Aberration.h

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// # Aberration.h: Aberration class
// # Copyright (C) 1995,1996,1997,1998
// # Associated Universities, Inc. Washington DC, USA.
// #
// # This library is free software; you can redistribute it and/or modify it
// # under the terms of the GNU Library General Public License as published by
// # the Free Software Foundation; either version 2 of the License, or (at your
// # option) any later version.
// #
// # This library is distributed in the hope that it will be useful, but WITHOUT
// # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// # FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Library General Public
// # License for more details.
// #
// # You should have received a copy of the GNU Library General Public License
// # along with this library; if not, write to the Free Software Foundation,
// # Inc., 675 Massachusetts Ave, Cambridge, MA 02139, USA.
// #
// # Correspondence concerning AIPS++ should be addressed as follows:
// #        Internet email: casa-feedback@nrao.edu.
// #        Postal address: AIPS++ Project Office
// #                        National Radio Astronomy Observatory
// #                        520 Edgemont Road
// #                        Charlottesville, VA 22903-2475 USA
 
#ifndef MEASURES_ABERRATION_H
#define MEASURES_ABERRATION_H
 
// # Includes
#include <mutex>
#include <casacore/casa/aips.h>
#include <casacore/casa/Quanta/MVPosition.h>
 
namespace casacore {  // # NAMESPACE CASACORE - BEGIN
 
// <summary>
// Aberration class and calculations
// </summary>
 
// <use visibility=export>
 
// <reviewed reviewer="UNKNOWN" date="before2004/08/25" tests="tMeasMath" demos="">
// </reviewed>
 
// <prerequisite>
//   <li> <linkto class=Measure>Measure</linkto> class,
//      especially <linkto class=MEpoch>MEpoch</linkto>
//   <li> <linkto class=MeasData>MeasData</linkto> class for constants
// </prerequisite>
//
// <etymology>
// Aberration
// </etymology>
//
// <synopsis>
// Aberration forms the class for Aberration calculations. It is a simple
// container with the selected method, and the mean epoch.<br>
// The method is selected from one of the following:
// <ul>
//   <li> Aberration::STANDARD   (at 1995/09/04 the IAU1980 definition)
//   <li> Aberration::NONE
//   <li> Aberration::B1950
// </ul>
// Epochs can be specified as the MJD (with defined constants MeasData::MJD2000
// and MeasData::MJDB1950 or the actual MJD),
// leading to the following constructors:
// <ul>
//   <li> Aberration() default; assuming JD2000, IAU1980
//   <li> Aberration(method) assuming the correct default epoch of
//      JD2000 or B1950
//   <li> Aberration(method,epoch) with epoch Double(MJD).
// </ul>
// Actual Aberration for a certain Epoch is calculated by the () operator
// as Aberration(epoch), with epoch Double MJD, values returned as an
// MVPosition.<br>
// The derivative (d<sup>-1</sup>) can be obtained as well by
// derivative(epoch).<br>
// The following details can be set with the
// <linkto class=Aipsrc>Aipsrc</linkto> mechanism:
// <ul>
//  <li> measures.aberration.d_interval: approximation interval as time
//  (fraction of days is default unit) over which linear approximation
//  is used
//  <li> measures.aberration.b_usejpl: use the JPL database values for IAU1980.
//  Else analytical expression, relative error about 10<sup>-9</sup>
//  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.
// </ul>
// </synopsis>
//
// <example>
// </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.<br>
// Using MJD (JD-2400000.5) rather than JD is for precision reasons.
// </motivation>
//
// <todo asof="1997/12/02">
// </todo>
 
class Aberration {
 public:
  // # Constants
  //  Interval to be used for linear approximation (in days)
  static constexpr Double INTV = 0.04;
 
  // # Enumerations
  //  Types of known Aberration calculations (at 1995/09/04 STANDARD == IAU1980)
  enum AberrationTypes { STANDARD, NONE, B1950 };
 
  // # Constructors
  //  Default constructor, generates default J2000 Aberration identification
  Aberration();
  // Copy constructor
  Aberration(const Aberration &other);
  // Constructor with type
  Aberration(AberrationTypes type);
  // Copy assignment
  Aberration &operator=(const Aberration &other);
 
  // # Destructor
  ~Aberration();
 
  // # Operators
  //  Operator () calculates the Aberration direction cosine vector
  const MVPosition &operator()(Double epoch);
 
  // # General Member Functions
  //  Return derivative of Aberration (d<sup>-1</sup>) w.r.t. time
  const MVPosition &derivative(Double epoch);
 
  // Re-initialise Aberration object
  // <group>
  void init(AberrationTypes type = Aberration::STANDARD);
  // </group>
 
  // Refresh calculations
  void refresh();
 
 private:
  // # Data menbers
  //  Method to be used
  AberrationTypes method;
  // Check epoch for linear approximation
  Double checkEpoch = 1e30;
  // Cached calculated angles
  Double aval[3];
  // Cached derivatives
  Double dval[3];
  // To be able to use referenced results in simple calculations, a circular
  // result buffer is used.
  // Current buffer pointer.
  Int lres;
  // Last calculation
  MVPosition result[4];
  // Interpolation interval
  inline static uInt interval_reg;
  // JPL use
  inline static uInt usejpl_reg;
  inline static std::once_flag initialize_once_flag;
 
  // # Member functions
  //  Copy
  void copy(const Aberration &other);
  // Fill an empty copy
  static void initialize();
  // Calculate Aberration angles for time t
  void calcAber(Double t);
};
 
}  // namespace casacore
 
#endif