Multiple file access functions

The following group of functions should be the preferred method to access to the library. They allow to access to multiple ephemeris files at the same time, even by multiple threads.

When an error occurs, these functions execute error handlers according to the behavior defined by the function calcephpy.seterrorhandler().

Time notes

The functions calcephpy.CalcephBin.compute(), calcephpy.CalcephBin.compute_unit(), calcephpy.CalcephBin.compute_order(), calcephpy.CalcephBin.orient_unit(), ... only accept a date expressed in the same timescale as the ephemeris files, which can be retrieved using the function calcephpy.CalcephBin.gettimescale(). Ephemeris files are generally expressed using the timescale TDB. If a date, expressed in the TT (Terrestrial Time) timescale, is supplied to them, these functions will return an erroneous position of the order of several tens of meters for the planets. If a date, expressed in the Coordinated Universal Time (UTC), is supplied to them, these functions will return a very large erroneous position over several thousand kilometers for the planets.

Thread notes

If the standard I/O functions such as fread are not reentrant then the CALCEPH I/O functions using them will not be reentrant either.

It's not safe for two threads to call the functions with the same object of type CalcephBin if and only if the function calcephpy.CalcephBin.isthreadsafe() returns a non-zero value. A previous call to the function calcephpy.CalcephBin.prefetch() is required for the function calcephpy.CalcephBin.isthreadsafe() to return a non-zero value.

It's safe for two threads to access simultaneously to the same ephemeris file with two different objects of type CalcephBin. In this case, each thread must open the same file.

Usage

The following examples, that can be found in the directory examples of the library sources, show the typical usage of this group of functions.

The example in Python language is pymultiple.py.

Functions

calcephpy.CalcephBin.open

calcephpy.CalcephBin.open(filename) → eph

Parameters:: filename (str) -- pathname of the file
Returns:: ephemeris descriptor
Return type:: calcephpy.CalcephBin

This function opens the file whose pathname is the string pointed to by filename, reads the two header blocks of this file and returns an ephemeris descriptor associated to it. This file must be compliant to the format specified by the 'original JPL binary' , 'INPOP 2.0 binary' or 'SPICE' ephemeris file. At the moment, supported SPICE files are the following :

text Planetary Constants Kernel (KPL/PCK) files

binary PCK (DAF/PCK) files.

binary SPK (DAF/SPK) files containing segments of type 1, 2, 3, 5, 8, 9, 12, 13, 14, 17, 18, 20, 21, 102, 103 and 120.

meta kernel (KPL/MK) files.

frame kernel (KPL/FK) files. Only a basic support is provided.

Just after the call of calcephpy.CalcephBin.open(), the function calcephpy.CalcephBin.prefetch() should be called to accelerate future computations.

The function calcephpy.CalcephBin.close() must be called to free allocated memory by this function.

The following example opens the ephemeris file example1.dat

from calcephpy import *

peph = CalcephBin.open("example1.dat")

# ...  computation ...

peph.close()

noindex:

calcephpy.CalcephBin.open(array_filename) → eph

Parameters:: array_filename (list) -- array of pathname of the files
Returns:: ephemeris descriptor
Return type:: calcephpy.CalcephBin

This function opens n files whose pathnames are the string pointed to by array_filename, reads the header blocks of these files and returns a single ephemeris descriptor associated to them.

These files must have the same type (e.g., all files are SPICE files or original JPL files). This file must be compliant to the format specified by the 'original JPL binary' , 'INPOP 2.0 or 3.0 binary' or 'SPICE' ephemeris file. At the moment, supported SPICE files are the following :

text Planetary Constants Kernel (KPL/PCK) files

binary PCK (DAF/PCK) files.

binary SPK (DAF/SPK) files containing segments of type 1, 2, 3, 5, 8, 9, 12, 13, 14, 17, 18, 20, 21, 102, 103 and 120.

meta kernel (KPL/MK) files.

frame kernel (KPL/FK) files. Only a basic support is provided.

The single descriptor internally maintains a table to respond to the following queries for computing the position-velocity vector between bodies present in these different files.

Just after the call of calcephpy.CalcephBin.open(), the function calcephpy.CalcephBin.prefetch() should be called to accelerate future computations.

The function calcephpy.CalcephBin.close() must be called to free allocated memory by this function.

The following example opens the ephemeris file example1.bsp and example1.tpc

from calcephpy import CalcephBin
peph = CalcephBin.open(['example1.bsp', 'example1.tpc'])

# ... computation ...

peph.close()

calcephpy.CalcephBin.prefetch

calcephpy.CalcephBin.prefetch()

This function prefetches to the main memory all files associated to the ephemeris descriptor. This prefetching operation will accelerate the further computations performed with calcephpy.CalcephBin.compute(), calcephpy.CalcephBin.compute_unit(), calcephpy.CalcephBin.compute_order(), calcephpy.CalcephBin.orient_unit(), ... .

It requires that the file is smaller than the main memory. If multiple threads (e.g. threads of openMP or Posix Pthreads) prefetch the data for the same ephemeris file, the used memory will remain the same as if the prefetch operation was done by a single thread if and if the endianess of the file is the same as the computer and if the operating system, such as Linux, MacOS X other unix, supports the function mmap.

calcephpy.CalcephBin.isthreadsafe

calcephpy.CalcephBin.isthreadsafe()

This function returns 1 if multiple threads can access the same ephemeris ephemeris descriptor, otherwise 0.

A previous call to the function calcephpy.CalcephBin.prefetch() is required, and the library should be compiled with --enable-thread=yes on Unix-like operating system, for the function calcephpy.CalcephBin.isthreadsafe() to return a non-zero value. If the file is not encoded with the same endian as the current hardware, then function may return 0.

If this function returns 1, several threads may use the same ephemeris descriptor for the computational functions calcephpy.CalcephBin.compute(), .... It allows to use the same object for the parallel loops.

calcephpy.CalcephBin.compute

calcephpy.CalcephBin.compute(JD0, time, target, center) → PV

Parameters:

JD0 (float/list/numpy.ndarray) -- Integer part of the Julian date (TDB or TCB)
time (float/list/numpy.ndarray) -- Fraction part of the Julian date (TDB or TCB)
target (int) -- The body or reference point whose coordinates are required (see the list, below).
center (int) -- The origin of the coordinate system (see the list, below). If target is 14, 15, 16 or 17 (nutation, libration, TT-TDB or TCG-TCB), center must be 0.

