Soyuz Spacecraft Returns to Earth: Year-In-Space Mission Ends

The image below shows the Soyuz TMA-18M spacecraft’s return to Earth, on March 2nd, 2016. Inside are NASA astronaut Scott Kelly, and Russian cosmonauts Mikhail Kornienko and Sergey Volkov. Both Kelly and Kornienko spent almost an entire year in space aboard the International Space Station, in a research effort to understand the health impacts of long-term spaceflight.

Soyuz TMA-18M spacecraft, floating back to Earth

Soyuz TMA-18M, floating back to Earth – Credit: (NASA/Bill Ingalls)

Click the image for an even gorgeous-er huge version.

Isn’t that image simply amazing?

In Memoriam: Captain Donald Edward Williams

Captain Donald Edward Williams


Captain Donald Edward Williams passed away on Tuesday, February 23, 2016. He was 74.

Early Life, Education, and Military Service

Donald Edward Williams was born on February 13, 1942, in Lafayette, Indiana. He grew up working on his father’s farm, spending his time after school running tractors, tending to animals, and completing general repairs. While working, he always took note of the jets flying overhead and thought to himself that being up there looked like a lot more fun that what he was doing down in the dirt. He graduated Otterbein High School, Otterbein, Indiana, in 1960 before earning a bachelor of science degree in Mechanical Engineering from Purdue University. At Purdue, he received his commission through the Naval Reserve Officers Training Corps (NROTC). He completed flight training in Florida, Mississippi, and Texas, earning his pilot wings in 1966.

Williams completed a total of  four deployments to Vietnam, aboard USS Enterprise, as a member of Attack Squadron 113 and Attack Squadron 97. During his deployments, he flew a total of 330 combat missions. After Vietnam, Williams enrolled at the Armed Services Staff College, graduating from the U.S. Naval Test Pilot School in 1974.

Williams was selected as a member of the NASA class of 1978, also known as Astronaut Group 8 or the Thirty Five New Guys (which, I must point out, included gals, too). This was the first new group of astronauts since 1969. He served in various capacities at NASA until being pegged to serve on two separate Space Shuttle missions:


STS-51-D Mission Patch

STS-51-D Mission Patch

He served as pilot on Space Shuttle mission STS-51-D, which was completed on shuttle Discovery in 1985. That mission included completing a number of experiments (including some utilizing simple toys, with the results being shared with school students), and launching a couple of satellites. One of the satellites malfunctioned upon deployment. As a result, NASA authorized its first unscheduled 3-hour EVA (extravehicular activity).

According to the book, Discovery: Champion of the Space Shuttle Fleet:

The mission became an ingenious effort to avert failure by improvising a difficult rescue without prior training. As engineers and astronauts on the ground devised a solution, they sent instructions to the crew to use on-board materials to make something like a flyswatter and a lacrosse stick.


Additionally, that Discovery mission included the first elected government official to fly in space. Utah Senator Edwin Garn joined the crew as Payload Specialist 2, acting as a congressional observer to the program. (Talk about perks of the job!)


STS-34 Mission Patch

STS-34 Mission Patch

Williams served as Commander of his second and final spaceflight in 1989, on mission STS-34 aboard shuttle Atlantis. A notable accomplishment of that mission was the deployment of the Galileo spacecraft, which became the first spacecraft to orbit and penetrate the atmosphere of an outer planet.

In a 2002 interview with Rebecca Wright, as part of a NASA Johnson Space Center Oral History Project, Williams reflected on the STS-34 mission:

I really enjoyed that mission probably even more so than the first because it was my goal to command a mission, first of all, and I got to do that. But secondly, because we knew that Galileo was going to be a lasting program as opposed to the first flight, [where] we deployed the two satellites, [but] it turned out to be a unique flight, too, because of the spacewalk. The Galileo mission we knew, if it was successful, the spacecraft was going to end up in orbit around Jupiter several years later and then there [were] going to be several years of data and images sent back. It was going to be a living, ongoing program, and we got to be a part of it. That was a really unique experience.


Williams retired from the U.S. Navy, having earned the rank of Captain, and left NASA. He completed numerous projects as a Division Manager with Science Applications International Corporation before his retirement in 2006.

During Williams’s career, he earned the following special awards and commendations: The Legion of Merit, Distinguished Flying Cross, Defense Superior Service Medal, 2 Navy Commendation Medals with Combat V, 2 Navy Unit Commendations, a Meritorious Unit Commendation, the National Defense Medal, an Armed Forces Expeditionary Medal, the NASA Outstanding Leadership Medal, the NASA Space Flight Medal, the NASA Exceptional Service Medal, the Vietnam Service Medal (with 4 stars), a Vietnamese Gallantry Cross (with gold star), and the Vietnam Campaign Medal.

