Package gaiasky.util.coord

Class NslSun

java.lang.Object

gaiasky.util.coord.NslSun

public class NslSun
extends java.lang.Object

Analytical representation of the Nominal Sun for the Gaia NSL. Uses a low precision formula for the solar longitude (apparent longitude) valid for the period 1980-2020 with an accuracy of 0.005 deg. The reference frame is the ecliptic equinox J2000. The analytical formula for calculating the longitude is written in terms of the number of days since J2000.0(TCB). Since the zero point for GaiaTime (the Mission Reference Epoch, see GAIA-CA-SP-ARI-BAS-003-06, rev. 1, Sect. 3.5) is different from J2000.0 (actually it is J2010.0), it is necessary to add the number of days from J2000.0 to the Mission Reference Epoch before doing the calculation. This number is given by missionReferenceEpochDaysFromJ2000. Since the time may be specified as the number of elapsed ns since a time origin that is a settable attribute of the attitude data server, the NslSun has a field timeOriginDaysFromJ2000 that can be set with setTimeOrigin(). By default the origin time is the Mission Reference Epoch.

Constructor Summary

Constructors

Constructor	Description
NslSun()	Constructor

Method Summary

Modifier and Type	Method	Description
double	angleBase(double x, int nRev)	Puts an angle in the base interval [ 0, nRev*2*PI )
Vector3d	getSolarDirection(Vector3d out)
double	getSolarLongitude()
double	getSolarLongitudeDot()
double	getSolarLongitudeMod4Pi()
Quaterniond	heliotropicToQuaternion(long t, double xi, double nu, double Omega)	Method to convert heliotropic angles to quaternion
void	setTime(double julianDate)	Calculate all fields for a given julian date.
void	setTime(long tNs)	Calculate all fields for a given time Author: F.

Methods inherited from class java.lang.Object

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

Constructor Detail

NslSun

public NslSun()

Constructor

Method Detail

setTime

public void setTime(double julianDate)

Calculate all fields for a given julian date.

Parameters:

julianDate - The julian date.

setTime

public void setTime(long tNs)

Calculate all fields for a given time Author: F. Mignard

Parameters:

tNs - time in [ns] since the time origin

getSolarLongitude

public double getSolarLongitude()

Returns:

solar longitude in [rad]

getSolarLongitudeMod4Pi

public double getSolarLongitudeMod4Pi()

Returns:

solar longitude in [rad], modulo 4*PI

getSolarLongitudeDot

public double getSolarLongitudeDot()

Returns:

time derivative of solar longitude in [rad/day]

getSolarDirection

public Vector3d getSolarDirection(Vector3d out)

Parameters:

out - The output vector.

Returns:

The output vector containing the solar direction as a unit 3-vector in BCRS.

heliotropicToQuaternion

public Quaterniond heliotropicToQuaternion(long t,
                                           double xi,
                                           double nu,
                                           double Omega)

Method to convert heliotropic angles to quaternion

Parameters:

t - time [ns]

xi - revolving angle (solar aspect angle) [rad]

nu - revolving phase [rad]

Omega - spin phase [rad]

Returns:

attitude quaternion

angleBase

public double angleBase(double x,
                        int nRev)

Puts an angle in the base interval [ 0, nRev*2*PI )

Parameters:

x - angle [rad]

nRev - number of revolutions in base interval

Returns:

angle in base interval [rad]