31 and the input output processing unit 32 to the distance measurement processing unit 33 of the operation control section 30 as distance measurement data whereupon the distance measurement processing unit 33 computes the distance and the rate of change in the distance observation of the distance and the rate of change in the distance is continued for e g 24 hours and such observation is carried out at a frequency of twice or three times a week the distance measurement data thus obtained is transferred via the data transfer unit 36 to the orbit determining unit 41 in the job scheduler section 40 based on the distance measurement data the orbit determining unit 41 computes orbit determination values representing the position and velocity of the satellite at a certain time the orbit determination values include six orbital elements i e the semimajor axis a of the elliptic orbit the eccentricity e the orbit inclination angle i which is the angle between the orbital plane and the equatorial plane the right ascension u03c9 of the ascending node of the orbital plane measured eastward from the vernal equinox along the equatorial plane the perigee argument u03c9 indicating the orientation of the orbit and the mean anomaly m the computed orbit determination values are supplied to the control command creating unit 42 the control command creating unit 42 determines based on the rates of change in the orbital elements whether any satellite is likely to deviate from the predetermined hold range if it is predicted that a satellite will deviate from the predetermined hold range the control command creating unit 42 formulates a control plan to avoid such deviation i.