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2. Antenna Structure |
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2. Antenna Structure |
2.3 Pointing Errors
The accuracy of the pointing correction increases with the observing frequency, i.e. as the antenna beam width decreases.
Commonly the following is assumed :
δp = pointing accuracy
HPBW = -3 dB beam width (main lobe)
For the Noto antenna the values are listed in the following :
|
Frequency (GHz) |
HPBW (') |
Error (') |
| 1.5 | 29 | ≤ 2.9 |
| 22 | 2 | ≤ 0.2 |
Tab. 2.4 : Beam and pointing errors
The systematic errors are usually quite high (some arcminute). Anyway they have been determined according to the antenna position (Az/El) after apposite astronomical observations (reference radio sources), and a correction model has been derived.
Once the model has been applied, the residual error is 0.1' (both in azimuth and elevation), exactly as required.
