Jian Yao is a scientist at the University Corporation for Atmospheric Research (UCAR), where he works on the orbits and clocks of GNSS and low-Earth-orbit satellites. He is also affiliated with Colorado State University as an adjunct associate professor. Prior to this, he worked at the U.S. National Institute of Standards and Technology (NIST) and the U.S. National Geodetic Survey (NGS) for several years. He has published more than 30 papers covering a variety of topics in the area of positioning, navigation, and timing (PNT), such as GNSS carrier-phase time transfer, optical-clock timescale architecture and algorithm, GNSS data processing and software development, and GNSS satellite clock estimation. He is also a guest editor for a special issue of GPS Solutions – “timekeeping in space.”