Adam Hall, Luke Jansen, Ethan Paslowski, Paige Ross, & Christopher Utigard
Figure: Saturn’s Rings (Artist’s Concept) Source: http://photojournal.jpl.nasa.gov/catalog/PIA03550 Permission: Public Domain (Courtesy of Wikimedia Commons)
Figure: Jupiter Smyrna Louvre Source: https://commons.wikimedia.org/wiki/File:Jupiter_Smyrna_Louvre_Ma13.jpg Permission: Public Domain (Courtesy Wikimedia Commons)
Introduction
In Roman mythology, there is a tale in which Jupiter, the king of gods, overthrows his tyrannical father, Saturn. In doing so, Jupiter causes Saturn to release all the sons he had eaten in his paranoia that his children would eventually depose him.1 Today, this folklore is more accurate than Roman mythologists could have ever realized. Following the discovery of the telescope and the age of space flight, Saturn has revealed more “sons” to astronomers in the form of moons. On Monday, October 7, 2019, the International Astronomical Union’s Minor Planer Centre announced that Saturn had deposed Jupiter as the reigning moon-count champion of the solar system.2 Saturn, also known as the ringed planet, achieved this title through the discovery of 20 moons by astronomers working with the Subaru Telescope in Hawaii.
The newly discovered moons are quite small and distant from Saturn; however, these “estranged children” are if profound importance to the study of astronomy. There is much yet to be understood about the nature of reality and the study of cosmology. Even today, scientists continue to puzzle over the rate of expansion of the universe and its enormous size, the existence of dark matter and dark energy, the composition of quantum foam, and much more. Although these small moons may appear irrelevant to such existential questions, it is important to note that the history of the solar system is a crucial testing ground for any theory of how this or other solar systems may have formed. The amalgam of this knowledge is essential to our understanding of the universe and plays a critical role in determining the fundamental laws of reality. The story of these moons spans roughly 400 years, from the earliest known iteration of the telescope to such technological marvels as the Subaru Telescope, and some crucial spacecraft in between. Advancements in technology have played a crucial role in this narrative.
This paper will investigate how advances in ground-based and space probe technology led to the recent discovery of Saturn’s additional 20 moons. To accomplish this, there will be a brief look at the history of Saturnian observation before delving into two branches of principle technological developments: the first being the Subaru Telescope in Hawaii; and the second being the Cassini Spacecraft which plunged into Saturn, to its demise on September 15, 2017.3 Finally, there is consideration dedicated to how these technologies resulted in the discovery of the newfound Saturnian moons.
Figure: Galileo Telescope Replica Source: https://commons.wikimedia.org/wiki/File:Galileo_telescope_replica.jpg?fbclid=IwAR38qITRmdqckhTnthjsJhve_d90Tu8hDo4O83c7u0WeGF-XxiL4ijDm1E8 Permission: Creative Commons (Courtesy of Wikimedia Commons)
Background
The first telescope and the numerous updated versions since, played a massive role in the discovery of the new moons. The 17th century invention created a parade of early astronomers – Galileo Galilei, Giovanni Cassini, William Herschel, and many others – that trained their telescopes on the ringed-planet, observing, recording, and sharing their findings with the astronomical community.4 Over the next three hundred years, their collective reports unmasked a variety of Saturnian features ranging from ring characteristics to the identification of various individual moons and their orbits, and in the case of Titan, Saturn’s largest moon, even a confirmation of its atmosphere.5
Nevertheless, these telescopic discoveries only accounted for eight of the 82 currently known moons. At the time, the principle obstruction was in the size and sophistication of the telescopes. Consider, for instance, that Galileo, using a telescope with an eight-times magnification, was unable to observe the rings of Saturn with his telescope, and thus, mistook the planet’s oblong shape for a deformity.6 Saturn’s rings require roughly 20-times magnification for observation. As such, they remained invisible until Christiaan Huygens trained a telescope of sufficient magnification upon the planet.7
Accordingly, the next crucial advance was telescopic photography. In the 19th century, astronomers began the practice of stellar photography, and in 1899, were able to identify a ninth moon: Phoebe.8 It would not be until 1966, about 67 years later, that another moon, Janus, would be discovered. Confirmation of this tenth moon was not realized until 1978.9 By this time, means of discovery had drifted into space travel. In the late 1970s, the Voyager 1 spacecraft was already on its way across the solar system.10 Through observations and photography of its own, Voyager 1 was able to initially raise the total moon count to 17.11 Careful reviews of the Voyager 1’s archival images revealed an additional moon, Pan, which was discovered in 1990.11
