PURPOSE: To measure a line of sight speed irrespective of the speed of an acceleration applied to a flying object, by a method wherein a plurality of oscillators, which produce a frequency deviation in proportion to the speed of acceleration and have frequency deviation rates being different from each other, are placed on the flying object.

CONSTITUTION: An artificial satellite 1, in which a first transmitter 2a and a second transmitter 2b, producing a frequency deviation in porportion to the speed of acceleration and having frequency deviation rates different from each other, are placed, transmits two signals from the 2a and 2b from an antenna 3 after they are composed by a composing device 8. Two waves are received by an antenna 5 at an observing point 4, they are detected and amplified by a receiver 6, are sent to frequency measuring device 7, and a line of sight speed to the observing point 4 of the artificial satellite 1 is determined irrespective of the speed of acceleration utilizing a relation between the received frequency and frequency deviation charateristics of a wave thereof to a known acceleration of a frequency oscillator and between the received frequency and a Doppler effect.