Cassini Week: Artistic Imagery

We’ve all marveled over Cassini’s images of the Saturn system for more than a decade. Saturn is a truly dynamic place, surrounded by equally dynamic worlds. But Cassini’s images did more than just capture images of these distant places; it created art. Breathtaking ‘landscapes’, magnificent portraits, and photographs perfectly timed and framed. Cassini has all of the skill and talent of a master photographer, with special thanks to its imaging team back on Earth. Below are just a few of my favorite Cassini photos.

Dione, Saturn, Rings, and Enceladus

Dione, Saturn, Rings, and Enceladus – Credit: NASA/JPL-Caltech/SSI

Quintet of Moons

Quintet of Moons – Credit: NASA/JPL-Caltech/Space Science Institute

Janus (179 kilometers, or 111 miles across) is on the far left. Pandora (81 kilometers, or 50 miles across) orbits between the A ring and the thin F ring near the middle of the image. Brightly reflective Enceladus (504 kilometers, or 313 miles across) appears above the center of the image. Saturn’s second largest moon, Rhea (1,528 kilometers, or 949 miles across), is bisected by the right edge of the image. The smaller moon Mimas (396 kilometers, or 246 miles across) can be seen beyond Rhea also on the right side of the image.

Dione, Epimetheus, and Rings

Dione, Epimetheus, and Rings – Credit: NASA/JPL-Caltech/Space Science Institute

Just one more day until Cassini’s Grand Finale. Stay tuned for more Cassini Week celebration.

Cassini Week: Rings

In the famous words of the 21st Century philosopher, Beyoncé, “if you like it then you shoulda put a ring on it”.

In that case, the Universe must have really liked Saturn.

While all of the gas giants in our solar system have rings, Saturn’s are by far the most prominent and celebrated. And while humans have been admiring Saturn’s rings for centuries (when Galileo first discovered them, he described them as Saturn’s ears), it was Cassini that brought them into razor-sharp focus.

Shadows cast on Saturn's A ring.

Shadows cast on Saturn’s A ring. – Credit: NASA/JPL/Space Science Institute

Several sets of shadows are cast onto the A ring in this image taken about a week after Saturn’s August 2009 equinox.

Near the middle of the image, shadows are cast by vertically extended clumps in the kinky, discontinuous ringlets of the Encke Gap in the A ring. These clumps are casting shadows approximately 275 kilometers (170 miles) long, implying a clump height about 600 meters (2,000 feet) above the ring plane.

In the middle left of the image, the waves created by Daphnis (8 kilometers, 5 miles across) on the edge of the Keeler Gap cast shadows on the A ring that are about 450 kilometers (280 miles) long, indicating waves that rise about one kilometer above the ring plane. The moon itself is not visible at this resolution, but it, too, orbits in the Keeler Gap of the A ring. Daphnis has an inclined orbit, and its gravitational pull perturbs the orbits of the particles of the A ring forming the Keeler Gap’s edge and sculpts the edge into waves having both horizontal (radial) and out-of-plane components. Material on the inner edge of the gap orbits faster than the moon so that the waves there lead the moon in its orbit. Material on the outer edge moves slower than the moon, so waves there trail the moon.

The Janus 2:1 spiral density wave

The Janus 2:1 spiral density wave – Credit: NASA/JPL-Caltech/SSI

This view from NASA’s Cassini spacecraft shows a wave structure in Saturn’s rings known as the Janus 2:1 spiral density wave. Resulting from the same process that creates spiral galaxies, spiral density waves in Saturn’s rings are much more tightly wound. In this case, every second wave crest is actually the same spiral arm which has encircled the entire planet multiple times.

Propeller in Saturn's A Ring

Propeller in Saturn’s A Ring – Credit: NASA/JPL-Caltech/Space Science Institute

NASA’s Cassini spacecraft captured these remarkable views of a propeller feature in Saturn’s A ring on Feb. 21, 2017. These are the sharpest images taken of a propeller so far, and show an unprecedented level of detail. The propeller is nicknamed “Santos-Dumont,” after the pioneering Brazilian-French aviator.

Have you heard of Saturn’s propellers before? They’re the result of a very small moon, unseen in the photo above, disturbing ring material. They offer a unique opportunity for researchers to track the orbits of unseen objects that are embedded within a disk of material.

Epimetheus and smog-enshrouded Titan, with Saturn's A and F rings stretching across the scene.

