短予熱時間高安定OCXOを用いた406MHz衛星系イーパブとその測位精度について

抄録

A 406MHz satellite EPIRB is the key component in the GMDSS. A distressed ship position can normally be obtained with 5km accuracy (90% probability) by Doppler positioning method using COSPAS-SARSAT satellites. Major positioning error factors are frequency stability of a satellite EPIRB, ionospheric layer refraction and effective frequency change due to an ocean current. A new OCXO with a short 3min. warming-up time and frequency stability of 5×10^<-11>/min. has been developed to get the ship position, in the case, a distress happens and soon after a satellite passes over it, and to minimize position error due to the satellite EPIRB. The positioing data achieved is 1.1km (90% probability, all day base) at CNES in France. Ionospheric layer refraction as major error factor is inferred from the error data in night-time and day-time are close to estimated ones respectively.