Repeat sun-synchronous orbit is one of the most frequently used orbits for earth observation missions

because the orbit can satisfy the requirement of illumination and temporal resolution. Q value is the connection between sun-synchronous orbit and repeat orbit

so Q value

which is one of the first considerable parameters in the design of repeat sun-synchronous orbit

plays an important role of repeat sun-synchronous orbit design. First of all

the characteristics of sun-synchronous orbit and repeat orbit are analyzed

and the relationship of Q value and repeat sun-synchronous orbit is established

according as which repeat sun-synchronous orbit can be designed. Second

with the analysis of repeat orbit characteristics

derive a Q value design method of repeat sun-synchronous orbit. In the end

it is presented how to design a repeat sun-synchronous orbit satisfying mission requirements with an example. The method finds the key point of repeat sun-synchronous orbit design in theory

and provides a credible and easy method for complex orbit design tasks.