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I'm in charge of the ADCS for a class project, which consists on a 25U-cubesat, in a 650-km dawn-dusk Sun-synchronous orbit or SSO.

What are the orbit correction/maintenance manouvers a spacecraft must perform in order to remain in a dawn-dusk SSO for two years, the operational lifetime of the satellite?

While Orbital Precession due to the Earth's oblateness will tend to keep the orbit's plane moving around the Earth at about once per year (the same speed that the dawn-dusk line moves) that's only approximate. Orbital imperfections and gravitational perturbations will inevitably lead to errors.

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    $\begingroup$ As this is a school project, you should include your ideas and what research you have done so far. $\endgroup$ – asdfex May 4 at 16:50
  • $\begingroup$ There is no such rule that you have to do one thing if it's a school project, or do a different thing if it isn't. That's got nothing to do with anything. Nonetheless I've added a bit of background to your question. To double check, is it a 25U, or a 2.5U cubesat? $\endgroup$ – uhoh May 4 at 22:23
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The answer depends on the accuracy required. What is the range of RAAN permitted in your mission to still be considered "SSO". What is the allowable altitude range that you are permitted?

Easiest execution, especially for a short term mission, is to let the orbit drift to one end of the allowable RAAN box. Then change altitude so that the RAAN starts drifting (relative to the ideal) in the opposite direction until it gets to the other end of the allowable RAAN box. Change altitude and start drifting in initial direction again. Repeat.

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