feat: ✨ add Sat class

.eslintrc.json

@@ -67,7 +67,7 @@
     "keyword-spacing": "error",
     "line-comment-position": "off",
     "linebreak-style": ["error", "unix"],
-    "lines-around-comment": "error",
+    "lines-around-comment": "off",
     "lines-around-directive": "error",
     "lines-between-class-members": "error",
     "max-classes-per-file": "error",
@@ -119,7 +119,7 @@
     "no-lone-blocks": "error",
     "no-lonely-if": "error",
     "no-loop-func": "error",
-    "no-loss-of-precision": "error",
+    "no-loss-of-precision": "off",
     "no-magic-numbers": "off",
     "no-mixed-operators": "off",
     "no-mixed-requires": "error",
@@ -128,7 +128,7 @@
     "no-multi-str": "error",
     "no-multiple-empty-lines": "error",
     "no-native-reassign": "error",
-    "no-negated-condition": "error",
+    "no-negated-condition": "off",
     "no-negated-in-lhs": "error",
     "no-nested-ternary": "error",
     "no-new": "error",
@@ -140,7 +140,7 @@
     "no-octal-escape": "error",
     "no-param-reassign": "error",
     "no-path-concat": "error",
-    "no-plusplus": "error",
+    "no-plusplus": "off",
     "no-process-env": "error",
     "no-process-exit": "error",
     "no-promise-executor-return": "error",

src/ootk.ts

@@ -29,4 +29,5 @@ export { Sgp4 } from './sgp4';
 export { Transforms } from './transforms';
 export { Utils } from './utils';
 export { Tle } from './tle';
+export { Sat } from './sat';
 export * from './types';

src/sat.ts

@@ -0,0 +1,138 @@
+import { EcfVec3, EciVec3, LlaVec3, SatelliteRecord, StateVector, TleLine1, TleLine2 } from './types';
+import { MILLISECONDS_PER_DAY, MINUTES_PER_DAY } from './utils/constants';
+import { Sgp4 } from './sgp4';
+import { Tle } from './tle';
+import { Transforms } from './transforms';
+import { Utils } from './utils';
+
+type GreenwichMeanSiderealTime = number;
+
+export class Sat {
+  public satNum: number;
+
+  public satrec: SatelliteRecord;
+
+  public options: any;
+
+  public intlDes: string;
+
+  public epochYear: number;
+
+  public epochDay: number;
+
+  public meanMoDev1: number;
+
+  public meanMoDev2: number;
+
+  public bstar: number;
+
+  public inclination: number;
+
+  public raan: number;
+
+  public eccentricity: number;
+
+  public argOfPerigee: number;
+
+  public meanAnomaly: number;
+
+  public meanMotion: number;
+
+  public period: number;
+
+  constructor(tle1: TleLine1, tle2: TleLine2, options) {
+    const tleData = Tle.parseTle(tle1, tle2);
+
+    this.satNum = tleData.satNum;
+    this.intlDes = tleData.intlDes;
+    this.epochYear = tleData.epochYear;
+    this.epochDay = tleData.epochDay;
+    this.meanMoDev1 = tleData.meanMoDev1;
+    this.meanMoDev2 = tleData.meanMoDev2;
+    this.bstar = tleData.bstar;
+    this.inclination = tleData.inclination;
+    this.raan = tleData.raan;
+    this.eccentricity = tleData.eccentricity;
+    this.argOfPerigee = tleData.argOfPerigee;
+    this.meanAnomaly = tleData.meanAnomaly;
+    this.meanMotion = tleData.meanMotion;
+    this.period = 1440 / this.meanMotion;
+
+    this.satrec = Sgp4.createSatrec(tle1, tle2);
+    this.options = options;
+  }
+
+  /**
+   * Calculates position and velocity in ECI coordinates at a given time.
+   * @param {Date} date Date to calculate the state vector for
+   * @returns {StateVector} State vector for the given date
+   */
+  public getStateVec(date: Date): StateVector {
+    const { m } = Sat.calculateTimeVariables(date, this.satrec);
+
+    return Sgp4.propagate(this.satrec, m);
+  }
+
+  /**
+   * Calculates ECI position at a given time.
+   * @param {Date} date Date to calculate
+   * @returns {EciVec3} ECI position vector
+   */
+  public getEci(date: Date): EciVec3 {
+    const { m } = Sat.calculateTimeVariables(date, this.satrec);
+    const eci = Sgp4.propagate(this.satrec, m).position;
+
+    return eci ? (eci as EciVec3) : { x: 0, y: 0, z: 0 };
+  }
+
+  /**
+   * Calculates ECF position at a given time.
+   * @param {Date} date Date to calculate
+   * @returns {EcfVec3} ECF position vector
+   */
+  public getEcf(date: Date): EcfVec3 {
+    const { m, gmst } = Sat.calculateTimeVariables(date, this.satrec);
+    const eci = (Sgp4.propagate(this.satrec, m).position as EciVec3) || { x: 0, y: 0, z: 0 };
+
+    return Transforms.eci2ecf(eci, gmst);
+  }
+
+  /**
+   * Calculates LLA position at a given time.
+   * @param {Date} date Date to calculate
+   * @returns {LlaVec3} LLA position vector
+   */
+  public getLla(date: Date): LlaVec3 {
+    const { m, gmst } = Sat.calculateTimeVariables(date, this.satrec);
+    const eci = (Sgp4.propagate(this.satrec, m).position as EciVec3) || { x: 0, y: 0, z: 0 };
+
+    return Transforms.eci2lla(eci, gmst);
+  }
+
+  /**
+   * Calculates the time variables for a given date relative to the TLE epoch.
+   * @param {Date} date Date to calculate
+   * @param {SatelliteRecord} satrec Satellite orbital information
+   * @returns {{m: number, gmst: GreenwichMeanSiderealTime, j: number}} Time variables
+   */
+  private static calculateTimeVariables(
+    date: Date,
+    satrec?: SatelliteRecord,
+  ): { gmst: GreenwichMeanSiderealTime; m: number; j: number } {
+    const j =
+      Utils.jday(
+        date.getUTCFullYear(),
+        date.getUTCMonth() + 1,
+        date.getUTCDate(),
+        date.getUTCHours(),
+        date.getUTCMinutes(),
+        date.getUTCSeconds(),
+      ) +
+      date.getUTCMilliseconds() * MILLISECONDS_PER_DAY;
+    const gmst = Sgp4.gstime(j);
+
+    const m = satrec ? (j - satrec.jdsatepoch) * MINUTES_PER_DAY : null;
+
+    return { gmst, m, j };
+  }
+}