provided that the object of interest does not move to fast.
The main disadvantage of program tracking is that prediction calculations for stationary satellites
always are only valid for a couple of days, then a new file must be calculated and loaded to the
ACU.
To use the program tracking facility of the ACU, follow the step by step instructions below:
1. Create a "program.txt" file with the antenna pointings you want to track. SatService GmbH
offers a PC Software for this purpose which calculates the antenna pointing from commonly
used ephemeris data sets for geostationary satellites. You also may create the file by your
own means. The file format is described in chapter
'8.5.2 File Format'
.
2. Set the 'tracking interval' parameter to a value significantly below the intervals between the
position entries in the file. Setting it to 60 seconds will work with most applications.
3. Switch the 'tracking mode' to 'PROGRAM'.
The antenna will move as defined in the "program.txt" file. The ACU polls the file every 'tracking
interval' seconds and moves the antenna if it finds a table entry which is time stamped within the
next 'tracking interval'. Be aware, that the clock in the ACU must be set precisely to make the
feature work as expected.
The "program.txt" file is a plain text file containing a three or four column table. Empty lines are
ignored, comments starting with a '#' as well. The numbers in the table are parsed as floating
point numbers which only may consist of decimal digits, one decimal point ans an optional leading
'-' if negative. The columns must be separated by an arbitrary number of space or tabulator
characters. They have the following meanings:
1. time stamp --- The time stamp must be a Julian date with the time of day coded as a
fraction of a day. Example: The Julian date for the common base of most computer clocks
(1970-01-01 00:00:00) is 2440587.5
2. azimuth angle --- The azimuth angle in degrees
3. elevation angle --- The elevation angle in degrees
4. polarization angle --- The polarization angle in degrees. This column is optional, no
polarization pointing is commanded if this column is missing.
The example below shows an excerpts of a program tracking file containing azimuth and elevation
angles
2459145.02083333 159.5000 32.2000
2459145.02222222 159.6000 32.2150
2459145.02361111 159.7000 32.2300
2459145.02500000 159.8000 32.2450
.
.
.
.
2459145.48194444 192.7000 37.1800
2459145.48333333 192.8000 37.1950
2459145.48472222 192.9000 37.2100
2459145.48611111 193.0000 37.2250
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www.satnms.com
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