Technological Advancement #1: The Subaru Telescope
Figure: Mauna Kea Subaru Source: https://commons.wikimedia.org/wiki/File:MaunaKea_Subaru.jpg Permission: Creative Commons (Courtesy of Wikimedia Commons)
The first of two crucial innovations in technology that allowed for the discovery of Saturn’s newfound 20 moons was the creation of the Subaru Telescope. The telescope was built by astronomers seeking to explore the unknowns of outer space and increase the base of knowledge of the universe.12 The Subaru Telescope has enabled the expansion of the observation of the galaxy, allowing astronomers to investigate planetary systems further.12 Through observation and data collection provided by the Subaru Telescope, scientists aim to determine the origins of life and provide a view of the universe far wider than ever before seen.12
Location, Location, Location
Figure: Map of Mauna Kea Source: https://commons.wikimedia.org/wiki/File:Location_Mauna_Kea.svg Permission: Public Domain (Courtesy of Wiki Commons)
The location of the Subaru Telescope plays a major role in its advanced imaging capabilities which allowed for the discovery of Saturn’s new moons. It is located on the summit of Mauna Kea, a dormant volcano on the Big Island of Hawaii.12 The top of Mauna Kea is an isolated peak that protrudes above most of the Earth’s weather systems, which means the air pressure is only two-thirds of that of the sea level.12 Clouds typically form below the summit where an inversion layer, which is a sudden increase in temperature, keeps the clouds from rising to the summit.12 Because Hawaii is isolated from any other landmass, trade winds blow smoothly over the islands, and there are few cities to pollute its dark skies.12 The location has been recognized as one of the best astronomical observing sites because of these distinct features; it has also been defined as an irreplaceable natural and cultural resource for scientific discovery.12
The Features
The technology of the Subaru Telescope is as revolutionary as it was pivotal in the discovery of the new moons. The discovery of Saturn’s 20 minuscule moons was enabled by the Subaru Telescope’s advanced imaging technology.13 The Subaru Telescope is an optical, infrared telescope. Infrared ins one of many types of radiation present on the electromagnetic spectrum; it has a longer wavelength than visible light and cannot be seen with the human eye.14 The telescope has a wide field imaging capability which is 200-times greater than that of the Hubble Space Telescope.12 Wide-field imaging is different from regular field imaging because it uses a wide-aperture lens to capture the image rather than a standard width lens.15 The aperture of a telescope determines how much light will be collected by the device; as such, the higher the aperture, the greater the amount of light collected, and the better the image is produced.16 This feature, coupled with the telescope’s large mirror, sensitive charged-coupled device detectors, and its optimal location, gives the Subaru Telescope the ability to capture unique imaging.12
The Subaru Telescope also has other distinct features, including the fact that the primary mirror is equipped with an 8.2-meter aperture which is combined with an active support system that can preserve an unprecedented high mirror surface accuracy.12 The amount of light that is collected by a telescope is proportional to the square of its diameter; therefore, the Subaru Telescope’s large diameter is especially impressive. It allows for greater light gathering ability and enhances the resolution of images which results in brighter, more resolved pictures. These features were crucial in the discovery of Saturn’s new moons because it made the appearance of the objects clear enough to decipher. The active support system was also contributory to the telescope’s ability to spot the moons. It is equipped with many notable features. The enclosed design suppresses local atmospheric turbulence which allows for smoother travel and clearer images. The system’s tracking mechanism is exceptionally precise which results in sharper pictures. This success is due to the prevention of drifting, which causes “smearing” of objects across the image frame.17
Figure: Subaru Telescope Under Daylight Source: https://en.wikipedia.org/wiki/File:Subaru_Telescope_under_daylight.jpg Permission: Creative Commons (Courtesy of Wikimedia Commons)
The Subaru Telescope also undergoes constant fine-tuning to ensure it has the highest resolving power possible, thus, producing sharper views of the features being observed.12 The telescope also comes equipped with a computer-controlled support system that keeps the smooth, single-piece primary mirror in shape.12 The mirror’s cylindrical shape enclosure minimizes air turbulence.12 Finally, the Subaru Telescope’s linear motors ensure that it is driven smoothly and accurately.12 The combination of the telescope’s unique features and impressive design allowed the device to capture high-quality images of Saturn’s new moons.
