-#!/usr/bin/perl -w
+#/usr/bin/perl -w
#
# This module was written by Steve Franke K9AN.
# November, 1999.
#
# $Id$
#
+# 2001/12/16 Fixed Julian_Date_of_Epoch and now I actually use it...
# 2001/09/15 some changes to take care of cases where the object
# doesn't rise or set on a given day...
sub Julian_Date_of_Epoch
{
my $epoch=shift;
- my $year=int($epoch*1e-3);
- $year=$year+2000 if ($year < 57);
- $year=$year+1900 if ($year >= 57);
- my $day=$epoch-$year*1e3;
+ my $year=int($epoch/1000);
+ my $day=$epoch-$year*1000;
+ if ($year < 57 ) {
+ $year=$year+2000;
+ }
+ else {
+ $year=$year+1900;
+ }
my $Julian_Date_of_Epoch=Julian_Date_of_Year($year)+$day;
return $Julian_Date_of_Epoch;
}
+
sub Julian_Date_of_Year
{
my $year=shift;
my ($alpha1,$alpha2,$alpha3,$delta1,$delta2,$delta3);
my ($m0,$m1,$m2,$theta,$alpha,$delta,$H,$az,$h,$h0,$aznow,$hnow,$corr);
my ($i,$arg,$argtest,$H0,$alphanow,$deltanow,$distance,$distancenow);
+ my ($ifrac,$ifracnow);
my $julianday=Julian_Day($year,$month,$day);
my $tt1 = ($julianday-1-2451545)/36525.;
}
if ( $sun0_moon1 == 1 ) {
- ($alpha1, $delta1, $distance)=get_moon_alpha_delta($tt1);
- ($alpha2, $delta2, $distance)=get_moon_alpha_delta($tt2);
- ($alpha3, $delta3, $distance)=get_moon_alpha_delta($tt3);
- ($alphanow, $deltanow, $distancenow)=get_moon_alpha_delta($ttnow);
+ ($alpha1, $delta1, $distance, $ifrac)=get_moon_alpha_delta($tt1);
+ ($alpha2, $delta2, $distance, $ifrac)=get_moon_alpha_delta($tt2);
+ ($alpha3, $delta3, $distance, $ifrac)=get_moon_alpha_delta($tt3);
+ ($alphanow, $deltanow, $distancenow, $ifracnow)=get_moon_alpha_delta($ttnow);
$h0=0.7275*$r2d*asin(6378.14/$distancenow)-34./60.;
$H=$thetanow-$lon-$alphanow;
$H=reduce_angle_to_360($H);
}
if ( $sun0_moon1 == 1 ) {
return (sprintf("%s", $risetime), sprintf("%s",$settime),
- $aznow+180,$hnow, -40*log10($distance/385000) );
+ $aznow+180,$hnow, -40*log10($distance/385000), $ifracnow );
}
}
sub get_moon_alpha_delta
#
# Calculate the moon's right ascension and declination
#
+ # As of October 2001, also calculate the illuminated fraction of the
+ # moon's disk... (why not?)
+ #
my $tt=shift;
my $Lp=218.3164477+481267.88123421*$tt-
my $delta=asin(cosdeg($beta)*sindeg($epsilon)*sindeg($lambda)+sindeg($beta)*cosdeg($epsilon))*$r2d;
$delta = reduce_angle_to_360($delta);
- return ($alpha,$delta,$distance);
+# $phase will be the "moon phase angle" from p. 346 of Meeus' book...
+ my $phase=180.0 - $D - 6.289 *sindeg($Mp)
+ + 2.100 *sindeg($M)
+ - 1.274 *sindeg(2.*$D - $Mp)
+ - 0.658 *sindeg(2.*$D)
+ - 0.214 *sindeg(2.*$Mp)
+ - 0.110 *sindeg($D);
+
+# $illum_frac is the fraction of the disk that is illuminated, and will be
+# zero at new moon and 1.0 at full moon.
+
+ my $illum_frac = (1.0 + cosdeg( $phase ))/2.;
+
+ return ($alpha,$delta,$distance,$illum_frac);
}
sub get_sun_alpha_delta
my $epoch = $sat_ref ->{epoch};
#printf("epoch = %10.2f\n",$epoch);
- my $epoch_year=int($epoch/1000);
- my $epoch_day=$epoch-int(1000*$epoch_year);
-#printf("epoch_year = %10.2f\n",$epoch_year);
-#printf("epoch_day = %17.12f\n",$epoch_day);
- my $ep_year=$epoch_year+2000 if ($epoch_year < 57);
- $ep_year=$epoch_year+1900 if ($epoch_year >= 57);
- my $jt_epoch=Julian_Date_of_Year($ep_year);
- $jt_epoch=$jt_epoch+$epoch_day;
+ my $jt_epoch=Julian_Date_of_Epoch($epoch);
#printf("JT for epoch = %17.12f\n",$jt_epoch);
my $tsince=($jtime-$jt_epoch)*24*60;
#printf("tsince (min) = %17.12f\n",$tsince);