Epimetheus, Titan, and rings. – Credit: NASA/JPL/Space Science Institute

Cassini delivers this stunning vista showing small, battered Epimetheus and smog-enshrouded Titan, with Saturn’s A and F rings stretching across the scene.

Stay tuned for more, as we continue our Cassini Week celebration.

Cassini Week: Moons Mimas and Pan

This week we’re celebrating the accomplishments of the Cassini spacecraft which, in just a few days, will plunge into Saturn’s atmosphere in its Grand Finale. Today, we take a look at just two of Saturn’s more than 60 moons: Mimas and Pan.


When it comes to Saturn’s moon Mimas, Cassini kept delivering surprise after surprise. First, there was a fantastic image showing us, in great detail, Mimas’s remarkable Herschel crater (Voyager 1 was the first to give us images of Herschel crater, but they paled in comparison to what Cassini revealed).

Mimas, with prominent Herschel crater.

Mimas, with prominent Herschel crater. – Source: NASA/JPL-Caltech

Then again, maybe…
Obi-Wan Kenobi: "That's no moon. It's a space station."

But Cassini revealed another surprise on Mimas. When it took a look at its infrared profile and created a temperature map, we found Pac-Man.

Mimas Temperature Map

Mimas Temperature Map – Source: NASA/JPL/Goddard/SWRI/SSI


While Mimas is quite a unique satellite of our beloved ringed planet, Pan certainly deserves some recognition as well.

Saturn's ravioli moon, Pan

Saturn’s ravioli moon, Pan – Source: NASA/JPL/Space Science Institute

The above image was captured in March of 2017, as Cassini zoomed within 15,300 miles (24,600 kilometers) of Pan.

I don’t know about you, but this moon makes me hungry for a pan of ravioli.
Will Riker rolling his eyes.

Stay tuned, more Cassini action to come as we prepare for the Grand Finale.

Sunday Matinee – NASA at Saturn: Cassini’s Grand Finale

The final chapter in a remarkable mission of exploration and discovery, Cassini’s Grand Finale is in many ways like a brand new mission. Twenty-two times, NASA’s Cassini spacecraft will dive through the unexplored space between Saturn and its rings. What we learn from these ultra-close passes over the planet could be some of the most exciting revelations ever returned by the long-lived spacecraft. This animated video tells the story of Cassini’s final, daring assignment and looks back at what the mission has accomplished.

Cassini’s Grand Finale

On September 15, one of the most fruitful space missions ever imagined will come to an end. After two decades in space, Cassini’s fuel supplies are close to being depleted. To avoid contaminating one of Saturn’s moons, including a pair that could harbor life–Enceladus and Titan–the decision was made to retire Cassini into Saturn’s atmosphere. Up until contact between the orbiter and Earth is lost, Cassini will continue to study our beloved ringed planet. New insight will be gleaned from this mission that’s only made possible by Cassini’s fatal approach to the gas giant. Among the data to be collected:

  • The spacecraft will make detailed maps of Saturn’s gravity and magnetic fields, revealing how the planet is arranged internally, and possibly helping to solve the irksome mystery of just how fast Saturn is rotating.
  • The final dives will vastly improve our knowledge of how much material is in the rings, bringing us closer to understanding their origins.
  • Cassini’s particle detectors will sample icy ring particles being funneled into the atmosphere by Saturn’s magnetic field.
  • Its cameras will take amazing, ultra-close images of Saturn’s rings and clouds.

Cassini launched on Oct. 15, 1997. After a seven-year journey the orbiter arrived at Saturn, carrying the European Space Agency’s Huygens probe. In 2005, the probe successfully landed on Saturn’s largest moon, Titan.

Quick facts about Titan:

  • Titan is the solar system’s second largest moon.
  • It’s the only moon in our solar system that has cloud systems and a dense, planet-like atmosphere.
  • Titan has liquid hydrocarbon lakes, mountains, and seasonal weather patterns.

For 13 years, Cassini has orbited Saturn and provided us with fascinating information about, not just the planet, but its intricate ring system and many moons.

Cassini mission overview infographic

Cassini mission overview infographic – Click for larger version – Source: NASA/JPL

In addition to the important scientific data that was collected by Cassini, are the breathtaking images that have been collected: storms and aurorae on Saturn, detailed views of the worlds that are Saturn moons, and remarkable visions of Saturn’s sensational rings.

For the next week, we celebrate Cassini’s achievements.

Still from the short film Cassini's Grand Finale, the spacecraft is shown diving between Saturn and the planet's innermost ring.

