/* Copyright 2002-2024 CS GROUP
    * Licensed to CS GROUP (CS) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * CS licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.orekit.propagation.analytical.tle;
  
  import java.io.Serializable;
  import java.text.DecimalFormat;
  import java.text.DecimalFormatSymbols;
  import java.util.Collections;
  import java.util.List;
  import java.util.Locale;
  import java.util.Objects;
  
  import org.hipparchus.CalculusFieldElement;
  import org.hipparchus.Field;
  import org.hipparchus.util.ArithmeticUtils;
  import org.hipparchus.util.FastMath;
  import org.hipparchus.util.MathUtils;
  import org.orekit.annotation.DefaultDataContext;
  import org.orekit.data.DataContext;
  import org.orekit.errors.OrekitException;
  import org.orekit.errors.OrekitInternalError;
  import org.orekit.errors.OrekitMessages;
  import org.orekit.propagation.FieldSpacecraftState;
  import org.orekit.propagation.analytical.tle.generation.TleGenerationAlgorithm;
  import org.orekit.time.DateComponents;
  import org.orekit.time.DateTimeComponents;
  import org.orekit.time.FieldAbsoluteDate;
  import org.orekit.time.FieldTimeStamped;
  import org.orekit.time.TimeComponents;
  import org.orekit.time.TimeScale;
  import org.orekit.utils.Constants;
  import org.orekit.utils.ParameterDriver;
  import org.orekit.utils.ParameterDriversProvider;
  
  /** This class is a container for a single set of TLE data.
   *
   * <p>TLE sets can be built either by providing directly the two lines, in
   * which case parsing is performed internally or by providing the already
   * parsed elements.</p>
   * <p>TLE are not transparently convertible to {@link org.orekit.orbits.Orbit Orbit}
   * instances. They are significant only with respect to their dedicated {@link
   * TLEPropagator propagator}, which also computes position and velocity coordinates.
   * Any attempt to directly use orbital parameters like {@link #getE() eccentricity},
   * {@link #getI() inclination}, etc. without any reference to the {@link TLEPropagator
   * TLE propagator} is prone to errors.</p>
   * <p>More information on the TLE format can be found on the
   * <a href="https://www.celestrak.com/">CelesTrak website.</a></p>
   * @author Fabien Maussion
   * @author Luc Maisonobe
   * @author Thomas Paulet (field translation)
   * @since 11.0
   * @param <T> type of the field elements
   */
  public class FieldTLE<T extends CalculusFieldElement<T>> implements FieldTimeStamped<T>, Serializable, ParameterDriversProvider {
  
      /** Identifier for default type of ephemeris (SGP4/SDP4). */
      public static final int DEFAULT = 0;
  
      /** Identifier for SGP type of ephemeris. */
      public static final int SGP = 1;
  
      /** Identifier for SGP4 type of ephemeris. */
      public static final int SGP4 = 2;
  
      /** Identifier for SDP4 type of ephemeris. */
      public static final int SDP4 = 3;
  
      /** Identifier for SGP8 type of ephemeris. */
      public static final int SGP8 = 4;
  
      /** Identifier for SDP8 type of ephemeris. */
      public static final int SDP8 = 5;
  
      /** Parameter name for B* coefficient. */
      public static final String B_STAR = "BSTAR";
  
      /** B* scaling factor.
       * <p>
       * We use a power of 2 to avoid numeric noise introduction
       * in the multiplications/divisions sequences.
       * </p>
       */
      private static final double B_STAR_SCALE = FastMath.scalb(1.0, -20);
  
      /** Name of the mean motion parameter. */
     private static final String MEAN_MOTION = "meanMotion";
 
     /** Name of the inclination parameter. */
     private static final String INCLINATION = "inclination";
 
     /** Name of the eccentricity parameter. */
     private static final String ECCENTRICITY = "eccentricity";
 
     /** International symbols for parsing. */
     private static final DecimalFormatSymbols SYMBOLS =
         new DecimalFormatSymbols(Locale.US);
 
