-#!/usr/bin/perl -w
+#/usr/bin/perl -w
#
# This module was written by Steve Franke K9AN.
# November, 1999.
#
# Copyright (c) 1999 - Steve Franke K9AN
#
-# $Id$
+#
#
+# 2005/02/25 add calculation of civil dawn and dusk, defined to be times
+# when solar zenith angle is 96 degrees.
+# 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...
package Sun;
-use POSIX;
require Exporter;
@ISA = qw(Exporter);
@EXPORT = qw($pi $d2r $r2d );
use strict;
-use vars qw($pi $d2r $r2d );
+
+use vars qw($pi $d2r $r2d);
$pi = 3.141592653589;
$d2r = ($pi/180);
$r2d = (180/$pi);
-sub julian_day
+use vars qw(%keps);
+use Keps;
+use DXVars;
+use DXUtil;
+use DXDebug;
+
+use POSIX qw(:math_h);
+
+# reload the keps data
+sub load
+{
+ my @out;
+ my $s = readfilestr("$main::root/local/Keps.pm");
+ if ($s) {
+ eval $s;
+ push @out, $@ if $@;
+ }
+ return @out;
+}
+
+sub Julian_Day
{
my $year = shift;
my $month = shift;
$julianday = int(365.25*($year+4716)+int(30.6001*($month+1)))+$day-13-1524.5;
return $julianday;
}
+sub Julian_Date_of_Epoch
+{
+ my $epoch=shift;
+ 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;
+ $year=$year-1;
+ my $A=int($year/100);
+ my $B=2-$A+int($A/4);
+ my $Julian_Date_of_Year=int(365.25*$year)+int(30.6001*14)+
+ 1720994.5+$B;
+ return $Julian_Date_of_Year;
+}
+sub ThetaG_JD
+{
+ my $jd=shift;
+ my $omega_E=1.00273790934; # earth rotations per sidereal day
+ my $secday=86400;
+ my $UT=($jd+0.5)-int($jd+0.5);
+ $jd=$jd-$UT;
+ my $TU=($jd-2451545.0)/36525;
+ my $GMST=24110.54841+$TU*(8640184.812866+$TU*(0.093104-$TU*6.2e-6));
+ my $thetag_jd=mod2p(2*$pi*($GMST/$secday+$omega_E*$UT));
+ return $thetag_jd;
+}
+
sub reduce_angle_to_360
{
my $angle = shift;
$angle=$angle+360 if( $angle < 0 );
return $angle;
}
+sub mod2p
+{
+ my $twopi=$pi*2;
+ my $angle = shift;
+
+ $angle=$angle-int($angle/$twopi)*$twopi;
+ $angle=$angle+$twopi if( $angle < 0 );
+ return $angle;
+}
sub sindeg
{
my $angle_in_degrees = shift;
my $lat = shift;
my $lon = shift;
my $sun0_moon1=shift; # 0 for sun, 1 for moon, 2 for venus...
