The planet module¶

Detailed Documentation¶

class pykep.planet._base(*args)¶

The base class for all planets, it cannot be instantiated as it contains pure virtual methods

__init__(*args)¶

pykep.planet._base(mu_central body, mu_self, radius, self_radius, name)

• mu_central_body: Gravity parameter of the central body (this is not used to compute the ephemerides)

• mu_self: Gravity parameter of the target

• radius: Radius of target body

• self_radius: Safe radius of target body

• name: Body name

eph(*args)¶

pykep.planet._base.eph(when)

• when: a pykep.epoch indicating the epoch at which the ephemerides are needed, it can also be a double in which case its interpreted as a mjd2000

Retuns a tuple containing the planet position and velocity in SI units

Note

This is a pure virtual method and must be reimplemented in the derived class

Example:

r,v = earth.eph(epoch(5433), 'mjd2000')
r,v = earth.eph(5433)

osculating_elements(*args)¶

Retruns a tuple containing the six osculating keplerian elements a,e,i,W,w,M at the reference epoch (SI units used). If no epoch is passed 0. is assumed

Example:

elem = earth.osculating_elements()
elem = earth.osculating_elements(epoch(2345.3, 'mjd2000'))

compute_period(*args)¶

The planet orbital period in [sec]

Example:

T = earth.compute_period()
T = earth.compute_period(epoch(2345.3, 'mjd2000'))

human_readable_extra(*args)¶

pykep.planet._base.human_readable_extra()

Retuns a string with extra information on the problem.

Note

This is a virtual method and can be reimplemented in the derived class. In which case __repr__ will append its returned value

mu_central_body¶

The central body gravity parameter in [m^3/s^2]

Example:

mu = earth.mu_central_body

mu_self¶

The body gravity parameter in [m^3/s^2]

Example:

mu_pla = earth.mu_self

radius¶

The planet radius in [m]

Example:

R = earth.radius

safe_radius¶

The body safe radius in [m](distance at which it is safe for spacecraft to fly-by)

Example:

Rs = earth.safe_radius
earth.safe_radius = 1.05

name¶

The body Name

Example:

name = earth.name

class pykep.planet.keplerian(*args)¶

A planet with Keplerian ephemerides, derives from pykep.planet._base

__init__(*args)¶

pykep.planet.keplerian(when,orbital_elements, mu_central_body, mu_self,radius, safe_radius [, name = ‘unknown’])

pykep.planet.keplerian(when,r,v, mu_central_body, mu_self,radius, safe_radius [, name = ‘unknown’])

• when: a pykep.epoch indicating the orbital elements reference epoch

• orbital_elements: a sequence of six containing a,e,i,W,w,M (SI units, i.e. meters and radiants)

• r,v: position and velocity of an object at when (SI units)

• mu_central_body: gravity parameter of the central body (SI units, i.e. m^2/s^3)

• mu_self: gravity parameter of the planet (SI units, i.e. m^2/s^3)

• radius: body radius (SI units, i.e. meters)

• safe_radius: mimimual radius that is safe during a fly-by of the planet (SI units, i.e. m)

• name: body name

Note

All classes having Keplerian ephemerides as pykep.planet.mpcorb inherit from this (c++) class

Example:

earth = planet(epoch(54000,"mjd"),(9.99e-01 * AU, 1.67e-02, 8.85e-04 * DEG2RAD, 1.75e+02 * DEG2RAD, 2.87e+02 * DEG2RAD, 2.57e+02 * DEG2RAD), MU_SUN, 398600e9, 6378000, 6900000,  'Earth')"

class pykep.planet.jpl_lp(*args)¶

A solar system planet that uses the JPL low-precision ephemerides, derives from pykep.planet._base

__init__(*args)¶

pykep.planet.jpl_lp(name)

• name: string containing the common planet name (e.g. ‘earth’, ‘venus’ etc.)

