ootk
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Orbital Object Toolkit including Multiple Propagators, Initial Orbit Determination, and Maneuver Calculations.
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JavaScript
/**
* @author @thkruz Theodore Kruczek
* @license AGPL-3.0-or-later
* @copyright (c) 2025 Kruczek Labs LLC
*
* 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/>.
*/
// / Container for cubic spline data.
export class CubicSpline {
t0;
p0;
m0;
t1;
p1;
m1;
// / Create a new [CubicSpline] object.
constructor(t0, p0, m0, t1, p1, m1) {
this.t0 = t0;
this.p0 = p0;
this.m0 = m0;
this.t1 = t1;
this.p1 = p1;
this.m1 = m1;
// Nothing to do here.
}
// / Interpolate position at the provided time [t] _(POSIX seconds)_.
position_(t) {
const t2 = t * t;
const t3 = t2 * t;
const r0 = this.p0.scale(2 * t3 - 3 * t2 + 1);
const v0 = this.m0.scale((t3 - 2 * t2 + t) * (this.t1 - this.t0));
const r1 = this.p1.scale(-2 * t3 + 3 * t2);
const v1 = this.m1.scale((t3 - t2) * (this.t1 - this.t0));
return r0.add(v0).add(r1).add(v1);
}
// / Interpolate velocity at the provided time [t] _(POSIX seconds)_.
velocity_(t) {
const t2 = t * t;
const r0 = this.p0.scale(6 * t2 - 6 * t);
const v0 = this.m0.scale((3 * t2 - 4 * t + 1) * (this.t1 - this.t0));
const r1 = this.p1.scale(-6 * t2 + 6 * t);
const v1 = this.m1.scale((3 * t2 - 2 * t) * (this.t1 - this.t0));
return r0
.add(v0)
.add(r1)
.add(v1)
.scale(1 / (this.t1 - this.t0));
}
/**
* Interpolates the position and velocity at a given time.
* (km) and velocity (km/s) vectors at the provided time.
* @param t The time value to interpolate at _(POSIX seconds)_.
* @returns An array containing the interpolated position and velocity as Vector3D objects.
*/
interpolate(t) {
const n = (t - this.t0) / (this.t1 - this.t0);
return [this.position_(n), this.velocity_(n)];
}
}
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