Johns Hopkins University Applied Physics Laboratory has been designing, building, and operating spacecraft for over 60 years. They have collected amazing data from the sun to Pluto and beyond. This paper discusses the reliability of APL’s spacecraft focusing on the probability of mission success and mission duration. Traditional and Bayesian methods quantify reliability by aggregating the impact of reliability analyses, data from primary and extended mission periods (operations past design life), operational anomalies, and science data quality.