Returns:

Depending on the target value, an array to receive the cartesian position (x,y,z) and the velocity (xdot, ydot, zdot), or a time scale transformation value, or the angles of the librations of the Moon and their derivatives, or the nutation angles and their derivatives.

Return type:

list

This function reads, if needed, in the ephemeris file self and interpolates a single object, usually the position and velocity of one body (target) relative to another (center) for the time JD0+time and stores the results to PV. The ephemeris file self must have been previously opened with the function calcephpy.CalcephBin.open().

The returned array PV has the following properties

If the target is TT-TDB, only the first element of this array will get the result. The time scale transformation TT-TDB is expressed in seconds.

If the target is TCG-TCB, only the first element of this array will get the result. The time scale transformation TCG-TCB is expressed in seconds.

If the target is Librations, the array contains the angles of the librations of the Moon and their derivatives. The angles of the librations of the Moon are expressed in radians and their derivatives are expressed in radians per day.

If the target is Nutations, the array contains the nutation angles and their derivatives. The nutation angles are expressed in radians and their derivatives are expressed in radians per day.

Otherwise the returned values is the cartesian position (x,y,z), expressed in Astronomical Unit (au), and the velocity (xdot, ydot, zdot), expressed in Astronomical Unit per day (au/day).

If JD0 and time are list or NumPy's array (1D) of double-precision floating-point values, the returned array PV is a list of 6 arrays. Each array contain a single component of position or velocity (e.g., PV[0] contains the coordinate X, PV[1] contains the coordinate Y, ...) .

The date (JD0, time) should be expressed in the same timescale as the ephemeris files, which can be retrieved using the function calcephpy.CalcephBin.gettimescale(). To get the best numerical precision for the interpolation, the time is splitted in two floating-point numbers. The argument JD0 should be an integer and time should be a fraction of the day. But you may call this function with time=0 and JD0, the desired time, if you don't take care about numerical precision.

Warning

If a date, expressed in the Coordinated Universal Time (UTC), is supplied to this function, a very large erroneous position will be returned.

The possible values for target and center are :

value	meaning
1	Mercury Barycenter
2	Venus Barycenter
3	Earth
4	Mars Barycenter
5	Jupiter Barycenter
6	Saturn Barycenter
7	Uranus Barycenter
8	Neptune Barycenter
9	Pluto Barycenter
10	Moon
11	Sun
12	Solar Sytem barycenter
13	Earth-moon barycenter
14	Nutation angles
15	Librations
16	TT-TDB
17	TCG-TCB
asteroid number + CALCEPH_ASTEROID	asteroid

These accepted values by this function are the same as the value for the JPL function PLEPH, except for the values TT-TDB, TCG-TCB and asteroids.

For example, the value "CALCEPH_ASTEROID+4" for target or center specifies the asteroid Vesta.

The following example prints the heliocentric coordinates of Mars at time=2442457.5 and at 2442457.9

from calcephpy import *

def printcoord(PV,name):
    print('{0} :\n{1}\n'.format(name,PV))

jd0=2442457
dt1=0.5E0
dt2=0.9E0

peph = CalcephBin.open("example1.dat")

PV1 = peph.compute(jd0, dt1, 4, 11)
printcoord(PV1,"heliocentric coordinates of Mars")

PV2 = peph.compute(jd0, dt2, 4, 11)
printcoord(PV2,"heliocentric coordinates of Mars")

peph.close()

calcephpy.CalcephBin.compute_unit

calcephpy.CalcephBin.compute_unit(JD0, time, target, center, unit) → PV

Parameters:

JD0 (float/list/numpy.ndarray) -- Integer part of the Julian date (TDB or TCB)
time (float/list/numpy.ndarray) -- Fraction part of the Julian date (TDB or TCB)
target (int) -- The body or reference point whose coordinates are required. The numbering system depends on the parameter unit.
center (int) -- The origin of the coordinate system. The numbering system depends on the parameter unit.
unit (int) --

The units of PV.

This integer is a sum of some unit constants (CALCEPH_UNIT_???) and/or the constant USE_NAIFID.

If the unit contains USE_NAIFID, the NAIF identification numbering system is used for the target and the center (NAIF identification numbers for the list).

If the unit doesnot contain USE_NAIFID, the old number system is used for the target and the center (see the list in the function calcephpy.CalcephBin.compute()).

Returns:

Depending on the target value, an array to receive the cartesian position (x,y,z) and the velocity (xdot, ydot, zdot), or a time scale transformation value, or the angles of the librations of the Moon and their derivatives, or the nutation angles and their derivatives.

Return type:

list

This function is similar to the function calcephpy.CalcephBin.compute(), except that the units of the output are specified.

This function reads, if needed, in the ephemeris file self and interpolates a single object, usually the position and velocity of one body (target) relative to another (center) for the time JD0+time and stores the results to PV. The ephemeris file self must have been previously opened with the function calcephpy.CalcephBin.open(). The output values are expressed in the units specified by unit.

This function checks the units if invalid combinations of units are given to the function.

The date (JD0, time) should be expressed in the same timescale as the ephemeris files, which can be retrieved using the function calcephpy.CalcephBin.gettimescale().

Warning

If a date, expressed in the Coordinated Universal Time (UTC), is supplied to this function, a very large erroneous position will be returned.

The returned array PV has the following properties

If the target is the time scale transformation TT-TDB, only the first element of this array will get the result.

If the target is the time scale transformation TCG-TCB, only the first element of this array will get the result.

If the target is Librations, the array contains the angles of the librations of the Moon and their derivatives.

If the target is Nutations, the array contains the nutation angles and their derivatives.

Otherwise the returned value is the cartesian position (x,y,z) and the velocity (xdot, ydot, zdot).