+ my ($alpha1,$delta1,$alpha2,$delta2,$alpha3,$delta3);
+ my ($aznow,$hnow,$alphanow,$deltanow,$distance,$distancenow);
+ my ($h0,$H);
+ my ($risetime,$settime);
+ my ($dawntime,$dusktime);
- my ($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 $julianday=Julian_Day($year,$month,$day);
my $tt1 = ($julianday-1-2451545)/36525.;
my $tt2 = ($julianday-2451545)/36525.;
my $tt3 = ($julianday+1-2451545)/36525.;
($alpha2, $delta2)=get_sun_alpha_delta($tt2);
($alpha3, $delta3)=get_sun_alpha_delta($tt3);
($alphanow, $deltanow)=get_sun_alpha_delta($ttnow);
- $h0=-0.8333;
$H=$thetanow-$lon-$alphanow;
$H=reduce_angle_to_360($H);
($aznow,$hnow)=get_az_el($H,$deltanow,$lat);
$hnow=$hnow +
1.02/(tandeg($hnow+10.3/($hnow+5.11)))/60;
+ $h0=-0.8333; # this is for sun rise and sun set
+ ($risetime,$settime)=
+ do_rise_set_calculations($h0,$theta0,$lat,$lon,$alpha1,$delta1,
+ $alpha2,$delta2,$alpha3,$delta3);
+ $h0=-6.0; # this is for civil dawn and dusk
+ ($dawntime,$dusktime)=
+ do_rise_set_calculations($h0,$theta0,$lat,$lon,$alpha1,$delta1,
+ $alpha2,$delta2,$alpha3,$delta3);
+ $dawntime = "------" if( $dawntime eq "NoRise" );
+ $dusktime = "------" if( $dusktime eq "NoSet " );
+
+ return (
+ sprintf("%s", $dawntime), sprintf("%s",$risetime),
+ sprintf("%s", $settime), sprintf("%s",$dusktime),
+ $aznow+180,$hnow
+ );
}
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);
- $h0=0.7275*$r2d*asin(6378.14/$distancenow)-34./60.;
+ ($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)-34.0/60.;
$H=$thetanow-$lon-$alphanow;
$H=reduce_angle_to_360($H);
($aznow,$hnow)=get_az_el($H,$deltanow,$lat);
$hnow=$hnow-$r2d*asin(sin(6378.14/$distancenow)*cosdeg($hnow))+
1.02/(tandeg($hnow+10.3/($hnow+5.11)))/60;
+ ($risetime,$settime)=
+ do_rise_set_calculations($h0,$theta0,$lat,$lon,$alpha1,$delta1,
+ $alpha2,$delta2,$alpha3,$delta3);
+ return (sprintf("%s", $risetime), sprintf("%s",$settime),
+ $aznow+180,$hnow, -40*log10($distance/385000), $ifracnow );
+
}
- $arg = (sindeg($h0)-sindeg($lat)*sindeg($delta2))/(cosdeg($lat)*cosdeg($delta2));
- $argtest = tandeg($lat)*tandeg($delta2);
+}
- if ( $argtest < -1. ) {
- return sprintf("Doesn't rise.");
- }
- if ( $argtest > 1. ) {
- return sprintf("Doesn't set.");
- }
+sub do_rise_set_calculations
+{
+ my $norise = 0;
+ my $noset = 0;
+ my ($risehr,$risemin,$risetime,$sethr,$setmin,$settime);
+ my ($m0,$m1,$m2,$theta,$alpha,$delta,$H,$az,$h,$corr);
+ my ($i,$arg,$argtest,$H0);
+
+ my $h0=shift;
+ my $theta0=shift;
+ my $lat=shift;
+ my $lon=shift;
+ my $alpha1=shift;
+ my $delta1=shift;
+ my $alpha2=shift;
+ my $delta2=shift;
+ my $alpha3=shift;
+ my $delta3=shift;
+
+ $arg = (sindeg($h0)-sindeg($lat)*sindeg($delta2))/(cosdeg($lat)*cosdeg($delta2));
+ if ( abs($arg) > 1. ) { # either up all day or down all day
+ $norise = 1; # leave it to the user to examine
+ $noset = 1; # the elevation angle (or look outside!)
+ } # to figure out which.
