Saturday September 09, 2017

Cassini's grand finale: 'Like a Jules Verne adventure come true'

Animation of Cassini flying the gap between Saturn's rings

Animation of Cassini flying the gap between Saturn's rings (NASA)

Listen 15:38

Cassini, the school bus-sized spacecraft that first launched in 1997, is entering its final days of exploration of the crown jewel of our solar system — Saturn.

Next week, it will perform its final function and plunge into and burn up in Saturn's atmosphere.

Throughout its nearly twenty year journey, one woman has been Cassini's second set of eyes here on Earth. Her name is Dr. Carolyn Porco. She's the head of Cassini's imaging team. Bob McDonald first spoke with Dr. Porco back in 2004 when the spacecraft flew by Jupiter on its way to Saturn. 

'I think it's going to be a spectacular decade to come because humanity will - by the time we arrive at Saturn we will have set up farthest human robotic outpost that we've ever established.' - Dr. Carolyn Porco on Quirks & Quarks in 2004
Cassini entering atmosphere

Since then, Cassini has surpassed everyone's wildest expectations. From the majestic views of the planet itself, to finding liquid methane lakes on Saturn's largest moon Titan, and even discovering an ocean of water on Enceledus.

Now before Cassini makes its final plunge into Saturn, it has to complete one last tricky task - that is to finish weaving through the narrow gaps between the planet and its inner rings. And effectively gripping the steering wheel at NASA's Jet Propulsion Labratory is Canadian scientist, Dr. Julie Bellerose. She's the orbit determination lead for Cassini's navigation team. 

'So if you can imagine Saturn and the rings, the trajectory is pretty much elliptical trajectory that's pretty much perpendicular to the rings. And so Cassini is flying over the North Pole, diving through the gap in between the rings and Saturn, and then leaving through the south pole, all the way to Titan's orbit, and coming back, so it's a much tighter orbit. It does that every seven days.' - Dr. Julie Bellerose
cassini dive

Rendition of Cassini preparing for its final dive (NASA)

This risky part of the mission is all part of Cassini's grand finale. And according to Dr. Bellerose, it's been keeping the navigation team on their toes. 

'So four or three weeks ago now, when we passed through the upper part of the atmosphere, I realized that Saturn atmospheric density was almost three times as dense as we thought it would be, so we've had to evaluate, do some analysis to figure out if that was safe for the spacecraft, then at the same time, evaluate if we wanted to go deeper in the atmosphere and how that would impact. So it's always a trade. We want to fly the mission, so that we get the most extraordinary science, for sure, and we can meet all the science objectives. At the same time, if we lose the spacecraft then the mission is over.' - Dr. Julie Bellerose

And now the countdown is on to Cassini's final goodbye on September 15th. 

Dr. Porco, who is a planetary scientist, has been the imaging team leader for the Cassini mission since day one, and for her the end is bittersweet.

'I'm having all these feelings. I'm sure many Cassini members feel the same. In fact, I think a lot of the members of the public are feeling the same. It's like the kind of feelings you feel as you are coming upon the end of something that has consumed your life. And of course, all those moments that scientists and in particular, explorers live for - the unexpected find, the surprising revelation, the startling and gorgeous vistas that we were able to see that you can't possibly see anywhere but Saturn. These are the moments that have made all the hard work worth it. So I'm wistful. I'm sentimental. I'm getting a bit weepy, but I also have this unbridled sense of pride and accomplishment. And I can tell you, I'm about to get very obnoxious in making sure it is not lost on anyone what it is we just did. Because we are concluding the longest, the deepest, the most comprehensive scientific exploration of a remote planetary system that was ever undertaken.' - Dr. Carolyn Porco

To hear the entire interview with Dr. Porco, hit the "Listen" button near the top of this page. 


NASA at Saturn - Cassini's Grand Finale