If JD0 and time are list or NumPy's array (1D) of double-precision floating-point values, the returned array PV is a list of 6 arrays. Each array contain a single component of position or velocity (e.g., PV[0] contains the coordinate X, PV[1] contains the coordinate Y, ...) .

The values stored in the array PV are expressed in the following units

The position and velocity are expressed in Astronomical Unit (au) if unit contains UNIT_AU.

The position and velocity are expressed in kilometers if unit contains UNIT_KM.

The velocity, TT-TDB, TCG-TCB, the derivatives of the angles of the nutation, or the derivatives of the librations of the Moon or are expressed in days if unit contains UNIT_DAY.

The velocity, TT-TDB, TCG-TCB, the derivatives of the angles of the nutation, or the derivatives of the librations of the Moon are expressed in seconds if unit contains UNIT_SEC.

The angles of the librations of the Moon or the nutation angles are expressed in radians if unit contains UNIT_RAD.

For example, to get the position and velocities expressed in kilometers and kilometers/seconds, the unit must be set to UNIT_KM + UNIT_SEC.

The following example prints the heliocentric coordinates of Mars at time=2442457.5

from calcephpy import *

def printcoord(PV,name):
    print('{0} :\n{1}\n'.format(name,PV))

jd0=2442457
dt=0.5E0

peph = CalcephBin.open("example1.dat")

PV1 = peph.compute_unit(jd0, dt, 4, 11, Constants.UNIT_KM+Constants.UNIT_SEC)
printcoord(PV1,"heliocentric coordinates of Mars")

PV2 = peph.compute_unit(jd0, dt, NaifId.MARS_BARYCENTER, NaifId.SUN,
                        Constants.UNIT_KM+Constants.UNIT_SEC+Constants.USE_NAIFID)
printcoord(PV2,"heliocentric coordinates of Mars")

peph.close()

calcephpy.CalcephBin.orient_unit

calcephpy.CalcephBin.orient_unit(JD0, time, target, unit) → PV

Parameters:

JD0 (float/list/numpy.ndarray) -- Integer part of the Julian date (TDB or TCB)
time (float/list/numpy.ndarray) -- Fraction part of the Julian date (TDB or TCB)
target (int) -- The body whose orientations are requested. The numbering system depends on the parameter unit.
unit (int) --

The units of PV.

This integer is a sum of some unit constants (CALCEPH_UNIT_???) and/or the constant USE_NAIFID.

If the unit contains USE_NAIFID, the NAIF identification numbering system is used for the target (NAIF identification numbers for the list).

If the unit does not contain USE_NAIFID, the old number system is used for the target (see the list in the function calcephpy.CalcephBin.compute()).

Returns:

An array to receive the euler angles, or nutation angles, and their derivatives for the orientation of the body.

Return type:

list

This function reads, if needed, in the ephemeris file self and interpolates the orientation of a single body (target) for the time JD0+time and stores the results to PV. The ephemeris file self must have been previously opened with the function calcephpy.CalcephBin.open(). The output values are expressed in the units specified by unit.

The date (JD0, time) should be expressed in the same timescale as the ephemeris files, which can be retrieved using the function calcephpy.CalcephBin.gettimescale().

This function checks the units if invalid combinations of units are given to the function.

The returned array PV has the following properties

If unit contains OUTPUT_NUTATIONANGLES, the array contains the nutation angles and their derivatives for the orientation of the body. At the present moment, only the nutation for the earth are supported in the original DE files.

If unit contains OUTPUT_EULERANGLES, or doesnot contain OUTPUT_NUTATIONANGLES, the array contains the euler angles and their derivatives for the orientation of the body.

If JD0 and time are list or NumPy's array (1D) of double-precision floating-point values, the returned array PV is a list of 6 arrays. Each array contain a single component of orientation.

The values stored in the array PV are expressed in the following units

The derivatives of the angles are expressed in days if unit contains UNIT_DAY.

The derivatives of the angles are expressed in seconds if unit contains UNIT_SEC.

The angles and their derivatives are expressed in radians if unit contains UNIT_RAD.

For example, to get the nutation angles of the Earth and their derivatives expressed in radian and radian/seconds using the NAIF identification numbering system, the target must be set to NAIFID_EARTH and the unit must be set to OUTPUT_NUTATIONANGLES + UNIT_RAD + UNIT_SEC.

The following example prints the angles of libration of the Moon at time=2442457.5

from calcephpy import *

jd0=2442457
dt=0.5E0

peph = CalcephBin.open("example1.dat")

PV = peph.orient_unit(jd0, dt, NaifId.MOON,
                      Constants.USE_NAIFID+Constants.UNIT_RAD+Constants.UNIT_SEC)
print(PV)

peph.close()

calcephpy.CalcephBin.rotangmom_unit

calcephpy.CalcephBin.rotangmom_unit(JD0, time, target, unit) → PV

Parameters:

JD0 (float) -- Integer part of the Julian date (TDB or TCB)
time (float) -- Fraction part of the Julian date (TDB or TCB)
target (int) -- The body whose orientations are requested. The numbering system depends on the parameter unit.
unit (int) --

The units of PV.

This integer is a sum of some unit constants (CALCEPH_UNIT_???) and/or the constant USE_NAIFID.

If the unit contains USE_NAIFID, the NAIF identification numbering system is used for the target (NAIF identification numbers for the list).

If the unit does not contain USE_NAIFID, the old number system is used for the target (see the list in the function calcephpy.CalcephBin.compute()).

Returns:

An array to receive the angular momentum due to its rotation, divided by the product of the mass and of the square of the radius, and the derivatives, of the body.

Return type:

list

This function reads, if needed, in the ephemeris file self and interpolates the angular momentum vector due to the rotation of the body, divided by the product of the mass $m$ and of the square of the radius $R$ , of a single body (target) for the time JD0+time and stores the results to PV. The ephemeris file self must have been previously opened with the function calcephpy.CalcephBin.open(). The angular momentum $L$ , due to the rotation of the body, is defined as the product of the inertia matrix $I$ by the angular velocity vector ${\omega}$ . So the returned value is $L/(mR^2)=(I\omega)/(mR^2)$

The date (JD0, time) should be expressed in the same timescale as the ephemeris files, which can be retrieved using the function calcephpy.CalcephBin.gettimescale().