Example:

earth = planet.jpl_lp('earth')

class pykep.planet.mpcorb(*args)¶

A planet from the MPCORB database, derives from pykep.planet.keplerian

__init__(*args)¶

pykep.planet.mpcorb(line)

• line: a line from the MPCORB database file

Example:

apophis = planet.mpcorb('99942   19.2   0.15 K107N 202.49545  126.41859  204.43202    3.33173  0.1911104  1.11267324   0.9223398  1 MPO164109  1397   2 2004-2008 0.40 M-v 3Eh MPCAPO     C802  (99942) Apophis            20080109')

H¶

The asteroid absolute magnitude. This is assuming an albedo of 0.25 and using the formula at www.physics.sfasu.edu/astro/asteroids/sizemagnitude.html Example:

H = apophis.H

n_observations¶

Number of observations made on the asteroid Example:

R = apophis.n_observations

n_oppositions¶

Numper of oppositions the asteroid has been observed in. Example:

R = apophis.n_oppositions

year_of_discovery¶

The year the asteroid was first discovered. In case the asteroid has been observed only once (n_observations), this number is, instead, the Arc Length in days Example:

R = apophis.year_of_discovery

class pykep.planet.tle(*args)¶

An Earth satellite defined from the TLE format, derives from pykep.planet._base

__init__(*args)¶

pykep.planet.tle(line1, line2)

• line1: string containing the first line of a TLE (69 well formatted chars)

• line2: string containing the second line of a TLE (69 well formatted chars)

Example:

line1 = '1 23177U 94040C   06175.45752052  .00000386  00000-0  76590-3 0    95'
line2 = '2 23177   7.0496 179.8238 7258491 296.0482   8.3061  2.25906668 97438'
arianne = planet.tle(line1, line2)

class pykep.planet.spice(*args)¶

A planet to use the ephemerides from a loaded SPICE kernel

__init__(*args)¶

pykep.planet.spice(target, observer, ref_frame, aberrations, mu_central_body, mu_self, radius, self_radius)

Args:

• target (string): Target body (see NAIF IDs)

• observer (string): Observer body (see NAIF IDs

• ref_frame (string): The reference frame (see SPICE supported frames)

• aberrations (string): Aberration correction type (see spkezr_c docs <http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/spkezr_c.html>`_)

• mu_central_body (`float`): Gravity parameter of the central body (this is not necessary to compute the ephemerides).

• mu_self (`float`): Gravity parameter of the target (this is not necessary to compute the ephemerides).

• radius (`float`): Radius of target body (this is not necessary to compute the ephemerides).

• self_radius (`float`): Safe radius of target body (this is not necessary to compute the ephemerides).

Example:

import pykep as pk
pk.load_spice_kernel("de405.bsp")
earth = pk.planet.spice('EARTH', 'SUN', 'ECLIPJ2000', 'NONE', MU_SUN, MU_EARTH, EARTH_R, EARTH_R * 1.05)
r,v = earth.eph(pk.epoch(9500))

Note

The presence in memory of the needed SPICE kernel files are only checked upon call to the ephemerides method. As a consequence this object can still be constructed with invalid arguments. Only later the ephemerides call will fail throwing an excpetion. To load SPICE kernels use the pykep.utils.load_spice_kernel() utility.

Note

mu_central_body must be set to compute the period of the orbital elements.

class pykep.planet.gtoc2(*args)¶

An asteroid from gtoc2, derives from pykep.planet.keplerian

__init__(*args)¶

pykep.planet.gtoc2(ast_id)

• ast_id: Construct from a consecutive id from 0 to 910 (Earth).The order is that of the original data file from JPL

• Group 1: 0 - 95

• Group 2: 96 - 271

• Group 3: 272 - 571

• Group 4: 572 - 909

• Earth: 910

Example:

earth_gtoc2 = planet.gtoc2(910)

class pykep.planet.gtoc5(*args)¶

An asteroid from gtoc5, derives from pykep.planet.keplerian

__init__(*args)¶

pykep.planet.gtoc5(ast_id)

• ast_id: a consecutive id from 1 to 7076 (Earth). The order is that of the originaldata file distributed by the Russian, see the (gtoc portal). Earth is 7076

Example:

russian_ast = planet.gtoc5(1)

class pykep.planet.gtoc6(*args)¶

A Jupiter moon from gtoc6, derives from pykep.planet.keplerian

__init__(*args)¶

pykep.planet.gtoc6(name)

• name: string containing the common planet name (e.g. ‘io’, ‘europa’, ‘callisto’ or ‘ganymede’)

Example:

io = planet.gtoc6('io')

class pykep.planet.gtoc7(*args)¶

An asteroid from gtoc7, derives from pykep.planet.keplerian

__init__(*args)¶

pykep.planet.gtoc7(ast_id)

• ast_id: a consecutive id from 0 (Earth) to 16256. The order is that of the original file , see the (gtoc portal).

Example:

earth = planet.gtoc7(0)