     /** Serializable UID. */
     private static final long serialVersionUID = -1596648022319057689L;
 
     /** The satellite number. */
     private final int satelliteNumber;
 
     /** Classification (U for unclassified). */
     private final char classification;
 
     /** Launch year. */
     private final int launchYear;
 
     /** Launch number. */
     private final int launchNumber;
 
     /** Piece of launch (from "A" to "ZZZ"). */
     private final String launchPiece;
 
     /** Type of ephemeris. */
     private final int ephemerisType;
 
     /** Element number. */
     private final int elementNumber;
 
     /** the TLE current date. */
     private final transient FieldAbsoluteDate<T> epoch;
 
     /** Mean motion (rad/s). */
     private final T meanMotion;
 
     /** Mean motion first derivative (rad/s²). */
     private final T meanMotionFirstDerivative;
 
     /** Mean motion second derivative (rad/s³). */
     private final T meanMotionSecondDerivative;
 
     /** Eccentricity. */
     private final T eccentricity;
 
     /** Inclination (rad). */
     private final T inclination;
 
     /** Argument of perigee (rad). */
     private final T pa;
 
     /** Right Ascension of the Ascending node (rad). */
     private final T raan;
 
     /** Mean anomaly (rad). */
     private final T meanAnomaly;
 
     /** Revolution number at epoch. */
     private final int revolutionNumberAtEpoch;
 
     /** First line. */
     private String line1;
 
     /** Second line. */
     private String line2;
 
     /** The UTC scale. */
     private final TimeScale utc;
 
     /** Driver for ballistic coefficient parameter. */
     private final transient ParameterDriver bStarParameterDriver;
 
     /** Simple constructor from unparsed two lines. This constructor uses the {@link
      * DataContext#getDefault() default data context}.
      *
      * <p>The static method {@link #isFormatOK(String, String)} should be called
      * before trying to build this object.</p>
      * @param field field utilized by default
      * @param line1 the first element (69 char String)
      * @param line2 the second element (69 char String)
      * @see #FieldTLE(Field, String, String, TimeScale)
      */
     @DefaultDataContext
     public FieldTLE(final Field<T> field, final String line1, final String line2) {
         this(field, line1, line2, DataContext.getDefault().getTimeScales().getUTC());
     }
 
     /** Simple constructor from unparsed two lines using the given time scale as UTC.
      *
      *<p>This method uses the {@link DataContext#getDefault() default data context}.
      *
      * <p>The static method {@link #isFormatOK(String, String)} should be called
      * before trying to build this object.</p>
      * @param field field utilized by default
      * @param line1 the first element (69 char String)
      * @param line2 the second element (69 char String)
      * @param utc the UTC time scale.
      */
     public FieldTLE(final Field<T> field, final String line1, final String line2, final TimeScale utc) {
 
         // zero and pi for fields
         final T zero = field.getZero();
         final T pi   = zero.getPi();
 
         // identification
         satelliteNumber = ParseUtils.parseSatelliteNumber(line1, 2, 5);
         final int satNum2 = ParseUtils.parseSatelliteNumber(line2, 2, 5);
         if (satelliteNumber != satNum2) {
             throw new OrekitException(OrekitMessages.TLE_LINES_DO_NOT_REFER_TO_SAME_OBJECT,
                                       line1, line2);
         }
         classification  = line1.charAt(7);
         launchYear      = ParseUtils.parseYear(line1, 9);
         launchNumber    = ParseUtils.parseInteger(line1, 11, 3);
         launchPiece     = line1.substring(14, 17).trim();
         ephemerisType   = ParseUtils.parseInteger(line1, 62, 1);
         elementNumber   = ParseUtils.parseInteger(line1, 64, 4);
 
         // Date format transform (nota: 27/31250 == 86400/100000000)
         final int    year      = ParseUtils.parseYear(line1, 18);
         final int    dayInYear = ParseUtils.parseInteger(line1, 20, 3);
         final long   df        = 27l * ParseUtils.parseInteger(line1, 24, 8);
         final int    secondsA  = (int) (df / 31250l);
         final double secondsB  = (df % 31250l) / 31250.0;
         epoch = new FieldAbsoluteDate<>(field, new DateComponents(year, dayInYear),
                                  new TimeComponents(secondsA, secondsB),
                                  utc);
 
