How smart are SETI@homers?

David Woolley wrote:

However, such an array is beyond the wildest dreams of even
conventional radio astronmers, let alone cash starved SETI
searchers. As well as the problems of surveying and placing
each element, the large amount of electronics involved will
result in a system that will start to lose elements quickly and
have no maintenance man to replace them.

Although I respect your technical expertise, I am not yet
convinced that this array would be expensive to make and
maintain. The array would be made of a large number of
identical, mass produced panels. Damaged panels can be
replaced with new ones. A small percentage of damaged
panels does not seriously degrade the image quality.

The main issue is how much data would have to be
processed. If the array cannot filter out obvious
noise, SETI@homers would be overwhelmed with noise.

In sci.space.policy Andrew Nowicki wrote:
David Woolley wrote:

However, such an array is beyond the wildest dreams of even
conventional radio astronmers, let alone cash starved SETI
searchers. As well as the problems of surveying and placing
each element, the large amount of electronics involved will
result in a system that will start to lose elements quickly and
have no maintenance man to replace them.

Although I respect your technical expertise, I am not yet
convinced that this array would be expensive to make and
maintain. The array would be made of a large number of
identical, mass produced panels. Damaged panels can be
replaced with new ones. A small percentage of damaged
panels does not seriously degrade the image quality.

*FIRST* you say that you respect his expertise and *THEN* immediately
contradict it?


The main issue is how much data would have to be
processed. If the array cannot filter out obvious
noise, SETI@homers would be overwhelmed with noise.

I don't think this would be a problem.

--
Sander

+++ Out of cheese error +++

In sci.space.policy Andrew Nowicki wrote:

Although I respect your technical expertise, I am not yet
convinced that this array would be expensive to make and
maintain. The array would be made of a large number of

Nothing on the far side of the moon, as hypothesized here, is
cheap to maintain!!! It more or less has to be fire and forget
from a maintenance point of view.

(There is another sub-thread about earth based, transmit, arrays.)

In sci.space.policy Andrew Nowicki wrote:
David Woolley wrote:

However, such an array is beyond the wildest dreams of even
conventional radio astronmers, let alone cash starved SETI
searchers. As well as the problems of surveying and placing
each element, the large amount of electronics involved will
result in a system that will start to lose elements quickly and
have no maintenance man to replace them.

Although I respect your technical expertise, I am not yet
convinced that this array would be expensive to make and
maintain. The array would be made of a large number of
identical, mass produced panels. Damaged panels can be
replaced with new ones. A small percentage of damaged
panels does not seriously degrade the image quality.

*FIRST* you say that you respect his expertise and *THEN* immediately
contradict it?


The main issue is how much data would have to be
processed. If the array cannot filter out obvious
noise, SETI@homers would be overwhelmed with noise.

I don't think this would be a problem.

--
Sander

+++ Out of cheese error +++

In sci.space.policy Andrew Nowicki wrote:

Although I respect your technical expertise, I am not yet
convinced that this array would be expensive to make and
maintain. The array would be made of a large number of

Nothing on the far side of the moon, as hypothesized here, is
cheap to maintain!!! It more or less has to be fire and forget
from a maintenance point of view.

(There is another sub-thread about earth based, transmit, arrays.)

David Woolley wrote:

However, such an array is beyond the wildest dreams of even
conventional radio astronmers, let alone cash starved SETI
searchers. As well as the problems of surveying and placing
each element, the large amount of electronics involved will
result in a system that will start to lose elements quickly and
have no maintenance man to replace them.

Although I respect your technical expertise, I am not yet
convinced that this array would be expensive to make and
maintain. The array would be made of a large number of
identical, mass produced panels. Damaged panels can be
replaced with new ones. A small percentage of damaged
panels does not seriously degrade the image quality.

The main issue is how much data would have to be
processed. If the array cannot filter out obvious
noise, SETI@homers would be overwhelmed with noise.

Andrew Nowicki writes:

Mark wrote:

At least we'll know that aliens with big non-directional
radio transmitters are rare.

We have already learned that.

Not really. First, we have only looked a small portion of the
frequency spectrum. If you turn on your TV, and see nothing
on the first two channels you try, you can't tell if there
is any signal (even a very strong one) on another channel. You
need to try all the channels (or at least most) to conclude
signals are rare.

Second, our searches tell us nothing about the directionality
of the source. We can't tell a bright omni-directional
source from a less bright but directional one.

What we need is a non-directional microwave receiver
on the far side of the Moon. It would be a sort of
phase-array radar in reverse -- lots of small receivers
but no directional antennas. To reduce the noise, it
would be used only during lunar night, when the surface
of the Moon is cold.

