Simulation of the SKA1 LOW single station response

Key stakeholders: LOW TDT (Daniel Heyden, Mark Waterson, Maria Grazia), System scientist (Robert Laing).

In order to support work to better understand the calibratability of SKA1-LOW stations we need to create a script and associated data sets which simulate the response of a single station based on realistic behaviour of station components. Ultimately, this simulation of the station response should include

1. A  physics physically-based model of the response of the individual receive paths between the antenna and the ADC (LNAs, analog filters, RFoF links, cables, etc.). In particular, this model should reflect the transfer function (gain) changes of those receive path over a day due to temperature and solar irradiation changes as well as variations in production tolerances among components.
2. A realistic antenna response based on EM-simulations validated by drone measurements on the AAVS prototype system. The simulation should be able to simulate data with an individual Embedded Element Pattern (EEP) for each antenna as well as with an identical EEP for all antennas equal to the average EEP provided by the EM-simulations.
3. A sky model that is relevant for station calibration, i.e., this sky model should include the diffuse emission from the Galaxy and the Sun.
4. A model for the ionosphere that describes the distortion of the sky as seen by a station under different ionospheric conditions. At the level of an individual station, the dominant effects are scintillation and position shifts of point sources that vary across the field-of-view. Diffuse emission from the Galaxy is hardly affected under reasonable ionospheric condition. In constructing the sky model mentioned above, it may thus be useful to have one that represents the diffuse emission and point sources separately.

First useful assessments can already be made when the simulation includes EEPs and a rudimentary sky model. This suggests the following order of "MVPs":

1. Simulation with a realistic antenna response and a rudimentary but representative sky model.
2. Extension of the previous simulation with a physics physically-based model of the response of individual receive paths.
3. Extension of the previous simulation with an improved sky model, ideally one that separates diffuse emission and point sources.
4. Extension of the previous simulation with ionospheric distortion on the received signals.

The aim of this ticket is to tick the first two items. Items 3 and 4 can be considers as stretch goals or scheduled for a later PI.