         // mean motion development
         // converted from rev/day, 2 * rev/day^2 and 6 * rev/day^3 to rad/s, rad/s^2 and rad/s^3
         meanMotion                 = pi.multiply(ParseUtils.parseDouble(line2, 52, 11)).divide(43200.0);
         meanMotionFirstDerivative  = pi.multiply(ParseUtils.parseDouble(line1, 33, 10)).divide(1.86624e9);
         meanMotionSecondDerivative = pi.multiply(Double.parseDouble((line1.substring(44, 45) + '.' +
                                                                      line1.substring(45, 50) + 'e' +
                                                                      line1.substring(50, 52)).replace(' ', '0'))).divide(5.3747712e13);
 
         eccentricity = zero.newInstance(Double.parseDouble("." + line2.substring(26, 33).replace(' ', '0')));
         inclination  = zero.newInstance(FastMath.toRadians(ParseUtils.parseDouble(line2, 8, 8)));
         pa           = zero.newInstance(FastMath.toRadians(ParseUtils.parseDouble(line2, 34, 8)));
         raan         = zero.newInstance(FastMath.toRadians(Double.parseDouble(line2.substring(17, 25).replace(' ', '0'))));
         meanAnomaly  = zero.newInstance(FastMath.toRadians(ParseUtils.parseDouble(line2, 43, 8)));
 
         revolutionNumberAtEpoch = ParseUtils.parseInteger(line2, 63, 5);
         final double bStarValue = Double.parseDouble((line1.substring(53, 54) + '.' +
                         line1.substring(54, 59) + 'e' +
                         line1.substring(59, 61)).replace(' ', '0'));
 
         // save the lines
         this.line1 = line1;
         this.line2 = line2;
         this.utc = utc;
 
         this.bStarParameterDriver = new ParameterDriver(B_STAR, bStarValue, B_STAR_SCALE,
                                                         Double.NEGATIVE_INFINITY,
                                                         Double.POSITIVE_INFINITY);
 
     }
 
     /**
      * <p>
      * Simple constructor from already parsed elements. This constructor uses the
      * {@link DataContext#getDefault() default data context}.
      * </p>
      *
      * <p>
      * The mean anomaly, the right ascension of ascending node Ω and the argument of
      * perigee ω are normalized into the [0, 2π] interval as they can be negative.
      * After that, a range check is performed on some of the orbital elements:
      *
      * <pre>
      *     meanMotion &gt;= 0
      *     0 &lt;= i &lt;= π
      *     0 &lt;= Ω &lt;= 2π
      *     0 &lt;= e &lt;= 1
      *     0 &lt;= ω &lt;= 2π
      *     0 &lt;= meanAnomaly &lt;= 2π
      * </pre>
      *
      *
      * @param satelliteNumber satellite number
      * @param classification classification (U for unclassified)
      * @param launchYear launch year (all digits)
      * @param launchNumber launch number
      * @param launchPiece launch piece (3 char String)
      * @param ephemerisType type of ephemeris
      * @param elementNumber element number
      * @param epoch elements epoch
      * @param meanMotion mean motion (rad/s)
      * @param meanMotionFirstDerivative mean motion first derivative (rad/s²)
      * @param meanMotionSecondDerivative mean motion second derivative (rad/s³)
      * @param e eccentricity
      * @param i inclination (rad)
      * @param pa argument of perigee (rad)
      * @param raan right ascension of ascending node (rad)
      * @param meanAnomaly mean anomaly (rad)
      * @param revolutionNumberAtEpoch revolution number at epoch
      * @param bStar ballistic coefficient
      * @see #FieldTLE(int, char, int, int, String, int, int, FieldAbsoluteDate, CalculusFieldElement, CalculusFieldElement,
      * CalculusFieldElement, CalculusFieldElement, CalculusFieldElement, CalculusFieldElement, CalculusFieldElement, CalculusFieldElement, int, double, TimeScale)
      */
     @DefaultDataContext
     public FieldTLE(final int satelliteNumber, final char classification,
                final int launchYear, final int launchNumber, final String launchPiece,
                final int ephemerisType, final int elementNumber, final FieldAbsoluteDate<T> epoch,
                final T meanMotion, final T meanMotionFirstDerivative,
                final T meanMotionSecondDerivative, final T e, final T i,
                final T pa, final T raan, final T meanAnomaly,
                final int revolutionNumberAtEpoch, final double bStar) {
         this(satelliteNumber, classification, launchYear, launchNumber, launchPiece,
                 ephemerisType, elementNumber, epoch, meanMotion,
                 meanMotionFirstDerivative, meanMotionSecondDerivative, e, i, pa, raan,
                 meanAnomaly, revolutionNumberAtEpoch, bStar,
                 DataContext.getDefault().getTimeScales().getUTC());
     }
 