From his roots as a rural farm-boy with his eyes in the sky, to serving his country valiantly in four deployments during the Vietnam war, and finally having the honor to fly two space shuttle missions as a Pilot and a Commander, Donald E. Williams was a true American hero. He was among the best of the best and should serve as an inspiration for centuries to come. We thank you for your service and honor your legacy.

Godspeed, Mr. Williams.

NASA Astronaut Don Williams aboard Space Shuttle Atlantis

NASA Astronaut Don Williams aboard Space Shuttle Atlantis – Source: NASA


John Glenn’s Orbital Journey

On this day in 1962, the Atlas rocket boosters that John Glenn, inside his Friendship 7 capsule, was strapped to the top of ignited. Millions of Americans watched as the resulting 350,000 pounds of thrust vibrated the vehicle that was about to take the first American into orbit around the Earth.

CAPCOM (Capsule Communicator): 3… 2… 1… 0.
John Glenn: Roger. The clock is operating. We’re underway.

Launch of Friendship 7

Launch of Friendship 7, the first American manned orbital space flight. Astronaut John Glenn aboard, the Mercury-Atlas rocket is launched from Pad 14. / Source: NASA

Minutes later, John Glenn became the fifth human in space and the first American to enter Earth orbit. Previously, Alan Shepard and Gus Grissom became the first and second, respectively, Americans in space; however, John Glenn was the first American to reach the important milestone of completing orbits of the Earth.

For the next 4 hours and 55 minutes, John Glenn completed three orbits of the Earth, reaching speeds greater than 17,000 miles per hour. NASA was still concerned about the effects of spaceflight on humans and this was the longest one an American astronaut had been subjected to yet. John Glenn remarked a number of times during the mission that he felt just fine, and was rather enjoying himself.

Five minutes into the mission:

John Glenn: Oh, that view is tremendous!

View of Earth from Friendship 7

View of earth taken by Astronaut John H. Glenn Jr. during his MA-6 spaceflight. / Source: NASA

John Glenn witnessed three sunsets from space during the flight.

John Glenn: The sky above is absolutely black, completely black. I can see stars though up above.

John Glenn: This is Friendship Seven. At this, MARK, at this present time, I still have some clouds visible below me, the sunset was beautiful. It went down very rapidly. I still have a brilliant blue band clear across the horizon almost covering my whole window. The redness of the sunset I can still see through some of the clouds way over to the left of my course. Over.

Sunset from Friendship 7

Orbital sunset photographed by Astronaut John H. Glenn Jr. aboard the \”Friendship 7\” during his Mercury-Atlas 6 (MA-6) flight. / Source: NASA

From his fantastic vantage point, he observed dust storms and fires in Africa and the lights of Perth, Australia.

And then there was his “fireflies”, which he first noticed at about 1 hour and 15 minutes into the flight:

John Glenn: This is Friendship Seven. I’ll try to describe what I’m in here. I am in a big mass of some very small particles, that are brilliantly lit up like they’re luminescent. I never saw anything like it. They round a little: they’re coming by the capsule, and they look like little stars. A whole shower of them coming by.

They swirl around the capsule and go in front of the window and they’re all brilliantly lighted. They probably average maybe 7 or 8 feet apart., but I can see them all down below me, also.

CAPCOM: Roger, Friendship Seven. Can you hear any impact with the capsule? Over.

John Glenn: Negative, negative. They’re very slow; they’re not going away from me more than maybe 3 or 4 miles per hour. They’re going at the same speed I am approximately. They’re only very slightly under my speed. Over.

They do, they do have a different motion, though, from me because they swirl around the capsule and then depart back the way I am looking.

Are you receiving? Over.

There are literally thousands of them.

These “fireflies”, as Glenn called them after the mission, were later determined to be ice crystals that would accumulate on the craft on the dark side of the Earth and then begin to break off of the capsule when the Sun’s heat returned. 1

Back on the ground, serious considerations were being made. A flight controller received a warning from a sensor on Friendship, indicating a loose heat shield. If the sensor was correct in its reading, the only thing holding the heat shield in place was the straps from the retrorocket package. After debate, a decision was made; Glenn was instructed to refrain from jettisoning the retropack — a normal procedure for re-entry — in hopes that it would hold the heat shield in place during re-entry; the alternative was the craft and Glenn disintegrating in the Earth’s atmosphere. Control offered no explanation for the procedure until after successful re-entry. Glenn suspected a problem with the heat shield, but remained focused on the parts of the craft he could control.

