feat: ✨ add caching for most common transforms

examples/commonjs/satellite-js-migration.cjs

@@ -69,6 +69,15 @@ const elevationDegrees = lookAngles.elevationDegrees; // Degrees
 const rangeSat = lookAngles.range; // Kilometers
 const rangeRate = lookAngles.rangeRate; // Kilometers/Second
 
+// There is a built in cache to allow fast retrieval of repeated calculations.
+// This means you can make repeat calls to `.rae()` for minimal performance hit.
+const rangeCache = satellite.rae(observer, exampleDate).range;
+const azimuthCached = satellite.rae(observer, exampleDate).azimuth;
+const elevationCached = satellite.rae(observer, exampleDate).elevation;
+const latitudeCached = satellite.lla(exampleDate).lat;
+const longitudeCached = satellite.lla(exampleDate).lon;
+const heightCached = satellite.lla(exampleDate).alt;
+
 // Geodetic coords are accessed via `longitude`, `latitude`, `height`.
 const longitude = positionGd.lon; // longitude is in degrees
 const latitude = positionGd.lat; // latitude is in degrees

examples/es6/satellite-js-migration.mjs

@@ -69,6 +69,15 @@ const elevationDegrees = lookAngles.elevationDegrees; // Degrees
 const rangeSat = lookAngles.range; // Kilometers
 const rangeRate = lookAngles.rangeRate; // Kilometers/Second
 
+// There is a built in cache to allow fast retrieval of repeated calculations.
+// This means you can make repeat calls to `.rae()` for minimal performance hit.
+const rangeCache = satellite.rae(observer, exampleDate).range;
+const azimuthCached = satellite.rae(observer, exampleDate).azimuth;
+const elevationCached = satellite.rae(observer, exampleDate).elevation;
+const latitudeCached = satellite.lla(exampleDate).lat;
+const longitudeCached = satellite.lla(exampleDate).lon;
+const heightCached = satellite.lla(exampleDate).alt;
+
 // Geodetic coords are accessed via `longitude`, `latitude`, `height`.
 const longitude = positionGd.lon; // longitude is in degrees
 const latitude = positionGd.lat; // latitude is in degrees

examples/typescript/satellite-js-migration.ts

@@ -94,6 +94,17 @@ const elevationDegrees = lookAngles.elevationDegrees; // Typed as Degrees
 const rangeSat = lookAngles.range; // Typed as Kilometers
 const rangeRate = lookAngles.rangeRate; // Kilometers/Second
 
+/*
+ * There is a built in cache to allow fast retrieval of repeated calculations.
+ * This means you can make repeat calls to `.rae()` for minimal performance hit.
+ */
+const rangeCache = satellite.rae(observer, exampleDate).range;
+const azimuthCached = satellite.rae(observer, exampleDate).azimuth;
+const elevationCached = satellite.rae(observer, exampleDate).elevation;
+const latitudeCached = satellite.lla(exampleDate).lat;
+const longitudeCached = satellite.lla(exampleDate).lon;
+const heightCached = satellite.lla(exampleDate).alt;
+
 // Geodetic coords are accessed via `longitude`, `latitude`, `height`.
 const longitude = positionGd.lon; // Longitude is in Degrees
 const latitude = positionGd.lat; // Latitude is in Degrees

src/interfaces/SatelliteParams.ts

@@ -1,9 +1,5 @@
 import { EciVec3, SpaceObjectType, TleLine1, TleLine2 } from '../types/types';
 
-/**
- * TODO: Reduce unnecessary calls to calculateTimeVariables using optional
- * parameters and caching.
- */
 /**
  * Information about a space object.
  */

src/objects/BaseObject.ts

@@ -36,7 +36,6 @@ export class BaseObject {
   position: EciVec3; // Where is the object
   totalVelocity: number; // How fast is the object moving
   velocity: EciVec3; // How fast is the object moving
-  time: Date; // When is the object
   active = true; // Is the object active
 
   constructor(info: BaseObjectParams) {
@@ -57,8 +56,6 @@ export class BaseObject {
       z: <Kilometers>0,
     }; // Default to 0 velocity until velocity is calculated
     this.totalVelocity = Math.sqrt(this.velocity.x ** 2 + this.velocity.y ** 2 + this.velocity.z ** 2);
-
-    this.time = info.time ?? new Date();
   }
 
   /**

src/objects/GroundPosition.ts

@@ -25,7 +25,7 @@ export class GroundPosition extends BaseObject {
     return false;
   }
 