This is sound in theory, but has a bunch of practical problems.
The biggest is that looking in all directions at once takes
an enormous amount of computer power, far more than we
have right now. (Basically, you need to phase and add all
the elements, and do this as many times as there are beams from
an equivalent sized conventional scope. There are shortcuts
but not enough to make it practical.) Also, given the
current technology, the lunar night is still not cold enough.

The advantage of the non-directional receiver is that
it can detect signals coming from a broad solid angle.

Very true, plus it can study transients, which is very hard for
conventional radio telescopes. The problem is that for the same
amount of money, it is far less sensitive than a conventional
telescope. So if you expect huge but infrequent signals, it's
better, but if you are looking for lower power but always on
signals, a conventional telescope is a better bet. It would
make sense to try both.

Lou Scheffer

In article ,
"Andrew Nowicki " wrote:

Mark wrote:

At least we'll know that aliens with big non-directional
radio transmitters are rare.

We have already learned that.

Even if we did detect a signal, we couldn't tell if it was directional
at source. (We are almost at the point of being able to detect our
analogue TV carriers at interstellar distances (see the 1 sq km array
below), and those, whilst directed to try and avoid wasting power,
are not strongly directional.

What we need is a non-directional microwave receiver
on the far side of the Moon. It would be a sort of
phase-array radar in reverse -- lots of small receivers

I would consider this to be multiple directional beams,
rather than non-directional reception. As far as I know, the
1 square km array, which will be an earth based equivalent, won't
normally attempt to form as many beams as there are elements, but
rather a small number.

However, such an array is beyond the wildest dreams of even
conventional radio astronmers, let alone cash starved SETI
searchers. As well as the problems of surveying and placing
each element, the large amount of electronics involved will
result in a system that will start to lose elements quickly and
have no maintenance man to replace them.

but no directional antennas. To reduce the noise, it
would be used only during lunar night, when the surface
of the Moon is cold.

Modern receiver noise temperatures are generally a long way below
ambient. The cryogenically cooled SERENDIP (S@H) receiver was actually
replace by a non-cooled one with a lower noise. I believe the total
system noise for this receiver is about 45K, of which about 12K is
galactic noise and big bang backround, which can't be eliminated.

Whilst I argue in another thread, that a pure phased array transmitter
is future, rather than current technology, it is not that far off that
it wouldn't be reasonable to assume that an ETI would form multiple
beams to allocate the total power more effectively to likely targets.

The advantage of the non-directional receiver is that
it can detect signals coming from a broad solid angle.

But only at the cost of doing a two dimensional fourier transform,
and then doing the followup signal processing a number of times
comparable to the number of elements. Remember that processing capability
for space qualified equipment is rather moderate compared with
what is on your desk top.

Incidentally, with respect to the subject, there was concern amongst
the professionals that the general public might expect a contact from
S@H when the professionals, whilst hoping for one, thought that setting
new upper bounds was the more likely outcome. This was before it went
fully live. The concern was that there might be a backlash from the
modern instant gratification culture, that might prevent funding of
more sensitive future work.

In sci.space.policy Rich wrote:


In semi-infinite wisdom Andrew Nowicki answered:
When a reasonable person fails to attain his
goal, he either abandons the goal or tries
a different method of attaining the goal.
An idiot is usually defined as someone who
responds to failure by doubling his efforts.

NASA is an ossified bureaucracy, but they are
not idiots. When their big SETI program failed,
they abandoned it.

No, congress told them to stop spending money
on SETI. NASA would spend trillions on SETI if
they had the funds. NASA cannot even account
for where their current funds go, after a GAO
audit.

Yes, but that was not the reason of that funding cut.


SETI@homers ignore their
failures and have little if any interest in
modifying their search method.

What failures? SETI@home is an open research
project. Some expect it to work, but many,
myself included, think even negative evidence
worth having. We'll know what ain't there at
least.


More correctly, we know what wasn't where some time
ago. Remember, radio signals move at a finite speed,
so instead of "now" it is always looking at the past.

A positive result depends on there having been a
civilisation that was a strong radio source emitter
k years ago at the distance of k lightyears. This
is where Drake equation comes into play and why you
need not pay attention to whetever it then goes off
to conquer the stars or not.

The chance of detecting a signal from stars that are
say 5000 - 10000 lightyears awy depends on the chance
of there having been a civbilsation in the radio noise
phase among that relatively largis amount of stars
during teh past 5000-10000 years ago (though to be
sure about outermost stars, we have to listen for 5000
more years). Its an odd kind of archeology ;-)


Rich


--
Sander

+++ Out of cheese error +++

Rich wrote in message ...
Some expect it to work, but many,
myself included, think even negative evidence
worth having. We'll know what ain't there at
least.

Ditto: I _expect_ seti@home to fail to find anything, but still think
that not finding anything would be a useful enough result to justify
the thousands of data blocks I've processed for them. At least we'll
know that aliens with big non-directional radio transmitters are rare.

Mark