usually fairly small.

Yes but I assume these are fairly well known for the
most easily received pulsars as I believe pulsars are
being considered as timing standards.

...
GD There seems to be a break around 10ms with quite a few in the
GD 4-8ms range. Of those only 3 are above 45mJy and the majority are
GD around 15mJy to 30mJy so I guess that would be the target
GD threshold.

GD Do you have a rough comparable figure for the background noise in
GD that band?

Take a look at URL:http://adil.ncsa.uiuc.edu/document/95.CH.01.01.
This is an all-sky map by Haslam et al. at 408 MHz. Pick your
favorite line of sight. You can scale to any other frequency by
scaling by (frequency)^{-2.55}.

Note that this map gives the sky brightness in units of "brightness
temperature."

Excellent, thanks. I've downloaded the FITS file so now
just need to figure out how to do the unit conversion.

If this is effectively a sky temperature, presumably
the received power in mJy would also depend on the
antenna beam width.

best regards
George

"Joseph Lazio" wrote in message
...
Take a look at URL:http://adil.ncsa.uiuc.edu/document/95.CH.01.01.
This is an all-sky map by Haslam et al. at 408 MHz. Pick your
favorite line of sight. You can scale to any other frequency by
scaling by (frequency)^{-2.55}.

Note that this map gives the sky brightness in units of "brightness
temperature."

In article ,
"George Dishman" writes:
If this is effectively a sky temperature, presumably
the received power in mJy would also depend on the
antenna beam width.

Yes, the surface brightness B = 2 k Tb / w^2, where k is Boltzmann's
constant, Tb is the brightness temperature, and w is the wavelength.
Use k in Joule/K and w in meters, and the result is in W m^-2 Hz^-1
sterad^-1 = 10^26 Jy/sterad. (I haven't dropped a factor of pi, have
I, Joe?) Multiply by steradians in the beam to get flux density.

The formula for B is just the Planck formula in the limit of long
wavelength (the "Rayleigh-Jeans limit").

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