dumb question...

what is the incident power density that SETI receivers are looking for? That
is, what is the sensitivity limit?

In article ,
"Bored Huge Krill" wrote:

what is the incident power density that SETI receivers are looking for? That
is, what is the sensitivity limit?

See the sci.astro.seti newsgroup FAQ. It depends on the effective capture
area of the antenna and the receiver noise level and stability. At least
at one time, that FAQ was at: http://gamma.nic.fi/~jknutar/FAQ.txt.

An amateur receiver will be detecting with something like a 12 foot dish,
and will have an effective capture area of about half the physical area,
about 56 square feet. The system noise temperature will be about 100K
(with about 12K of that from extraterrestial sources, at 1.42GHz).
The bandwidth supportable by the stability will be about 10Hz. The signal
will probably be integrated over several minutes, at least in part by eye.

SETI@Home has an effective dish diameter of about 100m, or about 30,000
square metres. The system noise temperature is about 45K (although
this is subsequently degraded by quantisation noise) and the effective
bandwidth is about 75 milli-hertz (mHz), for most of the processing.
There is no integration of the signal at this bandwidth, but the gaussian
and pulse processing do effectively integrate, but only for a maximum
of the 107 second work unit duration.

SERENDIP uses the Gregorian feed, which illuminates more of the dish,
and they almost certainly do integrate the measurements.

Parkes has a smaller dish, but I haven't looked up the exact size. The
1 square kilometre array will, obviously, have rather larger capture
area.

The signal needs to be several times mean noise to avoid too many false
positives. Simple spike detection in SETI@Home uses 22 times.

To an order of magnitude (it was based on an optimistic estimate
of the illumination efficiency at Arecibo) 1GW effective isotropic
radiated power, in the minimum bandwidth, at Proxima Centauri will
produce a S@H spike detection (assuming it is in the field of view).
Arecibo transmitting at 2.2GHz (typically for asteroid tracking, 50%
of which is done with narrow band CW) is capable of 10s of terrawatts,
so 1GW is easily achievable.

I think that the detection threshold for S@H spikes is around 1 Jansky
(to an order of magnitude, and subject to checking the figures - the
FAQ is written in terms of total power budgets and doesn't break out the
receiver sensitivity). If that is right, it is about 1E-26 Watts/square
meter/Hz. For medium range detections, an ideally narrow band signal
will degenerate to about 50mHz.

Narrow band optical SETI is generally quantum limited.

In article ,
"Bored Huge Krill" wrote:

what is the incident power density that SETI receivers are looking for? That
is, what is the sensitivity limit?

See the sci.astro.seti newsgroup FAQ. It depends on the effective capture
area of the antenna and the receiver noise level and stability. At least
at one time, that FAQ was at: http://gamma.nic.fi/~jknutar/FAQ.txt.

An amateur receiver will be detecting with something like a 12 foot dish,
and will have an effective capture area of about half the physical area,
about 56 square feet. The system noise temperature will be about 100K
(with about 12K of that from extraterrestial sources, at 1.42GHz).
The bandwidth supportable by the stability will be about 10Hz. The signal
will probably be integrated over several minutes, at least in part by eye.

SETI@Home has an effective dish diameter of about 100m, or about 30,000
square metres. The system noise temperature is about 45K (although
this is subsequently degraded by quantisation noise) and the effective
bandwidth is about 75 milli-hertz (mHz), for most of the processing.
There is no integration of the signal at this bandwidth, but the gaussian
and pulse processing do effectively integrate, but only for a maximum
of the 107 second work unit duration.

SERENDIP uses the Gregorian feed, which illuminates more of the dish,
and they almost certainly do integrate the measurements.

Parkes has a smaller dish, but I haven't looked up the exact size. The
1 square kilometre array will, obviously, have rather larger capture
area.

The signal needs to be several times mean noise to avoid too many false
positives. Simple spike detection in SETI@Home uses 22 times.

To an order of magnitude (it was based on an optimistic estimate
of the illumination efficiency at Arecibo) 1GW effective isotropic
radiated power, in the minimum bandwidth, at Proxima Centauri will
produce a S@H spike detection (assuming it is in the field of view).
Arecibo transmitting at 2.2GHz (typically for asteroid tracking, 50%
of which is done with narrow band CW) is capable of 10s of terrawatts,
so 1GW is easily achievable.

I think that the detection threshold for S@H spikes is around 1 Jansky
(to an order of magnitude, and subject to checking the figures - the
FAQ is written in terms of total power budgets and doesn't break out the
receiver sensitivity). If that is right, it is about 1E-26 Watts/square
meter/Hz. For medium range detections, an ideally narrow band signal
will degenerate to about 50mHz.

Narrow band optical SETI is generally quantum limited.

David Woolley wrote:

In article ,
"Bored Huge Krill" wrote:

what is the incident power density that SETI receivers are looking for?
That is, what is the sensitivity limit?

See the sci.astro.seti newsgroup FAQ. It depends on the effective capture
area of the antenna and the receiver noise level and stability. At least
at one time, that FAQ was at: http://gamma.nic.fi/~jknutar/FAQ.txt.

I hope there's no FAQ there anymore, since it'd be 3 years old or so. (Not
that it matters on this topic, though)
Mark Taylor was kind enough to take over maintainership, and the faq is now
located at:

http://www.setifaq.org

It's a surprisingly intuitive URL. :-)

David Woolley wrote:

In article ,
"Bored Huge Krill" wrote:

what is the incident power density that SETI receivers are looking for?
That is, what is the sensitivity limit?

