I had almost forgotten and might have missed it, had my wife not called to remind me that NASA TV coverage of Cassini’s last moments was about to begin. The Cassini spacecraft arrived in the Saturn system 13 years ago and since that time has provided a seemingly endless stream of incredible discoveries, breathtaking images, and enough data to keep doctoral students occupied for decades to come. But the “seemingly endless” was about to end. When I connected, there was less than one hour remaining in this awe inspiring space mission.
The atmosphere in the control room was a mixture of professionalism, nervous anticipation, and nostalgia. After all these years of discovery, the fuel Cassini required to remain safely in orbit was near exhaustion and stable flight could no longer be sustained. And so, on the 15th of September, Cassini would enter Saturn’s outer atmosphere and be destroyed. But this was much more than the end of a space mission; it was as if we were accompanying a friend on their death bed, a friend who had united a team for many years, had gone above and beyond all expectations regarding the length of their mission, but who had now reached the end of their life. The graphs from the “X” and “S” band radio receiver showed Cassini’s signal strength, but for me, it felt more like watching friend’s vital signs and waiting for the end.
The final minutes were now approaching. Cassini’s high gain antenna was directed toward earth by adjusting the orientation of the whole spacecraft using it’s now fuel starved thrusters. It was programmed to maintain its orientation – its “attitude” – to continue sending data as long as possible. Before long, the telemetry showed a rapid increase in thruster activity, for now Cassini was entering the upper atmosphere of Saturn and was struggling to maintain its attitude in the face of atmospheric drag. All eyes were now on the “X” and “S” band signal graphs… “S” band soon disappeared, then “X” band. Flatline… Our friend was now gone. For what seemed like an eternity, there was stunned silence in the control room. The time of Cassini’s destruction was predicted to within seconds of when it actually occurred, yet when it finally arrived, the feeling was almost of stunned disbelief. I suspect there was not a dry eye in the room. At last, the mission manager and flight director made the call. The Cassini mission had ended.
Cassini will leave behind a rich legacy in both scientific discovery and moments of unparalleled beauty, but it also serves as a rich metaphor for a fulfilling life and noble death. For Cassini was given a mission, a vocation, and equipped as well as possible by its creators. Eventually it was launched on this mission which would evolve as Cassini encountered the reality and harshness of space. It kept at it, completing each phase, and having new phases added as it seemed to say, “I have more fuel, I can do more, I can give more”. Finally after a very long and productive life, its resources were spent. It could do no more. But even then, to the last moment, it clung to life, struggling to keep that antenna pointed at earth to provide every possible bit of data until it literally had nothing left to give. And so its mission ended in what was probably a glorious fireball witnessed by none but God alone.
Cassini was a robotic spacecraft of course, not a person or a saint to be imitated. But the template of its mission was the product of many persons, whose dedication and effort is quite evident. Projecting the humanity of this team into the focal point of the mission, the Cassini spacecraft, is both natural and appropriate. It is ultimately this humanity that is experienced in the metaphoric life and death of Cassini and it is ultimately this humanity that will inspire the lives of generations to come.