     /**
      * <p>
      * Simple constructor from already parsed elements using the given time scale as
      * UTC.
      * </p>
      * <p>
      * The mean anomaly, the right ascension of ascending node Ω and the argument of
      * perigee ω are normalized into the [0, 2π] interval as they can be negative.
      * After that, a range check is performed on some of the orbital elements:
      *
      * <pre>
      *     meanMotion &gt;= 0
      *     0 &lt;= i &lt;= π
      *     0 &lt;= Ω &lt;= 2π
      *     0 &lt;= e &lt;= 1
      *     0 &lt;= ω &lt;= 2π
      *     0 &lt;= meanAnomaly &lt;= 2π
      * </pre>
      *
      *
      * @param satelliteNumber satellite number
      * @param classification classification (U for unclassified)
      * @param launchYear launch year (all digits)
      * @param launchNumber launch number
      * @param launchPiece launch piece (3 char String)
      * @param ephemerisType type of ephemeris
      * @param elementNumber element number
      * @param epoch elements epoch
      * @param meanMotion mean motion (rad/s)
      * @param meanMotionFirstDerivative mean motion first derivative (rad/s²)
      * @param meanMotionSecondDerivative mean motion second derivative (rad/s³)
      * @param e eccentricity
      * @param i inclination (rad)
      * @param pa argument of perigee (rad)
      * @param raan right ascension of ascending node (rad)
      * @param meanAnomaly mean anomaly (rad)
      * @param revolutionNumberAtEpoch revolution number at epoch
      * @param bStar ballistic coefficient
      * @param utc the UTC time scale.
      */
     public FieldTLE(final int satelliteNumber, final char classification,
                final int launchYear, final int launchNumber, final String launchPiece,
                final int ephemerisType, final int elementNumber, final FieldAbsoluteDate<T> epoch,
                final T meanMotion, final T meanMotionFirstDerivative,
                final T meanMotionSecondDerivative, final T e, final T i,
                final T pa, final T raan, final T meanAnomaly,
                final int revolutionNumberAtEpoch, final double bStar,
                final TimeScale utc) {
 
         // pi for fields
         final T pi = e.getPi();
 
         // identification
         this.satelliteNumber = satelliteNumber;
         this.classification  = classification;
         this.launchYear      = launchYear;
         this.launchNumber    = launchNumber;
         this.launchPiece     = launchPiece;
         this.ephemerisType   = ephemerisType;
         this.elementNumber   = elementNumber;
 
         // orbital parameters
         this.epoch = epoch;
         // Checking mean motion range
         this.meanMotion = meanMotion;
         this.meanMotionFirstDerivative = meanMotionFirstDerivative;
         this.meanMotionSecondDerivative = meanMotionSecondDerivative;
 
         // Checking inclination range
         this.inclination = i;
 
         // Normalizing RAAN in [0,2pi] interval
         this.raan = MathUtils.normalizeAngle(raan, pi);
 
