@xfanta/mars-time/src/marsLocalTime.ts

Mars time conversion library (MSD, MTC, Darian Calendar)

/**
 * Converts Mars Sol Date (MSD) and longitude to Local Mean Solar Time (LMST).
 * @param msd Mars Sol Date
 * @param longitude East longitude in degrees (0–360°E)
 * @returns LMST in HH:MM:SS format
 */
export function getLMST(msd: number, longitude: number): string {
    const lmst = (24 * ((msd + longitude / 360) % 1));
    return decimalHoursToHMS(lmst);
  }
  
  /**
   * Converts Mars Sol Date (MSD) and longitude to Local True Solar Time (LTST).
   * This version includes a simplified equation of time.
   * @param msd Mars Sol Date
   * @param longitude East longitude in degrees (0–360°E)
   * @returns LTST in HH:MM:SS format
   */
  export function getLTST(msd: number, longitude: number): string {
    const lmstHours = 24 * ((msd + longitude / 360) % 1);
    const eqTime = marsEquationOfTime(msd); // in minutes
    const ltstHours = (lmstHours + eqTime / 60 + 24) % 24;
    return decimalHoursToHMS(ltstHours);
  }
  
  /**
   * Approximate Mars Equation of Time in minutes (based on Allison & McEwen 2000)
   * @param msd Mars Sol Date
   * @returns Equation of time in minutes
   */
  function marsEquationOfTime(msd: number): number {
    const marsYear = (msd - 44796.0) / 668.6;
    const M = (19.3871 + 0.52402075 * (msd - 44796.0)) % 360; // Mean anomaly
    const alphaFMS = (270.3863 + 0.5240384 * (msd - 44796.0)) % 360; // Fiction mean sun
    const EOT = 2.861 * Math.sin(deg2rad(2 * M))
              - 0.071 * Math.sin(deg2rad(4 * M))
              + 0.002 * Math.sin(deg2rad(6 * M))
              - (alphaFMS - M); // Simplified EOT formula
    return EOT;
  }
  
  /**
   * Converts decimal hours to HH:MM:SS time format.
   * @param hours Time in decimal hours
   * @returns Time as a formatted string
   */
  function decimalHoursToHMS(hours: number): string {
    const h = Math.floor(hours);
    const m = Math.floor((hours - h) * 60);
    const s = Math.floor(((hours - h) * 60 - m) * 60);
    return [h, m, s].map(v => String(v).padStart(2, '0')).join(':');
  }
  
  /**
   * Converts degrees to radians.
   * @param deg Angle in degrees
   * @returns Angle in radians
   */
  function deg2rad(deg: number): number {
    return deg * Math.PI / 180;
  }