lband receiver on the carriage house (seti@home)
01jul02: Crosses on J0840+132
to check pointing and gain.
A 16 foot linefeed on the carriage house (lbch)
is dedicated to the serendip (seti@home) program. They observe full
time with this feed while other people use the dome or carriage house.
The pointing models for the dome are built with the carriage house at stow
position (8.8 degrees za) so most of the time the lbch feed is sitting
at 8.8 degrees. The feed will then be able to see +/- 8.8 degrees from
arecibo's declination (18 degrees). When the dome moves at sidereal rate
to track a source, the lbch will be moving at twice sidereal rate. As the
dome moves to lower zenith angle, the azimuth motion increases to keep
a constant rate on the sky. Since lbch stays fixed at 8.8 degrees za its
speed on the sky will increase by sin(8.8)/sin(zadome).
Azimuth/zenith angle crosses were done on the source
J0840+132 on 01jul02 to check the pointing. The source was tracked from
za=6 degrees until it set. A 5 Mhz bandwidth was detected with a 20 millisecond
time constant and sampled at 100 hz. Each leg of the cross was 30 arcminutes
(great circle) long. 23 crosses were taken and then 2-D gaussians
were fit to each cross giving Tsys, srcStrength, pointing errors in azimuth
and zenith angle, the beam widths for the major and minor axis of the beam
ellipse, and the rotation angle to go from azimuth to the major axis of
the ellipse. The plots
show the results of the data taking.
on J0840+132 to check pointing and gain.
Since i haven't checked this i'd give it about a 50% chance of being correct....
Take the recorded az1,za1, ast time from the serial link.
Compute the model offsets mazoff,mzaoff at az1,za1. The model values
are great circle so you need to divide the azimuth offset by sin(za) to
go from great circle to azimuth encoder.
Compute the values prior to the model: az2=az1-maz1, za2=za1-mza1
Take the great circle errors measured in fig2 above: merraz,merrza and
compute the encoder offsets: erraz=merraz/sin(za), errza=merrza.
compute the theoretical az,za that will be used to go back to ra, dec:
Take az3,za3, the time, and the ao lat,long to go back to ra,dec.