July 13, 2024

I, Science

The science magazine of Imperial College

On the 15 September 2017, after almost 20 years of unprecedented insight in to Saturn and its satellites, NASA's unmanned spacecraft, Cassini, will crash in to Saturn, marking the end of its journey. In this new series, we celebrate Cassini and some of its achievements.

Hello everyone,

My name is Cassini, a NASA spacecraft launched on the 15th October 1997. I am an audacious, energetic, and dedicated craft. Exploring the solar system, Saturn and Saturn’s satellites was my life’s goal, and as I near my final days, I wanted to share my story with you.

When I began my journey in 1997, I packed all of the essential equipment that I would need to complete my mission: thermal blankets to protect me from being burnt or frozen; a pair of glasses named ‘Imaging Science Subsystem’, to help me see what was around me and enable me to capture essential moments by taking photographs; and a highly sensitive magnetometer to act as my compass.

Energy has been an extremely important resource to sustain me. I have spent most of my time around Saturn, which is too distant from the Sun for me to use solar energy. I have maintained my life by using plutonium-238: a radioactive form of plutonium dioxide. It is a white silver metal and has acted as a radioisotope thermoelectric generator to provide me with the energy that I required. It has generated heat and direct current electricity of around 600 watts to maintain me. My friends, the Galileo, New Horizons and Ulysses spacecrafts, also use this kind of energy. However, I was the first utilise this form to ensure that I could complete such an ambitious mission lasting a minimum of 11 years. Although it was useful for me, it is dangerous to humans as it carries the risk of cancer.

My journey has lasted nearly 20 years with three different phase. The first phase was the 7 years it took me to get to Saturn. During this first leg, I swung around Earth and Jupiter to enable me to enter a gravity-assist trajectory towards Saturn. Thanks to universal gravitation, I was captured as a satellite of Saturn in 2004 and my travels then entered the second phase. However, this phase was a tough periods for me as I was separated from my friend, Huygens, who landed on Titan as part of a joint mission. After this, I entered the final phase of my journey where I have been orbiting Saturn for the last 14 years, taking pictures of the planet and its changing climates. I have sent more than 500GB of scientific data back to NASA and discovered 7 new satellites orbiting Saturn.

I am now preparing for my retirement on the 15th September 2017. It seems like a piece of grievous news, but my makers have already chosen a suitable place for me to enjoy the rest of my life. In the last few months, I have been focusing on my final mission: to complete close flybys of Saturn’s rings. So far, I have successfully completed several passes between the planet and its rings and I will keep lowering my orbit in the next few weeks. After 22 passes, it will be time for me to enter Saturn’s atmosphere and burn up, becoming a part of the planet. This method of retirement was chosen for me so that I do not contaminate some of Saturn’s satellites that may offer potential habitability.

So goodbye to you all, as I boldly go where no one has gone before.

Nuttapon Vachiraroj, Jingzi Huang, Jiawen Shan and Peishan Li – Centre for Academic English, Imperial College London

Banner image: NASA furnished image of Saturn, dottedyeti