Prof. Vladislav Demyanov was invited to visit National Time Service Center (NTSC) and collaborate on GNSS integrity monitoring and positioning availability from April 11^th to May 11^th, 2017. 

Prof. Demyanov works as a full-time professor in Irkutsk State Transport University, Russia, and has been researching for a long time at Institute of Solar-Terrestrial Physics, Siberian Branch of Russian Academy of Sciences, Irkutsk, Russia. His main research interest includes GNSS performance under Space Weather Hazards, GNSS integrity and availability algorithm etc. First research area of this visiting is WAAS Alerts and real GPS positioning quality under a moderate geomagnetic storm condition.

Prof. Demyanov presented report named “Effects of Solar Radio Flares and Ionospheric Irregularties on GNSS Performance” on May 5^th. Professor Decai Zou worked as the meeting chair.

The report showed that GNSS signal can be interfered by solar L-band radio flares and multi-scale ionosphere disturbance. Though powerful solar flares occur rarely and mostly are not considered as a potential threat to the stable GNSS performance, this Space Weather phenomenon can be considered as a global and free tool to find the real noise resistant threshold of GNSS equipment, define exact requirement to the ranging code structure and make choice of the best multi-channel access technique. The another important conclusion was that based on the modern consideration of mid latitudes as an area which is not free from irregular traveling multi-scale ionosphere disturbances it is necessary to revise the WAAS building concept. In order to achieve high confidence of WAAS positioning availability alerts real ionosphere measurements within wide area coverage zone as well as Space Weather alerts must be involved.

    After the report, questions such as SBAS local ionosphere prediction, hazardous space weather detection and relieving during the future modernization of BD/GLONASS and so on, are proposed and discussed among attendants.