The output values are expressed in the units specified by unit.

This function checks the units if invalid combinations of units are given to the function.

The values stored in the array PV are expressed in the following units

The angular momentum and its derivative are expressed in days if unit contains UNIT_DAY.

The angular momentum and its derivative are expressed in seconds if unit contains UNIT_SEC.

The following example prints the angular momentum, due to its rotation, for the Earth at time=2451419.5

from calcephpy import *

jd0=2451419
dt=0.5E0

peph = CalcephBin.open("example2_rotangmom.dat")

G = peph.rotangmom_unit(jd0, dt, NaifId.EARTH,
                      Constants.USE_NAIFID+Constants.UNIT_SEC)
print(G)

peph.close()

calcephpy.CalcephBin.compute_order

calcephpy.CalcephBin.compute_order(JD0, time, target, center, unit, order) → PVAJ

Parameters:

JD0 (float/list/numpy.ndarray) -- Integer part of the Julian date (TDB or TCB)
time (float/list/numpy.ndarray) -- Fraction part of the Julian date (TDB or TCB)
target (int) -- The body or reference point whose coordinates are required. The numbering system depends on the parameter unit.
center (int) -- The origin of the coordinate system. The numbering system depends on the parameter unit.
unit (int) --

The units of PVAJ.

This integer is a sum of some unit constants (CALCEPH_UNIT_???) and/or the constant USE_NAIFID.

If the unit contains USE_NAIFID, the NAIF identification numbering system is used for the target and the center (NAIF identification numbers for the list).

If the unit doesnot contain USE_NAIFID, the old number system is used for the target and the center (see the list in the function calcephpy.CalcephBin.compute()).
order (int) --
The order of derivatives
- = 0 , only the position is computed. The first three numbers of PVAJ are valid for the results.
- = 1 , only the position and velocity are computed. The first six numbers of PVAJ are valid for the results.
- = 2 , only the position, velocity and acceleration are computed. The first nine numbers of PVAJ are valid for the results.
- = 3 , the position, velocity and acceleration and jerk are computed. The first twelve numbers of PVAJ are valid for the results.
If order equals to 1, the behavior of calcephpy.CalcephBin.compute_order() is the same as calcephpy.CalcephBin.compute_unit().

Returns:

Depending on the target value, an array to receive the cartesian position (x,y,z), the velocity (xdot, ydot, zdot), the acceleration and the jerk, or a time scale transformation value, or the angles of the librations of the Moon and their successive derivatives, or the nutation angles and their successive derivatives.

Return type:

list

This function is similar to the function calcephpy.CalcephBin.compute_unit(), except that the order of the computed derivatives is specified.

This function reads, if needed, in the ephemeris file self and interpolates a single object, usually the position and their derivatives of one body (target) relative to another (center) for the time JD0+time and stores the results to PVAJ. The ephemeris file self must have been previously opened with the function calcephpy.CalcephBin.open(). The order of the derivatives are specified by order. The output values are expressed in the units specified by unit.

The returned array PVAJ has the following properties

If the target is the time scale transformation TT-TDB, only the first elements of each component will get the result.

If the target is the time scale transformation TCG-TCB, only the first elements of each component will get the result.

If the target is Librations, the array contains the angles of the librations of the Moon and their successive derivatives.

If the target is Nutations, the array contains the nutation angles and their successive derivatives.

Otherwise the returned value is the cartesian position (x,y,z), the velocity (xdot, ydot, zdot), the jerk and the acceleration.

The returned array PVAJ must be large enough to store the results.

PVAJ[1:3] contain the position (x,y,z) and is always valid.

PVAJ[4:6] contain the velocity (dx/dt,dy/dt,dz/dt) and is only valid if order is greater or equal to 1.

PVAJ[7:9] contain the acceleration (d^2x/dt^2,d^2y/dt^2,d^2z/dt^2) and is only valid if order is greater or equal to 2.

PVAJ[10:12] contain the jerk (d^3x/dt^3,d^3y/dt^3,d^3z/dt^3) and is only valid if order is equal to 3.

If JD0 and time are list or NumPy's array (1D) of double-precision floating-point values, the returned array PVAJ is a list of 3*(order+1) arrays. Each array contain a single component of position, velocity ... (e.g., PV[0] contains the coordinate X, PV[1] contains the coordinate Y, ...) .

The date (JD0, time) should be expressed in the same timescale as the ephemeris files, which can be retrieved using the function calcephpy.CalcephBin.gettimescale().

Warning

If a date, expressed in the Coordinated Universal Time (UTC), is supplied to this function, a very large erroneous position will be returned.

The values stored in the array PVAJ are expressed in the following units

The position, velocity, acceleration and jerk are expressed in Astronomical Unit (au) if unit contains UNIT_AU.

The position, velocity, acceleration and jerk are expressed in kilometers if unit contains UNIT_KM.

The velocity, acceleration, jerk, TT-TDB, TCG-TCB or the derivatives of the angles of the librations of the Moon are expressed in days if unit contains UNIT_DAY.

The velocity, acceleration, jerk, TT-TDB, TCG-TCB or the derivatives of the angles of the librations of the Moon are expressed in seconds if unit contains UNIT_SEC.

The angles of the librations of the Moon are expressed in radians if unit contains UNIT_RAD.

For example, to get the positions, velocities, accelerations and jerks expressed in kilometers and kilometers/seconds, the unit must be set to UNIT_KM + UNIT_SEC.

This function checks the units if invalid combinations of units are given to the function.

