The following contribution comes from space historian Jay Gallentine. His book on the turbulent early days, Ambassadors from Earth: Pioneering Explorations with Unmanned Spacecraft (Nebraska, 2014), won the 2009 Eugene M. Emme Award for astronautical literature. His new book Infinity Beckoned: Adventuring Through the Inner Solar System, 1969–1989 (Nebraska, 2016) examines our first intensive reconnaissance of the inner solar system. His next book will feature the Cassini mission to Saturn.
The Wintry Days of Cassini
Last week after some thirteen years in orbit around Saturn, the internationally-backed Cassini spacecraft plunged into the belly of our giant ringed gas planet. She expired in blazes of scientific grandeur and I miss her already.
I was saddened by Cassini’s demise… yet buoyed by the gobs of attention conferred upon her in these final, wintry days. She did not die alone.
The broad spotlight had been a long time coming. Envisaged in the mid-Eighties and launched in October of ‘97, Cassini germinated from a curious mix of desire and politics and budgetary jumbles to become one of NASA’s “battleship flyers,” as a colleague of mine phrased it.
The underlying prime mover of deep space exploration is scientific return. Planetary scientists the world over discuss and deliberate and, at regular intervals, issue strong recommendations for what should next be explored. This directly influences NASA objectives, which in turn leads to space missions. At the time of Cassini’s proposal, Saturn and its suburban neighborhood of moons was of prime importance to explore. We knew something about that area but not a ton. Well, how better to understand the joint than by parking an orbital research station out there for awhile?
People talk about how big the thing was (picture a $3 billion-dollar minivan with a radio dish) and how spaceships that huge don’t seem to get made any more. Understand that back then, a specific attitude prevailed about funding space missions. As the logic went: if you’re already forking out tons of money to fly someplace distant (like Saturn), why not tote along as many science experiments as possible; the next train out may not materialize in your lifetime. “Don’t propose a dinky mission!” chanted the scientists. “Because it won’t have enough experiments to justify the cost. And when you DO finally get funded, crowd on everything possible to get the most bang for the buck!” That translated into enormous one-shot missions lugging along enough sophisticated instrumentation to convince even the most tight-fisted member of Congress. This all-or-nothing attitude would fortunately begin changing in the early Nineties, after an eleven-year gap in planetary missions led NASA to explore scaled-back and lower-cost ventures.
Cassini was realized by a feverishly dedicated group of people whose inner being is propelled by curiosity. They labored for years on end, augmenting proposals and jockeying for dough and refining mission parameters and engineering hardware that’d never before existed. For years they persevered through development and testing, in a continual series of breath-holding moments which didn’t even subside after Cassini reached the launch facilities. Protesters attempted to storm the pad itself—freaked out by seventy-two pounds of plutonium the ship carried to power and warm her various onboard systems. “STOP CASSINI!” warned the protesters. Their concerns were historically and statistically unfounded, yet they came anyway—scaling barbed-wire fencing to be hauled off by law enforcement.
Ideally, those protesters ultimately had their minds changed by Cassini’s jawdropping scientific returns. One key highlight saw the craft drop a modest lander onto Saturn’s moon Titan—a hotbed of potentiality with liquid lakes and complex organics and possible life forms. On another moon called Enceladus, Cassini found plumes of liquid water billowing off its south pole (and later flew through them). The hits continued for over a dozen years.
While talking with a friend this morning, she confessed to knowing little about Cassini. Yet she felt intrigued by this business of deliberately shredding the craft in Saturn’s atmosphere. Was there something wrong with it, she asked? Was it broken?
I explained that Cassini is running low on maneuvering fuel. She could very likely still harbor Earth microbes, which wouldn’t exactly be the best thing to put on Titan or Enceladus should the machinery tumble out of control and pile into either one. And so, before Cassini even begins to lose footing, steps had been very carefully planned out to annihilate the craft so that she’d never pose a risk to any world. Saturn is just a massive gas ball so no issue there.
To achieve this collision, flight controllers orchestrated Cassini through a series of increasingly treacherous maneuvers past the planet itself and between segments of its rings. Maybe the ship could’ve been parked in a more stable orbit around Saturn. But these final acrobatic loops—never possible during regular operations—were of such enormous scientific merit that they justified the plunge. These maneuvers actually began in 2016 because space is large and can take awhile to navigate. They ended as intended and the beloved adventurer is no more.
Dear Cassini, we thank you for serving humanity—for extending our knowledge of the solar system, and for paving the way to even more expansive studies of the remarkable worlds beyond our own.