High Angle Range WU, what is the highest acceptable design value (PR - telescope)?

High Angle Range WU, what is the highest acceptable design value (PR -
telescope)?

Why is this not indiacted in the SETI client itself?
Why is the work unit not tagged as [meta-data] invalid for the PR telescope,
if such high Angle Ranges are reached?

Anyone ever see a wu with such an angle range...?
===============================
Name 20no03aa.23948.19874.742326.232
Recording Time 11/20/03 1:50 PM
Base Frequency 1,419,765,625
Start RA 22.818 End RA 37.066
Start DEC 24.85 End DEC 18.81
Angle Range 128.678
Receiver ao1420
Best Gaussian score 0.0 power 0.0 fit 0.0
Best Spike score 0.0 power 0.0
Best Pulse score 0.0 power 0.0
Best Triplet score 0.0 power 0.0
Tape Version 1.4
===============================

I'm not involved with SETI@Home and I'm not sure what the "angle range"
is supposed to represent, but I'll speculate anyway. The start and end
declinations are well within the available range for Arecibo (roughly 0
to 36 degrees). The end RA of 37.066 doesn't make sense since RA is
usually measured in hours, from 0 to 23:59:59). The value is ok if RA
has been converted to degrees (0 - 360).

If the "angle range" represents the movement of the antenna in azimuth,
the value could be reasonable. The end declination of 18.81 degrees is
very nearly directly overhead (the zenith) for the telescope. Tracking
or scanning near the zenith requires a lot of motion in the azimuthal
direction.

Peter Backus
SETI Institute

Max Power wrote:
High Angle Range WU, what is the highest acceptable design value (PR
-
telescope)?

Why is this not indiacted in the SETI client itself?
Why is the work unit not tagged as [meta-data] invalid for the PR
telescope,
if such high Angle Ranges are reached?

Anyone ever see a wu with such an angle range...?
===============================
Name 20no03aa.23948.19874.742326.232
Recording Time 11/20/03 1:50 PM
Base Frequency 1,419,765,625
Start RA 22.818 End RA 37.066
Start DEC 24.85 End DEC 18.81
Angle Range 128.678
Receiver ao1420
Best Gaussian score 0.0 power 0.0 fit 0.0
Best Spike score 0.0 power 0.0
Best Pulse score 0.0 power 0.0
Best Triplet score 0.0 power 0.0
Tape Version 1.4
===============================

"Max Power" wrote:

High Angle Range WU, what is the highest acceptable design value (PR -
telescope)?

URL: http://www.naic.edu/~astro/general_info/basic.shtml gives some
information from which this can be estimated:

Declination range -01:24:00 through +38:00:00
Azimuth Slew Rate 0.4 deg/s, 1440 deg/hour
Elevation Slew Rate 0.04 deg/s, 144.0 deg/hour
Zenith angle range 1.06 - 19.69 degrees

Azimuth can slew 42.8 degress in the 107 second duration of a S@H
classic WU. Starting at 201.4 deg. az. and ending at 244.8 deg. is
one possibility. If the elevation were fully depressed, the
declination for those points would be close to zero, and I estimate
the motion at about 28.7 degrees of angle range. The Earth's rotation
in those 107 seconds adds 0.45 degrees, so I'd say 29 degrees is
a reasonable figure for the largest possible angle range.

--
Joe

Josef W. Segur wrote:

"Max Power" wrote:

High Angle Range WU, what is the highest acceptable design value (PR -
telescope)?

URL: http://www.naic.edu/~astro/general_info/basic.shtml gives some
information from which this can be estimated:

Declination range -01:24:00 through +38:00:00
Azimuth Slew Rate 0.4 deg/s, 1440 deg/hour
Elevation Slew Rate 0.04 deg/s, 144.0 deg/hour
Zenith angle range 1.06 - 19.69 degrees

Azimuth can slew 42.8 degress in the 107 second duration of a S@H
classic WU. Starting at 201.4 deg. az. and ending at 244.8 deg. is
one possibility. If the elevation were fully depressed, the
declination for those points would be close to zero, and I estimate
the motion at about 28.7 degrees of angle range. The Earth's rotation
in those 107 seconds adds 0.45 degrees, so I'd say 29 degrees is
a reasonable figure for the largest possible angle range.

