# SETI: What would it take to monitor all probable bands.

1. Feb 17, 2008

### Taremos

SETI's current monitoring of RF is a noble cause (in my opinion). How can we hope to discover other intelligent life if we don't listen?

But as I understand it, it is sort of pathetic in terms of the handful of frequencies they actually monitor. So this lead me to these questions:

What would it take to monitor all practical bands of the EMS coming from all directions around Earth. Say if we wanted to be able to pick up any reasonably strong signal from within a 50 light-year sphere around us? "Reasonably strong" is not an exact number, and I don't know enough about the subject to present a number, but lets say if we broadcasted a TV show from one of our satellites into space instead of towards Earth.

We can't monitor everyone at once simultaneously (can we?), so let's say we want to scan for every frequency within that sphere once per year.

It would require a massive amount of equipment, but how much roughly would it take?

And perhaps more importantly, how much computing power would it take to search all that data for hints of an intelligent broadcast?

2. Feb 17, 2008

Staff Emeritus
Rough estimate - Seti@Home is looking at 0.01% of the frequency band space times sky space. So it would have to be 10,000x larger to do a search like you describe. This would certainly require many more telescopes.

Presently, Seti@Home uses 1.8M personal computers. This would have to grow to 18B. At $500 a pop, that's$9T. That dominates the cost: ALMA will build of order 60 telescopes for a billion dollars, so if you needed 1000 or even 10000, the dominant cost is computing. \$9T is approximately the entire economic output of the United States for a year.

3. Feb 17, 2008

### Taremos

Thanks for the reply.

Do you know if SETI@Home's current user base is processing ALL data received, or just a portion of it?

That cost is extremely large, but I think (and hope) that some day we will do it. It probably won't happen in my life time. It's sort of starting to think that even if we were being sent an alien transmission we only have a 0.01% chance of picking it up, even though we try to listen.

4. Feb 17, 2008

### ray b

some bands have too much natural stuff happening on them
others have too much man made use to be practical
so of the remaining bands what % does SETI listen to
I would think they try to pick their best guess at the ones with less problems
longest range at lower powers ect

5. Feb 17, 2008

### JamesBrown

My SETI Station will take 3,300 years or so

I made a calculation on the number of ‘channels’ I had to examine on my personal SETI station (www.SETI.Net). Here are the numbers:

Since you are all computer literate you understand the concept of address space.

If your computer has a gig of main memory and each address of that gig is a byte (8 bits) wide then you have an address space of 1,000,000,000 X 8 bits or 8 Gigabits. SETI Net has its own address space:

The Paraclipse antenna is 12 foot in diameter. At 1420 MHz this equates to a half power beam width of about 3 degrees (HPBW).

The antenna can be positioned in declination between -35 and +27degrees. Based on 3 degrees BW this is about 20 positions of DEC.

This declination band moves past the antenna every 24 hours of RA (360 degrees of earth rotation). At 3 degrees this is 120 positions of RA.

The Band Pass Filter (BPF) just after the LNA has a pass band from 1375 MHz to 1475 MHz for a total of 100 MHz wide search band.

The Icom R7000 receiver running with the DRM module has an Audio Band Width of 20,000 Hz (ABW)

So the address space of SETI Net is:

(BPF/ABW) * (RA/HPBW) * (DEC/HPBW) =

(100 E6 / 20 E3) * (360/3) * (62/3) = 12,000,000 channels to surf (I'd better get started hu).

If I spend 2,000 seconds on each channel then: ~ 2.4E10 seconds or ~ 3,300 years to look ONCE in all my address space

And remember this is from my own *very* limited station.

Regards...... Jim