geometry.c File Reference

#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <math.h>
#include <mwalib.h>
#include <star/pal.h>
#include <star/palmac.h>
#include "vcsbeam.h"
#include "gpu_macros.h"

Include dependency graph for geometry.c:

Functions
void	calc_geometric_delays (beam_geom *beam_geom_vals, uint32_t freq_hz, MetafitsMetadata *obs_metadata, gpuDoubleComplex *phi)
	Calculates the phase delays required for phasing up each antenna. More...
void	vmCalcPhi (vcsbeam_context *vm, beam_geom *beam_geom_vals)
	Calculates the phase delays for all relevant frequencies and pointings. More...
void	vmCreateGeometricDelays (vcsbeam_context *vm)
	Allocates memory for the delay phase arrays on both host and device. More...
void	free_geometric_delays (geometric_delays *gdelays)
	Frees memory for the delay phase arrays on both host and device. More...
void	vmPushPhi (vcsbeam_context *vm)
	Copies the delay phase arrays from CPU memory to GPU memory. More...
void	calc_beam_geom (double ras_hours, double decs_degs, double mjd, beam_geom *bg)
	Populates a beam_geom struct with pointing information derived from a given set of RAs, Decs, and MJDs. More...
void	dec2hms (char *out, double in, int sflag)
	Converts a decimal RA to the format "HH:MM:SS.S". More...
void	mjd2lst (double mjd, double *lst)
	Convert MJD to LST. More...
double	parse_ra (char *ra_hhmmss)
	Parse an RA string. More...
double	parse_dec (char *dec_ddmmss)
	Parse a Dec string. More...
double	calc_array_factor (MetafitsMetadata *obs_metadata, uint32_t freq_hz, beam_geom *bg1, beam_geom *bg2)
	Calculates the array factor. More...

Function Documentation

calc_array_factor()

double calc_array_factor	(	MetafitsMetadata *	obs_metadata,
		uint32_t	freq_hz,
		beam_geom *	bg1,
		beam_geom *	bg2
	)

Calculates the array factor.

Parameters

[in]	obs_metadata	The observation metadata
[in]	freq_hz	The frequency in Hz
[in]	bg1	The look-direction
[in]	bg2	The direction in which to calculate the array factor

Returns

The array factor

This function computes the array factor as described in the appendix of Meyers et al. (2017).

calc_beam_geom()

void calc_beam_geom	(	double	ras_hours,
		double	decs_degs,
		double	mjd,
		beam_geom *	bg
	)

Populates a beam_geom struct with pointing information derived from a given set of RAs, Decs, and MJDs.

Parameters

[in]	ras_hours	An array of RAs (in decimal hours)
[in]	decs_degs	An array of Decs (in decimal degrees)
[in]	mjd	The Modified Julian Date
[out]	bg	The struct containing various geometric quantities

The quantities which are calculated are

Quantity	Description
bg->mean_ra	The mean RA of the pointing
bg->mean_dec	The mean Dec of the pointing
bg->az	The azimuth of the pointing
bg->el	The elevation of the pointing
bg->lmst	The local mean sidereal time
bg->fracmjd	The fractional part of the MJD
bg->intmjd	The integer part of the MJD
bg->unit_N	The normalised projection of the look-direction onto local North
bg->unit_E	The normalised projection of the look-direction onto local East
bg->unit_H	The normalised projection of the look-direction onto local "Up"

Todo:

Put the table describing the beam_geom struct where it belongs: with the documentation for the beam_geom struct!

calc_geometric_delays()

void calc_geometric_delays	(	beam_geom *	beam_geom_vals,
		uint32_t	freq_hz,
		MetafitsMetadata *	obs_metadata,
		gpuDoubleComplex *	phi
	)

Calculates the phase delays required for phasing up each antenna.

Parameters

[in]	beam_geom_vals	Struct containing pointing information for the requested beams.
[in]	freq_hz	The frequency in Hz
[in]	obs_metadata	The observation metadata
[out]	phi	The calculated phase delays

This function calculates the phase delays for the given look-direction and frequency, for each antenna. This consists of both a "geometric delay" component, related to the different times a planar wavefront coming from a particular direction arrives at each antenna, and a "cable delay" component, related to the physical lengths of the cables connecting the antennas to the rest of the system.

The equations implemented here are the first three equations in Ord et al. (2019).

dec2hms()

void dec2hms	(	char *	out,
		double	in,
		int	sflag
	)

Converts a decimal RA to the format "HH:MM:SS.S".

Parameters

[out]	out	A buffer for the output string
[in]	in	The decimal RA
	sflag	Whether to include a leading '+'

The out buffer must already be allocated.

Todo:

Figure out whether dec2hms() is actually just for RAs, or whether it is more general than that (and, if so, change the name to reflect this).

free_geometric_delays()

void free_geometric_delays

(

geometric_delays *

gdelays

)

Frees memory for the delay phase arrays on both host and device.

Todo:

Convert free_geometric_delays() into a "vm" function.

mjd2lst()

void mjd2lst	(	double	mjd,
		double *	lst
	)

Convert MJD to LST.

Parameters

[in]	mjd	The Modified Julian Date
[out]	lst	The Local Sidereal Time

Todo:

Consider removing mjd2lst(), since it consists only of a single call to a pal function.

parse_dec()

double parse_dec

(

char *

dec_ddmmss

)

Parse a Dec string.

Parameters

[in]

dec_ddmmss

A string representing a Dec in the DD:MM:SS.S format

Returns

The Dec in decimal degrees.

parse_ra()

double parse_ra

(

char *

ra_hhmmss

)

Parse an RA string.

Parameters

[in]

ra_hhmmss

A string representing an RA in the HH:MM:SS.S format

Returns

The RA in decimal hours.

vmCalcPhi()

void vmCalcPhi	(	vcsbeam_context *	vm,
		beam_geom *	beam_geom_vals
	)

Calculates the phase delays for all relevant frequencies and pointings.

Calls calc_geometric_delays() for all frequencies in the relevant coarse channel, and for all requested pointings.

Todo:

Incorporate the beam_geom struct into the vm struct.

vmCreateGeometricDelays()

void vmCreateGeometricDelays

(

vcsbeam_context *

vm

)

Allocates memory for the delay phase arrays on both host and device.

Free with free_geometric_delays()

vmPushPhi()

void vmPushPhi

(

vcsbeam_context *

vm

)

Copies the delay phase arrays from CPU memory to GPU memory.