Todo

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sensitivity_calculator.utilities

Module holding functions that handle celestial emission, atmospheric behaviour and Telescope Parameters

class sensitivity_calculator.utilities.Atmosphere[source]

Class to handle atmospheric properties

static calculate_Tatm(weather, obs_freq)[source]

Calculate Atmospheric Temperature

Parameters

weather (float) – PWV in mm
obs_freq (astropy.units.Quantity) – observing frequency

Returns

Brightness temperature of atmosphere

Return type

astropy.units.Quantity

static get_tauz_atm(weather, obs_freq)[source]

Calculate atmospheric optical depth at zenith

Parameters

weather (float) – PWV in mm
obs_freq (astropy.units.Quantity) – observing frequency

Returns

optical depth

Return type

float

static tau_atm(weather, obs_freq, elevation)[source]

Get atmospheric optical depth at given elevation.

Parameters

weather (str) – “Good”, “Average” or “Bad”
obs_freq (astropy.units.Quantity) – observing frequency
elevation (astropy.units.Quantity) – target elevation

Returns

optical depth

Return type

float

class sensitivity_calculator.utilities.Celestial[source]

Class to handle Celestial emission

calculate_Tgal(target, obs_freq, dish_type, alpha)[source]

Calculate Galactic Temperature TODO: Make use of target direction.

Parameters

target (astropy.coordinates.SkyCoord) – target direction
obs_freq (numpy array astropy.units.Quantity) – observing frequency
dish_type (DishType) – the type of dish
alpha (float) – spectral index of emission

Returns

brightness temperature of Galactic emission in beam

Return type

astropy.units.Quantity

class sensitivity_calculator.utilities.DishType(value)[source]: Enumeration for different dish types

class sensitivity_calculator.utilities.TelParams[source]

Class for handling Telescope Parameters

static calculate_Trcv(obs_freq, obs_band, dish_type)[source]

Calculate Receiver Temperature. Works using obs freq only, not band. For SKA1 where bands overlap e.g. band 1, 2, returns the value reflecting the better performer.

Parameters

obs_freq (astropy.units.Quantity) – the observing frequency
obs_band (str) – the observing band [“Band 1”, “Band 2”, “Band 3”, “Band 4”, “Band 5a”, “Band 5b”]
dish_type (DishType) – the type of dish

Returns

T receiver

Return type

astropy.units.Quantity

static calculate_Tspl(dish_type)[source]

Calculate spillover temperature. This is signal from the ground that gets onto the detector. In reality it could depend on the alt/az pointing of the dish - for now it is assumed to be 3K for SKA1 and 4K for MeerKAT.

Parameters: dish_type (DishType) – the type of dish
Returns: T spillover
Return type: astropy.units.Quantity

static calculate_dish_efficiency(obs_freq, dish_type)[source]

Calculate aperture efficiency taking into account losses from feedhorn illumination of the aperture, phase errors at the dish surface, and diffraction.

Parameters

obs_freq (astropy.units.Quantity) – the observing frequency
dish_type (DishType) – the type of dish

Returns

dish aperture efficiency

Return type

astropy.units.Quantity

static dish_area(dish_type)[source]

Calculate geometric area of a specified dish type.

Parameters: dish_type (DishType) – the type of dish
Returns: the dish area
Return type: astropy.units.Quantity

static dish_fwhm(obs_freq, dish_type)[source]

Calculate the full-width at half-maximum (FWHM) of the dish at the observing frequency.

Parameters

obs_freq (astropy.units.Quantity) – the observing frequency
dish_type (DishType) – the type of dish

Returns

the fwhm

Return type

astropy.units.Quantity

static mid_core_location()[source]

Return the astropy EarthLocation of the SKA Mid core site. The data are taken from Wikipedia as astropy does not yet hold site information for the SKA.

Returns: the location of the SKA Mid core site
Return type: astropy.coordinates.EarthLocation

class sensitivity_calculator.utilities.Utilities[source]

Class to contain generally useful methods

static Tx(freq, T)[source]: Function to apply correction to Rayleigh-Jeans temperature to describe the roll-off at high frequency of ‘Johnson noise’ in a resistor. Typically denoted by adding a subscript “x” to the temperature