Validity and reliability are crucial when conducting research to ensure the truthfulness of an instrument. This study investigated the measurement functioning of an instrument on students' awareness of space science. The instrument was administered to 206 secondary school students involved in the Sudden Ionospheric Disturbance p outreach program. Two experts evaluated the content validity of the instrument. Data were analyzed using the Winsteps 3.71.0.1 software to obtain the Rasch model analysis (RMA) on item reliability and persons' separation, item measure, item fit based on PTMEA CORR, polarity items, misfit items, unidimensionality, and a person-item map. The findings revealed that the items are valid, reliable, and appropriate to measure awareness of space science.