The following example prints the heliocentric coordinates of Mars at time=2442457.5

from calcephpy import *

jd0=2442457
dt=0.5E0

peph = CalcephBin.open("example1.dat")

# compute only the heliocentric position of Mars in km
P = peph.compute_order(jd0, dt, NaifId.MARS_BARYCENTER, NaifId.SUN,
                        Constants.UNIT_KM+Constants.UNIT_SEC+Constants.USE_NAIFID, 0)
print(P)

# compute positions, velocities, accelerations and jerks of Mars in km and seconds
PVAJ = peph.compute_order(jd0, dt, NaifId.MARS_BARYCENTER, NaifId.SUN,
                        Constants.UNIT_KM+Constants.UNIT_SEC+Constants.USE_NAIFID, 3)
print(PVAJ)

peph.close()

calcephpy.CalcephBin.orient_order

calcephpy.CalcephBin.orient_order(JD0, time, target, unit, order) → PVAJ

Parameters:

JD0 (float/list/numpy.ndarray) -- Integer part of the Julian date (TDB or TCB)
time (float/list/numpy.ndarray) -- Fraction part of the Julian date (TDB or TCB)
target (int) -- The body whose orientations are requested. The numbering system depends on the parameter unit.
unit (int) --

The units of PV.

This integer is a sum of some unit constants (CALCEPH_UNIT_???) and/or the constant USE_NAIFID.

If the unit contains USE_NAIFID, the NAIF identification numbering system is used for the target (NAIF identification numbers for the list).

If the unit does not contain USE_NAIFID, the old number system is used for the target (see the list in the function calcephpy.CalcephBin.compute()).
order (int) --
The order of derivatives.
- = 0 , only the angles is computed. The first three numbers of PVAJ are valid for the results.
- = 1 , only the angles and the first derivative are computed. The first six numbers of PVAJ are valid for the results.
- = 2 , only the angles and the first and second derivatives are computed. The first nine numbers of PVAJ are valid for the results.
- = 3 , the angles and the first, second and third derivatives are computed. The first twelve numbers of PVAJ are valid for the results.
If order equals to 1, the behavior of calcephpy.CalcephBin.orient_order() is the same as calcephpy.CalcephBin.orient_unit().

Returns:

An array to receive the euler angles, or nutation angles, and their derivatives for the orientation of the body.

Return type:

list

This function is similar to the function calcephpy.CalcephBin.orient_unit(), except that the order of the computed derivatives is specified.

This function reads, if needed, in the ephemeris file self and interpolates the orientation of a single body (target) for the time JD0+time and stores the results to PVAJ. The order of the derivatives are specified by order. The ephemeris file self must have been previously opened with the function calcephpy.CalcephBin.open(). The output values are expressed in the units specified by unit.

This function checks the units if invalid combinations of units are given to the function.

The returned array PVAJ has the following properties

If unit contains OUTPUT_NUTATIONANGLES, the array contains the nutation angles and their successive derivatives for the orientation of the body. At the present moment, only the nutation for the earth are supported in the original DE files.

If unit contains OUTPUT_EULERANGLES, or doesnot contain OUTPUT_NUTATIONANGLES, the array contains the euler angles and their successive derivatives for the orientation of the body.

The returned array PVAJ must be large enough to store the results.

PVAJ[1:3] contain the angles and is always valid.

PVAJ[4:6] contain the first derivative and is only valid if order is greater or equal to 1.

PVAJ[7:9] contain the second derivative and is only valid if order is greater or equal to 2.

PVAJ[10:12] contain the third derivative and is only valid if order is equal to 3.

If JD0 and time are list or NumPy's array (1D) of double-precision floating-point values, the returned array PVAJ is a list of 3*(order+1) arrays. Each array contain a single component of the orientation.

The values stored in the array PVAJ are expressed in the following units

The derivatives of the angles are expressed in days if unit contains UNIT_DAY.

The derivatives of the angles are expressed in seconds if unit contains UNIT_SEC.

The angles and their derivatives are expressed in radians if unit contains UNIT_RAD.

The date (JD0, time) should be expressed in the same timescale as the ephemeris files, which can be retrieved using the function calcephpy.CalcephBin.gettimescale().

The following example prints only the angles of libration of the Moon at time=2442457.5

from calcephpy import *

jd0=2442457
dt=0.5E0

peph = CalcephBin.open("example1.dat")

P = peph.orient_order(jd0, dt, NaifId.MOON,
                      Constants.USE_NAIFID+Constants.UNIT_RAD+Constants.UNIT_SEC, 0)
print(P)

peph.close()

calcephpy.CalcephBin.rotangmom_order

calcephpy.CalcephBin.rotangmom_order(JD0, time, target, unit, order) → PVAJ

Parameters:

JD0 (float) -- Integer part of the Julian date (TDB or TCB)
time (float) -- Fraction part of the Julian date (TDB or TCB)
target (int) -- The body whose orientations are requested. The numbering system depends on the parameter unit.
unit (int) --

The units of PV.

This integer is a sum of some unit constants (CALCEPH_UNIT_???) and/or the constant USE_NAIFID.

If the unit contains USE_NAIFID, the NAIF identification numbering system is used for the target (NAIF identification numbers for the list).

If the unit does not contain USE_NAIFID, the old number system is used for the target (see the list in the function calcephpy.CalcephBin.compute()).
order (int) --
The order of derivatives.
- = 0 , only the angular momentum is computed. The first three numbers of PVAJ are valid for the results.
- = 1 , only the angular momentum and the first derivative are computed. The first six numbers of PVAJ are valid for the results.
- = 2 , only the angular momentum and the first and second derivatives are computed. The first nine numbers of PVAJ are valid for the results.
- = 3 , the angular momentum and the first, second and third derivatives are computed. The first twelve numbers of PVAJ are valid for the results.
If order equals to 1, the behavior of calcephpy.CalcephBin.rotangmom_order() is the same as calcephpy.CalcephBin.rotangmom_unit().

Returns:

An array to receive the angular momentum due to its rotation, divided by the product of the mass and of the square of the radius, and their different order of the derivatives, of the body.

Return type:

list

This function is similar to the function calcephpy.CalcephBin.orient_unit(), except that the order of the computed derivatives is specified.

This function reads, if needed, in the ephemeris file self and interpolates the angular momentum vector due to the rotation of the body, divided by the product of the mass $m$ and of the square of the radius $R$ , of a single body (target) for the time JD0+time and stores the results to PVAJ. The angular momentum $L$ , due to the rotation of the body, is defined as the product of the inertia matrix $I$ by the angular velocity vector ${\omega}$ . So the returned value is $L/(mR^2)=(I\omega)/(mR^2)$ The order of the derivatives are specified by order. The ephemeris file self must have been previously opened with the function calcephpy.CalcephBin.open(). The output values are expressed in the units specified by unit.

