PtoleMetric.c File Reference

Author:

Jones D.Computes metric components for a pulsar search in the ``Ptolemaic'' approximation. Both the Earth's spin and orbit are included.

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#include <math.h>
#include <stdlib.h>
#include <gsl/gsl_matrix.h>
#include <lal/AVFactories.h>
#include <lal/DetectorSite.h>
#include <lal/LALStdlib.h>
#include <lal/PtoleMetric.h>
#include <lal/PulsarTimes.h>
#include <lal/StackMetric.h>

Include dependency graph for PtoleMetric.c:

Go to the source code of this file.

Defines
#define	MIN_DURATION   (LAL_DAYSID_SI/LAL_TWOPI)
#define	MIN_MAXFREQ   1.
Functions
	NRCSID (PTOLEMETRICC,"$Id: PtoleMetric.c,v 1.32 2007/11/09 18:02:58 kwwette Exp $")
void	LALPtoleMetric (LALStatus *status, REAL8Vector *metric, PtoleMetricIn *input)
void	LALPulsarMetric (LALStatus *stat, REAL8Vector **metric, PtoleMetricIn *input)
	Unified "wrapper" to provide a uniform interface to LALPtoleMetric() and LALCoherentMetric(), from DopplerScan.c, written by Reinhard Prix.
int	XLALFindMetricDim (const REAL8Vector *metric)
	Figure out dimension of a REAL8Vector-encoded (see PMETRIC_INDEX) metric.
gsl_matrix *	XLALSpindownMetric (UINT4 dimension, REAL8 Tspan)
	Frequency and frequency derivative components of the metric, suitable for a directed search with only one fixed sky position.

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Detailed Description

Author:

Jones D.Computes metric components for a pulsar search in the ``Ptolemaic'' approximation. Both the Earth's spin and orbit are included.

I., Owen, B. J., and Whitbeck, D. M.

Date:

2001-2005

Id

PtoleMetric.c,v 1.32 2007/11/09 18:02:58 kwwette Exp

Description

This function computes metric components in a way that yields results very similar to those of LALCoherentMetric() called with the output of LALTBaryPtolemaic(). The CPU demand, however, is less, and the metric components can be expressed analytically, lending themselves to better understanding of the behavior of the parameter space. For short durations (less than about 70000 seconds or 20 hours) a Taylor series expansion is used to improve the accuracy with which several terms are computed.

Algorithm

For speed and checking reasons, a minimum of numerical computation is involved. The metric components can be expressed analytically (though not tidily) in terms of trig functions and are much too large to be worth writing down here. More comprehensive documentation on the derivation of the metric components can be found in the pulgroup CVS archive as docs/S2/FDS/Isolated/ptolemetric.tex. Jones, Owen, and Whitbeck will write up the calculation and some tests as a journal article.

The function LALGetEarthTimes() is used to calculate the spin and rotational phase of the Earth at the beginning of the observation.

On output, the metric->data is arranged with the same indexing scheme as in LALCoherentMetric(). The order of the parameters is .

Notes

The analytic metric components were derived separately by Jones and Whitbeck (and partly by Owen) and found to agree. Also, the output of this function has been compared against that of the function combination (CoherentMetric + TDBaryPtolemaic), which is a numerical implementation of the Ptolemaic approximation, and found to agree up to the fourth significant figure or better. Even using DTEphemeris.c for the true Earth's orbit only causes errors in the metric components of order 10%, with (so far) no noticeable effect on the sky coverage.

At present, only one spindown parameter can be included with the sky location. The code contains (commented out) expressions for spindown-spindown metric components for an arbitrary number of spindowns, but the (commented out) spindown-sky components neglect orbital motion. A separate routine, XLALSpindownMetric(), has been added to compute the metric for multiple spindowns but for fixed sky position, suitable for e.g. directed searches.

Definition in file PtoleMetric.c.

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Define Documentation

#define MIN_DURATION   (LAL_DAYSID_SI/LAL_TWOPI)

Definition at line 99 of file PtoleMetric.c.

#define MIN_MAXFREQ   1.

Definition at line 101 of file PtoleMetric.c.

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Function Documentation

NRCSID	(	PTOLEMETRICC	,
		"$Id: PtoleMetric.	c,
		v 1.32 2007/11/09 18:02:58 kwwette Exp $"
	)

void LALPtoleMetric	(	LALStatus *	status,
		REAL8Vector *	metric,
		PtoleMetricIn *	input
	)

Definition at line 106 of file PtoleMetric.c.

void LALPulsarMetric	(	LALStatus *	stat,
		REAL8Vector **	metric,
		PtoleMetricIn *	input
	)

Unified "wrapper" to provide a uniform interface to LALPtoleMetric() and LALCoherentMetric(), from DopplerScan.c, written by Reinhard Prix.

The parameter structure of LALPtoleMetric() was used, because it's more compact

Definition at line 649 of file PtoleMetric.c.

int XLALFindMetricDim

(

const REAL8Vector *

metric

)

Figure out dimension of a REAL8Vector-encoded (see PMETRIC_INDEX) metric.

Return error if input-vector is NULL or not consistent with a quadratic matrix

Definition at line 798 of file PtoleMetric.c.

gsl_matrix* XLALSpindownMetric	(	UINT4	dimension,
		REAL8	Tspan
	)

Frequency and frequency derivative components of the metric, suitable for a directed search with only one fixed sky position.

The units are those expected by ComputeFstat. This routine allocates a gsl_matrix which should be freed with gsl_matrix_free.

Parameters:

dimension	[in] Dimension of the metric
Tspan	[in] Time span of the data set

Definition at line 834 of file PtoleMetric.c.

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