$H0 = acos($arg)*$r2d;
my $aa=$alpha2-$alpha1;
$corr=-$H/360;
$m0=$m0+$corr;
$m0=$m0+1 if( $m0 < 0 );
- $m0=$m0-1 if( $m0 > 1 );
+ $m0=$m0-1 if( $m0 >= 1 );
}
- $m1 = $m0 - $H0/360.;
- $m1=$m1+1 if( $m1 < 0 );
- $m1=$m1-1 if( $m1 > 1 );
- for ($i=1; $i<=2; $i++) {
- $theta = $theta0+360.985647*$m1;
- $alpha=$alpha2+$m1*($aa+$ba+$m1*$ca)/2;
- $delta=$delta2+$m1*($ad+$bd+$m1*$cd)/2;
- $H=$theta-$lon-$alpha;
- $H=reduce_angle_to_360($H);
- ($az,$h)=get_az_el($H,$delta,$lat);
- $corr=($h-$h0)/(360*(cosdeg($delta)*cosdeg($lat)*sindeg($H)));
- $m1=$m1+$corr;
+
+ if( !$norise ){
+ $m1 = $m0 - $H0/360.;
$m1=$m1+1 if( $m1 < 0 );
$m1=$m1-1 if( $m1 > 1 );
+ for ($i=1; $i<=2; $i++) {
+ $theta = $theta0+360.985647*$m1;
+ $alpha=$alpha2+$m1*($aa+$ba+$m1*$ca)/2;
+ $delta=$delta2+$m1*($ad+$bd+$m1*$cd)/2;
+ $H=$theta-$lon-$alpha;
+ $H=reduce_angle_to_360($H);
+ ($az,$h)=get_az_el($H,$delta,$lat);
+ $corr=($h-$h0)/(360*(cosdeg($delta)*cosdeg($lat)*sindeg($H)));
+ $m1=$m1+$corr;
+# $norise=1 if( $m1 < 0 || $m1 > 1);
+ $m1=$m1-1 if( $m1 >= 1);
+ $m1=$m1+1 if( $m1 < 0);
+ }
}
- $m2 = $m0 + $H0/360.;
- $m2=$m2+1 if( $m2 < 0 );
- $m2=$m2-1 if( $m2 > 1 );
- for ($i=1; $i<=2; $i++) {
- $theta = $theta0+360.985647*$m2;
- $alpha=$alpha2+$m2*($aa+$ba+$m2*$ca)/2;
- $delta=$delta2+$m2*($ad+$bd+$m2*$cd)/2;
- $H=$theta-$lon-$alpha;
- $H=reduce_angle_to_360($H);
- ($az,$h)=get_az_el($H,$delta,$lat);
- $corr=($h-$h0)/(360*(cosdeg($delta)*cosdeg($lat)*sindeg($H)));
- $m2 = $m2 + $corr;
- $m2=$m2+1 if( $m2 < 0 );
- $m2=$m2-1 if( $m2 > 1 );
- }
- my ($risehr,$risemin,$sethr,$setmin);
- $risehr=int($m1*24);
- $risemin=($m1*24-int($m1*24))*60+0.5;
- if ( $risemin >= 60 ) {
- $risemin=$risemin-60;
- $risehr=$risehr+1;
- }
- $sethr=int($m2*24);
- $setmin=($m2*24-int($m2*24))*60+0.5;
- if ( $setmin >= 60 ) {
- $setmin=$setmin-60;
- $sethr=$sethr+1;
+ if( !$norise ) {
+ $risehr=int($m1*24);
+ $risemin=($m1*24-int($m1*24))*60+0.5;
+ if ( $risemin >= 60 ) {
+ $risemin=$risemin-60;
+ $risehr=$risehr+1;
+ }
+ $risehr=0 if($risehr==24);
+ $risetime=sprintf("%02d:%02dZ",$risehr,$risemin);
+ } else {
+ $risetime="NoRise";
}
- if ( $sun0_moon1 == 0 ) {
- return (sprintf("%02d:%02dZ", $risehr,$risemin), sprintf("%02d:%02dZ",$sethr,$setmin),$aznow+180,$hnow);
- }
- if ( $sun0_moon1 == 1 ) {
- return (sprintf("%02d:%02dZ", $risehr,$risemin), sprintf("%02d:%02dZ",$sethr,$setmin),
- $aznow+180,$hnow, -40*log10($distance/385000) );
+ if( !$noset ){
+ $m2 = $m0 + $H0/360.;
+ $m2=$m2+1 if( $m2 < 0 );
