| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 950.1 | | skylab.zko.dec.com::FISHER | I've advocated term limits for 19 years! - Rep Bob Dornan | Tue Oct 31 1995 15:43 | 14 |
| I was there yesterday at the dedication. It was very exciting to see Frank
Drake and Paul Horowitz, and to see the official turn-on.
We also got a tour through the control room. There was a graduate student
around to answer questions. They have several gigs of memory, largely used by
special hardware to to 250-million point (I may have the number wrong) FFTs.
Then then transfer the FFT output to 21 Pentium PCs to do data reduction.
Most exciting, after a while they moved the dish so it pointed straight up and
we got to climb up into it. Some people even climbed the parabolic surface up
to the edge to look off at Boston. I was not quite that brave. I was quite
amazed how strong the thing is, though.
Burns
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| 950.2 | Upgrading of parts of a system defines "new" legitimately | NETCAD::BATTERSBY | | Tue Oct 31 1995 20:06 | 8 |
| It's new electronics. So in a sense, the Herald is right the new
electronics combined with the existing dish makes for a "new"
radio telescope capable of improved resolution & performance.
Stretching the definition of things is not new to the print media.
I've been up there in years past, & would like to go through one
of their tours now that they have upgraded things.
Bob
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| 950.3 | | skylab.zko.dec.com::FISHER | I've advocated term limits for 19 years! - Rep Bob Dornan | Wed Nov 01 1995 12:04 | 34 |
| Oops...I guess I did not read the entire first post.
Yes, Bob is 100% correct. The stuff in the control room is new. The dish is
old. (Gave one pause to go climbing around on it, actually!)
I suspect that there may be at least some new electronics in the dish as well.
They described that one of the mechanisms for detecting false alarms is that
there are two antennae in the dish offset from one another by a small amount on
the East/West line. A real extra-terrestrial signal will show up first in the
east feedhorn and then in the west (as the Earth rotates). If it seems to do
the right thing, they sweep the dish to the east of the source and let it pass
through again. In any case, I believe that they must have added the new
receivers.
I'm not sure what actually lives in the antenna itself. Surely they must have
LNAs (low-noise amplifiers), but I'm not sure if they mix the signal down to a
lower frequency or not. I do know that the A/D converters are in the building,
and I know that the FFT processing is the way they manage to get the 250 million
channels (at about 1/2-Hertz wide). That means that we actually have some RF
(or IF) going into the building.
You know, I wish I had asked the following question, but I had not worked it out
at the time. The dish appears to only move on a single axis. That axis appears
to run E/W. There was an axis that ran parallel to the Earth's axis, but I
believe they only use that once in a *great* while (maybe only once 40 years
ago!) to calibrate. It was clearly not used frequently. In any case, given
that this is all true, how do they sweep the east of the source to let it come
through again? I'm sure from the explanation that they don't wait till the next
day...that was the whole point of this system...you can get some checks right
away. I'm confused. Do they move the feedhorns? (I wonder how far you can
move them and still be within a region where you are gettin reasonable signal
from the dish?)
Burns
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| 950.4 | Inside view | NETCAD::MORRISON | Bob M. LKG2-A/R5 226-7570 | Fri Apr 11 1997 14:46 | 14 |
| This winter I took an adult education course in Harvard (town) taught by
Joe Caruso, an astronmer at Oak Ridge Observatory. We went to the observatory
twice. We spent most of the time on optical astronomy, but I talked him into
taking me and part of the class on a tour of the SETI equipment.
It actually was sort of an anticlimax. I had pictured a large roomful of
equipment. In fact, the equipment fills an area of about 100 square feet.
There is a "bakery cart" on which the 21 Pentium computers reside (just the
boxes, no monitors or keyboards), butted up against each other. The BETA array
itself consists of several hundred circuit boards in a single-bay rack.
There is a control panel consisting of a workstation computer and a rack of
gauges and dials. That's about it.
It's entirely run by remote control from Cambridge. There is nobody in the
building most of the time. They have a dedicated Ethernet link to Cambridge
to transmit the processed data.
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