A key component of the Advanced Test Reactor (ATR) National Scientific User Facility (NSUF) effort is to develop and evaluate in-pile instrumentation capable of providing real-time measurements of key parameters during irradiation. This paper describes the strategy for prioritizing instrumentation needs and the program to develop new or enhanced sensors to address these needs. Accomplishments from this program are illustrated by describing new sensors now available to users of the ATR NSUF with data from irradiation tests using these sensors. In addition, progress is reported on research efforts to provide users advanced methods for detecting temperature, fuel thermal conductivity, and changes in sample geometry.