Part of the book: Advances in Spacecraft Systems and Orbit Determination
Once spacecraft are launched, it is impossible for engineers to physically repair anything that breaks onboard the vehicle. Instead, remote solutions must be employed to address spacecraft anomalies and fault conditions. To achieve this goal, telemetered data from the spacecraft are collected and assess by ground personnel to resolve problems. However, if the ground-to-spacecraft communication system breaks down, or the vehicle delivers an anomalous signal, a rigorous protocol must be employed in order to re-establish or fix the telecommunications link. There are several factors that can contribute to link problems, such as malfunctions or mishandling of the ground station equipment, onboard failures of the spacecraft’s flight software coding, or even mishaps caused by the space environment itself. This chapter details the anomaly recovery protocols developed for the Cassini Mission-to-Saturn project, to resolve anomalous link problems as well re-acquisition of the spacecraft should a complete Loss of Signal (LOS) condition occur.
Part of the book: Space Flight
Robotic interplanetary spacecraft sent to the outer planets of our solar system face many challenges: maintaining internal health and functionality of spacecraft subsystems handling material stresses from solar heating close to Earth, the cold of deep space once the destination is reached, solar radiation and bombardment of cosmic rays; maintaining adequate power to support engineering devices and science instruments; handling time-critical onboard faults in the presence of the long round-trip light time; and preserving one-time “crucial event” activities such as moon/planet flybys, deployment of the probe, and selected science targets. As an example, this chapter details the strategy implemented on the Cassini Mission-to-Saturn spacecraft, how its onboard subsystems are protected and maintained, the advantage of automated onboard fault protection monitor/response routines, protocols implemented to preclude human error in uplinked sequences, and updating onboard flight software as new discoveries are uncovered about the adverse flight environment, so that mission objectives are met under the presence of an ever-increasing delay between ground issued commands and the Cassini spacecraft as it approaches the Saturnian system, safeguarding planetary protection constraints as the spacecraft was deposited into the planet in a final fiery plunge.
Part of the book: Aerospace Engineering