Hi all friend. I am a student studying space system engineering at Myanmar Aerospace Engineering University. I am interested in orbit. ACE orbit is special. The line of apsides ( line between apogee and perigee)rotates 360 degree per year. I want know how this happen. If you know, share me some information or link of free book.
And I am also trying to simulate an orbit and ground track for an nanosatellite of eccentricity(0.65) , inclination(19 deg), semimajor axis ( 40600km). I want know what you consider to simulate an orbit( 2D or 3D). How to consider about rotation of earth. If you have some m-files for molniya. Thank you all.
Quote from: Thiha Kyaw on 06/29/2014 11:44 amI assume from your description you're talking about an Apogee at Constant time of day Equatorial orbit (that's the only orbit that fits your description that ACE makes sense in). This is just due to nodal precession. Wikipedia explains it decently: http://en.wikipedia.org/wiki/Nodal_precessionSince you want one rotation of the line of apsides per year, you can calculate the rate of procession and plug that in, along with your other known variables, to solve for whatever you're looking for.The code you've posted above does that. If you want to create a ground track of a Molniya orbit, put in those parameters.The general process would be to convert your position vector in Earth-Centered Inertial (ECI) coordinates to Earth-Centered Earth-Fixed (ECEF) coordinates. This transformation is a function of the current time (thus accounting for the rotation of the earth). Then, convert from ECEF to geodetic (latitude, longitude, elevation) coordinates. MATLAB has a function for this (ecef2geodetic), although you could write your own if you want a better understanding how it works.Thank you Mr.Andrewwski. Now, I am trying to understand nodal precession with the help of your link. And then, I am learning the build-in function (ecef2geodetic). But this is difficult to me. If you don’t mind, and have some m-files that use the function (ecef2geodetic), please share me. Thanks for your time.
I assume from your description you're talking about an Apogee at Constant time of day Equatorial orbit (that's the only orbit that fits your description that ACE makes sense in). This is just due to nodal precession. Wikipedia explains it decently: http://en.wikipedia.org/wiki/Nodal_precessionSince you want one rotation of the line of apsides per year, you can calculate the rate of procession and plug that in, along with your other known variables, to solve for whatever you're looking for.The code you've posted above does that. If you want to create a ground track of a Molniya orbit, put in those parameters.The general process would be to convert your position vector in Earth-Centered Inertial (ECI) coordinates to Earth-Centered Earth-Fixed (ECEF) coordinates. This transformation is a function of the current time (thus accounting for the rotation of the earth). Then, convert from ECEF to geodetic (latitude, longitude, elevation) coordinates. MATLAB has a function for this (ecef2geodetic), although you could write your own if you want a better understanding how it works.