org.orekit.forces.drag

Class DTM2000

java.lang.Object

org.orekit.forces.drag.DTM2000

All Implemented Interfaces:

Serializable, Atmosphere

public class DTM2000
extends Object
implements Atmosphere

This atmosphere model is the realization of the DTM-2000 model.

It is described in the paper:
The DTM-2000 empirical thermosphere model with new data assimilation and constraints at lower boundary: accuracy and properties
S. Bruinsma, G. Thuillier and F. Barlier
Journal of Atmospheric and Solar-Terrestrial Physics 65 (2003) 1053–1070

Two computation methods are proposed to the user:

• one OREKIT independent and compliant with initial FORTRAN routine entry values: getDensity(int, double, double, double, double, double, double, double, double).
• one compliant with OREKIT Atmosphere interface, necessary to the drag force model computation.

This model provides dense output for altitudes beyond 120 km. Computed data are:

• Temperature at altitude z (K)
• Exospheric temperature above input position (K)
• Vertical gradient of T a 120 km
• Total density (kg/m³)
• Mean atomic mass
• Partial densities in (kg/m³) : hydrogen, helium, atomic oxygen, molecular nitrogen, molecular oxygen, atomic nitrogen

The model needs geographical and time information to compute general values, but also needs space weather data : mean and instantaneous solar flux and geomagnetic indices.

Mean solar flux is (for the moment) represented by the F10.7 indices. Instantaneous flux can be set to the mean value if the data is not available. Geomagnetic activity is represented by the Kp indice, which goes from 1 (very low activity) to 9 (high activity).

All these data can be found on the NOAA (National Oceanic and Atmospheric Administration) website.

Author:

R. Biancale, S. Bruinsma: original fortran routine, Fabien Maussion (java translation)

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static int	ATOMIC_NITROGEN Identifier for atomic nitrogen.
static int	ATOMIC_OXYGEN Identifier for atomic oxygen.
static int	HELIUM Identifier for helium.
static int	HYDROGEN Identifier for hydrogen.
static int	MOLECULAR_NITROGEN Identifier for molecular nitrogen.
static int	MOLECULAR_OXYGEN Identifier for molecular oxygen.

Constructor Summary

Constructors

Constructor and Description
DTM2000(DTM2000InputParameters parameters, PVCoordinatesProvider sun, BodyShape earth) Simple constructor for independent computation.

Method Summary

Methods

Modifier and Type	Method and Description
double	getDensity(AbsoluteDate date, Vector3D position, Frame frame) Get the local density.
double	getDensity(int day, double alti, double lon, double lat, double hl, double f, double fbar, double akp3, double akp24) Get the local density with initial entries.
Frame	getFrame() Get the frame of the central body.
double	getMam() Get the local mean atomic mass.
double	getPartialDensities(int identifier) Get the local partial density of the selected element.
double	getT() Get the local temperature.
double	getTinf() Get the current exospheric temperature above input position.
Vector3D	getVelocity(AbsoluteDate date, Vector3D position, Frame frame) Get the inertial velocity of atmosphere molecules.

Methods inherited from class java.lang.Object

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

Field Detail

HYDROGEN

public static final int HYDROGEN

Identifier for hydrogen.

See Also:

Constant Field Values

HELIUM

public static final int HELIUM

Identifier for helium.

See Also:

Constant Field Values

ATOMIC_OXYGEN

public static final int ATOMIC_OXYGEN

Identifier for atomic oxygen.

See Also:

Constant Field Values

MOLECULAR_NITROGEN

public static final int MOLECULAR_NITROGEN

Identifier for molecular nitrogen.

See Also:

Constant Field Values

MOLECULAR_OXYGEN

public static final int MOLECULAR_OXYGEN

Identifier for molecular oxygen.

See Also:

Constant Field Values

ATOMIC_NITROGEN

public static final int ATOMIC_NITROGEN

Identifier for atomic nitrogen.

See Also:

Constant Field Values

Constructor Detail

DTM2000

public DTM2000(DTM2000InputParameters parameters,
       PVCoordinatesProvider sun,
       BodyShape earth)
        throws OrekitException

Simple constructor for independent computation.

Parameters:

parameters - the solar and magnetic activity data

sun - the sun position

earth - the earth body shape

Throws:

OrekitException - if some resource file reading error occurs

Method Detail

getFrame

public Frame getFrame()

Get the frame of the central body.

Specified by:

getFrame in interface Atmosphere

Returns:

frame of the central body.

getDensity

public double getDensity(int day,
                double alti,
                double lon,
                double lat,
                double hl,
                double f,
                double fbar,
                double akp3,
                double akp24)
                  throws OrekitException

Get the local density with initial entries.

Parameters:

day - day of year

alti - altitude in meters

lon - local longitude (rad)

lat - local latitude (rad)

hl - local solar time in rad (O hr = 0 rad)

f - instantaneous solar flux (F10.7)

fbar - mean solar flux (F10.7)

akp3 - 3 hrs geomagnetic activity index (1-9)

akp24 - Mean of last 24 hrs geomagnetic activity index (1-9)

Returns:

the local density (kg/m³)

Throws:

OrekitException - if altitude is outside of supported range

getTinf

public double getTinf()

Get the current exospheric temperature above input position. getDensity method must be called before calling this function.

Returns:

the exospheric temperature (K)

getT

public double getT()

Get the local temperature. getDensity method must be called before calling this function.

Returns:

the temperature at altitude z (K)

getMam

public double getMam()

Get the local mean atomic mass. getDensity method must be called before calling this function.

Returns:

the local mean atomic mass

getPartialDensities

public double getPartialDensities(int identifier)

Get the local partial density of the selected element. getDensity method must be called before calling this function.

Parameters:

identifier - one of the six elements : HYDROGEN, HELIUM, ATOMIC_OXYGEN, MOLECULAR_NITROGEN, MOLECULAR_OXYGEN, ATOMIC_NITROGEN

Returns:

the local partial density (kg/m³)

getDensity

public double getDensity(AbsoluteDate date,
                Vector3D position,
                Frame frame)
                  throws OrekitException

Get the local density.

Specified by:

getDensity in interface Atmosphere

Parameters:

date - current date

position - current position in frame

frame - the frame in which is defined the position

Returns:

local density (kg/m³)

Throws:

OrekitException - if date is out of range of solar activity model or if some frame conversion cannot be performed

getVelocity

public Vector3D getVelocity(AbsoluteDate date,
                   Vector3D position,
                   Frame frame)
                     throws OrekitException

Get the inertial velocity of atmosphere molecules. Here the case is simplified : atmosphere is supposed to have a null velocity in earth frame.

Specified by:

getVelocity in interface Atmosphere

Parameters:

date - current date

position - current position in frame

frame - the frame in which is defined the position

Returns:

velocity (m/s) (defined in the same frame as the position)

Throws:

OrekitException - if some frame conversion cannot be performed