ootk-core
Version:
Orbital Object Toolkit. A modern typed replacement for satellite.js including SGP4 propagation, TLE parsing, Sun and Moon calculations, and more.
109 lines • 4.11 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 { secondsPerDay } from '../utils/constants.js';
// / Base class for [Epoch] data.
export class Epoch {
posix;
/*
* Create a new [Epoch] object given the number of seconds elapsed since the
* [posix] epoch _(`1970-01-01T00:00:00.000`)_ in the [Epoch] time scale.
*/
constructor(posix) {
this.posix = posix;
if (posix < 0) {
throw new Error('Epoch cannot be negative');
}
}
toString() {
return this.toDateTime().toISOString();
}
// / Convert this to an Excel spreadsheet string.
toExcelString() {
return this.toString().substring(0, 19);
}
// / Return the difference _(s)_ between this and another [epoch]/
difference(epoch) {
return this.posix - epoch.posix;
}
// / Check if this has the same timestamp as the provided [epoch].
equals(epoch) {
return this.posix === epoch.posix;
}
// / Convert to a [DateTime] object.
toDateTime() {
return new Date(this.posix * 1000);
}
toEpochYearAndDay() {
const currentDateObj = this.toDateTime();
const epochYear = currentDateObj.getUTCFullYear().toString().slice(2, 4);
const epochDay = this.getDayOfYear_(currentDateObj);
const timeOfDay = (currentDateObj.getUTCHours() * 60 + currentDateObj.getUTCMinutes()) / 1440;
const epochDayStr = (epochDay + timeOfDay).toFixed(8).padStart(12, '0');
return {
epochYr: epochYear,
epochDay: epochDayStr,
};
}
getDayOfYear_(date) {
const dayCount = [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334];
const mn = date.getUTCMonth();
const dn = date.getUTCDate();
let dayOfYear = dayCount[mn] + dn;
if (mn > 1 && this.isLeapYear_(date)) {
dayOfYear++;
}
return dayOfYear;
}
isLeapYear_(dateIn) {
const year = dateIn.getUTCFullYear();
if ((year & 3) !== 0) {
return false;
}
return year % 100 !== 0 || year % 400 === 0;
}
// / Convert to Julian date.
toJulianDate() {
return this.posix / secondsPerDay + 2440587.5;
}
// / Convert to Julian centuries.
toJulianCenturies() {
return (this.toJulianDate() - 2451545) / 36525;
}
// / Check if this is later than the [other] epoch.
operatorGreaterThan(other) {
return this.posix > other.posix;
}
// / Check if this is later or the same as the [other] epoch.
operatorGreaterThanOrEqual(other) {
return this.posix >= other.posix;
}
// / Check if this is earlier than the [other] epoch.
operatorLessThan(other) {
return this.posix < other.posix;
}
// / Check if this is earlier or the same as the [other] epoch.
operatorLessThanOrEqual(other) {
return this.posix <= other.posix;
}
}
//# sourceMappingURL=Epoch.js.map