         // Checking eccentricity range
         this.eccentricity = e;
 
         // Normalizing PA in [0,2pi] interval
         this.pa = MathUtils.normalizeAngle(pa, pi);
 
         // Normalizing mean anomaly in [0,2pi] interval
         this.meanAnomaly = MathUtils.normalizeAngle(meanAnomaly, pi);
 
         this.revolutionNumberAtEpoch = revolutionNumberAtEpoch;
         this.bStarParameterDriver = new ParameterDriver(B_STAR, bStar, B_STAR_SCALE,
                                                        Double.NEGATIVE_INFINITY,
                                                        Double.POSITIVE_INFINITY);
 
         // don't build the line until really needed
         this.line1 = null;
         this.line2 = null;
         this.utc = utc;
 
     }
 
     /**
      * Get the UTC time scale used to create this TLE.
      *
      * @return UTC time scale.
      */
     TimeScale getUtc() {
         return utc;
     }
 
     /** Get the first line.
      * @return first line
      */
     public String getLine1() {
         if (line1 == null) {
             buildLine1();
         }
         return line1;
     }
 
     /** Get the second line.
      * @return second line
      */
     public String getLine2() {
         if (line2 == null) {
             buildLine2();
         }
         return line2;
     }
 
     /** Build the line 1 from the parsed elements.
      */
     private void buildLine1() {
 
         final StringBuilder buffer = new StringBuilder();
 
         buffer.append('1');
 
         buffer.append(' ');
         buffer.append(ParseUtils.buildSatelliteNumber(satelliteNumber, "satelliteNumber-1"));
         buffer.append(classification);
 
         buffer.append(' ');
         buffer.append(ParseUtils.addPadding("launchYear",   launchYear % 100, '0', 2, true, satelliteNumber));
         buffer.append(ParseUtils.addPadding("launchNumber", launchNumber, '0', 3, true, satelliteNumber));
         buffer.append(ParseUtils.addPadding("launchPiece",  launchPiece, ' ', 3, false, satelliteNumber));
 
         buffer.append(' ');
         DateTimeComponents dtc = epoch.getComponents(utc);
         int fraction = (int) FastMath.rint(31250 * dtc.getTime().getSecondsInUTCDay() / 27.0);
         if (fraction >= 100000000) {
             dtc =  epoch.shiftedBy(Constants.JULIAN_DAY).getComponents(utc);
             fraction -= 100000000;
         }
         buffer.append(ParseUtils.addPadding("year", dtc.getDate().getYear() % 100, '0', 2, true, satelliteNumber));
         buffer.append(ParseUtils.addPadding("day",  dtc.getDate().getDayOfYear(),  '0', 3, true, satelliteNumber));
         buffer.append('.');
         // nota: 31250/27 == 100000000/86400
 
         buffer.append(ParseUtils.addPadding("fraction", fraction,  '0', 8, true, satelliteNumber));
 
         buffer.append(' ');
         final double n1 = meanMotionFirstDerivative.divide(pa.getPi()).multiply(1.86624e9).getReal();
         final String sn1 = ParseUtils.addPadding("meanMotionFirstDerivative",
                                                  new DecimalFormat(".00000000", SYMBOLS).format(n1),
                                                  ' ', 10, true, satelliteNumber);
         buffer.append(sn1);
 
         buffer.append(' ');
         final double n2 = meanMotionSecondDerivative.divide(pa.getPi()).multiply(5.3747712e13).getReal();
         buffer.append(formatExponentMarkerFree("meanMotionSecondDerivative", n2, 5, ' ', 8, true));
 
         buffer.append(' ');
         buffer.append(formatExponentMarkerFree("B*", getBStar(), 5, ' ', 8, true));
 
         buffer.append(' ');
         buffer.append(ephemerisType);
 
         buffer.append(' ');
         buffer.append(ParseUtils.addPadding("elementNumber", elementNumber, ' ', 4, true, satelliteNumber));
 
         buffer.append(Integer.toString(checksum(buffer)));
 
         line1 = buffer.toString();
 
