ootk
Version:
Orbital Object Toolkit including Multiple Propagators, Initial Orbit Determination, and Maneuver Calculations.
196 lines • 8.57 kB
JavaScript
/**
* @author @thkruz Theodore Kruczek
* @description Orbital Object ToolKit (ootk) is a collection of tools for working
* with satellites and other orbital objects.
* @license AGPL-3.0-or-later
* @copyright (c) 2025 Kruczek Labs LLC
*
* Many of the classes are based off of the work of @david-rc-dayton and his
* Pious Squid library (https://github.com/david-rc-dayton/pious_squid) which
* is licensed under the MIT license.
*
* Orbital Object ToolKit is free software: you can redistribute it and/or modify it under the
* terms of the GNU Affero General Public License as published by the Free Software
* Foundation, either version 3 of the License, or (at your option) any later version.
*
* Orbital Object ToolKit is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
* without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License along with
* Orbital Object ToolKit. If not, see <http://www.gnu.org/licenses/>.
*/
import { AngularDistanceMethod } from '../enums/AngularDistanceMethod.js';
import { Vector3D } from '../operations/Vector3D.js';
import { DEG2RAD, RAD2DEG, TAU } from '../utils/constants.js';
import { angularDistance } from '../utils/functions.js';
import { radecToPosition, radecToVelocity } from './ObservationUtils.js';
/**
* Represents a topocentric right ascension and declination observation.
*
* Topocentric coordinates take into account the observer's exact location on the Earth's surface. This model is crucial
* for precise measurements of local astronomical events and nearby celestial objects, where the observer's latitude,
* longitude, and altitude can significantly affect the observed position due to parallax. Topocentric coordinates are
* particularly important for observations of the Moon, planets, and artificial satellites.
*/
export class RadecTopocentric {
epoch;
rightAscension;
declination;
range;
rightAscensionRate;
declinationRate;
rangeRate;
constructor(epoch, rightAscension, declination, range, rightAscensionRate, declinationRate, rangeRate) {
this.epoch = epoch;
this.rightAscension = rightAscension;
this.declination = declination;
this.range = range;
this.rightAscensionRate = rightAscensionRate;
this.declinationRate = declinationRate;
this.rangeRate = rangeRate;
// Nothing to do here.
}
/**
* Create a new RadecTopocentric object, using degrees for the angular values.
* @param epoch UTC epoch.
* @param rightAscensionDegrees Right-ascension in degrees.
* @param declinationDegrees Declination in degrees.
* @param range Range in km.
* @param rightAscensionRateDegrees Right-ascension rate in degrees per second.
* @param declinationRateDegrees Declination rate in degrees per second.
* @param rangeRate Range rate in km/s.
* @returns A new RadecTopocentric object.
*/
static fromDegrees(epoch, rightAscensionDegrees, declinationDegrees, range, rightAscensionRateDegrees, declinationRateDegrees, rangeRate) {
const rightAscensionRate = rightAscensionRateDegrees
? rightAscensionRateDegrees * DEG2RAD
: null;
const declinationRate = declinationRateDegrees
? declinationRateDegrees * DEG2RAD
: null;
return new RadecTopocentric(epoch, rightAscensionDegrees * DEG2RAD, declinationDegrees * DEG2RAD, range, rightAscensionRate, declinationRate, rangeRate);
}
/**
* Create a new RadecTopocentric object from a J2000 state vector.
* @param state Inertial state vector.
* @param site Site vector.
* @returns A new RadecTopocentric object.
*/
static fromStateVector(state, site) {
const p = state.position.subtract(site.position);
const pI = p.x;
const pJ = p.y;
const pK = p.z;
const pMag = p.magnitude();
const declination = Math.asin(pK / pMag);
const pDot = state.velocity.subtract(site.velocity);
const pIDot = pDot.x;
const pJDot = pDot.y;
const pKDot = pDot.z;
const pIJMag = Math.sqrt(pI * pI + pJ * pJ);
let rightAscension;
if (pIJMag !== 0) {
rightAscension = Math.atan2(pJ, pI);
}
else {
rightAscension = Math.atan2(pJDot, pIDot);
}
const rangeRate = p.dot(pDot) / pMag;
const rightAscensionRate = (pIDot * pJ - pJDot * pI) / (-(pJ * pJ) - pI * pI);
const declinationRate = (pKDot - rangeRate * Math.sin(declination)) / pIJMag;
return new RadecTopocentric(state.epoch, rightAscension % TAU, declination, pMag, rightAscensionRate, declinationRate, rangeRate);
}
/**
* Gets the right ascension in degrees.
* @returns The right ascension in degrees.
*/
get rightAscensionDegrees() {
return this.rightAscension * RAD2DEG;
}
/**
* Gets the declination in degrees.
* @returns The declination in degrees.
*/
get declinationDegrees() {
return this.declination * RAD2DEG;
}
/**
* Gets the right ascension rate in degrees per second.
* @returns The right ascension rate in degrees per second, or null if it is not available.
*/
get rightAscensionRateDegrees() {
return this.rightAscensionRate
? this.rightAscensionRate * RAD2DEG
: null;
}
/**
* Gets the rate of change of declination in degrees per second.
* @returns The rate of change of declination in degrees per second, or null if the declination rate is not defined.
*/
get declinationRateDegrees() {
return this.declinationRate
? this.declinationRate * RAD2DEG
: null;
}
/**
* Return the position relative to the observer site.
*
* An optional range value can be passed to override the value contained in this observation.
* @param site Observer site.
* @param range Range in km.
* @returns A Vector3D object.
*/
position(site, range) {
const r = range ?? this.range ?? 1.0;
return radecToPosition(this.rightAscension, this.declination, r).add(site.position);
}
/**
* Return the velocity relative to the observer site.
*
* An optional range and rangeRate value can be passed to override the values contained in this observation.
* @param site Observer site.
* @param range Range in km.
* @param rangeRate Range rate in km/s.
* @returns A Vector3D object.
*/
velocity(site, range, rangeRate) {
if (!this.rightAscensionRate || !this.declinationRate) {
throw new Error('Velocity unsolvable, missing ra/dec rates.');
}
const r = range ?? this.range ?? 1.0;
const rd = rangeRate ?? this.rangeRate ?? 0.0;
return radecToVelocity(this.rightAscension, this.declination, r, this.rightAscensionRate, this.declinationRate, rd).add(site.velocity);
}
/**
* Calculates the line of sight vector in the topocentric coordinate system.
* The line of sight vector points from the observer's location towards the celestial object.
* @returns The line of sight vector as a Vector3D object.
*/
lineOfSight() {
const ca = Math.cos(this.rightAscension);
const cd = Math.cos(this.declination);
const sa = Math.sin(this.rightAscension);
const sd = Math.sin(this.declination);
return new Vector3D(cd * ca, cd * sa, sd);
}
/**
* Calculate the angular distance between this and another RadecTopocentric object.
* @param radec - The other RadecTopocentric object.
* @param method - The angular distance method to use.
* @returns The angular distance.
*/
angle(radec, method = AngularDistanceMethod.Cosine) {
return angularDistance(this.rightAscension, this.declination, radec.rightAscension, radec.declination, method);
}
/**
* Calculate the angular distance between this and another RadecTopocentric object.
* @param radec - The other RadecTopocentric object.
* @param method - The angular distance method to use.
* @returns The angular distance
*/
angleDegrees(radec, method = AngularDistanceMethod.Cosine) {
return this.angle(radec, method) * RAD2DEG;
}
}
//# sourceMappingURL=RadecTopocentric.js.map