Still from the short film Cassini’s Grand Finale, the spacecraft is shown diving between Saturn and the planet’s innermost ring. – Credit: NASA/JPL-Caltech

Explorer 1: America’s First Space Satellite

Explorer 1

Explorer 1 – Source: NASA

You probably know that the Russian Sputnik satellite was the first human-made satellite to be placed into orbit. If not, I’m guessing you’ve at least heard of it. While the Russians beat the United States in that first declaration of space dominancy, America wasn’t far behind. Today we learn the story of the United States’s first orbital satellite: Explorer 1 1.

Towards the end of 1957, news of the Russians’ space accomplishments was rocketing around the world. Their successful Sputnik spacecrafts had recorded new entries in world history: Sputnik 1 was the first human-made object put into Earth orbit; and Sputnik 2 carried the first living creature larger than a microbe, a poor dog sacrificed in the name of science, named Laika.

The United States’s credibility was in question. Could the US compare to the Russia’s space prowess?

News of Sputnik’s milestones kickstarted an otherwise stalled United States space satellite program. The United States Army Ballistic Missile Agency (ABMA), directed by Wernher von Braun, teamed up with the federally-funded research facility, JPL (Jet Propulsion Laboratory) under the direction of Dr. William H. Pickering. JPL designed the Explorer 1 craft, while the ABMA modified one of its Jupiter-C rockets (gaining the designation Juno 1) to carry Explorer 1 payload into orbit.

A few months prior, in December of 1957, the United States Navy had attempted to put the first US satellite in orbit. That rocket made it about four feet above the launchpad before failing catastrophically in a magnificent ball of fire. Its failure earned such laughable nicknames as: Flopnik, Stayputnik, Oopsnik, and my favorite, Kaputnik.

Rapid work began on the satellite and launch system, and in only 84 days they had completed the design, construction, and assembly of Explorer 1 and its complementary rocket.

Explorer 1 schematic

Explorer 1 schematic – Source: NASA

Explorer 1 consisted of two major components: the 37.25 inch scientific portion, containing science and communication instruments, mated to a 45.5 inch rocket booster. This package was placed atop the 70-foot-tall Juno 1: a four-stage, Redstone-family booster rocket.

Explorer 1 launched from Cape Canaveral, Florida, at 10:48pm local time on January 31, 1958.

Explorer 1 entered an eccentric orbit around Earth, with the closest point in its orbit at 358 kilometers (222 miles) and its furthest at 2,550 kilometers (1,580 miles). It completed an orbit every 114.8 minutes. Mercury batteries powered the craft’s high-power transmitter for 31 days, with the low-power transmitter operational for 105 days. Explorer 1’s final transmission was received on May 23, 1958. The silent Explorer 1 continued to orbit for more than 12 years, its orbit finally decaying to the point of re-entry and destruction in the atmosphere over the Pacific on March 31, 1970. By then, it had completed more than 58,000 orbits.

Explorer 1 effectively initiated the Cold War space race. But it did more than just prove that the United States could compete with the Russians in putting things in orbit. Explorer 1 conducted real science and made some important discoveries that would be important to understand as the world progressed into a space-faring society.

Explorer 1 contained two main scientific instruments: one for detecting cosmic rays, and another for studying micrometeorites.

The micrometeorite package consisted of a “wire grid (arrayed around the aft section of the rocket body) and an acoustic detector (placed in contact with the midsection)“. Over the course of the experiment, 145 micrometeorite hits were detected.

The cosmic ray detection equipment made even greater discoveries. This was accomplished by an “Anton 314 omnidirectional Geiger tube detector“, which measured the flux of charged particles hitting the detector. The experiment was overseen by Prof. James A. Van Allen.

A peculiarity was noted in this experiment: the expected radiation count was approximately 30 per second, but the detector would occasionally return a result of zero. It was determined that these zero count intervals coincided with altitudes greater than 2,000 kilometers (1,200 miles). Further research determined that at those altitudes, the detector was actually being over-saturated and overwhelmed by the radiation. This led to the discovery of an energetic belt of charged particles that surround magnetized planets , such as Earth. This belt was named after James Van Allen, and today are known as Van Allen radiation belts. Knowledge of this region would become essential to the survival of humans that would travel through them in later space programs. The discovery was designated as one of the greatest of the International Geophysical Year.

William Hayward Pickering, James Van Allen, and Wernher von Braun at a press conference announcing the orbital insertion of Explorer 1.

