Dr. Jian Yao is a scientist at the University Corporation for Atmospheric Research (UCAR), which manages the National Center for Atmospheric Research (NCAR). There, he works on the orbits & clocks of GNSS (Global Navigation Satellite System) and LEO (low-Earth-orbit) satellites, and applies precise satellite orbits & clocks to GNSS radio occultation and atmospheric density sensing. He is also an adjunct faculty member at Colorado State University where he teaches GNSS courses and supervises students. He used to work at the U.S. National Institute of Standards and Technology (NIST) and NOAA’s National Geodetic Survey, for many years. He has published ~ 40 papers covering a variety of topics in the area of positioning, navigation, and timing (PNT), such as GNSS satellite ephemeris, GNSS data processing, precise orbit determination, GNSS time transfer, and atomic-clock timing systems. He is a member of the editorial board of GPS Solutions and IOP Measurement Science and Technology. He has also served as Guest Editor for GPS Solutions and as Session Chair for several PNT meetings. In 2014, he received a Ph.D. degree from the University of Colorado at Boulder.