+ $m2=$m2-1 if( $m2 >= 1 );
+ for ($i=1; $i<=2; $i++) {
+ $theta = $theta0+360.985647*$m2;
+ $alpha=$alpha2+$m2*($aa+$ba+$m2*$ca)/2;
+ $delta=$delta2+$m2*($ad+$bd+$m2*$cd)/2;
+ $H=$theta-$lon-$alpha;
+ $H=reduce_angle_to_360($H);
+ ($az,$h)=get_az_el($H,$delta,$lat);
+ $corr=($h-$h0)/(360*(cosdeg($delta)*cosdeg($lat)*sindeg($H)));
+ $m2 = $m2 + $corr;
+# $noset=1 if( $m2 < 0 || $m2 > 1);
+ $m2=$m2-1 if( $m2 >= 1);
+ $m2=$m2+1 if( $m2 < 0);
+ }
}
+
+ if( !$noset ) {
+ $sethr=int($m2*24);
+ $setmin=($m2*24-int($m2*24))*60+0.5;
+ if ( $setmin >= 60 ) {
+ $setmin=$setmin-60;
+ $sethr=$sethr+1;
+ }
+ $sethr=0 if($sethr==24);
+ $settime=sprintf("%02d:%02dZ",$sethr,$setmin);
+ } else {
+ $settime="NoSet ";
+ }
+ return $risetime,$settime;
}
+
+
+
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
{
- #
- # Calculate Sun's right ascension and declination
- #
+#
+# Calculate Sun's right ascension and declination
+#
my $tt = shift;
my $L0 = 280.46646+36000.76983*$tt+0.0003032*($tt^2);
return ($alpha,$delta);
}
+sub get_satellite_pos
+{
+#
+# This code was translated more-or-less directly from the Pascal
+# routines contained in a report compiled by TS Kelso and based on:
+# Spacetrack Report No. 3
+# "Models for Propagation of NORAD Element Sets"
+# Felix R. Hoots, Ronald L Roehrich
+# December 1980
+#
+# See TS Kelso's web site for more details...
+# Only the SGP propagation model is implemented.
+#
+# Steve Franke, K9AN. 9 Dec 1999.
+
+#
+#NOAA 15
+#1 25338U 98030A 99341.00000000 +.00000376 +00000-0 +18612-3 0 05978
+#2 25338 098.6601 008.2003 0011401 112.4684 042.5140 14.23047277081382
+#TDRS 5
+#1 21639U 91054B 99341.34471854 .00000095 00000-0 10000-3 0 4928
+#2 21639 1.5957 88.4884 0003028 161.6582 135.4323 1.00277774 30562
+#OSCAR 16 (PACSAT)
+#1 20439U 90005D 99341.14501399 +.00000343 +00000-0 +14841-3 0 02859
+#2 20439 098.4690 055.0032 0012163 066.4615 293.7842 14.30320285515297
+#
+#Temporary keps database...
+#
+ my $jtime = shift;
+ my $lat = shift;
+ my $lon = shift;
+ my $alt = shift;
+ my $satname = shift;
+ my $sat_ref = $keps{$satname};
+#printf("$jtime $lat $lon $alt Satellite name = $satname\n");
+
+ my $qo=120;
+ my $so=78;
+ my $xj2=1.082616e-3;
+ my $xj3=-.253881e-5;
+ my $xj4=-1.65597e-6;
+ my $xke=.743669161e-1;
+ my $xkmper=6378.135;
+ my $xmnpda=1440.;
+ my $ae=1.;
+ my $ck2=.5*$xj2*$ae**2;
+ my $ck4=-.375*$xj4*$ae**4;
+ my $qoms2t=(($qo-$so)*$ae/$xkmper)**4;
+ my $s=$ae*(1+$so/$xkmper);
+
+ my $epoch = $sat_ref ->{epoch};
+#printf("epoch = %10.2f\n",$epoch);
