Usage of sensitivity

Return to directory of Todd's CASA extensions

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.)


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)
    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.


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
Topic revision: r4 - 2012-06-27, ToddHunter
This site is powered by FoswikiCopyright © by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding NRAO Public Wiki? Send feedback