The Future of the Device
Despite the Subaru Telescope’s innovative technology and first-class image gathering ability, there are still improvements to be made. Astronomers intend to upgrade the adaptive optic system by adding actuators; this alteration will increase the telescope’s efficiency under poor visibility conditions and improve it for use at shorter wavelengths.18 They also plan to introduce a laser guide star system, which will hopefully allow the telescope to view a greater number of observable objects.18 The new adaptive optics system will demand a bright guide star near the observation target to allow the measurement of disturbances in wavelength.18 The concept behind the laser guide system is to provide astronomers with an artificial guide star when a natural guide star is missing.18 The objective of implementing these improvements is to allow the bulk of the sky to be observed and accessible from Mauna Kea.18 As discussed, the Subaru Telescope and its many features were vital in the discovery of the new moons. The telescope’s advanced technology allowed astronomers the first look at faint spots of light which were hypothesized to be additional moons.19 These intriguing points of light and computer techniques allowed multiple years of telescope imagining data to be analyzed. In turn, this examining enabled astronomers to confirm that the 20 dots of light were orbiting Saturn.19
Technological Advancement #2: The Cassini Spacecraft
The second of the two critical innovations in technology that enabled the discovery of Saturn’s additional moons was the Cassini spacecraft. The most recent discoveries mark a momentous leap forward in space exploration. Improvements in technology have allowed scientists to record multiple years of telescope images which in combination present a clear enough image to confirm the new moons.19 Accompanying the innovation of the telescope, was the Cassini-Huygens Mission. Previous missions, such as the Voyager flyby in the 1970s and the Pioneer flyby in the 1980s, introduced rough drafts of Saturn’s moons.20 However, neither of these flybys was as focused and extensive as the Cassini spacecraft, as they did not have the capability on board to latch onto Saturn’s orbit.21 During its many years in Saturn’s orbit, the Cassini spacecraft viewed previously undetermined moons and aided knowledge relating to the known objects.22
Figure: Voyager Spacecraft Source: https://en.wikipedia.org/wiki/File:Voyager_spacecraft.jpg Permission: Public Domain (Courtesty of Wikipedia)
The History of the Mission
On October 15, 1997, the Cassini spacecraft was launched as part of the Cassini-Huygens mission.23 The spacecraft was the first of its kind dedicated to observing Saturn and its surrounding system.24 Its namesake is Giovanni Cassini, the astronomer responsible for discovering four of Saturn’s moons, including Lapethus, in 1671; Rhea in 1672; Tethys, in 1686, and Dione, in 1684.24 The Cassini-Huygens mission combined three major space agencies: the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA), and the Italian Space Agency (ASI).25 Designed to explore Saturn’s rings and moons, with a special focus on Titan, the mission came at the cost of 3.3 billion US dollars.24 The spacecraft was launched on October 15, 1996, however, the mission did not commence until July 1, 2004.24 Prior to the Cassini launch, there were 18 confirmed moons orbiting Saturn.26 During the spacecraft’s travel, 13 more moons were confirmed via Earth-based telescopes.27
The Cassini Spacecraft’s Visit
Figure: Cassini Spacecraft Source: https://commons.wikimedia.org/wiki/File:Cassini_spacecraft_raw_uncompressed.png Permission: Public Domain (Courtesy of Wiki Commons)