+ 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);
+
+ my $mm1 = $sat_ref ->{mm1};
+ my $mm2 = $sat_ref ->{mm2};
+ my $bstar=$sat_ref ->{bstar}; # drag term for sgp4 model
+ my $inclination=$sat_ref->{inclination}; # inclination in degrees
+ my $raan=$sat_ref->{raan}; # right ascension of ascending node in degs
+ my $eccentricity=$sat_ref ->{eccentricity}; # eccentricity - dimensionless
+ my $omegao=$sat_ref ->{argperigee}; # argument of perigee in degs
+ my $xmo=$sat_ref ->{meananomaly}; # mean anomaly in degrees
+ my $xno=$sat_ref ->{meanmotion}; # mean motion in revs per day
+
+#printf("%10.6f %10.6f %10.6f %10.6f %10.6f %10.6f %10.6f %10.6f %10.6f\n",
+#$mm1,$mm2,$bstar,$inclination,$raan,$eccentricity,$omegao,$xmo,$xno);
+ $raan=$raan*$d2r;
+ $omegao=$omegao*$d2r;
+ $xmo=$xmo*$d2r;
+ $inclination=$inclination*$d2r;
+ my $temp=2*$pi/$xmnpda/$xmnpda;
+ $xno=$xno*$temp*$xmnpda;
+ $mm1=$mm1*$temp;
+ $mm2=$mm2*$temp/$xmnpda;
+
+ my $c1=$ck2*1.5;
+ my $c2=$ck2/4.0;
+ my $c3=$ck2/2.0;
+ my $c4=$xj3*$ae**3/(4*$ck2);
+ my $cosio=cos($inclination);
+ my $sinio=sin($inclination);
+ my $a1=($xke/$xno)**(2./3.);
+ my $d1=$c1/$a1/$a1*(3*$cosio*$cosio-1)/(1-$eccentricity*$eccentricity)**1.5;
+ my $ao=$a1*(1-1./3.*$d1-$d1*$d1-134./81.*$d1*$d1*$d1);
+ my $po=$ao*(1-$eccentricity*$eccentricity);
+ $qo=$ao*(1-$eccentricity);
+ my $xlo=$xmo+$omegao+$raan;
+ my $d10=$c3*$sinio*$sinio;
+ my $d20=$c2*(7.*$cosio*$cosio-1);
+ my $d30=$c1*$cosio;
+ my $d40=$d30*$sinio;
+ my $po2no=$xno/($po*$po);
+ my $omgdt=$c1*$po2no*(5.*$cosio*$cosio-1);
+ my $xnodot=-2.*$d30*$po2no;
+ my $c5=0.5*$c4*$sinio*(3+5*$cosio)/(1+$cosio);
+ my $c6=$c4*$sinio;
+
+ my $a=$xno+(2*$mm1+3*$mm2*$tsince)*$tsince;
+ $a=$ao*($xno/$a)**(2./3.);
+ my $e=1e-6;
+ $e =1-$qo/$a if ($a > $qo);
+ my $p=$a*(1-$e*$e);
+ my $xnodes=$raan+$xnodot*$tsince;
+ my $omgas=$omegao+$omgdt*$tsince;
+ my $xls=mod2p($xlo+($xno+$omgdt+$xnodot+($mm1+$mm2*$tsince)*$tsince)*$tsince);
+
+ my $axnsl=$e*cos($omgas);
+ my $aynsl=$e*sin($omgas)-$c6/$p;
+ my $xl=mod2p($xls-$c5/$p*$axnsl);
+
+ my $u=mod2p($xl-$xnodes);
+ my $item3;
+ my $eo1=$u;
+ my $tem5=1;
+ my $coseo1=0;
+ my $sineo1=0;
+ for ($item3=0; abs($tem5) >= 1e-6 && $item3 < 10; $item3++ )
+ {
+ $sineo1=sin($eo1);
+ $coseo1=cos($eo1);
+ $tem5=1-$coseo1*$axnsl-$sineo1*$aynsl;
+ $tem5=($u-$aynsl*$coseo1+$axnsl*$sineo1-$eo1)/$tem5;
+ my $tem2=abs($tem5);
+ $tem5=$tem2/$tem5 if ($tem2 > 1);
+ $eo1=$eo1+$tem5;
+ }
+
+ $sineo1=sin($eo1);
+ $coseo1=cos($eo1);