William Hayward Pickering, James Van Allen, and Wernher von Braun at a press conference announcing the successful orbit insertion of Explorer 1 – Source: NASA

At around 1:00 am on February 1, 1958, just hours after Explorer 1’s successful orbit insertion was verified, William Hayward Pickering, James Van Allen, and Wernher von Braun were ushered to the National Academy of Sciences building in Washington, D.C.  to conduct a press conference that would make headlines around the globe.

That press conference produced one of the most iconic images of the Space Age. In the image, Pickering, Van Allen, and von Braun stand triumphantly, holding a model of Explorer 1 high above their heads.

A Moment in Time: Explorer 1 – Each of these three men thus represented a component of Explorer 1’s success: the rocket, the satellite and the science payload. Each represented an institutional underpinning crucial to the fledgling American space program: the Army, the Jet Propulsion Laboratory and scientific research as represented by the University of Iowa. Each had converged from his own path to the singular moment depicted in the triumphal image.


The success of Explorer 1 can’t be overstated. It proved the efficiency that could be achieved through collaboration between civilian and military agencies, it was one of the major sparks that ignited the Cold War space race, and it confirmed the United States as a powerful contender to the Russians.

  1. At the time of launch, also designated as Alpha 1958

The Pioneer Plaque: Our Calling Card to the Cosmos

In 1972 and 1973, Pioneer 10 and 11, respectively, left planet Earth with one-way tickets out of the Solar System. These two pioneers (heh) explored Jupiter, Saturn, and their associated moons before heading out into the great unknown on an uncharted interstellar voyage. Each of them carried a plaque, dubbed the Pioneer Plaques, and that’s what this story is about.

Eric Burgess, science correspondent for the Christian Science Monitor, recognized that by being the first spacecraft designed to leave our Solar System, it too would be planet Earth’s emissary to the stars. He believed the Pioneers should contain a message from its creators, one that could serve as an introduction and greeting from any being that might make contact with the Pioneers thousands or millions or more years from now. This thought spawned the idea for what became the Pioneer plaques. Burgess approached Carl Sagan, who was at NASA’s Jet Propulsion Laboratory in Pasadena, CA, working in connection with the Mariner 9 program. Sagan was thrilled with the idea and agreed to promote the idea with NASA officials.

Two identical plaques were made–one for Pioneer 10 and one for Pioneer 11. They are 9 inches by 6 inches, .05 inches thick, and constructed of gold-anodized aluminum. They were constructed and engraved by Precision Engravers of California, a company that is still in business today and sells replica plaques. The design itself was created by Carl Sagan and Frank Drake, with the artistic help of Sagan’s then-wife Linda Salzman Sagan. NASA accepted the idea and their design, and received approval to have them flown aboard Pioneer 10 and 11. They would be attached to the craft’s antenna supports, positioned such that they would be protected from erosion caused by interstellar dust.

The design consists of a few different elements symbolizing humanity’s place within the galaxy, and information about our species.

The Pioneer Plaque

Beginning in the top-left is a schematic representing the hyperfine transition of  neutral hydrogen.Hyperfine transition of neutral hydrogen extracted from the Pioneer plaque

Wait! Don’t go! Give me a chance to try and unpack that gobbledygook for you. 

This piece of the plaque is actually kind of important, because it serves as a reference for the other elements of the plaque. For this explanation, consider that the electrons in atoms exist in one of two states: spin up and spin down. Hydrogen was chosen for the diagram due to it being the most abundant element in the Universe as well as one of the simplest, containing a single electron. Basically, the magnetic field of an electron can either be oriented parallel to the magnetic field of the atom’s nucleus, or it can be oriented in the opposite direction. These are the two states I referred to. The diagram shows both of these phases connected by a line that represents the transition–a hyperfine transition I might add–between these two states. When this occurs, a photon is emitted with a specific wavelength of about 21 centimeters and a frequency of 1420 MHz. A being that might one day come into contact with the plaque would hopefully understand the distance and frequency represented, for if they could they would then be able to use it as a reference for the other diagrams on the plaque.

Like, for example, the diagram of us.

Depiction of humans on the Pioneer plaque


Here, the plaque depicts a nude male and female human. To the right of the woman figure are hash marks indicating the top and bottom of her height. Between those marks is the symbol “| – – -“, which is the binary symbol for 8. The woman is 8 tall. 8 what, you’re asking? 8 feet? 8 inches? Remember when we created our scale using the hydrogen transition thingamajig, and came up with 21 centimeters? That’s right, the woman is 8 x 21 cm, which equals 168 cm (just a skosh over 5′ 6”). Make sense?