-  rae(sat: Satellite, date: Date = this.time): RaeVec3<Kilometers, Degrees> {
+  rae(sat: Satellite, date: Date = new Date()): RaeVec3<Kilometers, Degrees> {
     return sat.raeOpt(this, date);
   }
 
@@ -38,18 +38,12 @@ export class GroundPosition extends BaseObject {
     return llaRad2ecf(this.llaRad());
   }
 
-  eci(date: Date = this.time): EciVec3<Kilometers> {
+  eci(date: Date = new Date()): EciVec3<Kilometers> {
     const { gmst } = calcGmst(date);
 
     return lla2eci(this.llaRad(), gmst);
   }
 
-  setTime(date: Date): this {
-    this.time = date;
-
-    return this;
-  }
-
   llaRad(): LlaVec3<Radians, Kilometers> {
     return {
       lat: (this.lat * DEG2RAD) as Radians,

src/objects/Satellite.ts

@@ -60,11 +60,6 @@ import { dopplerFactor } from './../utils/functions';
 import { BaseObject } from './BaseObject';
 import { GroundPosition } from './GroundPosition';
 
-/**
- * TODO: #2 Reduce unnecessary calls to calculateTimeVariables using optional
- * parameters and caching.
- */
-
 /**
  * Represents a satellite object with orbital information and methods for calculating its position and other properties.
  */
@@ -182,7 +177,7 @@ export class Satellite extends BaseObject {
    *
    * @optimized
    */
-  az(observer: GroundPosition, date: Date = this.time): Degrees {
+  az(observer: GroundPosition, date: Date = new Date()): Degrees {
     return (this.raeOpt(observer, date).az * RAD2DEG) as Degrees;
   }
 
@@ -192,7 +187,7 @@ export class Satellite extends BaseObject {
    *
    * @expanded
    */
-  rae(observer: GroundPosition, date: Date = this.time): RAE {
+  rae(observer: GroundPosition, date: Date = new Date()): RAE {
     const rae = this.raeOpt(observer, date);
     const rae2 = this.raeOpt(observer, new Date(date.getTime() + 1000));
     const epoch = new EpochUTC(date.getTime());
@@ -216,7 +211,7 @@ export class Satellite extends BaseObject {
    *
    * @optimized
    */
-  ecf(date: Date = this.time): EcfVec3<Kilometers> {
+  ecf(date: Date = new Date()): EcfVec3<Kilometers> {
     const { gmst } = Satellite.calculateTimeVariables(date);
 
     return eci2ecf(this.eci(date).position, gmst);
@@ -227,7 +222,7 @@ export class Satellite extends BaseObject {
    *
    * @optimized
    */
-  eci(date: Date = this.time): PosVel<Kilometers> {
+  eci(date: Date = new Date()): PosVel<Kilometers> {
     const { m } = Satellite.calculateTimeVariables(date, this.satrec);
 
     if (!m) {
@@ -249,7 +244,7 @@ export class Satellite extends BaseObject {
    * @returns The J2000 coordinates for the specified date.
    * @throws Error if propagation fails.
    */
-  getJ2000(date: Date = this.time): J2000 {
+  getJ2000(date: Date = new Date()): J2000 {
     const { m } = Satellite.calculateTimeVariables(date, this.satrec);
 
     if (!m) {
@@ -276,29 +271,30 @@ export class Satellite extends BaseObject {
    *
    * @optimized
    */
-  el(observer: GroundPosition, date: Date = this.time): Degrees {
+  el(observer: GroundPosition, date: Date = new Date()): Degrees {
     return (this.raeOpt(observer, date).el * RAD2DEG) as Degrees;
   }
 
   /**
    * Calculates LLA position at a given time.
    */
-  lla(date: Date = this.time): LlaVec3<Degrees, Kilometers> {
+  lla(date: Date = new Date()): LlaVec3<Degrees, Kilometers> {
     const { gmst } = Satellite.calculateTimeVariables(date, this.satrec);
     const pos = this.eci(date).position;
+    const lla = eci2lla(pos, gmst);
 
-    return eci2lla(pos, gmst);
+    return lla;
   }
 
-  getGeodetic(date: Date = this.time): Geodetic {
+  getGeodetic(date: Date = new Date()): Geodetic {
     return this.getJ2000(date).toITRF().toGeodetic();
   }
 
-  getITRF(date: Date = this.time): ITRF {
+  getITRF(date: Date = new Date()): ITRF {
     return this.getJ2000(date).toITRF();
   }
 