See the sci.astro.seti newsgroup FAQ. It depends on the effective capture
area of the antenna and the receiver noise level and stability. At least
at one time, that FAQ was at: http://gamma.nic.fi/~jknutar/FAQ.txt.

I hope there's no FAQ there anymore, since it'd be 3 years old or so. (Not
that it matters on this topic, though)
Mark Taylor was kind enough to take over maintainership, and the faq is now
located at:

http://www.setifaq.org

It's a surprisingly intuitive URL. :-)

thanks!

"David Woolley" wrote in message
...
In article ,
"Bored Huge Krill" wrote:

what is the incident power density that SETI receivers are looking for?
That
is, what is the sensitivity limit?

See the sci.astro.seti newsgroup FAQ. It depends on the effective capture
area of the antenna and the receiver noise level and stability. At least
at one time, that FAQ was at: http://gamma.nic.fi/~jknutar/FAQ.txt.

An amateur receiver will be detecting with something like a 12 foot dish,
and will have an effective capture area of about half the physical area,
about 56 square feet. The system noise temperature will be about 100K
(with about 12K of that from extraterrestial sources, at 1.42GHz).
The bandwidth supportable by the stability will be about 10Hz. The signal
will probably be integrated over several minutes, at least in part by eye.

SETI@Home has an effective dish diameter of about 100m, or about 30,000
square metres. The system noise temperature is about 45K (although
this is subsequently degraded by quantisation noise) and the effective
bandwidth is about 75 milli-hertz (mHz), for most of the processing.
There is no integration of the signal at this bandwidth, but the gaussian
and pulse processing do effectively integrate, but only for a maximum
of the 107 second work unit duration.

SERENDIP uses the Gregorian feed, which illuminates more of the dish,
and they almost certainly do integrate the measurements.

Parkes has a smaller dish, but I haven't looked up the exact size. The
1 square kilometre array will, obviously, have rather larger capture
area.

The signal needs to be several times mean noise to avoid too many false
positives. Simple spike detection in SETI@Home uses 22 times.

To an order of magnitude (it was based on an optimistic estimate
of the illumination efficiency at Arecibo) 1GW effective isotropic
radiated power, in the minimum bandwidth, at Proxima Centauri will
produce a S@H spike detection (assuming it is in the field of view).
Arecibo transmitting at 2.2GHz (typically for asteroid tracking, 50%
of which is done with narrow band CW) is capable of 10s of terrawatts,
so 1GW is easily achievable.

I think that the detection threshold for S@H spikes is around 1 Jansky
(to an order of magnitude, and subject to checking the figures - the
FAQ is written in terms of total power budgets and doesn't break out the
receiver sensitivity). If that is right, it is about 1E-26 Watts/square
meter/Hz. For medium range detections, an ideally narrow band signal
will degenerate to about 50mHz.

Narrow band optical SETI is generally quantum limited.

thanks!

"David Woolley" wrote in message
...
In article ,
"Bored Huge Krill" wrote:

what is the incident power density that SETI receivers are looking for?
That
is, what is the sensitivity limit?

See the sci.astro.seti newsgroup FAQ. It depends on the effective capture
area of the antenna and the receiver noise level and stability. At least
at one time, that FAQ was at: http://gamma.nic.fi/~jknutar/FAQ.txt.

An amateur receiver will be detecting with something like a 12 foot dish,
and will have an effective capture area of about half the physical area,
about 56 square feet. The system noise temperature will be about 100K
(with about 12K of that from extraterrestial sources, at 1.42GHz).
The bandwidth supportable by the stability will be about 10Hz. The signal
will probably be integrated over several minutes, at least in part by eye.

SETI@Home has an effective dish diameter of about 100m, or about 30,000
square metres. The system noise temperature is about 45K (although
this is subsequently degraded by quantisation noise) and the effective
bandwidth is about 75 milli-hertz (mHz), for most of the processing.
There is no integration of the signal at this bandwidth, but the gaussian
and pulse processing do effectively integrate, but only for a maximum
of the 107 second work unit duration.

SERENDIP uses the Gregorian feed, which illuminates more of the dish,
and they almost certainly do integrate the measurements.

Parkes has a smaller dish, but I haven't looked up the exact size. The
1 square kilometre array will, obviously, have rather larger capture
area.

The signal needs to be several times mean noise to avoid too many false
positives. Simple spike detection in SETI@Home uses 22 times.

To an order of magnitude (it was based on an optimistic estimate
of the illumination efficiency at Arecibo) 1GW effective isotropic
radiated power, in the minimum bandwidth, at Proxima Centauri will
produce a S@H spike detection (assuming it is in the field of view).
Arecibo transmitting at 2.2GHz (typically for asteroid tracking, 50%
of which is done with narrow band CW) is capable of 10s of terrawatts,
so 1GW is easily achievable.

I think that the detection threshold for S@H spikes is around 1 Jansky
(to an order of magnitude, and subject to checking the figures - the
FAQ is written in terms of total power budgets and doesn't break out the
receiver sensitivity). If that is right, it is about 1E-26 Watts/square
meter/Hz. For medium range detections, an ideally narrow band signal
will degenerate to about 50mHz.

Narrow band optical SETI is generally quantum limited.