There have been claims made that the original drawing had the man and woman holding hands, but that a conscious decision was made to separate the two out of concern that an alien gazing upon the plaque would think of the two humans as a single being. There are also rumors that the original design included a more anatomically-correct woman body, but that single extra line needed to be erased to garner top NASA official authorization.

What a wonderful time to have been around JPL for those discussions. There’s a lot we can learn about ourselves within a debate on how to present ourselves to alien beings thousands or millions of years into the future.

Moving on…

Silhouette of the Pioneer spacecraft relative to the size of the humans.Behind us (the humans), there’s a silhouette of the Pioneer spacecraft, showing the relative size of humans to the craft. I guess this is there in case the aliens are too lazy to do the hydrogen transition conversion thing we just talked about.

At the bottom of the plaque, we have a depiction of our solar system and where Pioneer came from. Also, more hash marks. I hope the aliens realize that this time they’re supposed to be multiplying by 1/10th of the distance of Mercury’s orbit from the Sun, and not 21 cm like they were to do with the human models. If not, they’ll have a hard time finding us if they’re looking for tiny planets that have orbits mere hundreds of centimeters from their star. I really hope aliens enjoy puzzles.


The Solar System with the trajectory of the Pioneer spacecraft.


I also hope that by the time they see this part of the plaque that word hasn’t gotten to them about Pluto being downgraded to dwarf planet….

But ours is only one of millions of solar systems within our corner of the galaxy. Providing a map of our solar system won’t help them if they have no way to find it to begin with. That brings us to the next part of the plaque:


This schematic shows the location of Sol (our sun) relative to the center of the Milky Way and 14 pulsars. I’m going to spare you the technical details and give you the bare bones version. The length of the lines indicate the relative distance between the Sun and the various pulsars. The long binary numbers give the periods of the pulsars, basically their signature. One thing worth noting about the periods of the pulsars, is that their frequency will change over time. Knowing this, a being deciphering this part of the plaque would be able to not only figure out where in the galaxy the Pioneers originated from, but also when they left Earth. Depending on where the plaque is encountered, only some of the pulsars might be visible thus the redundancy of including 14. This should be enough to allow for triangulation back to us. There’s a 15th line coming out of the center of the figure (which, if you haven’t guessed already is where the Sun is located); it’s the long one pointing to the right. It shows the relative distance from the Sun to the center of the Milky Way galaxy.

So there you have it. The Pioneer Plaque: a representation of humans and their size, a celestial map to the place and time the craft and its plaque originated from, and a tool to use as a standard unit of measure to decode all of the details.

If only we put so much effort into the selfies we post of ourselves on Facebook.

Waiting For Curiosity

Even though there’s still just under five months remaining until the Mars Science Laboratory Curiosity rover lands on Mars’ surface, I almost find myself counting down the days. I woke up early to watch the launch of MSL live on NASA-TV last November and have followed the updates on its progress since then. One of the neat features you can find on the MSL website is the “Where Is Curiosity?” page, where simulated views of its progress from Earth to Mars are updated daily over its 36-week journey.

Watching the slight change in the images from day to day gave me an idea: these images could be made into a cool animation! So I hopped over to the Jet Propulsion Laboratory/California Institute of Technology’s Solar System Simulator website, fiddled around with the various options, and then started collecting images for each day that the mission has been elapsed up until today. I put them together into a little video, added some music, and now I offer it to you for your interplanetary enjoyment.

In the top left, you can watch the days tick by. The MSL is labeled in green in the center of the video. If you’re interested in reading some of the details related to distance traveled and the speed of the craft, you’ll want to watch the video in HD and full-screen.

You’ll probably notice that around 14 seconds into the video (specifically, beginning with the frame for January 14), the perspective changes slightly. I’m not exactly sure what causes it, but its the way the simulator changed the images it spit out starting with that date. I’m going to contact the designer with JPL/Caltech and see if they can help me out with different perspectives. I hope to update it from time-to-time between now and August, to put Curiosity’s progress in perspective.

And Curiosity is Off!

Screencap of MSL launch

At around 10am EST (7 PST) this morning, the Mars Science Laboratory carrying the Curiosity rover, lifted off from NASA’s Kennedy Space Center in Florida. The powerful Atlas V rocket had no hesitation after it ignited and propelled the MSL off of the launchpad. Within a few minutes, the MSL was in orbit. 44 minutes after launch the spacecraft separated from the rocket putting it on a trajectory to reach Mars in August of 2012.

Good travels, Curiosity!