+ my $ecose=$axnsl*$coseo1+$aynsl*$sineo1;
+ my $esine=$axnsl*$sineo1-$aynsl*$coseo1;
+ my $el2=$axnsl*$axnsl+$aynsl*$aynsl;
+ my $pl=$a*(1-$el2);
+ my $pl2=$pl*$pl;
+ my $r=$a*(1-$ecose);
+ my $rdot=$xke*sqrt($a)/$r*$esine;
+ my $rvdot=$xke*sqrt($pl)/$r;
+ $temp=$esine/(1+sqrt(1-$el2));
+ my $sinu=$a/$r*($sineo1-$aynsl-$axnsl*$temp);
+ my $cosu=$a/$r*($coseo1-$axnsl+$aynsl*$temp);
+ my $su=atan2($sinu,$cosu);
+
+ my $sin2u=($cosu+$cosu)*$sinu;
+ my $cos2u=1-2*$sinu*$sinu;
+ my $rk=$r+$d10/$pl*$cos2u;
+ my $uk=$su-$d20/$pl2*$sin2u;
+ my $xnodek=$xnodes+$d30*$sin2u/$pl2;
+ my $xinck=$inclination+$d40/$pl2*$cos2u;
+
+ my $sinuk=sin($uk);
+ my $cosuk=cos($uk);
+ my $sinnok=sin($xnodek);
+ my $cosnok=cos($xnodek);
+ my $sinik=sin($xinck);
+ my $cosik=cos($xinck);
+ my $xmx=-$sinnok*$cosik;
+ my $xmy=$cosnok*$cosik;
+ my $ux=$xmx*$sinuk+$cosnok*$cosuk;
+ my $uy=$xmy*$sinuk+$sinnok*$cosuk;
+ my $uz=$sinik*$sinuk;
+ my $vx=$xmx*$cosuk-$cosnok*$sinuk;
+ my $vy=$xmy*$cosuk-$sinnok*$sinuk;
+ my $vz=$sinik*$cosuk;
+
+ my $x=$rk*$ux*$xkmper/$ae;
+ my $y=$rk*$uy*$xkmper/$ae;
+ my $z=$rk*$uz*$xkmper/$ae;
+ my $xdot=$rdot*$ux;
+ my $ydot=$rdot*$uy;
+ my $zdot=$rdot*$uz;
+ $xdot=($rvdot*$vx+$xdot)*$xkmper/$ae*$xmnpda/86400;
+ $ydot=($rvdot*$vy+$ydot)*$xkmper/$ae*$xmnpda/86400;
+ $zdot=($rvdot*$vz+$zdot)*$xkmper/$ae*$xmnpda/86400;
+#printf("x=%17.6f y=%17.6f z=%17.6f \n",$x,$y,$z);
+#printf("xdot=%17.6f ydot=%17.6f zdot=%17.6f \n",$xdot,$ydot,$zdot);
+ my ($sat_lat,$sat_lon,$sat_alt,$sat_theta)=Calculate_LatLonAlt($x,$y,$z,$jtime);
+ my ($az, $el, $distance) = Calculate_Obs($x,$y,$z,$sat_theta,$xdot,$ydot,$zdot,$jtime,$lat,$lon,$alt);
+ return ($sat_lat,$sat_lon,$sat_alt,$az,$el,$distance);
+}
+
+sub Calculate_LatLonAlt
+{
+#
+# convert from ECI coordinates to latitude, longitude and altitude.
+#
+ my $x=shift;
+ my $y=shift;
+ my $z=shift;
+ my $time=shift;
+
+ my $theta=atan2($y,$x);
+ my $lon=mod2p($theta-ThetaG_JD($time));
+ my $range=sqrt($x**2+$y**2);
+ my $f=1/298.26; # earth flattening constant
+ my $e2=$f*(2-$f);
+ my $xkmper=6378.135;
+ my $lat=atan2($z,$range);
+ my ($phi,$c);
+ do
+ {
+ $phi=$lat;
+ $c=1/sqrt(1-$e2*sin($phi)**2);
+ $lat=atan2($z+$xkmper*$c*$e2*sin($phi),$range);
+ } until abs($lat-$phi) < 1e-10;
+ my $alt=$range/cos($lat)-$xkmper*$c;
+ return ($lat,$lon,$alt,$theta); # radians and kilometers
+
+}
+
+sub Calculate_User_PosVel
+{
+# change from lat/lon/alt/time coordinates to earth centered inertial (ECI)
+# position and local hour angle.