This function checks the units if invalid combinations of units are given to the function.

The returned array PVAJ must be large enough to store the results.

PVAJ[1:3] contain the angular momentum and is always valid.

PVAJ[4:6] contain the first derivative and is only valid if order is greater or equal to 1.

PVAJ[7:9] contain the second derivative and is only valid if order is greater or equal to 2.

PVAJ[10:12] contain the third derivative and is only valid if order is equal to 3.

The values stored in the array PVAJ are expressed in the following units

The angular momentum and its derivatives are expressed in days if unit contains UNIT_DAY.

The angular momentum and its derivatives are expressed in seconds if unit contains UNIT_SEC.

The date (JD0, time) should be expressed in the same timescale as the ephemeris files, which can be retrieved using the function calcephpy.CalcephBin.gettimescale().

The following example prints only the angular momentum, due to its rotation, of the Earth at time=2451419.5

from calcephpy import *

jd0=2451419
dt=0.5E0

peph = CalcephBin.open("example2_rotangmom.dat")

G = peph.rotangmom_order(jd0, dt, NaifId.EARTH,
                      Constants.USE_NAIFID+Constants.UNIT_SEC, 0)
print(G)

peph.close()

calcephpy.CalcephBin.getconstant

calcephpy.CalcephBin.getconstant(name) → value

Parameters:: name (str) -- name of the constant
Returns:: first value of the constant
Return type:: float

This function returns the value associated to the constant name in the header of the ephemeris file self. Only the first value is returned if multiple values are associated to a constant, such as a list of values.

This function is the same function as calcephpy.CalcephBin.getconstantsd().

The following example prints the value of the astronomical unit stored in the ephemeris file

from calcephpy import *

peph = CalcephBin.open("example1.dat")
AU = peph.getconstant("AU")
print(AU)
peph.close()

calcephpy.CalcephBin.getconstantsd

calcephpy.CalcephBin.getconstantsd(name) → value

Parameters:: name (str) -- name of the constant
Returns:: first value of the constant
Return type:: float

This function returns, as a floating-point number, the value associated to the constant name in the header of the ephemeris file self. Only the first value is returned if multiple values are associated to a constant, such as a list of values. The value must be a floating-point or integer number, otherwise an error is reported.

This function is the same function as calcephpy.CalcephBin.getconstant().

The following example prints the value of the astronomical unit stored in the ephemeris file

from calcephpy import *

peph = CalcephBin.open("example1.dat")
AU = peph.getconstantsd("AU")
print(AU)
peph.close()

calcephpy.CalcephBin.getconstantvd

calcephpy.CalcephBin.getconstantvd(name) → arrayvalue

Parameters:: name (str) -- name of the constant
Returns:: array of values for the constant
Return type:: list

This function returns, as floating-point numbers, all values associated to the constant name in the header of the ephemeris file self.

The values must be floating-point or integer numbers, otherwise an error is reported.

The following example prints the body radii of the earth stored in the ephemeris file

from calcephpy import *

peph = CalcephBin.open("example1.dat")
radii = peph.getconstantvd("BODY399_RADII")
print(radii)
peph.close()

calcephpy.CalcephBin.getconstantss

calcephpy.CalcephBin.getconstantss(name) → value

Parameters:: name (str) -- name of the constant
Returns:: first value of the constant
Return type:: str

This function returns, as a string of character, the value associated to the constant name in the header of the ephemeris file self. Only the first value is returned if multiple values are associated to a constant, such as a list of values. The value must be a string, otherwise an error is reported.

The following example prints the value of the unit stored in the ephemeris file

from calcephpy import *

peph = CalcephBin.open("example1.dat")
UNIT = peph.getconstantss("UNIT")
print(UNIT)
peph.close()

calcephpy.CalcephBin.getconstantvs

calcephpy.CalcephBin.getconstantvs(name) → arrayvalue

Parameters:: name (str) -- name of the constant
Returns:: array of values for the constant
Return type:: list

This function returns, as strings of characters, all values associated to the constant name in the header of the ephemeris file self.

The values must be strings, otherwise an error is reported.

The following example prints the units of the mission stored in the ephemeris file

from calcephpy import *

peph = CalcephBin.open("example1.dat")
mission_units = peph.getconstantvs("MISSION_UNITS")
print(mission_units)
peph.close()

calcephpy.CalcephBin.getconstantindex

calcephpy.CalcephBin.getconstantindex(index) → name, value

Parameters:: index (int) -- index of the constant, between 1 and calcephpy.CalcephBin.getconstantcount()
Returns:: name of the constant, first value of the constant
Return type:: str, float

This function returns the name and its value of the constant available at the specified index in the header of the ephemeris file self. The value of index must be between 1 and calcephpy.CalcephBin.getconstantcount().

Only the first value is returned if multiple values are associated to a constant, such as a list of values. If the first value is not an floating-point number, such as a string, then the function returns 0 without raising an error.

The following example displays the name of the constants, stored in the ephemeris file, and their values

from calcephpy import *

peph = CalcephBin.open("example1.dat")
n = peph.getconstantcount()
for j in range(1, n+1):
    name, value = peph.getconstantindex(j)
    print(name, value)

peph.close()

calcephpy.CalcephBin.getfileversion

calcephpy.CalcephBin.getfileversion()

Returns:: version of the ephemeris file
Return type:: str

This function returns the version of the ephemeris file, as a string. For example, the argument version will contain 'INPOP10B', 'EPM2017' or 'DE405', ... .

If the file is an original JPL binary planetary ephemeris, then the version of the file can always be determined. If the file is a spice kernel, the version of the file is retrieved from the constant INPOP_PCK_VERSION, EPM_PCK_VERSION, or PCK_VERSION.

