l Use case：check satellite information
Brief description：log in the system check the information of the satellite you want check
User ：administrator or user
Basic Flows：1.log in the system choose function about check satellite information.
2.input the satellite you want check
3.Operate succeed
Precodition：login succeed.
PostCodition：the system list the information of the satellite you check
l Use case：change satellite information
Brief description：the system judge the person login if a administrator and you can change the information of satellite
User ：administrator
Basic Flows：1.Administrator login the system choose function about change satellite information
2.Administrator input new satellite information
3.Operate succeed
Precodition：the person login is administrator
PostCodition：the information of the satellite has change
l Use case：calculate the danger of satellite
Brief description：the system can calculate the satellite and judge if the satellite has dangers
User: users
Basic Flows：1.log in the system choose function about calculate satellite information.
2.input the satellite you want calculate
3.Operate succeed
Precodition：login succeed.
PostCodition: the system calculate the satellite if dangerous and output it.