+ my $lat=shift;
+ my $lon=shift;
+ my $alt=shift;
+ my $time=shift;
+ my $theta=mod2p(ThetaG_JD($time)+$lon);
+ my $omega_E=1.00273790934; # earth rotations per sidereal day
+ my $secday=86400;
+ my $mfactor=2*$pi*$omega_E/$secday;
+ my $f=1/298.26; # earth flattening constant
+ my $xkmper=6378.135;
+ my $c=1/sqrt(1+$f*($f-2)*sin($lat)**2);
+ my $s=(1-$f)*(1-$f)*$c;
+ my $achcp=($xkmper*$c+$alt)*cos($lat);
+ my $x_user=$achcp*cos($theta);
+ my $y_user=$achcp*sin($theta);
+ my $z_user=($xkmper*$s+$alt)*sin($lat);
+ my $xdot_user=-$mfactor*$y_user;
+ my $ydot_user=$mfactor*$x_user;
+ my $zdot_user=0;
+ return ($x_user,$y_user,$z_user,$xdot_user,$ydot_user,$zdot_user,$theta);
+}
+sub Calculate_Obs
+{
+# calculate the azimuth/el of an object as viewed from observers position
+# with object position given in ECI coordinates and observer in lat/long/alt.
+#
+# inputs: object ECI position vector (km)
+# object velocity vector (km/s)
+# julian time
+# observer lat,lon,altitude (km)
+ my $x=shift;
+ my $y=shift;
+ my $z=shift;
+ my $theta_s=shift;
+ my $xdot=shift;
+ my $ydot=shift;
+ my $zdot=shift;
+ my $time=shift;
+ my $lat=shift;
+ my $lon=shift;
+ my $alt=shift;
+
+ my ($x_o,$y_o,$z_o,$xdot_o,$ydot_o,$zdot_o,$theta)=
+ Calculate_User_PosVel($lat,$lon,$alt,$time);
+ my $xx=$x-$x_o;
+ my $yy=$y-$y_o;
+ my $zz=$z-$z_o;
+ my $xxdot=$xdot-$xdot_o;
+ my $yydot=$ydot-$ydot_o;
+ my $zzdot=$zdot-$zdot_o;
+
+ my $sin_lat=sin($lat);
+ my $cos_lat=cos($lat);
+ my $sin_theta=sin($theta);
+ my $cos_theta=cos($theta);
+
+ my $top_s=$sin_lat*$cos_theta*$xx
+ + $sin_lat*$sin_theta*$yy
+ - $cos_lat*$zz;
+
+ my $top_e=-$sin_theta*$xx
+ + $cos_theta*$yy;
+
+ my $top_z=$cos_lat*$cos_theta*$xx
+ + $cos_lat*$sin_theta*$yy
+ + $sin_lat*$zz;
+
+ my $az=atan(-$top_e/$top_s);
+ $az=$az+$pi if ( $top_s > 0 );
+ $az=$az+2*$pi if ( $az < 0 );
+
+ my $range=sqrt($xx*$xx+$yy*$yy+$zz*$zz);
+ my $el=asin($top_z/$range);
+ return ($az, $el, $range);
+}
+
+sub Calendar_date_and_time_from_JD
+{
+ my ($jd,$z,$frac,$alpha,$a,$b,$c,$d,$e,$dom,$yr,$mon,$day,$hr,$min);
+ $jd=shift;
+ $jd=$jd+0.5;
+ $z=int($jd);
+ $frac=$jd-$z;
+ $alpha = int( ($z-1867216.5)/36524.25 );
+ $a=$z + 1 + $alpha - int($alpha/4);
+ $a=$z if( $z < 2299161 );
+ $b=$a+1524;
+ $c=int(($b-122.1)/365.25);
+ $d=int(365.25*$c);
+ $e=int(($b-$d)/30.6001);
+ $dom=$b-$d-int(30.6001*$e)+$frac;
+ $day=int($dom);
+ $mon=$e-1 if( $e < 14 );
+ $mon=$e-13 if( $e == 14 || $e == 15 );
+ $yr = $c-4716 if( $mon > 2 );
+ $yr = $c-4715 if( $mon == 1 || $mon == 2 );
+ $hr = int($frac*24);
+ $min= int(($frac*24 - $hr)*60+0.5);
+ if ($min == 60) { # this may well prove inadequate DJK
+ $hr += 1;
+ $min = 0;
+ }
+ return ($yr,$mon,$day,$hr,$min);
+}
+
+
projects / spider.git / blobdiff