Controlling the antenna

The direction of the antenna can be specified in several different frames of reference, as follows (units degrees, km):

Local azimuth, elevation frame. Specify azimuth and elevation of local antenna.
A point in space described by:
Longitude, latitude and height.
The azimuth and elevation of the Tromsø antenna together with the range from the Tromsø antenna to that point.
The azimuth and elevation of the Tromsø antenna together with the geocentric height of that point.
As for 3 and 4 above but with respect to an arbitrary reference-site (that is other than Tromsø). The reference-site is set by the command 'CHANGE-REFERENCE-SITE'.

Notes:

The antenna-servo systems are not designed for continous scanning but rather to point antenna to fixed positions.
The time taken for the antenna movements can be (crudely) calculated from the following:
- i) max. velocity of the antenna is ca. 1.3 degrees/second
- ii) max. acceleration of the antenna is 1.3 degrees/second/second.
To achieve the maximum velocity the antenna accelerates for 1 second during which time it moves 0.7 degrees. Likewise the antenna needs 1 second to stop, during which time it moves 0.7 degrees. (When only one motor is operating in either azimuth or elevation drives the maximum velocity is reduced to ca. 1.0 degrees/second).
E.g. to move 45 degrees:
Time = (45 - 2*0.7)/1.3 + 2 = 35 seconds (approximately).
The velocities of the azimuth and elevation drives are independant.
The time taken for all three antennas to move to a common point is the maximum of all the individual antenna scans.
Elevation values up to 95 degrees can be commanded but scan-patterns requiring an individual antenna to scan through zenith are inadvisable because of the large angular changes in azimuth that are required together with any accompanying changes to the polarisers that must be made.

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