Oops, I tried to work too much of that in my head and sent it without
double checking. I revise my estimate of the angle range due to feed
motion to half the above, giving 15 degrees as a reasonable max angle
range.

--
Joe

Josef W. Segur wrote:
[...]
the motion at about 28.7 degrees of angle range. The Earth's rotation
in those 107 seconds adds 0.45 degrees, so I'd say 29 degrees is
a reasonable figure for the largest possible angle range.

That could be increased if the antenna were being scanned as was the
case for the special WUs for the s@h 24 hours of follow-up searches.

Then again, a few WUs could have bad numbers just as some have bad
coordinates that have rolled past 24h...

Regards,
Martin

--
---------- OS? What's that?! (Martin_285 on Mandrake)
- Martin - To most people, "Operating System" is unknown & strange.
- 53N 1W - Mandrake 10.1 GNU Linux - An OS for Supercomputers & PCs
---------- http://www.mandrakelinux.com/en-gb/concept.php3

In article ,
Max Power wrote:

High Angle Range WU, what is the highest acceptable design value (PR -
telescope)?

Something around 63 degrees, although possibly not in 107 seconds.

This is actually more difficult to compute than it at first seems. There
will always be a component of about 0.5 degrees due to earth rotation, but
this needs to be combined in a vector manner with the rest of the range.
For useful work units, the telescope is either locked down or is
tracking with the carriage house or Gregorian receivers. When locked down,
only the 0.5 or so degrees component will apply. When tracking with the
carriage house, one would expect an approximately zero range. When the
Gregorian is tracking, the carriage house will, typically, be swept in
an arc, but that arc will be a small part of the possible motion during
any one work unit.

When repositioning, there could be a much larger angle range. Moreover,
the motion may not be uniform. Generally such work units are not terribly
useful.

The telescope pointing data is only available at the start of each block
of data on the data logger tapes (these positions are included in the full
work unit header). The latest BOINC working version of the splitter
computes the overall angle range by summing up the great circle angles
between the starts and ends of each block:

for (j=2;jTAPE_FRAMES_PER_WU;j++) {
wugrp.data_desc.true_angle_range+=angdist(tapehead er[startframe+j-1].tels
tr,tapeheader[startframe+j].telstr);
}

The maximum possible excess angle range over that from earth rotation, in
one hop, is from minimum altitude in one direction (about 70 degrees)
to minimum in the opposite, i.e. about 40 degrees. The maximum possible
non-earth rotation component, integrated around the whole path, for a
motion that doesn't double back on itself, is probably that for a 180
degree azimuth rotation with the carriage house at 70 degrees declination
(where it is most of the time). Although one should really use spherical
trig, I think a reasonable approximation would be to assume pi/2 times
the 40 degrees for the direct motion, giving about 63 degrees. To get
a more accurate figure one needs to account for earth rotation, spherical
trig and for the measurements on the tape defining an inscribed polygon,
not the actual circular motion.

A direct, great circle, motion over the 40 degree range isn't really
possible because the Gregorian will block the carriage house, so it
would have to be done with an azimuth swing.

The real maximum may well be less as it may not be possible to slew
through 180 degrees in 107 seconds. That information is probably
available on the Arecibo web site.

Why is this not indiacted in the SETI client itself?

Probably the same reason that your spelling error isn't *indicated* by
my newsreader.

Why is the work unit not tagged as [meta-data] invalid for the PR telescope,
if such high Angle Ranges are reached?

Presumably because the client doesn't expect the splitters to create this
sort of error and, given that it does, it doesn't matter in that the bad
work unit can be rejected later, if it otherwise looks interesting.

In this case, I suspect that there was a gap in the data and the angle range
has actually be computed over several hours, rather than 107 seconds.

Max Power wrote:
High Angle Range WU, what is the highest acceptable design value (PR -
telescope)?

David Woolley covered this ...


