Anomaly Trends for Long-Life Robotic Spacecraft

Abstract

Three unmanned planetary spacecraft to the outer planets have been controlled and operated successfully in space for an accumulated total of 68 years. The Voyager 1 and 2 spacecraft each have been in space for more than 27 years. The Galileo spacecraft was in space for 14 years, including eight years in orbit about Jupiter. During the flight operations for these missions, a total of 3300 anomalies for the ground data and the flight systems have been tracked using the Jet Propulsion Laboratory’s anomaly reporting tool. Methods and results are described for classifying and identifying trends relative to ground system vs flight system, software vs hardware, and corrective actions. Several lessons learned from these assessments can significantly benefit the design and planning for long-life missions of the future. These include the necessity for redundancy to ensure successful operation of the spacecraft, awareness that anomaly reporting is dependent on mission activity not the age of the spacecraft, and the need for having a program to maintain and transfer operation knowledge and tools to replacement flight team members. PERATING long-life interplanetary spacecraft involves the monitoring of spacecraft functionality for both nominal and anomalous behavior. During flight operations for the Voyager and Galileo spacecraft, a total of 3300 anomalies has been tracked using the Jet Propulsion Laboratory’s anomaly reporting tool for ground data and flight systems operations. These anomalous events require evaluation for the proper response required to ensure the continuation of the spacecraft’s mission. For this study, a long-life spacecraft is defined as one designed to function reliably for 10 or more years in the space environment. Although not specifically designed as such, the Voyager and Galileo spacecraft can be viewed as prototypes of long-life spacecraft because of their successful operation spanning several decades. The two Voyager spacecraft launched in 1977 have successfully completed flybys of several outer planets and now are leaving our solar system and flying trajectories taking them into interstellar space. Based on current consumables usage and continued mission operations attention, the spacecraft are expected to continue to return data until 2020. The Galileo orbiter was launched in 1989 and orbited Jupiter from 1995 to 2003 when it was intentionally impacted into the atmosphere of Jupiter just before its consumables were depleted.