CAPCOM: This is Texas Cap Com, Friendship Seven. We are recommending that you leave the retropackage on through the entire reentry.

John Glenn: This is Friendship Seven. What is the reason for this? Do you have any reason? Over.

CAPCOM: Not at this time; this is the judgment of Cape Flight.

The sensor ultimately proved to be faulty and the heat shield remained securely attached to Friendship. 2

Aside from using more fuel than expected for attitude corrections, a hot spacesuit that had to be regularly adjusted for cooling, and excess cabin humidity, the rest of the flight was essentially flawless.

Glenn fired his retrorockets and descended back to Earth. He splashed down in the Atlantic, 40 miles downrange from the expected landing site. The USS Noa reached Friendship seventeen minutes later and hoisted it onto the ship. Glenn was supposed to exit the capsule from the top hatch, but instead decided to blow the side hatch instead. With a loud bang, the hatch blew open and Glenn emerged and jumped to the deck of the Noa. With a smile, his first words were: “It was hot in there.”

Astronaut John H. Glenn Jr. in his Mercury spacesuit

Astronaut John H. Glenn Jr. in his Mercury spacesuit. / Source: NASA

Glenn returned to a hero’s welcome and a ecstatic ticker-tape parade in New York City. Americans were energized with the progress in the race with the Soviets. And with John Glenn’s help, America — and mankind itself — took another step forward into the uncharted heavens above.

*This post was originally published February 20, 2011. Small updates have been made since then.

  1. In fact, it was solved during the next Mercury mission, Aurora 7, by Scott Carpenter. To test his theory, he banged on the side of the capsule and watched as they broke off of the exterior of the craft!
  2. And it provided a nice fireworks show for Glenn during re-entry. “My condition is good, but that was a real fireball, boy. I had great chunks of that retropack breaking off all the way through.”

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.

A Space Discovery Milestone, as Kepler Confirms 1000th Exoplanet

Kepler Mission Logo

Kepler Mission logo

It was just a few years ago, and I was excitedly reporting to you the first few exoplanets that the NASA Kepler space instrument was detecting and verifying. In fact, it was almost exactly 4 years ago today that I was telling you about confirmed exoplanet find number 9. That exoplanet, Kepler-10b, was the first confirmed find of a rocky world outside of our own solar system, and at the time was the smallest exoplanet ever discovered, at 1.4 times the diameter of Earth. Then, at the end of that year, I was telling you about the first exoplanet located by Kepler in the “habitable zone”. And in a short period of time, I was telling you about dozens of more exoplanets being confirmed, and mini-planetary systems, and exoplanets that orbit two different stars.

Well since then, Kepler’s been hard at work confirming exoplanet after exoplanet. Today, that count has reached a milestone:

NASA’s Kepler Marks 1,000th Exoplanet Discovery, Uncovers More Small Worlds in Habitable Zones

1,000 confirmed other worlds, orbiting other stars. Let me put that significance into perspective: if you were born in 1988 or earlier, you are the exoplanet generation, for 1988 was the year the first exoplanet was confirmed. I don’t know about you, but that fact really resonates with me. It proclaims to me that I live in a fantastic moment of human history. I was alive when Earthlings first knew for certain that there were planets outside of our own Solar system. And in less than three decades, we’ve found over 1,000 more. There are worlds out there, and we’re alive precisely at the time to first know it. And what’s even cooler, at least eight of those are roughly the same size as our own world and orbit their host star in what’s referred to as the habitable zone.

Artist's depiction of the 8 Earthlike planets confirmed by Kepler.


The Kepler mission will always be one of the most exciting for me personally, and is expected to confirm thousands more exoplanets over the coming years. What a time to be alive!

If this is as interesting to you as it is to me, here are a couple of other articles posted about Kepler discoveries that I think you’ll particularly appreciate:

Exciting Kepler News – Part 1: Mini-Planetary System

Exciting Kepler News – Part 2: New Circumbinary Planets

Kepler Finds First Earth-Sized Planets

NASA's State of the Solar System

Here’s an excellent infographic that details NASA’s current Solar System (and beyond!) spacecraft missions. It lists every craft NASA out exploring various bodies and their current status.

Click the image to make it a little bigger.

State of the Solar System infographic

State of the Solar System infographic



New Horizons Awakens

If everything has gone according to its meticulous plan, by the time you are reading this NASA’s New Horizons spacecraft will have awoken from its electronic hibernation for the last time and begun its careful preparations to encounter Pluto in July of 2015.

