Problem 45800. SatCom #6: Inclination of a Sun-Synchronous Orbit
Satellite and Space Engineering - Problem #5
This is part of a series of problems looking at topics in satellite and space communications and systems engineering.
A particularly interesting (and useful) orbit is the 'Sun-Synchronous Orbit.' This orbit has the special feature that the plane of the orbit precesses (rotates) in inertial space at exactly the same rate as the earth rotates around the sun. Therefore, the orbit plane always maintains a fixed angle with respect to the sun, which means that the satellite always passes over the same point on the ground at the same local mean solar time. Now, satellite orbits, in the absence of external forces, will not precess, but will remain on a plane fixed with respect to inertial space. However, the unequal forces on the satellite caused by the equatorial bulge of the Earth tends to make inclined orbits precess, and by tuning the orbit inclination and altitude (actually the semi-major axis and eccentricity of the orbit ellipse), the orbit can be made to precess at just the right angular rate to maintain a fixed direction towards the sun. (See: <https://en.wikipedia.org/wiki/Sun-synchronous_orbit> for more information about such orbits.)
You are given the satellite orbit's apogee and perigee altitudes (in km). Calculate the inclination needed to achieve a sun-synchronous orbit.
You should take the radius of the Earth to be 6371km.
Hint : If you are not sure about how to derive the semi-major axis and eccentricity of the orbit given its apogee altitude, perigee altitude and the Earth's radius, you probably ought to try Problem 45797. SatCom #5: Determine Elliptical Orbit Parameters first ( <https://www.mathworks.com/matlabcentral/cody/problems/45797-satcom-5-determine-elliptical-orbit-parameters> ).
Example: The CLOUDSAT satellite has an apogee of 710 km and a perigee of 709 km. It's orbit inclination is approximately 98.2 degrees.
Some future problems in this series will build on work done in previous problems, so if you get a working solution I suggest you hang onto the code!
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3 Comments
Matteo Valentinuzzi
on 30 Aug 2021
The link for the first hint doesn't work. Using the equations and coefficients in the wikipedia page gives me results close to the solutions, but not close enough for the solution check to pass. Could you please write the values of the coefficients to be used, or provide some info that was contained in the first hint?
Chris
on 30 Aug 2021
Yeah, I used real J2, RAAN* and mu with no love. http://www.satobs.org/seesat/Dec-2018/0040.html Use this guy's equation and it works.
Augusto Mazzei
on 26 Feb 2022
If all next problems are gonna give wikipedia-based hints while the solution is built with other method this problem group totally no-sense. dislike
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