11 October 2018
Cassini-Huygens: Explorer of Saturn
The Cassini-Huygens Spacecraft was the largest interplanetary spacecraft built by NASA to date. This mission was funded as a collaboration between NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI). The total cost of this mission has been estimated at $3.26 billion USD. Upon the completion of the spacecraft’s assembly, it measured 22 feet high and 13 feet wide. The final mass of the orbiter probe weighed at 4,740 lbs. while the probe weighed 770 lbs.
The Cassini-Huygens space mission was designed with 5 primary objectives in mind. The first objective was to study the planet, Saturn. The collaboration hoped to learn more about the properties of Saturn’s clouds, atmospheric conditions, rotation, horizontal motions (storms, waves, eddies), and the structure and evolution of the planet. The second objective was focused on Saturn’s rings. The collaboration hoped to learn more about the composition of the rings, their microscale properties, age, 3D structure, and dynamic behaviors. Third, the collaboration wanted to study Saturn’s moon, Titan. Once on Titan, they hoped to learn about the constituents of its atmosphere, its winds and temperature, physical state and topography, cloud physics, and seasons. Fourth, the collaboration was interested in the icy satellites orbiting Saturn. They wanted to determine the surface and sub- surface geology of these satellites including the sources of their surface and subsurface structures. Also, they wanted to study the interaction of these satellites with Saturn’s magnetosphere, ionosphere, and atmosphere.
Finally, the collaboration aimed to study the 3D structure and dynamics of Saturn’s magnetosphere. Specifically, they wanted to better understand its electrical currents and how they relate to solar wind, Titan, and the surrounding satellites and rings.
The Cassini-Huygens spacecraft was designed with 2 substituents: Cassini and Huygens. Cassini, would reside within Saturn’s orbit throughout its lifespan while Huygens, a probe, would be propelled onto the surface of Saturn’s moon, Titan. Huygens was designed with two constituent parts: the entry assembly module and the descent module. The entry module was designed to carry the equipment necessary to control Huygens after its separation from Cassini. This module contained a shield that would act as a brake in addition to providing thermal protection from the high amount of heat absorbed upon entering Titan’s atmosphere. The descent module was composed of many scientific instruments to collect data from Titan’s surface as well as 3 distinct parachutes to aid in landing.
While there were many scientific instruments aboard the Cassini-Huygens spacecraft, I will focus on 3 primary instruments: The Cassini Plasma spectrometer (CAPS), the surface science package (SSP), and the imaging science subsystem (ISS). First, as the spacecraft was orbiting around Saturn, the CAPS allowed Cassini to analyze ions and electrons present in various locations around Saturn. The data collected from this instrument provided scientists insight on characteristics of Saturn’s magnetosphere. Second, The SSP consisted of nine independent sensor systems which allowed for the determination of characteristics on Titan’s surface at the landing site (thermal, optical, acoustic, etc.). The SSP allowed scientists to gain a better understanding of the major constituents of Titan’s surface as well as atmospheric and oceanic evolution. Finally, the ISS served as the spacecraft’s main eyes. The ISS captured the majority of its images in visible light and supplied us with hundreds of thousands of images of Saturn, its moons, and its rings.
On October 15, 1997, the Cassini- Huygens spacecraft was successfully launched from Cape Canaveral’s Launch Complex 40 aboard the Titan IVB/Centaur rocket. This rocket was the US Air Force’s most powerful, single use rocket. The Titan IVB was developed as a member of a family of missiles based on the original Titan Intercontinental Ballistic Missile. The rocket, with a height equivalent to a 22-story building, was launched at 4:43 EDT. Two minutes and 23 seconds later, the Titan IVB launch vehicle separated. At this moment, the 4,740 lb. object was traveling at a speed over 7,000 km/ hr. After 42 minutes and 40 seconds of flight time, the Centaur upper stage separated from the spacecraft- allowing it to fly on its own for the first time. 10 minutes later, communication between the spacecraft and NASA was confirmed.
In order to travel through space, the Cassini-Huygens spacecraft generated power from the decay of 33 kg of plutonium- the largest amount of radioactive element ever launched into space. In order for the Cassini-Huygens to reach its target, however, gravity assist was used. When a spacecraft enters and leaves the gravitational sphere of a planetary body, its velocity or trajectory may be changed relative to the sun. This common maneuver used in interplanetary travel allows the spacecraft to reach its final destination with much less fuel. The Cassini-Huygens spacecraft used the VVEJGA (Venus- Venus- Earth- Jupiter Gravity Assist) trajectory in order to reach Saturn. This trajectory allowed the spacecraft to reach Saturn in 6.7 years (July 1, 2004). Shortly after its arrival to Saturn, Huygens was released (December 25, 2004) and landed on Titan. Cassini, on the other hand, continued to orbit Saturn.
In conclusion, Cassini-Huygens provided scientists with a vast array of new information.
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