An Unknown Remnant of NASA’s Cassini Mission
Cassini/Huygens was probably one of the most ambitious space missions ever. After years of measurements and observations NASA’s Cassini probe plunged into Saturn, leaving only the dead lander Huygens on the moon Titan. Only?
Cassini- Huygens. One of the most ambitious unmanned NASA/ESA space missions ever revolved the majestic ring planet Saturn from 2004 to 2017. After deploying the lander Huygens on the moon Titan, completing almost 300 orbits around the planet and collecting over half a Terabyte of raw scientific data Cassini plunged into Saturn …. becoming one with the planet it accompanied for half an orbit around the Sun (orbit of Saturn around the Sun: around 29 years).
Thankfully, I was part of this great mission. I remember reading about it when I was in elementary school, and years later I was there, sitting in front of large screens with dozens of other scientists at Caltech. Waiting for the last signal or “breath” of Cassini to take. Time passed … and Cassini already plunged into the Gas Giant but it took some more minutes for the signal to arrive Earth. The last signal of Cassini was received.
This very short introduction of Cassini’s final moments does not remotely cover the emotions of the scientists and engineers who participated at this event. The people that designed, built and operated this master piece as well as the scientists that analyzed all the data were sitting there, for a moment, in silence.
Cassini/Huygens left a large digital legacy for us. Tons of data, images, spectra and much more are still there for analyzing. Dozens of Ph.D. thesis, papers and books will be filled for decades. NASA’s last “Cassini-Huygens by the numbers” summary as shown below speaks for itself:
But, Cassini left also a physical remnant: The landing probe Huygens that was deployed in the beginning of this century on Saturn’s largest moon: Titan. A world, deadly for humans and life as we know it here on Earth, but also somehow close with its covering clouds, a dense atmosphere, (methane) lakes and rivers … In the beginning of the 1980 Carl Sagan pushed for a mission to this moon.
Back to the day of the Cassini’s last day: In the evening we had a team meeting in a nearby restaurant. Some colleagues were talking about their first calibration experiments, the “good old times” and then there were the new scientists (like me) that stepped into the project while Cassini was already revolving Saturn for years.
We talked also about the things that Cassini left behind: the huge amount of data and of course the lander.
Talking about the instrument we worked on, the Cosmic Dust Analyzer (CDA), we had some discussions about Cassini’s interplanetary cruise phase durning the 1990s. Then, one thing came into our mind: the protection plate of the instrument. Take a look at the following images:
Both images show the Cosmic Dust Analyzer (CDA) that was later mounted on the Cassini spacecraft. The right image shows the instrument with its 50 cm diameter opening. The concept of CDA: a “telescope” for dust particles to measure their entry velocity, charge, direction and chemical composition. The left image shows the “final” state of the instrument, covered in MLI foil (the golden foil) and an aluminium plate that covers the opening of the instrument. This cover plate was also launched into space to protect CDA during in the beginning from contamination.
But what happened with the plate in space? Was it a cover that was mounted on a simple hinge to open and close the instrument?
Well … not exactly. After leaving Earth’s vicinity Cassini entered its interplanetary cruise phase to reach Saturn. During this phase CDA got rid of its cover plate. The plate’s lock was released and some attached mechanical springs pushed the plate away. CDA was now ready for its first measurement campaigns, while the cover floated away.
The ejection speed, the properties of the plate, the time of the release and other parameters were later, in 2018, considered to conduct a simple simulation of the plate’s dynamics and can be seen in the video below.
The result: another remnant of Cassini is still floating in space. A 50 cm diameter aluminium plate. Maybe it was already discovered as a Near-Earth Object (NEO) and is now considered in one of the large astronomical catalogues. Maybe it is still hidden. Somewhere … out there … between Earth and Saturn, remembering one of the most iconic unmanned spacecraft missions ever made.
Thomas
