On Cassini’s last day of service, we pay tribute to the spacecraft that has spent the last 13 years diligently exploring Saturn and its moons. Today, at around 11:55 GMT, the $4-billion-dollar exploratory spacecraft will perform a planned crash into Saturn. Cassini’s final moments will be reflected on Earth with NASA’s Jet Propulsion Lab (JPL) simply losing communications with the spacecraft. This, however, will be long after its actual demise as it takes 20 minutes for signals to be relayed back to Earth.
For many who have worked on the project, some since its inception in the 1980s, the moment will be a bittersweet one. “It’s been part of my life for so long, this spacecraft, it’s going to be a shock to have this happen,” said Thomas Burk, a JPL engineer who has worked on the Cassini mission for over 20 years. Continuing, Burk shared how he felt about the upcoming demise of Cassini saying, “It’s bittersweet in that regard. But it’s a really exciting ending. When we stop getting data, that will be the moment of truth.”
The dramatic finale of Cassini is an unavoidable reality for JPL. The spacecraft is almost out of fuel and its mission has been extended years beyond what it was originally built for. Without its final plunge, Cassini would drift aimless risking contaminating one of Saturn’s moons with microbes from Earth, moons like the ice world Enceladus or Titan, where it rains methane. The plunge will also offer valuable data to JPL scientists as it collects readings of Saturn’s atmosphere, an environment impossible to observe without such dramatic measures.
Leading up to “ the grand finale”, Cassini performed one last flyby of Saturn’s largest moon, Titan. The flyby which quite dramatically (and tragically) has been referred to as the “the goodbye kiss” by mission engineers, took the spacecraft within 119,049 kilometers of the giant moon. In addition to allowing the spacecraft to take its last readings of Titan, the flyby will utilise the moon’s gravity to place Cassini on its final trajectory. “Cassini has been in a long-term relationship with Titan, with a new rendezvous nearly every month for more than a decade,” said Earl Maize, the JPL Project Manager for Cassini. “This final encounter is something of a bittersweet goodbye, but as it has done throughout the mission, Titan’s gravity is once again sending Cassini where we need it to go.”
During its 13-year mission, Cassini has made some astounding discoveries. This is made all the more remarkable when you consider that it was running off just 885 watts at its peak (633 watts at end of mission), the equivalent of an average household coffee machine. With its tiny allotment of power, Cassini traveled 7.9 billion kilometers, performed 162 targeted flybys and completed 294 orbits.
Cassini’s mission highlights include:
- The discovery of icy jets active on Enceladus and the realisation that the moon could be nurturing life within its subsurface oceans.
- Landing the Huygens lander on the surface of Titan. The landing led to the realisation that Titan is far more Earth-like than first thought with rain, rivers, lakes, and seas. The Huygens lander only remained operational for a handful of precious hours, eventually succumbing to the moon’s extreme environment.
- The confirmation of the existence of the hexagon storm (first hinted at by Voyager) in the north pole and the discovery that giant hurricanes rage at both of Saturn’s poles.
- Observing Saturn’s F ring change over time. When Cassini arrived, the ring had vastly different geometry than when it was observed by the Voyager probes.
- The discovery of an additional 40 moons and eight provisional (unconfirmed) moons orbiting Saturn. Before the Cassini mission astronomers had only discovered 18 of Saturn’s moons, 13 of which were discovered by Earth-based telescopes.
Cassini-Huygens was launched on October 15, 1997, from Cape Canaveral, Florida. The spacecraft spent the next five years completing flybys around Earth, Venus, and Jupiter. It finally entered orbit around Saturn on July 1, 2004. For the next 13 years, it gave us a guided tour of Saturn and its 53 moons. On September 15, 2017, Cassini plunged into Saturn’s atmosphere for its grand finale never to be heard from again.