     }
 
     /** Format a real number without 'e' exponent marker.
      * @param name parameter name
      * @param d number to format
      * @param mantissaSize size of the mantissa (not counting initial '-' or ' ' for sign)
      * @param c padding character
      * @param size desired size
      * @param rightJustified if true, the resulting string is
      * right justified (i.e. space are added to the left)
      * @return formatted and padded number
      */
     private String formatExponentMarkerFree(final String name, final double d, final int mantissaSize,
                                             final char c, final int size, final boolean rightJustified) {
         final double dAbs = FastMath.abs(d);
         int exponent = (dAbs < 1.0e-9) ? -9 : (int) FastMath.ceil(FastMath.log10(dAbs));
         long mantissa = FastMath.round(dAbs * FastMath.pow(10.0, mantissaSize - exponent));
         if (mantissa == 0) {
             exponent = 0;
         } else if (mantissa > (ArithmeticUtils.pow(10, mantissaSize) - 1)) {
             // rare case: if d has a single digit like d = 1.0e-4 with mantissaSize = 5
             // the above computation finds exponent = -4 and mantissa = 100000 which
             // doesn't fit in a 5 digits string
             exponent++;
             mantissa = FastMath.round(dAbs * FastMath.pow(10.0, mantissaSize - exponent));
         }
         final String sMantissa = ParseUtils.addPadding(name, (int) mantissa,
                                                        '0', mantissaSize, true, satelliteNumber);
         final String sExponent = Integer.toString(FastMath.abs(exponent));
         final String formatted = (d <  0 ? '-' : ' ') + sMantissa + (exponent <= 0 ? '-' : '+') + sExponent;
 
         return ParseUtils.addPadding(name, formatted, c, size, rightJustified, satelliteNumber);
 
     }
 
     /** Build the line 2 from the parsed elements.
      */
     private void buildLine2() {
 
         final StringBuilder buffer = new StringBuilder();
         final DecimalFormat f34   = new DecimalFormat("##0.0000", SYMBOLS);
         final DecimalFormat f211  = new DecimalFormat("#0.00000000", SYMBOLS);
 
         buffer.append('2');
 
         buffer.append(' ');
         buffer.append(ParseUtils.buildSatelliteNumber(satelliteNumber, "satelliteNumber-2"));
 
         buffer.append(' ');
         buffer.append(ParseUtils.addPadding(INCLINATION, f34.format(FastMath.toDegrees(inclination).getReal()), ' ', 8, true, satelliteNumber));
         buffer.append(' ');
         buffer.append(ParseUtils.addPadding("raan", f34.format(FastMath.toDegrees(raan).getReal()), ' ', 8, true, satelliteNumber));
         buffer.append(' ');
         buffer.append(ParseUtils.addPadding(ECCENTRICITY, (int) FastMath.rint(eccentricity.getReal() * 1.0e7), '0', 7, true, satelliteNumber));
         buffer.append(' ');
         buffer.append(ParseUtils.addPadding("pa", f34.format(FastMath.toDegrees(pa).getReal()), ' ', 8, true, satelliteNumber));
         buffer.append(' ');
         buffer.append(ParseUtils.addPadding("meanAnomaly", f34.format(FastMath.toDegrees(meanAnomaly).getReal()), ' ', 8, true, satelliteNumber));
 
         buffer.append(' ');
         buffer.append(ParseUtils.addPadding(MEAN_MOTION, f211.format(meanMotion.divide(pa.getPi()).multiply(43200.0).getReal()), ' ', 11, true, satelliteNumber));
         buffer.append(ParseUtils.addPadding("revolutionNumberAtEpoch", revolutionNumberAtEpoch,
                                             ' ', 5, true, satelliteNumber));
 
         buffer.append(Integer.toString(checksum(buffer)));
 
         line2 = buffer.toString();
 
     }
 
     /** {@inheritDoc}.
      * <p>Get the drivers for TLE propagation SGP4 and SDP4.
      * @return drivers for SGP4 and SDP4 model parameters
      */
     @Override
     public List<ParameterDriver> getParametersDrivers() {
         return Collections.singletonList(bStarParameterDriver);
     }
 