Upon its arrival, the Cassini spacecraft used its new-age technology to discover two new moons: Methone and Pallene.28 Before the mission’s first year ended, it uncovered a third new moon, Polydeuces.24 November 2016 through April 2017, the Cassini spacecraft encountered and confirmed four smaller moons: Atlas, Daphnis, Pan, and Pandora.24 These seven moons are included in the twenty newly confirmed moons. The spacecraft was left to orbit Saturn for over a decade, during which it was able to observe the planet’s moons.29 The records of observation were used to improve the accuracy of information about the understanding of the moons’ relationship with Saturn’s rings.30
The Technology Behind the Success of the Mission
The Cassini spacecraft was equipped with advanced technology, including several instruments with the ability to view wavelengths of light and energy.31 The spacecraft used optical remote sensing for a variety of tasks, such as calculating measurements from far away, determining the quantity and composition of dust particles, as well as assessing the strength of plasma and radio waves.32 Simply phrased, remote sensing is measuring a characteristic from a distance, like radar reading the speed of a passing vehicle.33 The sensing component of the spacecraft is composed of a composite infrared spectrometer, an imaging science subsystem, an ultraviolet imaging spectrograph, and a visible and infrared mapping spectrometer.34 The instruments used to study Saturn’s environment, including dust, plasma, and magnetic fields, were the Cassini plasma spectrometer, a cosmic dust analyzer, an ion and neutral mass spectrometer, a magnetometer, a magnetospheric imaging instrument, and radio and plasma wave science.35 Additionally, the Cassini spacecraft used radio waves to map the atmosphere and determine the mass of the moons. Its radar, and radio science subsystem were used to unveil the surface of Titan.20 Essentially, the use and combination of these advanced scientific features on the space vessel were able to confirm the accuracy of images provided by other means, such as ground-based telescopes.
The findings made possible by this technology have an important context in modern astronomy. For example, the data collected provides evidence that some of the moons’ characteristics make them potentially habitable. The information harnessed from the Cassini-Huygens mission has also encouraged future endeavors in search of other solar systems.24 In conclusion, the Cassini-Huygens mission is linked to the discovery of Saturn’s 20 newly discovered moons as it was responsible for confirming the existence of seven of them.36 The cutting-edge technology onboard the spacecraft was able to provide scientists with enough accurate information and imaging to justify the confirmation of nearly half of the new moons.
Figure: Artist’s concept of Cassini and Saturn Source: https://www.nasa.gov/mission_pages/cassini/media/cassini-071204.html?fbclid=IwAR11ok0uMRIAebH3DpUlSQyxwN8021D1hQ-mtOqOQ-uaoSG4JmFGN4uLbBo Permission: Public Domain (Courtesy of NASA)
The Moons of Saturn
As explained, the combination of two technologies, the Subaru Telescope and the Cassini spacecraft, has contributed to a deeper understanding of Saturn’s moons. This insight of the moons sheds light on many questions surrounding their existence: where did they come from, why did scientists not see them before, and are there more moons out there? The following content will address these concerns and provide an explanation for the importance of their discovery.
How Are Moons Created?
In general, moons are created through the compaction of debris, such as comets or asteroids, captured by a planet’s gravity.37 Astronomers, such as Scott Shepard of the Carnegie Institute for Science, propose that these moons were created from impacts with Saturn. Sheppard and his colleagues theorize that the moon clusters formed from larger satellites captured by Saturn shortly after its formation.38 The parent bodies were then broken up over time by collisions which created the moon fragments now seen by astronomists.39 Scientists also note that due to their proximity from Saturn, it is likely that these moons were formed more recently, even in the past 100 million years, than the rest of the solar system.40
Why Did Scientists Not See Them Before?
