Dear Frank,
First a warning. 2D antenna patterns in ARTS are implemented in a crude
way and result in slow calculations. In addition, hardly used and
accordingly not very well tested.
Not sure where you need help. I would suggest to start without
polarization. You seem to have what is needed. The max response of the
antenna pattern, the boresight, should be placed at zenith=0 and
azimuth=0. If comparing to lat/lon, zenith=0 should be placed at the
equator, so a change in e.g. 0.001 deg in zenith and azimuth give equal
changes at some distance. I hope the description of antenna_response is
clear enough to understand how to fill the variable/file.
Even if your antenna data are normalized, I still recommend to set
sensor_norm=1. Otherwise, discretization inside ARTS could have an effect.
Set antenna_dlos to [[0]].
The tricky part is to set mblock_dlos_grid. This variable is a bit
special. It contains a set of relative deviations from the boresight, as
pairs of zenith and azimuth deviations. mblock_dlos_grid descrives the
"pattern" of pencil beam calculations done, to estimate the radiance
field seen by the antenna.
If you look at sensor_responseAntenna, there are two options. I
recommend the "interp_response" option. Here you basically define a
dza_grid and daa_grid, and put all combinations in mblock_dlos_grid in
the order described.
When you get this to work and results look OK, then add polarisation.
You could be the first one to use 2D antennas with polarisation. So
maybe also do this with 1D antenna to verify.
I hope this is of help. Don't hesitate to ask if something still is
unclear, or you get stuck.
Bye,
Patrick
On 2022-10-17 18:42, Werner, Frank (329D) wrote:
Dear ARTS team,
After playing around with a 1d Gaussian antenna response (using the
workspace variable ‘AntennaConstantGaussian1D’), I now want to set a
custom antenna pattern from actual lab measurements.
I have vectors for the zenith and azimuth angles, as well as a grid of
normalized antenna responses for each Stokes vector element. The
normalization follows the ARTS behavior, where the integral of the
responses over all angle increments is 1.
Can you guys help me out with correctly using that info in ARTS? I
briefly looked at creating a workspace variable named ‘antenna_response’
with ‘GriddedField4’, but somehow the format confuses me. Also, I am
pretty sure that this is not enough and there probably are more steps I
need to take for ARTS to accept that variable as the antenna pattern.
Thanks for your help and best wishes,
Frank
--
Frank Werner
Mail Stop 183-701, Jet Propulsion Laboratory
4800 Oak Grove Drive, Pasadena, California 91109, United States
Phone: +1 818 354-1918