     /** Get the satellite id.
      * @return the satellite number
      */
     public int getSatelliteNumber() {
         return satelliteNumber;
     }
 
     /** Get the classification.
      * @return classification
      */
     public char getClassification() {
         return classification;
     }
 
     /** Get the launch year.
      * @return the launch year
      */
     public int getLaunchYear() {
         return launchYear;
     }
 
     /** Get the launch number.
      * @return the launch number
      */
     public int getLaunchNumber() {
         return launchNumber;
     }
 
     /** Get the launch piece.
      * @return the launch piece
      */
     public String getLaunchPiece() {
         return launchPiece;
     }
 
     /** Get the type of ephemeris.
      * @return the ephemeris type (one of {@link #DEFAULT}, {@link #SGP},
      * {@link #SGP4}, {@link #SGP8}, {@link #SDP4}, {@link #SDP8})
      */
     public int getEphemerisType() {
         return ephemerisType;
     }
 
     /** Get the element number.
      * @return the element number
      */
     public int getElementNumber() {
         return elementNumber;
     }
 
     /** Get the TLE current date.
      * @return the epoch
      */
     public FieldAbsoluteDate<T> getDate() {
         return epoch;
     }
 
     /** Get the mean motion.
      * @return the mean motion (rad/s)
      */
     public T getMeanMotion() {
         return meanMotion;
     }
 
     /** Get the mean motion first derivative.
      * @return the mean motion first derivative (rad/s²)
      */
     public T getMeanMotionFirstDerivative() {
         return meanMotionFirstDerivative;
     }
 
     /** Get the mean motion second derivative.
      * @return the mean motion second derivative (rad/s³)
      */
     public T getMeanMotionSecondDerivative() {
         return meanMotionSecondDerivative;
     }
 
     /** Get the eccentricity.
      * @return the eccentricity
      */
     public T getE() {
         return eccentricity;
     }
 
     /** Get the inclination.
      * @return the inclination (rad)
      */
     public T getI() {
         return inclination;
     }
 
     /** Get the argument of perigee.
      * @return omega (rad)
      */
     public T getPerigeeArgument() {
         return pa;
     }
 
     /** Get Right Ascension of the Ascending node.
      * @return the raan (rad)
      */
     public T getRaan() {
         return raan;
     }
 
     /** Get the mean anomaly.
      * @return the mean anomaly (rad)
      */
     public T getMeanAnomaly() {
         return meanAnomaly;
     }
 
     /** Get the revolution number.
      * @return the revolutionNumberAtEpoch
      */
     public int getRevolutionNumberAtEpoch() {
         return revolutionNumberAtEpoch;
     }
 
     /** Get the ballistic coefficient.
      * @return bStar
      */
     public double getBStar() {
         return bStarParameterDriver.getValue(getDate().toAbsoluteDate());
     }
 
     /** Get a string representation of this TLE set.
      * <p>The representation is simply the two lines separated by the
      * platform line separator.</p>
      * @return string representation of this TLE set
      */
     public String toString() {
         try {
             return getLine1() + System.getProperty("line.separator") + getLine2();
         } catch (OrekitException oe) {
             throw new OrekitInternalError(oe);
         }
     }
 
     /**
      * Convert Spacecraft State into TLE.
      *
      * @param state Spacecraft State to convert into TLE
      * @param templateTLE first guess used to get identification and estimate new TLE
      * @param generationAlgorithm TLE generation algorithm
      * @param <T> type of the element
      * @return a generated TLE
      * @since 12.0
      */
     public static <T extends CalculusFieldElement<T>> FieldTLE<T> stateToTLE(final FieldSpacecraftState<T> state, final FieldTLE<T> templateTLE,
                                                                              final TleGenerationAlgorithm generationAlgorithm) {
         return generationAlgorithm.generate(state, templateTLE);
     }
 
