ootk-core
Version:
Orbital Object Toolkit. A modern typed replacement for satellite.js including SGP4 propagation, TLE parsing, Sun and Moon calculations, and more.
137 lines • 5.74 kB
JavaScript
/**
* @author Theodore Kruczek.
* @license MIT
* @copyright (c) 2022-2025 Theodore Kruczek Permission is
* hereby granted, free of charge, to any person obtaining a copy of this
* software and associated documentation files (the "Software"), to deal in the
* Software without restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do
* so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
import { DEG2RAD, MS_PER_DAY, RAD2DEG, secondsPerWeek, TAU } from '../utils/constants.js';
import { evalPoly } from '../utils/functions.js';
import { DataHandler } from './../data/DataHandler.js';
import { Epoch } from './Epoch.js';
import { EpochGPS } from './EpochGPS.js';
import { EpochTAI } from './EpochTAI.js';
import { EpochTDB } from './EpochTDB.js';
import { EpochTT } from './EpochTT.js';
export class EpochUTC extends Epoch {
static now() {
return new EpochUTC(new Date().getTime() / 1000);
}
static fromDate({ year, month, day, hour = 0, minute = 0, second = 0 }) {
return new EpochUTC(EpochUTC.dateToPosix_({ year, month, day, hour, minute, second }));
}
static fromDateTime(dt) {
return new EpochUTC(dt.getTime() / 1000);
}
static fromDateTimeString(dateTimeString) {
const dts = dateTimeString.trim().toUpperCase().endsWith('Z') ? dateTimeString : `${dateTimeString}Z`;
return new EpochUTC(new Date(dts).getTime() / 1000);
}
static fromJ2000TTSeconds(seconds) {
const tInit = new EpochUTC(seconds + 946728000);
const ls = DataHandler.getInstance().getLeapSeconds(tInit.toJulianDate());
return tInit.roll(-32.184 - ls);
}
static fromDefinitiveString(definitiveString) {
const fields = definitiveString.trim().split(' ');
const dateFields = fields[0].split('/');
const day = parseInt(dateFields[0]);
const year = parseInt(dateFields[1]);
// eslint-disable-next-line prefer-destructuring
const timeField = fields[1];
// Add day - 1 days in milliseconds to the epoch.
const dts = new Date(`${year}-01-01T${timeField}Z`).getTime() + (day - 1) * MS_PER_DAY;
return new EpochUTC(dts / 1000);
}
roll(seconds) {
return new EpochUTC(this.posix + seconds);
}
toMjd() {
return this.toJulianDate() - 2400000.5;
}
toMjdGsfc() {
return this.toMjd() - 29999.5;
}
toTAI() {
const ls = DataHandler.getInstance().getLeapSeconds(this.toJulianDate());
return new EpochTAI(this.posix + ls);
}
toTT() {
return new EpochTT(this.toTAI().posix + 32.184);
}
toTDB() {
const tt = this.toTT();
const tTT = tt.toJulianCenturies();
const mEarth = (357.5277233 + 35999.05034 * tTT) * DEG2RAD;
const seconds = 0.001658 * Math.sin(mEarth) + 0.00001385 * Math.sin(2 * mEarth);
return new EpochTDB(tt.posix + seconds);
}
toGPS() {
const referenceTime = EpochUTC.fromDateTimeString('1980-01-06T00:00:00.000Z');
const ls = DataHandler.getInstance().getLeapSeconds(this.toJulianDate());
const delta = this.roll(ls - EpochGPS.offset).difference(referenceTime);
const week = delta / secondsPerWeek;
const weekFloor = Math.floor(week);
const seconds = (week - weekFloor) * secondsPerWeek;
return new EpochGPS(weekFloor, seconds, referenceTime);
}
gmstAngle() {
const t = this.toJulianCenturies();
const seconds = evalPoly(t, EpochUTC.gmstPoly_);
let result = ((seconds / 240) * DEG2RAD) % TAU;
if (result < 0) {
result += TAU;
}
return result;
}
gmstAngleDegrees() {
return this.gmstAngle() * RAD2DEG;
}
static gmstPoly_ = new Float64Array([
-6.2e-6,
0.093104,
876600 * 3600 + 8640184.812866,
67310.54841,
]);
static dayOfYearLookup_ = [
[0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334],
[0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335],
];
static isLeapYear_(year) {
return (year % 4 === 0 && year % 100 !== 0) || year % 400 === 0;
}
static dayOfYear_(year, month, day) {
const dex = EpochUTC.isLeapYear_(year) ? 1 : 0;
const dayOfYearArray = EpochUTC.dayOfYearLookup_[dex];
const daysBeforeCurrentMonth = dayOfYearArray[month - 1];
return daysBeforeCurrentMonth + day - 1;
}
static dateToPosix_({ year, month, day, hour, minute, second }) {
const days = EpochUTC.dayOfYear_(year, month, day);
const yearMod = year - 1900;
return (minute * 60 +
hour * 3600 +
days * 86400 +
(yearMod - 70) * 31536000 +
Math.floor((yearMod - 69) / 4) * 86400 -
Math.floor((yearMod - 1) / 100) * 86400 +
Math.floor((yearMod + 299) / 400) * 86400 +
second);
}
}
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