casacore::Aberration Class Reference

Aberration class and calculations. More...

#include <Aberration.h>

Public Types
enum	AberrationTypes {   STANDARD,   NONE,   B1950 }
	Types of known Aberration calculations (at 1995/09/04 STANDARD == IAU1980) More...

Public Member Functions
	Aberration ()
	Default constructor, generates default J2000 Aberration identification. More...
	Aberration (const Aberration &other)
	Copy constructor. More...
	Aberration (AberrationTypes type)
	Constructor with type. More...
Aberration &	operator= (const Aberration &other)
	Copy assignment. More...
	~Aberration ()
const MVPosition &	operator() (Double epoch)
	Operator () calculates the Aberration direction cosine vector. More...
const MVPosition &	derivative (Double epoch)
	Return derivative of Aberration (d-1) w.r.t. More...
void	init ()
	Re-initialise Aberration object. More...
void	init (AberrationTypes type)
void	refresh ()
	Refresh calculations. More...

Static Public Attributes
static const Double	INTV
	Interval to be used for linear approximation (in days) More...

Private Member Functions
void	copy (const Aberration &other)
	Copy. More...
void	fill ()
	Fill an empty copy. More...
void	calcAber (Double t)
	Calculate Aberration angles for time t. More...

Private Attributes
AberrationTypes	method
	Method to be used. More...
Double	checkEpoch
	Check epoch for linear approximation. More...
Double	aval [3]
	Cached calculated angles. More...
Double	dval [3]
	Cached derivatives. More...
Int	lres
	To be able to use referenced results in simple calculations, a circular result buffer is used. More...
MVPosition	result [4]
	Last calculation. More...

Static Private Attributes
static uInt	interval_reg
	Interpolation interval. More...
static uInt	usejpl_reg
	JPL use. More...

Detailed Description

Aberration class and calculations.

Intended use:

Public interface

Review Status

Reviewed By:

UNKNOWN

Date Reviewed:

before2004/08/25

Test programs:

tMeasMath

Prerequisite

• Measure class, especially MEpoch
• MeasData class for constants

Etymology

Aberration

Synopsis

Aberration forms the class for Aberration calculations. It is a simple container with the selected method, and the mean epoch.
The method is selected from one of the following:

• Aberration::STANDARD (at 1995/09/04 the IAU1980 definition)
• Aberration::NONE
• Aberration::B1950

Epochs can be specified as the MJD (with defined constants MeasData::MJD2000 and MeasData::MJDB1950 or the actual MJD), leading to the following constructors:

• Aberration() default; assuming JD2000, IAU1980
• Aberration(method) assuming the correct default epoch of JD2000 or B1950
• Aberration(method,epoch) with epoch Double(MJD).

Actual Aberration for a certain Epoch is calculated by the () operator as Aberration(epoch), with epoch Double MJD, values returned as an MVPosition.
The derivative (d^-1) can be obtained as well by derivative(epoch).
The following details can be set with the Aipsrc mechanism:

• measures.aberration.d_interval: approximation interval as time (fraction of days is default unit) over which linear approximation is used
• measures.aberration.b_usejpl: use the JPL database values for IAU1980. Else analytical expression, relative error about 10^-9 Note that the JPL database to be used can be set with measures.jpl.ephemeris (at the moment of writing DE200 (default), or DE405). If using the JPL database, the d_interval (and the output of derivative()) are irrelevant.

Example

Motivation

To calculate the Aberration angles. An alternate route could have been a global function, but having a simple container allows caching of some calculations for speed.
Using MJD (JD-2400000.5) rather than JD is for precision reasons.

Definition at line 109 of file Aberration.h.

Member Enumeration Documentation

enum casacore::Aberration::AberrationTypes

Types of known Aberration calculations (at 1995/09/04 STANDARD == IAU1980)

Enumerator
STANDARD
NONE
B1950

Definition at line 118 of file Aberration.h.

Constructor & Destructor Documentation

casacore::Aberration::Aberration

(

)

Default constructor, generates default J2000 Aberration identification.

casacore::Aberration::Aberration

(

const Aberration &

other

)

Copy constructor.

casacore::Aberration::Aberration

(

AberrationTypes

type

)

Constructor with type.

casacore::Aberration::~Aberration

(

)

Member Function Documentation

void casacore::Aberration::calcAber ( Double  t )

private

Calculate Aberration angles for time t.

void casacore::Aberration::copy ( const Aberration &  other )

private

Copy.

const MVPosition& casacore::Aberration::derivative

(

Double

epoch

)

Return derivative of Aberration (d^-1) w.r.t.

time

void casacore::Aberration::fill ( )

private

Fill an empty copy.

void casacore::Aberration::init

(

)

Re-initialise Aberration object.

void casacore::Aberration::init

(

AberrationTypes

type

)

const MVPosition& casacore::Aberration::operator()

(

Double

epoch

)

Operator () calculates the Aberration direction cosine vector.

Aberration& casacore::Aberration::operator=

(

const Aberration &

other

)

Copy assignment.

void casacore::Aberration::refresh

(

)

Refresh calculations.

Member Data Documentation

Double casacore::Aberration::aval[3]

private

Cached calculated angles.

Definition at line 157 of file Aberration.h.

Double casacore::Aberration::checkEpoch

private

Check epoch for linear approximation.

Definition at line 155 of file Aberration.h.

Double casacore::Aberration::dval[3]

private

Cached derivatives.

Definition at line 159 of file Aberration.h.

uInt casacore::Aberration::interval_reg

staticprivate

Interpolation interval.

Definition at line 167 of file Aberration.h.

const Double casacore::Aberration::INTV

static

Interval to be used for linear approximation (in days)

Definition at line 114 of file Aberration.h.

Int casacore::Aberration::lres

private

To be able to use referenced results in simple calculations, a circular result buffer is used.

Current buffer pointer.

Definition at line 163 of file Aberration.h.

AberrationTypes casacore::Aberration::method

private

Method to be used.

Definition at line 153 of file Aberration.h.

MVPosition casacore::Aberration::result[4]

private

Last calculation.

Definition at line 165 of file Aberration.h.

uInt casacore::Aberration::usejpl_reg

staticprivate

JPL use.

Definition at line 169 of file Aberration.h.

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The documentation for this class was generated from the following file:

• casa/casacore/measures/Measures/Aberration.h