Shadow Conditions of Earth Satellites  Kozai orbit propagation

11092022, 05:48 PM
(This post was last modified: 11092022 06:12 PM by cdeaglejr.)
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Shadow Conditions of Earth Satellites  Kozai orbit propagation
Accurate predictions of shadow conditions for any type of satellite orbit can be determined by using a combination of onedimensional minimization and root finding. The algorithm used in this computer program searches for minimum values of the angle between the shadow axis and the satellite’s position vector as a function of time. If this angle lies within the penumbra angle, the algorithm uses Brent's rootfinding method to look backward and forward relative to this minimum time to find entrance and exit conditions. This method can also be used to determine entrance and exit relative to the umbra, penumbra and cylindrical shadows.
The information required by the software is "hardwired" in the source code starting with the initial calendar date and UTC time followed by the classical orbital elements. The type of shadow to model and the simulation duration in days is the next section of userprovided data. // initial calendar date (month, day, year) month := 6; day := 14; year := 1990; // initial utc time (hours, minutes, seconds) uthr := 23.0; utmin := 0.0; utsec := 0.0; /////////////////////////// // initial orbital elements /////////////////////////// // semimajor axis (kilometers) oev1(1) := 24450.0; // eccentricity oev1(2) := 0.725; // orbital inclination (degrees > radians) oev1(3) := 18.0 * dtr; // argument of perigee (degrees > radians) oev1(4) := 180.0 * dtr; // raan (degrees > radians) oev1(5) := 68.0 * dtr; // true anomaly (degrees > radians) oev1(6) := 0.0 * dtr; ///////////////////////////// // type of shadow calculation ///////////////////////////// // 1 = penumbra shadow // 2 = umbra shadow // 3 = cylinder shadow ishadow := 2; // simulation duration in days ndays := 5; The zipped file for this program, shadow2.zip, can be downloaded from https://www.dropbox.com/s/dit2re9t1q2sqx...2.zip?dl=0 

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