The antenna manager makes sure the antenna is at the specified position at the specified time. Interpolation between lines in the table is done by requiring smooth changes of coordinate velocities. It is recommended that the time interval in the table be the time it takes for the object to move by about one HPBW, or less.
The coordinates, in all cases, should be topocentric.
When tracking major planets, there is no need for a user table. GO will generate the ephemeris automatically if you select the planet name under "New Origin".
# The first 3 lines are header/comments. # # UTC RA___apparent___DEC 2002 08 18 16:00:00 11:49:29.63 +31:46:18.1 2002 08 18 16:01:00 11:49:15.59 +31:44:23.8 2002 08 18 16:02:00 11:49:01.59 +31:42:29.6 2002 08 18 16:03:00 11:48:47.64 +31:40:35.6 2002 08 18 16:04:00 11:48:33.72 +31:38:41.8 2002 08 18 16:05:00 11:48:19.84 +31:36:48.1 2002 08 18 16:06:00 11:48:06.01 +31:34:54.6One must select the Coordinate Mode in GO to match what is used in the table (ApparentRaDec in this case).
# PRN14 tracking table (angles in degrees) # visible 01:30 to 3:00 UT # UT date and time Azimuth Elevation 2004 05 16 01:30:06 103.1822 43.0174 2004 05 16 01:30:14 103.2464 42.9721 2004 05 16 01:30:22 103.3105 42.9268 2004 05 16 01:30:30 103.3745 42.8814 2004 05 16 01:30:38 103.4384 42.8360 2004 05 16 01:30:46 103.5023 42.7906Here we must select the coordinate mode in GO to be AzEl.
When running a GO Table like this, the antenna will be at the
specified position (ra,dec) at the specified start time, moving
with the specified rates.
The GO Table format is quite flexible, and depends on the
keywords specified in the header line. One example is as follows:
Another GO Table example includes tracking velocities:
Using a GO Table with rates.
An alternate method is to use a GO Table (activated by clicking the
"GO Tables" button on the main GO screen, typing in the path
to the table, clicking "Load", then clicking "Run").
There may be ten seconds of software overhead when activating
each line of the table, meaning that the GBT may not be
exactly on the right position for a few seconds as it begins
each scan. Using a GO table like this means that each
line of the table will start a new scan with a new scan number.
(On the other hand, if you use a User Table as described above,
the scan length is chosen in GO independently of the table,
e.g. the entire time covered by the table can be one scan.)
#
header \
sc.starttime ra dec ra_rate dec_rate procedure
16:00:00 11:49:29.63 +31:46:18.1 -2.969 -1.900 track
16:05:00 11:48:19.84 +31:36:48.1 -2.931 -1.887 track
16:10:00 11:47:11.06 +31:27:22.0 -2.894 -1.874 track
16:15:00 11:46:03.26 +31:17:59.9 -2.857 -1.860 track
16:20:00 11:44:56.44 +31:08:41.8 -2.821 -1.847 track
16:25:00 11:43:50.57 +30:59:27.6 -2.786 -1.834 track
#
NOTE: there must be no blank spaces following the backslash (\)
in the "header" line !!!
The start times are in UT, and
the ra_rate and dec_rate are in units of arcminutes per minute of time.
Before running one of these tables, set the "New Origin" in GO
to "Off", and set the "secant(dec)" to "Yes", set the Primary
coordinate mode to match the "ra" and "dec" columns in the table,
and set the Offset coordinate mode to match the rates.
header \
sc.source_name ra dec ra_rate dec_rate lo1.srcvel sc.stoptime proc
encke1205 17:55:22.85 -00:39:12.50 -0.05688 -0.05614 18.052860 12:30:00 Track
encke1205 17:55:20.57 -00:39:46.20 -0.05692 -0.05612 18.060560 12:40:00 Track
encke1205 17:55:18.29 -00:40:19.90 -0.05697 -0.05611 18.068960 12:50:00 Track
encke1205 17:55:16.02 -00:40:53.50 -0.05701 -0.05610 18.078060 13:00:00 Track
In this example, the antenna will be at the specified position with
the specified rate at the specified stoptime. One may select whether
the starttime or stoptime refers to UTC or LST by selection of the
UTC/LST button in the GO main screen.
**HPBW
For observing wavelength (&lambda) in cm,
the half-power beamwidth (HPBW) of the GBT in arcminutes
is given by:
HPBW = 0.42λ
Modified by F.Ghigo, May 17, 2004