Introduction to the special issue on the 2019 URSI AP-RASC student paper competition

The 2019 URSI Asia-Pacific Radio Science Conference (URSI AP-RASC 2019) was held at the India Habitat Centre, New Delhi, India, during March 10-14, 2019 [1, 2]. This special issue of the Radio Science Bulletin provides a collection of invited papers authored by the recipients of the awards from the URSI AP-RASC 2019 Student Paper Competition.