Usage of sensitivity
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Calculates the rms flux density sensitivity as a function of frequency, bandwidth, integration time, weather, and
target elevation of various telescopes. This is simply a wrapper function for the simutil sensitivity calculator, which
was designed to match the results of the ALMA OT. For the case of ALMA, it also calls simutil.noisetemp() and
the resulting components of the aperture efficiency and receiver temperature are also listed.
(I assume that is uses dual-pol for ALMA and VLA, and single-pol for SMA, but I should check.)
Usage:
au.sensitivity(freq, bandwidth, etime, elevation=None, pwv=None,
antennalist=None, doimnoise=None, integration=None, debug=None,
t_amb=270, airmass=None, tau=None, t_sky=None)
Parameters:
freq: string with units
bandwidth: string with units
time: string with units of seconds
elevation: value in degrees, or string with units
airmass: the airmass (alternative to specifying the elevation)
(if neither elevation nor airmass is specified, then zenith is used)
pwv: value in mm
antennalist: telescope antenna configuration file (standard CASA path will be searched)
domimnoise: default is None
integration: length of individual integration (string with units)
debug: T/F
t_amb: the ambient temperature in K
tau: the opacity to use (instead of the atm model result)
t_sky: the sky temperature to use (instead of the atm model result)
tsys_only: T/F, T=only compute and return the Tsys, not the sensitivity
t_rx: the receiver temperature to use (rather than automatic)
Note: Except for the tsys_only=True mode, this function does not yet work in casa 3.4.0 due to the cal table format change.
Examples:
CASA <2>: au.sensitivity('660GHz', '3.75GHz', '60s', pwv=0.472, antennalist = 'alma_cycle1_2.cfg')
elevation = 90.00, airmass = 1.000
Antenna efficiency: eta_p=0.6198 (25.0 um rms)
Forward efficiency: eta_s=0.9500
Subreflector blockage efficiency: eta_b=0.9961
Illumination efficiency: eta_t=0.8000
Aperture efficiency: p*s*b*t eta_a=0.4692
Correlator quantum efficiency: eta_q=0.8800
Receiver temperature: T_rx = 110.0K
Computed tau=0.558344, t_sky=106.059807 (airmass=1.000000)
Using tau=0.558344, t_sky=106.059807
Tsys = 825.16 K, Tsky = 106.06 K
Sensitivity = 0.991982 mJy
CASA <2>: au.sensitivity('22GHz', '1.0GHz', '60s', elevation='80deg', pwv=5,antennalist= 'vla.a.cfg')
elevation = 80.00, airmass = 1.015
Sensitivity = 0.224718 mJy
CASA <3>: au.sensitivity('345GHz', '3.75GHz', '420s', elevation=80, pwv=0.472, antennalist='/usr/lib64/casapy/data/alma/simmos/alma_cycle1_2.cfg')
elevation = 80.00, airmass = 1.015
Sensitivity = 0.133443 mJy
CASA <5>: au.sensitivity('236GHz', '3.75GHz', '60s', elevation='45deg', pwv=0.472, antennalist='/usr/lib64/casapy/data/alma/simmos/sma.compact.cfg')
elevation = 45.00, airmass = 1.414
Sensitivity = 4.36855 mJy
--
ToddHunter - 2012-06-22