These newly discovered moons were previously undetected due to their size. Measuring around three miles wide, these satellites were too small to be seen with past telescopes. As mentioned, the Subaru Telescope was only able to discover them because of its excellent light-gathering and resolving power and the Cassini spacecraft because of its ability to travel to proximity. It is also important to note that these moons barely fell into the realm of the Subaru telescope’s detection limit.38 As such, recent research suggests that there may be as many as 100 moons orbiting Saturn, but many are even smaller, under one kilometer wide, and unable to be detected by current telescope technology.39
Figure: Group Portrait Source: https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA12797 Permission: Public Domain (Courtesy of NASA)
All About the Moons
The batch of 20 new moons falls into two categories of orbit: retrograde and prograde. Seventeen of the moons orbit Saturn in retrograde, while the other three circle the planet in prograde.38 Retrograde means that the moon’s orbit follows the opposite direction of Saturn’s rotation, whereas prograde means that they travel in the same direction as the planet’s rotation.41 The moons are also divided further into satellite groups. Saturn’s moons are organized into three satellite groups based on the direction and inclination of their orbit: the Norse Group, which orbit in retrograde; the Inuit Group, which orbit in prograde at inclinations between 40 and 50 degrees; and the Gallic Group, which also orbit in prograde but at inclinations between 35 and 40 degrees.42 The group of seventeen fit into the Norse Group. Then two of the remaining three are part of the Inuit Group with the last belonging to the Gallic Group.38 To date, the twenty new moons remain unnamed but will be labeled with a culturally appropriate name according to which group they fall under.
Are There More Moons Out There?
Considering how Shepard and his team were able to make a similar moon discovery related to Jupiter last year, using the same technology, it is likely that astronomers will continue to uncover more objects orbiting the solar system.43 These types of discoveries have a tremendous impact on the scientific community, as they can answer questions about how planets were formed and how they have evolved. For example, moons can indicate what collisions took place in the formation of the solar system.38 More specifically, Saturn’s moons are of interest to astronomers because they can collect material from Saturn’s rings and magnetosphere, which is a region of the planet that is magnetically charged.30 The composition of a moon can also tell astronomers more about the materials present in our solar system.
As a result of this discovery and others, there are currently three missions in progress: NASA’s Europa Clipper, NASA’s Dragonfly mission, and the ESA’s JUICE mission.38 The Europa Clipper is due to launch in 2025 and will arrive at Jupiter’s moon, Europa, by 2030.44 These missions, like the Cassini-Huygens mission, will be used to collect information on the compositions of moons surrounding the giant planets: Titan, the largest moon orbiting Saturn; and Europa, and the icy moons, circling Jupiter.45
Figure: Space Future Source: https://pixabay.com/photos/space-future-world-planet-fantasy-3953457/ Permission: Creative Commons (Courtesy of Pixabay)
Conclusion
The past half-century has seen an unprecedented explosion of Saturnian knowledge due to rapid innovation in telescope and spaceflight technologies. As discussed, the Subaru Telescope contributed to spotting the new moons, as its excellent light-gathering ability and high resolving power enabled it to see further and clearer than previous telescopes. The Cassini spacecraft’s proximity and specialized stellar photography instruments provided the partial confirmation of the new moons. Accordingly, the discovery of these 20 new moons is vital to astronomy because it can provide astronomers information as to how the solar system formed, what types of materials are present surrounding Saturn, and insight as to how to improve the technologies to see even further. This information illuminates the history of the solar system like never before, yet new questions continue to arise and multiply. Still, the great success of these technologies will serve to guide the three missions in progress and many subsequent endeavors. Hopefully, in another half-century, astronomers will be publishing new discoveries being made with technologies created in the future based on the telescopes and spacecraft used today which will make questions like those discussed in this paper seem as outdated as Galileo’s observations.
