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simulator.setnoise - Function
2.4.1 Set the noise level fixed sigma (mode=simplenoise) or Brown’s equation using
the ATM model for frequency-dependent atmospheric opacity (mode=tsys-atm) or
Brown’s equation, manually specifying the zenith opacity (constant across the band)
and atmospheric temperature (mode=tsys-manual)
Description
Set various system parameters from which the thermal (ie, random additive)
noise level will be calculated.
For mode=simplenoise, one specifies the standard deviation for the noise to be added to real and imaginary parts of the visibility.
For mode=tsys-atm or tsys-atm, the noise will vary with dish diameter,
antenna efficiency, system temperature, opacity, sky temperature, etc. The
noise will increase with the airmass if tau is greater than zero. The noise is
calculated according to the Brown Equation (ie, R.L. Brown’s calculation of
MMA sensitivity, 3Oct95): dS = 4 sqrt(2) [ T_rx e
+ T_atm ( e
- epsilon_l) + T_cmb] / [ epsilon_q epsilon_a pi D
sqrtDelta nu Delta t ]
For mode=tsys-atm, the sky brightness temperature is calculated using an atmospheric model created for the user-input PWV. For mode=tsys-manual, the user specifies the sky brightness temperature manually.
Arguments
| Inputs |
| ||
| mode |
| Mode of operation.
| |
| allowed: | string |
|
| Default: | simplenoise ’simplenoise’ ’tsys-atm’ ’tsys-manual’ |
|
| table |
| Name of optional cal table to write
| |
| allowed: | string |
|
| Default: | ” | |
| simplenoise |
| Level of noise if not calculated
| |
| allowed: | any |
|
| Default: | variant 0.1Jy |
|
| pground |
| Ground pressure for ATM model (if tsys-atm)
| |
| allowed: | any |
|
| Default: | variant 560mbar |
|
| relhum |
| ground relative humidity for ATM model (if tsys-atm)
| |
| allowed: | double | |
| Default: | 20.0 |
|
| altitude |
| site altitude for ATM model (if tsys-atm)
| |
| allowed: | any |
|
| Default: | variant 5000m |
|
| waterheight |
| Height of water layer for ATM model (if tsys-atm)
| |
| allowed: | any |
|
| Default: | variant 200m |
|
| pwv |
| Precipitable Water Vapor ATM model (if tsys-atm)
| |
| allowed: | any |
|
| Default: | variant 1mm |
|
| tatmos |
| Temperature of atmosphere [K] (if tsys-manual)
| |
| allowed: | double | |
| Default: | 250.0 |
|
| tau |
| Zenith Atmospheric Opacity (if tsys-manual)
| |
| allowed: | double |
|
| Default: | 0.1 |
|
| antefficiency |
| Antenna efficiency
| |
| allowed: | double |
|
| Default: | 0.8 |
|
| spillefficiency |
| Forward spillover efficiency
| |
| allowed: | double |
|
| Default: | 0.85 |
|
| correfficiency |
| Correlation efficiency
| |
| allowed: | double |
|
| Default: | 0.88 |
|
| trx |
| Receiver temp (ie, all non-atmospheric Tsys
contributions) [K]
| |
| allowed: | double |
|
| Default: | 50 |
|
| tground |
| Temperature of ground/spill [K]
| |
| allowed: | double |
|
| Default: | 270.0 |
|
| tcmb |
| Temperature of cosmic microwave background [K]
| |
| allowed: | double |
|
| Default: | 2.73 |
|
| OTF |
| calculate noise on-the-fly (WARNING: only experts with
high-RAM machines should use False)
| |
| allowed: | bool |
|
| Default: | true |
|
| senscoeff |
| sensitivity constant (1./sqrt(2) for interferometer
[default]; 1. for total power)
| |
| allowed: | double |
|
| Default: | 0. |
|
| rxtype |
| Receiver type; 0=2SB, 1=DSB e.g. ALMA B9
| |
| allowed: | int |
|
| Default: | 0 |
|
bool
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Copyright © 2016 Associated Universities Inc., Washington, D.C.
This code is available under the terms of the GNU General Public Lincense
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