The following example prints the version of the ephemeris file.

from calcephpy import *

peph = CalcephBin.open("example1.dat")
version = peph.getfileversion()
print(version)
peph.close()

calcephpy.CalcephBin.getidbyname

calcephpy.CalcephBin.getidbyname(name, unit) → id

Parameters:

name (str) -- name of the body
unit (int) --

The unit of id.

This integer is 0 or the constant USE_NAIFID.

If the unit equals USE_NAIFID, the NAIF identification numbering system is used for the id (NAIF identification numbers for the list).

If the unit equals 0, the old number system is used for the idr (see the list in the function calcephpy.CalcephBin.compute()).

Returns:

identification number of the body

Return type:

int or None

This function returns the identification number of the body associated to the given name. If no such name exists in the mapping, then the value None is returned.

The function is not sensitive to the case of the characters of the string name. Leading and trailing spaces are ignored. At least one space character is required between the words. For example, 'Saturn Barycenter' is the same as ' Saturn Barycenter ', but is different from 'SaturnBarycenter'.

The library has a default mapping listed in the list NAIF identification numbers. The mapping name/id may be overriden by the text constants NAIF_BODY_CODE and NAIF_BODY_NAME in the 'SPICE' ephemeris files.

The following example prints the identification number of the Moon.

from calcephpy import *

peph = CalcephBin.open("example1.dat")
# print the id of the Moon using the old numbering system
moon = peph.getidbyname('Moon', 0)
print(moon)
# print the id of the Moon using the NAIF identification numbering system
moon = peph.getidbyname('Moon', Constants.USE_NAIFID)
print(moon)
print(NaifId.MOON)
peph.close()

calcephpy.CalcephBin.getnamebyidss

calcephpy.CalcephBin.getnamebyidss(id, unit) → name

Parameters:

id (int) -- identification number of the body
unit (int) --

The unit of id.

This integer is 0 or the constant USE_NAIFID.

If the unit equals USE_NAIFID, the NAIF identification numbering system is used for the id (NAIF identification numbers for the list).

If the unit equals 0, the old number system is used for the idr (see the list in the function calcephpy.CalcephBin.compute()).

Returns:

name of the body

Return type:

str or None

This function returns the first given name of the body associated to the identification number id. If no such name exists in the mapping, then the value None is returned.

The library has a default mapping listed in the list NAIF identification numbers. The mapping name/id may be overriden by the text constants NAIF_BODY_CODE and NAIF_BODY_NAME in the 'SPICE' ephemeris files.

The following example prints the name of the Earth-Moon barycenter.

from calcephpy import *

peph = CalcephBin.open("example1.dat")
#  print the name of the Earth-Moon barycenter using the old numbering system
emb = peph.getnamebyidss(13, 0)
print(emb)
# print the name of the Earth-Moon barycenter using the NAIF identification numbering system
emb = peph.getnamebyidss(3, Constants.USE_NAIFID)
print(emb)
peph.close()

calcephpy.CalcephBin.gettimescale

calcephpy.CalcephBin.gettimescale()

Returns:: time scale of the ephemeris file
Return type:: int

This function returns the timescale of the ephemeris file self :

1 if the quantities of all bodies are expressed in the TDB time scale.

2 if the quantities of all bodies are expressed in the TCB time scale.

The following example prints the time scale available in the ephemeris file

from calcephpy import *

peph = CalcephBin.open("example1.dat")
timescale = peph.gettimescale()
print(timescale)
peph.close()

calcephpy.CalcephBin.gettimespan

calcephpy.CalcephBin.gettimespan() → firsttime, lasttime, continuous

Returns:: first and last available time, availability of the quantities of the bodies over the time span
Return type:: float, float, int

This function returns the first and last time available in the ephemeris file self. The Julian date for the first and last time are expressed in the time scale returned by calcephpy.CalcephBin.gettimescale() .

It returns the following value in the parameter continuous :

1 if the quantities of all bodies are available for any time between the first and last time.

2 if the quantities of some bodies are available on discontinuous time intervals between the first and last time.

3 if the quantities of each body are available on a continuous time interval between the first and last time, but not available for any time between the first and last time.

The following example prints the first and last time available in the ephemeris file

from calcephpy import *

peph = CalcephBin.open("example1.dat")
firsttime, lasttime, continuous = peph.gettimespan()
print(firsttime, lasttime, continuous)
peph.close()

calcephpy.CalcephBin.getpositionrecordcount

calcephpy.CalcephBin.getpositionrecordcount()

Returns:: number of position's records
Return type:: int

This function returns the number of position's records available in the ephemeris file self. Usually, the number of records is equal to the number of bodies in the ephemeris file if the timespan is continuous. If the timespan is discontinuous for the target and center bodies, then each different timespan is counted as a different record. If the ephemeris file contain timescale transformations' records, such as TT-TDB or TCG-TCB, then these records are included in the returned value.

The following example prints the number of position's records available in the ephemeris file

from calcephpy import *

peph = CalcephBin.open("example1.dat")
n = peph.getpositionrecordcount()
print("number of position's record", n)
peph.close()

calcephpy.CalcephBin.getpositionrecordindex

calcephpy.CalcephBin.getpositionrecordindex(index) → target, center, firsttime, lasttime, frame

Parameters:

index (int) -- index of the position's record, between 1 and calcephpy.CalcephBin.getpositionrecordcount()

Returns:

target : the target body
center : the origin body
firsttime : julian date of the first time
lasttime : julian date of the last time
frame  : reference frame (see the list, below)

Return type:

int, int, float, float, int

This function returns the target and origin bodies, the first and last time, and the reference frame available at the specified index for the position's records of the ephemeris file self. The NAIF identification numbering system is used for the target and center integers (NAIF identification numbers for the list). The Julian date for the first and last time are expressed in the time scale returned by calcephpy.CalcephBin.gettimescale().

