jephem.astro
Class AstroContext

java.lang.Object
  |
  +--jephem.astro.AstroContext

All Implemented Interfaces:

SolarSystemConstants, SpaceConstants, TimeConstants, UnitsConstants

public class AstroContext

extends java.lang.Object

implements SolarSystemConstants, SpaceConstants, TimeConstants, UnitsConstants

Conductor of ephemeris calculation.
Each time a calculation needs to be done, a AstroContext object must be created ; this AstroContext is then in charge of the coherence of calculations.

An AstroContext is characterized by :

its julian day

its bodies, an array of instances of class Body.

The main method is calcBodyCoords() whose role is :

For each body, call the appropriate low-level computation classes depending on the required precision.

Perform the necessary coordinate transformations to express the coordinates in the right frame.

Perform the conversions to get the right units for positions and velocities.

Field Summary

static java.lang.String	JEPHEM Constant used to designate JEphem as the astro engine.
static java.lang.String	SWISS_EPHEMERIS Constant used to designate Swiss Ephemeris as the astro engine.

Fields inherited from interface jephem.astro.solarsystem.SolarSystemConstants

E0_1900, E0_1950, E0_2000, EARTH, JUPITER, KM_PER_AU, MARS, MERCURY, MOON, NB_BODIES, NEPTUNE, PLUTO, SATURN, SIDERAL_RATE, SUN, URANUS, VENUS

Fields inherited from interface jephem.astro.spacetime.SpaceConstants

CARTESIAN, COORD_V0, COORD_V1, COORD_V2, COORD_X0, COORD_X1, COORD_X2, COORDGROUP_DELTA_BETA_LAMBDA, COORDGROUP_DIST_ALPHA_DELTA, COORDGROUP_RLB, COORDGROUP_XYZ, FRAME_EC_HELIO_GEOMETRIC, FRAME_ECLIPTIC, FRAME_EQUATORIAL, FRAME_GALACTIC, FRAME_HORIZONTAL_TOPOCENTRIC, FRAME_THEORY, LIGHT_VELOCITY, NB_COORDS, SPHERICAL

Fields inherited from interface jephem.astro.spacetime.TimeConstants

DAYS_PER_CENTURY, DAYS_PER_MILLENIUM, DAYS_PER_YEAR, JD1900, JD2000, JD2100, SECONDS_PER_DAY, TT_TDB, UTC

Fields inherited from interface jephem.astro.spacetime.UnitsConstants

ANGULAR_SPEED_UNIT_ARCSEC_PER_DAY, ANGULAR_SPEED_UNIT_ARCSEC_PER_S, ANGULAR_SPEED_UNIT_DEG_PER_DAY, ANGULAR_SPEED_UNIT_DEG_PER_S, ANGULAR_SPEED_UNIT_RAD_PER_DAY, ANGULAR_UNIT_ARCSEC, ANGULAR_UNIT_DEG, ANGULAR_UNIT_RAD, BASE_ANGULAR_SPEED_UNIT, BASE_ANGULAR_UNIT, BASE_DISTANCE_UNIT, BASE_LINEAR_SPEED_UNIT, DEGREES_DECIMAL, DEGREES_DMS, DELTA_BETWEEN_BASES, DISTANCE_UNIT_AU, DISTANCE_UNIT_KM, DISTANCE_UNIT_M, LINEAR_SPEED_UNIT_AU_PER_D, LINEAR_SPEED_UNIT_KM_PER_D, LINEAR_SPEED_UNIT_KM_PER_HOUR, LINEAR_SPEED_UNIT_M_PER_S, TYPE_ANGULAR, TYPE_ANGULAR_SPEED, TYPE_DISTANCE, TYPE_LINEAR_SPEED, UNITGROUP_AU_AU_AU, UNITGROUP_AU_DEG_DEG, UNITGROUP_AU_RAD_RAD, UNITGROUP_AUD_AUD_AUD, UNITGROUP_KM_KM_KM

Constructor Summary

AstroContext(double jd, int timeFrame, int[] bodyIndexes)
The only constructor.

Method Summary

void	calcBodyCoords(int frame, boolean velocities) Call to calcBodyCoords(int, int, double, boolean, int[]) with default values : sphereCart is set to spherical, units are set to ua, degrees, degrees for the positions and to ua/d, deg/d, deg/d for the velocities.
void	calcBodyCoords(int frame, int sphereCart, double precision, boolean velocities, int[] units) Main calculation method for body coordinate calculation.
Body[]	getBodies() Returns the bodies handled by this AstroContext.
Body	getBody(int whichBody) Returns the Body handled by this AstroContext whose index is 'whichBody'.
double	getJd() Returns the julian day of this AstroContext.
static void	setAstroEngine(java.lang.String astroEngine) Permits to indicate which implementation to use for the computations.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

JEPHEM

public static final java.lang.String JEPHEM

Constant used to designate JEphem as the astro engine.

See Also:

Constant Field Values

SWISS_EPHEMERIS

public static final java.lang.String SWISS_EPHEMERIS

Constant used to designate Swiss Ephemeris as the astro engine.

See Also:

Constant Field Values

Constructor Detail

AstroContext

public AstroContext(double jd,
                    int timeFrame,
                    int[] bodyIndexes)

The only constructor.
Example of use, in a class implementing SolarSystemConstants (for constant names) :
int[] bodyIndexes = {MERCURY, VENUS};
AstroContext ac = new AstroContext(jd, bodyIndexes);

Parameters:

jd - Number of Julian Days elapsed since jan 0.5 4712 BC.

timeFrame - The time frame used to express 'jds'. Use TimeConstants constants.

bodyIndexes - Array containing indexes of bodies this AstroContext must handle ; use constants from SolarSystemConstants.

Method Detail

calcBodyCoords

public void calcBodyCoords(int frame,
                           boolean velocities)
                    throws AstroException

Call to calcBodyCoords(int, int, double, boolean, int[]) with default values :

sphereCart is set to spherical,

units are set to ua, degrees, degrees for the positions and to ua/d, deg/d, deg/d for the velocities.

AstroException

calcBodyCoords

public void calcBodyCoords(int frame,
                           int sphereCart,
                           double precision,
                           boolean velocities,
                           int[] units)
                    throws AstroException

Main calculation method for body coordinate calculation.
The calculation will be done for all the bodies of this AstroContext.

Parameters:

frame - Coordinate system in which the coordinates are expressed ; use SpaceConstants constants.

sphereCart - Expression mode of the coordinates (spherical, cartesian) ; Use SpaceConstants constants.

precision - Precision required for the calculations, expressed in arcseconds.

velocities - Indicates if the velocities need to be also calculated.

units - the desired units to express the coordinates. Use UnitsConstants constants.
WARNING : this array must contain 3 or 6 elements (depending on parameter 'velocities'), and contain units of the right type (linear, angular etc...).

Throws:

AstroException - if an unrecoverable error occured during computation.

getBodies

public Body[] getBodies()

Returns the bodies handled by this AstroContext.

getBody

public Body getBody(int whichBody)

Returns the Body handled by this AstroContext whose index is 'whichBody'.

Parameters:

whichBody - the index charcterizing the body to retrieve, using SolarSystemConstants constants.

Returns:

the corresponding body if it is handled by this AstroContext, null otherwise.

getJd

public double getJd()

Returns the julian day of this AstroContext.

setAstroEngine

public static void setAstroEngine(java.lang.String astroEngine)

Permits to indicate which implementation to use for the computations.
If not set, JEphem is used.

Parameters:

astroEngine - Use constants of this class to specify it.