-  getRIC(reference: Satellite, date: Date = this.time): RIC {
+  getRIC(reference: Satellite, date: Date = new Date()): RIC {
     return RIC.fromJ2000(this.getJ2000(date), reference.getJ2000(date));
   }
 
@@ -307,7 +303,7 @@ export class Satellite extends BaseObject {
    *
    * @optimized
    */
-  raeOpt(observer: GroundPosition, date: Date = this.time): RaeVec3<Kilometers, Degrees> {
+  raeOpt(observer: GroundPosition, date: Date = new Date()): RaeVec3<Kilometers, Degrees> {
     const { gmst } = Satellite.calculateTimeVariables(date, this.satrec);
     const eci = this.eci(date).position;
     const ecf = eci2ecf(eci, gmst);
@@ -320,7 +316,7 @@ export class Satellite extends BaseObject {
    *
    * @optimized
    */
-  range(observer: GroundPosition, date: Date = this.time): Kilometers {
+  range(observer: GroundPosition, date: Date = new Date()): Kilometers {
     return this.raeOpt(observer, date).rng;
   }
 
@@ -350,20 +346,6 @@ export class Satellite extends BaseObject {
     return dopplerFactor(observer.eci(date), position.position, position.velocity);
   }
 
-  /**
-   * Propagates the satellite position to the given date using the SGP4 model.
-   *
-   * This method changes the position and time properties of the satellite object.
-   */
-  propagateTo(date: Date): this {
-    const pv = this.eci(date);
-
-    this.position = pv.position as EciVec3;
-    this.time = date;
-
-    return this;
-  }
-
   /**
    * Calculates the time variables for a given date relative to the TLE epoch.
    * @param {Date} date Date to calculate

src/objects/Sensor.ts

@@ -70,7 +70,7 @@ export class Sensor extends GroundPosition {
     return true;
   }
 
-  calculatePasses(planningInterval: number, sat: Satellite, date: Date = this.time) {
+  calculatePasses(planningInterval: number, sat: Satellite, date: Date = new Date()) {
     let isInViewLast = false;
     let maxElThisPass = <Degrees>0;
     const msnPlanPasses: Lookangle[] = [];
@@ -139,16 +139,10 @@ export class Sensor extends GroundPosition {
     return true;
   }
 
-  isSatInFov(sat: Satellite, date: Date = this.time): boolean {
+  isSatInFov(sat: Satellite, date: Date = new Date()): boolean {
     return this.isRaeInFov(this.rae(sat, date));
   }
 
-  setTime(date: Date): this {
-    this.time = date;
-
-    return this;
-  }
-
   isDeepSpace(): boolean {
     return this.maxRng > 6000;
   }

src/objects/Star.ts

@@ -66,7 +66,7 @@ export class Star extends BaseObject {
     this.vmag = info.vmag;
   }
 
-  eci(lla: LlaVec3 = { lat: <Degrees>180, lon: <Degrees>0, alt: <Kilometers>0 }, date: Date = this.time): EciVec3 {
+  eci(lla: LlaVec3 = { lat: <Degrees>180, lon: <Degrees>0, alt: <Kilometers>0 }, date: Date = new Date()): EciVec3 {
     const rae = this.rae(lla, date);
     const { gmst } = Star.calculateTimeVariables_(date);
 
@@ -76,7 +76,7 @@ export class Star extends BaseObject {
 
   rae(
     lla: LlaVec3<Degrees, Kilometers> = { lat: <Degrees>180, lon: <Degrees>0, alt: <Kilometers>0 },
-    date: Date = this.time,
+    date: Date = new Date(),
   ): RaeVec3 {
     const starPos = Celestial.azEl(date, lla.lat, lla.lon, this.ra, this.dec);
 

src/transforms/TransformCache.ts

@@ -0,0 +1,24 @@
+export class TransformCache {
+  private static cache_: Map<string, unknown> = new Map();
+
+  static get(key: string): unknown {
+    const value = this.cache_.get(key);
+
+    if (value) {
+      // eslint-disable-next-line no-console
+      console.log(`Cache hit for ${key}`);
+    }
+
+    return value;
+  }
+  static add(key: string, value: unknown) {
+    this.cache_.set(key, value);
+
+    // Max of 1000 items in the cache
+    if (this.cache_.size > 1000) {
+      const firstKey = this.cache_.keys().next().value;
+
+      this.cache_.delete(firstKey);
+    }
+  }
+}