Environment effect on two way satellite time and frequency transfer

Two-way time and frequency transfer (TWSTFT) is a high precision time transfer because TWSTFT via the GEO satellite can eliminate path delay mostly. Many factors affect the time transfer precision, such as: the modem time delay, the uplink and downlink path delay, a satellite transponder delay and delay of Sagnac effect etc.. These effects can be measured or calculated. However, Temperature and humidity will reduce the performance of time transfer[1]. Besides, it can not be measured and calculated. In this text, we analyzed several years´ TWSTFT data including the temperature and humidity value between NTSC (National Time Service Center) earth station and international earth stations and discussed the correlation between the external environment and TWSTFT comparison result. On the other hand, we did the experiment using satellite simulation, measured the earth stations equipment time delay and recorded the temperature and humidity. In the last, we drew the conclusion with the external environment and TWSTFT comparison result and had the advice to compensate for it.