//Variables from filename
$orbit = $data[1]*1; //orbit number
$degree = substr($data[2],0,4)/10; //degree from equator on "night side"

//Constants that must be precise
//6814 is calculated orbital period of MRO
//90 is a "tweak"-number found by testing.. 
$mro_orbital_period = 6814-90; 
$mars_rotational_period = 88642.6632;

//Initial value
$i_orbit = 823;
$i_degree = 172.0;
$it_latitude = -7.8;
$it_longitude = 279.5;

//Calculate the longitude at "degree" 0 on the initial orbit (823)
$i_longitude = $it_longitude -
(180-(($i_degree/360*$mro_orbital_period)/$mars_rotational_period)*360);

//Calculate the time passed since this first orbit
$time_since_initial_value = ($orbit-$i_orbit)*$mro_orbital_period +
$degree/360*$mro_orbital_period;

//Calculate an orbit offset, due to the rotation of mars
$longitude_offset =
($time_since_initial_value/$mars_rotational_period*360)%360;

//Treat the different cases of degree
if($degree > 90 && $degree < 270)
{
    $longitude_offset += 180;
    $latitude = $degree - 180;
}
else if($degree < 90)
    $latitude = -$degree;
else if($degree >= 270)
    $latitude = 360-$degree;
	    
//Do the final longitude calculation
$longitude = (($i_longitude-$longitude_offset)%360+360)%360;