orb

orb offers a few simple methods for several common problems of orbital mechanics, like transformations between various coordinate systems and simple orbit propagation using Keplerian elements.

Installation

npm install orbjs

Usage

ES5 - CommonJS

var orb = require('orbjs');

ES6

import orb from 'orbjs';

ES5 - Browser

<script src="dist/orb.min.js"></script>

API

orb.constants

# orb.constants.common

# orb.constants.time

# orb.constants.earth

# orb.constants.earth.wgs84

# orb.constants.earth.grs80

orb.common

# orb.common.deg2rad(deg) Converts degree to radian

# orb.common.rad2deg(rad) Converts radian to degree

orb.time

# orb.time.JDtoMJD(jd) JD to MJD [days]

# orb.time.MJDtoJD(mjd) MJD to JD [days]

# orb.time.TAItoTT(tai) TAI to TT

# orb.time.TTtoTAI(tt) TT to TAI

# orb.time.TAItoUTC(tai) TAI to UTC

# orb.time.UTCtoTAI(utc) UTC to TAI

# orb.time.TAItoGPS(tai) TAI to GPS

# orb.time.GPStoTAI(gps) GPS to TAI

# orb.time.UTCtoGPS(utc) UTC to GPS

# orb.time.GPStoUTC(gps) GPS to UTC

# orb.time.leapSeconds(date) Amount of leap seconds that occurred before date. date is a JS Date object.

# orb.time.dateToJD(date) Convert a date to Julian Date. date is either a Date object, or an array of the form [Y, M, D, h, m, s, ms].

orb.transformations

# orb.transformations.sphericalToCartesian(x)

• Input:
  • x: [λ, φ, r] Spherical (longitude, (geocentric) latitude, radius)
• Output:
  • x: [x, y, z] Cartesian

# orb.transformations.cartesianToSpherical(x)

• Input:
  • x: [x, y, z] Cartesian
• Output:
  • x: [λ, φ, r] Spherical (longitude, (geocentric) latitude, radius)

# orb.transformations.ellipsoidalToCartesian(x, a, e)

• Input:
  • x: [L, β] Ellipsoidal (longitude, reduced latitude)
  • a: semimajor-axis of body
  • e: eccentricity of body
• Output:
  • x: [x, y, z] Cartesian

# orb.transformations.cartesianToEllipsoidal(x, a, e)

• Input:
  • x: [x, y, z] Cartesian
  • a: semimajor-axis of body
  • e: eccentricity of body
• Output:
  • x: [L, β] Ellipsoidal (longitude, reduced latitude)

# orb.transformations.geodeticToCartesian(x, a, e)

• Input:
  • x: [L, B, h] Geodetic (longitude, geodetic latitude, height above ellipsoid)
  • a: semimajor-axis of body
  • e: eccentricity of body
• Output:
  • x: [x, y, z] Cartesian

# orb.transformations.cartesianToGeodetic(x, a, e)

• Input:
  • x: [x, y, z] Cartesian
  • a: semimajor-axis of body
  • e: eccentricity of body
• Output:
  • x: [L, B, h] Geodetic (longitude, geodetic latitude, height above ellipsoid)

# orb.transformations.orbitalPlaneToInertial(x, Ω, ω, i)

• Input:
  • x: [x, y] Position of object in orbital plane
  • Ω: right ascension of the ascending node
  • ω: argument of periapsis
  • i: inclination
• Output:
  • x: [x, y, z] Inertial

# orb.transformations.inertialToFixed(x, α, axis)

• Input:
  • x: [x, y, z] Inertial
  • α: angle between the inertial and fixed systems
  • axis: 1, 2 or 3
• Output:
  • x: [x, y, z] Fixed

# orb.transformations.fixedToInertial(x, α, axis)

• Input:
  • x: [x, y, z] Fixed
  • α: angle between the fixed and inertial systems
  • axis: 1, 2 or 3
• Output:
  • x: [x, y, z] Inertial

# orb.transformations.fixedToTopocentric(x, obs, a, e, nwu)

• Input:
  • x: [x, y, z] Fixed
  • obs: [L, B, h]
  • a: semimajor-axis of body
  • e: eccentricity of body
• Output:
  • x: [x, y, z] Topocentric

# orb.transformations.topocentricToFixed(x, obs, a, e, nwu)

• Input:
  • x: [x, y, z] Topocentric
  • obs: [L, B, h]
  • a: semimajor-axis of body
  • e: eccentricity of body
• Output:
  • x: [x, y, z] Fixed

# orb.transformations.topocentricToHorizontal(x)

• Input:
  • x: [x, y, z] Topocentric
• Output:
  • x: [azimuth, elevation, distance] Horizontal

# orb.transformations.horizontalToTopocentric(x)

• Input:
  • x: [azimuth, elevation, distance] Horizontal
• Output:
  • x: [x, y, z] Topocentric

orb.position

# orb.position.keplerEquation(e, M)

• Input:
  • e: eccentricity
  • M: mean anomaly
• Output:
  • ν: true anomaly

# orb.position.keplerian(a, e, i, Ω, ω, t, t0, M0, m1, m2)

• Input:
  • a: semimajor-axis of orbit
  • e: eccentricity
  • i: inclination
  • Ω: right ascension of the ascending node
  • ω: argument of periapsis
  • t: time t
  • t0: epoch of given elements
  • M0: mean anomaly at epoch (optional, default: 0)
  • m1: mass of body 1 (optional, default: GM = orb.constants.earth.GM)
  • m2: mass of body 2 (optional, default: 0)
• Output:
  • [ x, xDot ]
    • x: [x, y, z] Position in inertial CRS
    • xDot: [vx, vy, vz] Velocity in inertial CRS

# orb.position.stateToKepler(x, xDot, t, m1, m2)

• Input:
  • x: [x, y, z] Position in inertial CRS
  • xDot: [vx, vy, vz] Velocity in inertial CRS
  • t: time t
  • m1: mass of body 1 (optional, default: GM = orb.constants.earth.GM)
  • m2: mass of body 2 (optional, default: 0)
• Output:
  • [a, e, i, Ω, ω, T0]
    • a: semimajor-axis of orbit (or focal parameter for e = 1)
    • e: eccentricity
    • i: inclination
    • Ω: right ascension of the ascending node
    • ω: argument of periapsis
    • T0: time of perihelion passage

orb.functions

# orb.functions.era(days)

• Input:
  • days: UT1 days since J2000.0
• Output:
  • era: ERA (radians)

orb.vector

Common vector and matrix operations, these are only included to make dependencies unnecessary. Don’t use these, there are a lot of better, more comprehensive and well tested libraries to do this.

License

MIT