References
1 New World Encyclopedia, Jupiter (Mythology), https://www.newworldencyclopedia.org/entry/Jupiter_(mythology) (Accessed 5 November 2019)
2 W. Dunham, Saturn is the solar system’s ‘moon king,’ with 20 more spotted, https://www.reuters.com/article/us-space-saturn/saturn-is-the-solar-systems-moon-king-with-20-more-spotted-idUSKBN1WO2VD (Accessed 5 November 2019)
3 EarthSky, Goodbye, Cassini!, https://earthsky.org/space/cassini-finale-sept-15-2017-how-to-follow-online (Accessed 21 November 2019)
4 N. English, Chronicling the Golden Age of Astronomy, (Springer International Publishing, 2018), p. 35
5 N. Redd, Titan: Facts About Saturn’s Largest Moon, https://www.space.com/15257-titan-saturn-largest-moon-facts-discovery-sdcmp.html (Accessed 21 November 2019)
6 NASA, Galileo’s Observations of the Moon, Jupiter, Venus and the Sun, https://solarsystem.nasa.gov/news/307/galileos-observations-of-the-moon-jupiter-venus-and-the-sun/ (Accessed 5 November 2019)
7 P. Louwman, Christiaan Huygens and his telescopes, (Springer Netherlands, 2004), p. 103-114
8 M. Williams, The moons of Saturn, https://phys.org/news/2015-09-moons-saturn.html (Accessed 6 November 2019)
9 NASA, Janus, https://solarsystem.nasa.gov/moons/saturn-moons/janus/in-depth/ (Accessed 5 November 2019)
10 NASA, Planetary Voyage, https://voyager.jpl.nasa.gov/mission/science/planetary-voyage/ (Accessed 21 November 2019)
11 NASA, Fact Sheet: The Voyager Planetary Mission, https://voyager.jpl.nasa.gov/frequently-asked-questions/fact-sheet/ (Accessed 6 November 2019)
12 Subaru Telescope, Subaru Telescope: The Challenge, https://subarutelescope.org/Introduction/overview.html (Accessed 6 November 2019)
13 Subaru Telescope, Subaru Telescope: Basic Design, https://subarutelescope.org/Introduction/outline.html (Accessed 6 November 2019)
14 NASA, Tour of the Electromagnetic Spectrum, https://science.nasa.gov/ems/07_infraredwaves (Accessed 10 November 2019)
15 A. Pavuluri, Astrophotography 101: Getting Started With Wide Field Astrophotography, https://www.firstpost.com/tech/news-analysis/astrophotography-101-getting-started-with-wide-field-astrophotography-4052261.html (Accessed 21 November 2019)
16 T. Vorenkamp, Understanding Exposure, Part 2: Aperture, https://www.bhphotovideo.com/explora/photography/tips-and-solutions/understanding-exposure-part-2-aperture (Accessed 10 November 2019)
17 Telescopes Plus, Computerized Go To and GPS Telescopes, https://www.telescopesplus.com/blogs/helpful-information/18961988-computerized-goto-and-gps-telescopes (Accessed 19 November 2019)
18 Subaru Telescope, AO System, https://www.subarutelescope.org/Introduction/instrument/AO.html (Accessed 5 November 2019)
19 M. Greshko, Discovery of 20 new moons gives Saturn a solar system record, https://www.nationalgeographic.com/science/2019/10/discovery-20-new-moons-gives-saturn-solar-system-record/ (Accessed 4 November 2019)
20 NASA, Cassini, https://solarsystem.nasa.gov/missions/cassini/mission/spacecraft/cassini-orbiter/ (Accessed 7 November 2019)
21 W. Harwood, Saturn Orbit Insertion is a time of nervous anticipation, https://www.spaceflightnow.com/cassini/040612soi.html (Accessed 21 November 2019)
22 S. Bates, With 20 new moons, Saturn now has the most of any solar system planet, https://www.sciencenews.org/article/20-new-moons-saturn-now-most-any-solar-system-planet (Accessed 5 November 2019)
23 NASA, Mission to Saturn: Cassini-Huygens, https://www.jpl.nasa.gov/missions/cassini-huygens/ (Accessed 20 November 2019)
24 E. Howell, Cassini-Huygens: Exploring Saturn’s System, https://www.space.com/17754-cassini-huygens.html (Accessed 7 November 2019)
