What is a sun-synchronous orbit and how is it achieved?

A sun-synchronous orbit (SSO) maintains constant angle between orbital plane and Sun direction throughout the year. Earth's J2 oblateness causes nodal regression; at specific inclination and altitude, regression rate equals Earth's revolution rate around Sun (0.9856 deg/day). For ~600 km altitude, inclination is ~97.8 degrees (retrograde). Applications: Consistent lighting for Earth observation, Thermal environment stability (avoiding terminator transits), Regular ground station passes at same local time. Design: Choose desired Local Time of Ascending Node (LTAN, e.g., 10:30 AM for morning), Calculate required inclination for chosen altitude, and Launch into correct plane. Variations: Dawn-dusk SSO (LTAN 6:00/18:00) for continuous solar illumination and solar observation. SSO is slightly retrograde, requiring more launch energy than prograde orbits.