     /** Check the lines format validity.
      * @param line1 the first element
      * @param line2 the second element
      * @return true if format is recognized (non null lines, 69 characters length,
      * line content), false if not
      */
     public static boolean isFormatOK(final String line1, final String line2) {
         return TLE.isFormatOK(line1, line2);
     }
 
     /** Compute the checksum of the first 68 characters of a line.
      * @param line line to check
      * @return checksum
      */
     private static int checksum(final CharSequence line) {
         int sum = 0;
         for (int j = 0; j < 68; j++) {
             final char c = line.charAt(j);
             if (Character.isDigit(c)) {
                 sum += Character.digit(c, 10);
             } else if (c == '-') {
                 ++sum;
             }
         }
         return sum % 10;
     }
 
     /**
      * Convert FieldTLE into TLE.
      * @return TLE
      */
     public TLE toTLE() {
         final TLE regularTLE = new TLE(getSatelliteNumber(), getClassification(), getLaunchYear(), getLaunchNumber(), getLaunchPiece(), getEphemerisType(),
                                        getElementNumber(), getDate().toAbsoluteDate(), getMeanMotion().getReal(), getMeanMotionFirstDerivative().getReal(),
                                        getMeanMotionSecondDerivative().getReal(), getE().getReal(), getI().getReal(), getPerigeeArgument().getReal(),
                                        getRaan().getReal(), getMeanAnomaly().getReal(), getRevolutionNumberAtEpoch(), getBStar(), getUtc());
 
         for (int k = 0; k < regularTLE.getParametersDrivers().size(); ++k) {
             regularTLE.getParametersDrivers().get(k).setSelected(getParametersDrivers().get(k).isSelected());
         }
 
         return regularTLE;
 
     }
 
     /** Check if this tle equals the provided tle.
      * <p>Due to the difference in precision between object and string
      * representations of TLE, it is possible for this method to return false
      * even if string representations returned by {@link #toString()}
      * are equal.</p>
      * @param o other tle
      * @return true if this tle equals the provided tle
      */
     @Override
     public boolean equals(final Object o) {
         if (o == this) {
             return true;
         }
         if (!(o instanceof FieldTLE)) {
             return false;
         }
         @SuppressWarnings("unchecked")
         final FieldTLE<T> tle = (FieldTLE<T>) o;
         return satelliteNumber == tle.satelliteNumber &&
                 classification == tle.classification &&
                 launchYear == tle.launchYear &&
                 launchNumber == tle.launchNumber &&
                 Objects.equals(launchPiece, tle.launchPiece) &&
                 ephemerisType == tle.ephemerisType &&
                 elementNumber == tle.elementNumber &&
                 Objects.equals(epoch, tle.epoch) &&
                 meanMotion.getReal() == tle.meanMotion.getReal() &&
                 meanMotionFirstDerivative.getReal() == tle.meanMotionFirstDerivative.getReal() &&
                 meanMotionSecondDerivative.getReal() == tle.meanMotionSecondDerivative.getReal() &&
                 eccentricity.getReal() == tle.eccentricity.getReal() &&
                 inclination.getReal() == tle.inclination.getReal() &&
                 pa.getReal() == tle.pa.getReal() &&
                 raan.getReal() == tle.raan.getReal() &&
                 meanAnomaly.getReal() == tle.meanAnomaly.getReal() &&
                 revolutionNumberAtEpoch == tle.revolutionNumberAtEpoch &&
                 getBStar() == tle.getBStar();
     }
 
     /** Get a hashcode for this tle.
      * @return hashcode
      */
     @Override
     public int hashCode() {
         return Objects.hash(satelliteNumber,
                 classification,
                 launchYear,
                 launchNumber,
                 launchPiece,
                 ephemerisType,
                 elementNumber,
                 epoch,
                 meanMotion,
                 meanMotionFirstDerivative,
                 meanMotionSecondDerivative,
                 eccentricity,
                 inclination,
                 pa,
                 raan,
                 meanAnomaly,
                 revolutionNumberAtEpoch,
                 getBStar());
     }
 
 }