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In addition to the reference position(s) set up above, the 4 following
elements have to be computed:
- lambda offset from reference position,
- beta offset,
- azimuth,
- elevation
All these elements are available in the Antenna Slow table, at
a typical sampling rate of 1 Hz. Since the spectra dumps can be
produced at different time sampling (no assumption is made on the rate
or its variations), each spectrum positions are interpolated from the
Antenna table thanks to their respective Modified Julian Day
values:
 |
(5) |
where
is the spectrum MJD value, and
is the MJD
value of the
trace in the Antenna Slow table.
is computed
thanks to a dichotomic search in the table such as:
 |
(6) |
being the interpolation fraction between the
and
trace, the positions are interpolated by:
 |
(7) |
where
and
are the spectrum and antenna lambda offsets
respectively. Same formula applies for the beta, azimuth, and
elevation values.
If
is found beyond the Antenna Slow table limits, the boundary
values are applied without extrapolation. However, this is not
expected to happen since such spectra should be rejected since they
are out of the on-track range.
Next: Antenna Slow and Fast
Up: Positions
Previous: Reference
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Gildas manager
2015-03-19