25 I. Muiller-Wodarg, C. Griffith, E. Lellouch, and T. Cravens, Titan: Interior, Surface, Atmosphere, and Space Environment, (Cambridge University Press, 2014) p. 1
26 NASA, Cassini Mission Press Kit, https://www.jpl.nasa.gov/news/press_kits/cassini.pdf (Accessed 21 November 2019)
27 N. Redd, Saturn’s Moons: Facts About the Ringed Planet’s Satellites, https://www.space.com/20812-saturn-moons.html (Accessed 20 November 2019)
28 J. Rogerson, Understanding Saturn, its rings, and its moons: The Cassini-Huygens Mission, https://ingeniumcanada.org/channel/articles/understanding-saturn-its-rings-and-its-moons-the-cassini-huygens-mission (Accessed 19 November 2019)
29 B. Resnick, NASA crashed the $4 billion Cassini spacecraft into Saturn. It was awesome., https://www.vox.com/science-and-health/2017/9/13/16294502/cassini-finale-2017-saturn-rings-crash-nasa (Accessed 19 November 2019)
30 NASA, Saturn Moons, https://solarsystem.nasa.gov/moons/saturn-moons/overview/?page=0&per_page=40&order=name+asc&search=&placeholder=Enter+moon+name&condition_1=38%3Aparent_id&condition_2=moon%3Abody_type%3Ailike (Accessed 7 November 2019)
31 ESA, Cassini-Huygens, https://sci.esa.int/web/cassini-huygens/-/34954-instruments (Accessed 20 November 2019)
32 L. Spilker, Passage to a Ringed World, (NASA, 1997) p. 101
33 Natural Resources Canada, Fundamentals of Remote Sensing, https://www.nrcan.gc.ca/sites/www.nrcan.gc.ca/files/earthsciences/pdf/resource/tutor/fundam/pdf/fundamentals_e.pdf (Accessed 10 November 2019)
34 NASA, Visible and Infrared Mapping Spectrometer (VIMS), https://solarsystem.nasa.gov/missions/cassini/mission/spacecraft/cassini-orbiter/visible-and-infrared-mapping-spectrometer/ (Accessed 20 November 2019)
35 NASA, Ion and Neutral Mass Spectrometer (INMS), https://solarsystem.nasa.gov/missions/cassini/mission/spacecraft/cassini-orbiter/ion-and-neutral-mass-spectrometer/ (Accessed 19 November 2019)
36 E. Howell, Cassini’s 13 Greatest Discoveries During Its 13 Years at Saturn, https://www.space.com/38142-cassini-greatest-saturn-discoveries.html (Accessed 20 November 2019)
37 ESA, ESA – Space for Kids – Moons, https://www.esa.int/kids/en/learn/Our_Universe/Planets_and_moons/Moons (Accessed 7 November 2019)
38 M. Greshko, Discovery of 20 new moons gives Saturn a solar system record, https://www.nationalgeographic.com/science/2019/10/discovery-20-new-moons-gives-saturn-solar-system-record/ (Accessed 7 November 2019)
39 M. Dunn, Discovery of 20 new moons puts Saturn ahead of Jupiter, https://www.kcbd.com/2019/10/07/discovery-new-moons-puts-saturn-ahead-jupiter/ (Accessed 7 November 2019)
40 L. Shekhtman, 10 Things: Unsolved Mysteries of Saturn’s Moons – NASA Solar System Exploration, https://solarsystem.nasa.gov/news/911/10-things-unsolved-mysteries-of-saturns-moons/ (Accessed 7 November 2019)
41 Merriam-Webster, Definition of RETROGRADE, https://www.merriam-webster.com/dictionary/retrograde (Accessed 7 November 2019)
42 M. Wall, 20 New Moons Found Around Saturn, Snagging Satellite Record from Jupiter, https://www.space.com/saturn-20-newfound-moons-naming-contest.html (Accessed 7 November 2019)
43 Carnegie Institute for Science, A dozen new moons of Jupiter discovered, including one “oddball”, https://carnegiescience.edu/news/dozen-new-moons-jupiter-discovered-including-one-%E2%80%9Coddball%E2%80%9D (Accessed 7 November 2019)
44 B. Dunbar, Europa Clipper’s Mission to Jupiter’s Icy Moon Confirmed, https://www.nasa.gov/feature/europa-clippers-mission-to-jupiter-s-icy-moon-confirmed/ (Accessed 7 November 2019)
45 C. Choi, Jupiter: Our Solar System’s Largest Planet, https://www.space.com/7-jupiter-largest-planet-solar-system.html (Accessed 20 November 2019)