Why is this not indiacted in the SETI client itself?
Why is the work unit not tagged as [meta-data] invalid for the PR telescope,
if such high Angle Ranges are reached?

Good question ...
I don't know the answer ...
(I'm not helping much so far ...)



Anyone ever see a wu with such an angle range...?

Aha! Yes, I've recieved a number of these WU with angle range of 128.678
just as you have indicated in the table below.

They are all from 20 Nov 2003 at 13:50:05UTC just as you indicate in the
table below. This is the time frame that Project Phoenix was at Arecibo
doing their data collection. Perhaps Peter Backus can check the logs to
see what was going on at this time?

Even though the End RA is wrong (should be 37.066 - 24.000 = 13.066
hours), I think the angle range is right. That is, I don't think the End
RA being wrong caused the angle range to be calculated in error.
Al

===============================
Name 20no03aa.23948.19874.742326.232
Recording Time 11/20/03 1:50 PM
Base Frequency 1,419,765,625
Start RA 22.818 End RA 37.066
Start DEC 24.85 End DEC 18.81
Angle Range 128.678
Receiver ao1420
Best Gaussian score 0.0 power 0.0 fit 0.0
Best Spike score 0.0 power 0.0
Best Pulse score 0.0 power 0.0
Best Triplet score 0.0 power 0.0
Tape Version 1.4
===============================

Project Phoenix typically observed from 5PM to 8 AM AST. I checked the
log for 20 Nov 2003 and we indeed went off the telescope at 8:00 AM
AST, 1200 UT. The Electronics Department was scheduled to perform
maintenance from 8AM until about 1:30 PM (1730UT). So that would cover
the time in question, 1350 UT.

Peter Backus
Project Phoenix

PS: You can check the Arecibo schedule on the web at:
http://www.naic.edu/vscience/schedule/scedfra2.htm


Alfred A. Aburto Jr. wrote:
Max Power wrote:
High Angle Range WU, what is the highest acceptable design value
(PR -
telescope)?

David Woolley covered this ...


Why is this not indiacted in the SETI client itself?
Why is the work unit not tagged as [meta-data] invalid for the PR
telescope,
if such high Angle Ranges are reached?

Good question ...
I don't know the answer ...
(I'm not helping much so far ...)



Anyone ever see a wu with such an angle range...?

Aha! Yes, I've recieved a number of these WU with angle range of
128.678
just as you have indicated in the table below.

They are all from 20 Nov 2003 at 13:50:05UTC just as you indicate in
the
table below. This is the time frame that Project Phoenix was at
Arecibo
doing their data collection. Perhaps Peter Backus can check the logs
to
see what was going on at this time?

Even though the End RA is wrong (should be 37.066 - 24.000 = 13.066
hours), I think the angle range is right. That is, I don't think the
End
RA being wrong caused the angle range to be calculated in error.
Al

===============================
Name 20no03aa.23948.19874.742326.232
Recording Time 11/20/03 1:50 PM
Base Frequency 1,419,765,625
Start RA 22.818 End RA 37.066
Start DEC 24.85 End DEC 18.81
Angle Range 128.678
Receiver ao1420
Best Gaussian score 0.0 power 0.0 fit 0.0
Best Spike score 0.0 power 0.0
Best Pulse score 0.0 power 0.0
Best Triplet score 0.0 power 0.0
Tape Version 1.4
===============================

wrote:
Project Phoenix typically observed from 5PM to 8 AM AST. I checked the
log for 20 Nov 2003 and we indeed went off the telescope at 8:00 AM
AST, 1200 UT. The Electronics Department was scheduled to perform
maintenance from 8AM until about 1:30 PM (1730UT). So that would cover
the time in question, 1350 UT.

Peter Backus
Project Phoenix

PS: You can check the Arecibo schedule on the web at:
http://www.naic.edu/vscience/schedule/scedfra2.htm

Thank you Peter. I forgot about the Arecibo schedule. I used to check it
now and then to see what my WU were doing (more or less that is since we
are generally at the other end of the declination arm).

It seems that we have been processing data that should have been thrown
out however. Rats!
Al

[snip,snip]