It returns the following value in the parameter frame :

value	Name
1	ICRF

The following example displays the position's records stored in the ephemeris file.

from calcephpy import *

peph = CalcephBin.open("example1.dat")
n = peph.getpositionrecordcount()
for j in range(1, n+1):
    itarget, icenter, firsttime, lasttime, iframe = peph.getpositionrecordindex(j)
    print(itarget, icenter, firsttime, lasttime, iframe)

peph.close()

calcephpy.CalcephBin.getpositionrecordindex2

calcephpy.CalcephBin.getpositionrecordindex2(index) → target, center, firsttime, lasttime, frame, segid

Parameters:

index (int) -- index of the position's record, between 1 and calcephpy.CalcephBin.getpositionrecordcount()

Returns:

target : the target body
center : the origin body
firsttime : julian date of the first time
lasttime : julian date of the last time
frame  : reference frame (see the list, below)
segid  : segment type (see the details, below)

Return type:

int, int, float, float, int, int

This function returns the target and origin bodies, the first and last time, the reference frame, and the segment type available at the specified index for the position's records of the ephemeris file self. The NAIF identification numbering system is used for the target and center integers (NAIF identification numbers for the list). The Julian date for the first and last time are expressed in the time scale returned by calcephpy.CalcephBin.gettimescale().

It returns the following value in the parameter frame :

value	Name
1	ICRF

It returns in the parameter segid one of the predefined constants Constants.SEGTYPE_... (Constants).

The following example displays the position's records stored in the ephemeris file.

from calcephpy import *

peph = CalcephBin.open("example1.dat")
n = peph.getpositionrecordcount()
for j in range(1, n+1):
    itarget, icenter, firsttime, lasttime, iframe, iseg = peph.getpositionrecordindex2(j)
    print(itarget, icenter, firsttime, lasttime, iframe, iseg)

peph.close()

calcephpy.CalcephBin.getorientrecordcount

calcephpy.CalcephBin.getorientrecordcount()

Returns:: number of orientation's records
Return type:: int

This function returns the number of orientation's records available in the ephemeris file self. Usually, the number of records is equal to the number of bodies in the ephemeris file if the timespan is continuous. If the timespan is discontinuous for the target body, then each different timespan is counted as a different record.

The following example prints the number of orientation's records available in the ephemeris file

from calcephpy import *

peph = CalcephBin.open("example1.dat")
n = peph.getorientrecordcount()
print("number of orientation's record", n)
peph.close()

calcephpy.CalcephBin.getorientrecordindex

calcephpy.CalcephBin.getorientrecordindex(index) → target, firsttime, lasttime, frame

Parameters:

index (int) -- index of the orientation's record, between 1 and calcephpy.CalcephBin.getorientrecordcount()

Returns:

target : the target body
firsttime : julian date of the first time
lasttime : julian date of the last time
frame  : reference frame (see the list, below)

Return type:

int, float, float, int

This function returns the target body, the first and last time, and the reference frame available at the specified index for the orientation's records of the ephemeris file self. The NAIF identification numbering system is used for the target body (NAIF identification numbers for the list). The Julian date for the first and last time are expressed in the time scale returned by calcephpy.CalcephBin.gettimescale().

It returns the following value in the parameter frame :

value	Name
1	ICRF

The following example displays the orientation's records stored in the ephemeris file.

from calcephpy import *

peph = CalcephBin.open("example1.dat")
n = peph.getorientrecordcount()
for j in range(1, n+1):
    itarget, firsttime, lasttime, iframe = peph.getorientrecordindex(j)
    print(itarget, firsttime, lasttime, iframe)

peph.close()

calcephpy.CalcephBin.getorientrecordindex2

calcephpy.CalcephBin.getorientrecordindex2(index) → target, firsttime, lasttime, frame, segid

Parameters:

index (int) -- index of the orientation's record, between 1 and calcephpy.CalcephBin.getorientrecordcount()

Returns:

target : the target body
firsttime : julian date of the first time
lasttime : julian date of the last time
frame  : reference frame (see the list, below)
segid  : segment type (see the details, below)

Return type:

int, float, float, int, int

This function returns the target body, the first and last time, the reference frame and the segment type available at the specified index for the orientation's records of the ephemeris file self. The NAIF identification numbering system is used for the target body (NAIF identification numbers for the list). The Julian date for the first and last time are expressed in the time scale returned by calcephpy.CalcephBin.gettimescale().

It returns the following value in the parameter frame :

value	Name
1	ICRF

It returns in the parameter segid one of the predefined constants Constants.SEGTYPE_... (Constants).

The following example displays the orientation's records stored in the ephemeris file.

from calcephpy import *

peph = CalcephBin.open("example1.dat")
n = peph.getorientrecordcount()
for j in range(1, n+1):
    itarget, firsttime, lasttime, iframe, iseg = peph.getorientrecordindex2(j)
    print(itarget, firsttime, lasttime, iframe, iseg)

peph.close()

Multiple file access functions

Time notes

Thread notes

Usage

Functions

calcephpy.CalcephBin.open

calcephpy.CalcephBin.prefetch

calcephpy.CalcephBin.isthreadsafe

calcephpy.CalcephBin.compute

calcephpy.CalcephBin.compute_unit

calcephpy.CalcephBin.orient_unit

calcephpy.CalcephBin.rotangmom_unit

calcephpy.CalcephBin.compute_order

calcephpy.CalcephBin.orient_order

calcephpy.CalcephBin.rotangmom_order

calcephpy.CalcephBin.getconstant

calcephpy.CalcephBin.getconstantsd

calcephpy.CalcephBin.getconstantvd

calcephpy.CalcephBin.getconstantss

calcephpy.CalcephBin.getconstantvs

calcephpy.CalcephBin.getconstantcount

calcephpy.CalcephBin.getconstantindex

calcephpy.CalcephBin.getfileversion

calcephpy.CalcephBin.getidbyname

calcephpy.CalcephBin.getnamebyidss

calcephpy.CalcephBin.gettimescale

calcephpy.CalcephBin.gettimespan

calcephpy.CalcephBin.getpositionrecordcount

calcephpy.CalcephBin.getpositionrecordindex

calcephpy.CalcephBin.getpositionrecordindex2

calcephpy.CalcephBin.getorientrecordcount

calcephpy.CalcephBin.getorientrecordindex

calcephpy.CalcephBin.getorientrecordindex2

calcephpy.CalcephBin.close