#!/usr/local/bin/perl
use FileHandle;

# ***************************************************
# add_tle.pl
# 
# This Perl module will read in the latest five orbital elements
# from the file five.tle (which was created by get_tle.pl) and
# add any new orbital elements to the file FUSE.TLE.  The file
# FUSE.TLE is in descending order (i.e. the most recent elements
# are first).  In order to prepend the new TLE onto the old list
# I found it was easiest to store everything in a temporary file
# TEMP.TLE and rewrite FUSE.TLE.
#
# Author: Ed Murphy
#
# History:  Written  July 27, 1999
#
# ***************************************************

# Define the file names.  old_maintle_filename is not actually opened,
# but is used in a system call at the end of the program. 

$input_filename = "/data1/fuse/calfuse/caltemp/five.tle";
$maintle_filename = "/data1/fuse/calfuse/calfiles/FUSE.TLE";
$old_maintle_filename = "/data1/fuse/calfuse/caltemp/FUSE.OLD";
$temp_filename = "/data1/fuse/calfuse/caltemp/TEMP.TLE";

# Open the files.
open (TLE_INFILE, "<$input_filename") || die "Cannot open $input_filename";
open (TLE_TEMPFILE, ">$temp_filename") || die "Cannot open $temp_filename";
open (TLE_MAINFILE, "<$maintle_filename") || die "Cannot open $maintle_filename";

# Read the first two lines from the maintle file to get the date of the
# most recent set of TLEs.  Save these lines for later output.
    $lineout1 = <TLE_MAINFILE>;
    $lineout2 = <TLE_MAINFILE>;
    $last_date = substr($lineout2,18,14);

# get rid of the blank line at the beginning of five.tle file
    $line = <TLE_INFILE>;  

# Cycle through the five.tle file and look for files more recent than
# last_date.  
    while ($line1 = <TLE_INFILE>) {
        $sat_name = substr($line1,0,4);
        $line2 = <TLE_INFILE>;
        $line3 = <TLE_INFILE>;
        $tle_date = substr($line2,18,14);
        $id2 = substr($line2, 2, 5);
        $id3 = substr($line3, 2, 5);
        # if the TLE is more recent, print it out to the TEMP file.
        if (($tle_date > $last_date+0.05) && ($sat_name eq "FUSE") && ($id2 == 25791) && ($id3 == 25791)) {
            &check_tle;
            print TLE_TEMPFILE $line1;
            print TLE_TEMPFILE $line2;
            print TLE_TEMPFILE $line3;
            # Send this output to screen to make sure TLEs look OK
            if ($tle_flag != 0) {
		print STDOUT "ERROR: Possible error in TLE:\n";
            }
            print STDOUT "The new TLEs are:\n";
            print STDOUT $line1;
            print STDOUT $line2;
            print STDOUT $line3;
	}

    }

# Now add the MAINTLE file to the end of the TEMPFILE
    print TLE_TEMPFILE $lineout1;
    print TLE_TEMPFILE $lineout2;
    while ($line1 = <TLE_MAINFILE>) {
            print TLE_TEMPFILE $line1;
    }
 
    close (TLE_INFILE);
    close (TLE_MAINFILE);
    close (TLE_TEMPFILE);

# Move the MAINFILE into the old_maintle filename
# Move the TEMPFILE to be the MAINFILE
# Remove the five.tle file.
    system("mv $maintle_filename $old_maintle_filename");
    system("mv $temp_filename $maintle_filename");
    system("chmod ug+rw $maintle_filename");
    system("chgrp sdp $maintle_filename");
    system("rm -f $input_filename");

### end of Perl script

sub check_tle {

    $tle_flag = 0;

    &parse_lines;

    &calculate_a0;

    &calculate_orbs;

    if (($mean_mot > 14.391) || ($mean_mot < 14.389)) {
	$tle_flag = 1;
        print STDOUT "Possible error in mean motion $mean_mot \n";
    }
    if (($incl > 24.990) || ($incl < 24.975)) {
	$tle_flag = 1;
        print STDOUT "Possible error in inclination $incl \n";
    }
    if (($eccen > 0.00120) || ($eccen < 0.00108)) {
	$tle_flag = 1;
        print STDOUT "Possible error in eccentricity $eccen \n";
    }
    if (($semiax > 7145.0) || ($semiax < 7143.0)) {
	$tle_flag = 1;
        print STDOUT "Possible error in semi-major axis $semia \n";
    }
    if (($apogee > 777.0) || ($apogee < 773.0)) {
	$tle_flag = 1;
        print STDOUT "Possible error in apogee $apogee \n";
    }
    if (($perigee > 760.0) || ($perigee < 756.0)) {
	$tle_flag = 1;
        print STDOUT "Possible error in perigee $perigee \n";
    }

}

sub parse_lines {
$year = substr($line2, 18, 2);
$doy = substr($line2, 20, 3);
$dayfrac = substr($line2, 23, 9);
$epoch = $year.$doy.$dayfrac;
$incl = substr($line3, 9, 8);
$raan = substr($line3, 17,8);
$eccen = substr($line3, 26, 7);
$eccen = "0." . $eccen;
$mean_mot = substr($line3, 52, 11);
$mean_anom = substr($line3, 43, 8);
$arg_perig = substr($line3, 34, 8);


if ($year > 50) {
    $year += 1900;
} else {
    $year += 2000;
}

$dayfrac = "0".$dayfrac;

}

sub calculate_a0 {

$mu = 3.986005E5;
$pi = 3.14159265358979;
$radian = 0.0174532925200;

$mm=2.0*$pi*$mean_mot/(24.0*60.0);
$ke=0.74366916E-1;
$k2=5.413080E-4;
$a1=($ke/$mm)**(2.0/3.0);
$inrad = $incl * $radian;

$d1=3.0/2.0*$k2/($a1*$a1)*(3.0*cos($inrad)*cos($inrad)-1.0)/((1.0-$eccen*$eccen)
**(3.0/2.0));
$a0=$a1*(1.0-$d1/3.0-$d1*$d1-134.0/81.0*$d1*$d1*$d1);
$d0=3.0/2.0*$k2/($a0*$a0)*(3.0*cos($inrad)*cos($inrad)-1.0)/((1.0-$eccen*$eccen)
**(3.0/2.0));
$semiax=$a0/(1-$d0)*6378.135;

}

sub calculate_orbs {

$period = 60.0*24.0/($mean_mot/(1+$d0));
$cax=$eccen*$semiax;
$perigee=$semiax-$cax-6378.1;
$apogee=$semiax+$cax-6378.1;

}