Maybe I should back up for those that aren’t familiar with New Horizons, or just want a little recap:

New Horizons is the name of a NASA spacecraft and mission to complete a fly-by mission of Pluto and its moons, and then on to view other Kuiper-Belt objects. New Horizons will give us shiny new photos of our favorite dwarf planet and a wealth of other scientific data. It’s about time, too. I mean, just look at the current best image we have of what we–at least  used to–consider 1/9th of our solar system’s planetary awesomeness:

Pluto as imaged by Hubble in 2010.

Pluto as imaged by Hubble in 2010.

Yuck! And NASA was impressed enough to brag about these “most detailed and dramatic images ever taken of the distant dwarf planet“. I’m looking forward to which adjectives they’ll use when we get real images courtesy of New Horizons. But I digress.

On January 19, 2006, New Horizons lifted-off from its Cape Canaveral launchpad and screamed into the heavens. In fact, nothing before or since has left the Earth with such a sense of urgency. New Horizons holds the record for the fastest launch of any spacecraft. It left the Earth with a velocity of 36,373 miles per hour (58,356 kilometers/hour), fast enough to propel it not just out of the Earth’s orbit, but completely out of the solar system (referred to as a solar escape velocity).

Subsequently, New Horizons continued to voyage towards its 2015 encounter with Pluto. Along the way, it came within 1.4 million miles (2.3 million kilometers) of Jupiter, on February 28, 2007, and actually used its proximity to gain a gravity assist boost from the massive gas giant. This gave New Horizons a speed boost of about 9,000 miles per hour (14,000 kilometers/hour). Taking advantage of that graviational slingshot, the voyage to Pluto was shortened by three full years. Score! Free energy!

New Horizons zoomed along, passing Saturn’s orbit in June of 2008, Uranus’s in March of 2011, and then Neptune’s in August of this year.

Next up: Pluto.

Throughout its journey, New Horizons has gone through hibernation/wake cycles more than a dozen times, in fact, spending about 2/3 of its time in an electronic slumber. During hibernation, most of the craft’s systems are powered down or entered into an extremely low-functioning state. This “reduced wear and tear on the spacecraft’s electronics, it lowered operations costs and freed up NASA Deep Space Network tracking and communication resources for other missions”.  Today, however, New Horizons is waking for good.

Beginning in February, the main observation objectives begin. Around the beginning of May, New Horizons will be capturing images of Pluto exceeding the resolution that Hubble was able to produce. For the next two months, Pluto will become more accessible to all of the spacecraft’s instruments. The closest approach is projected for July 14, where New Horizons will be within 6,200 miles (10,000 kilometers) of Pluto. New Horizons’s Long Range Reconnaissance Imager (LORRI) is expected to capture images on the scale of 50 meters per pixel and accomplish a handful of other primary and secondary scientific objectives.

But wait, there’s more!

In addition to Pluto, New Horizons will be observing and recording images and data from Pluto’s known moons: Charon, Hydra, Nix, Styx, and Kerberos.

And that’s still not all. Remember how I mentioned that New Horizons is on a solar system escape trajectory? That means the craft is going to continue hurtling away from the Earth and Sun, away from Pluto, and out beyond the ends of our solar system and into intergalactic space. Included in the craft and mission design, is fly-by opportunities for one ore more Kuipier-Belt Objects (KBOs), the residents of the Kuiper Belt. If you’re not familiar with the Kuiper Belt, think asteroid belt except much larger but instead of rocky asteroids, these bodies consist more of frozen gases such as methane, ammonia, and water. (Some of the moons of our solar system are believed to be former residents of the Kuiper Belt, but that’s another story for another time.) The ability to complete this mission will depend on targetable candidates and remaining fuel supplies.

After all of this, New Horizons slips into the furthest reaches of the Sun’s influence, the fascinating realm known as the outer heliosphere, including the heliosheath and heliopause (again, another story/another time). If the craft is still alive at this point, New Horizons will continue the work of the Voyagers in mapping this interesting environment.

That’s it for today. Stay tuned for updates on this historical mission, and much, much more!

Pioneer Non-Anomaly

Artist depiction of Pioneer spacecraft in deep space.

Artist depiction of Pioneer spacecraft in deep space. Image Credit: NASA

Pioneer 10 and 11 launched in 1972 and 1973, respectively, and were Earthkind’s  first explorers of the outer planets and emissaries to deep space.  Pioneer 10 became the first spacecraft to pass through the asteroid belt and observe Jupiter up-close, providing us with details of the gas giant’s interior, atmosphere, magnetic fields, and some of the most breath-taking images of Jupiter we had ever seen. Pioneer 11 wasn’t far behind, and after making its own observations of Jupiter, it went on to Saturn to open our eyes to the mighty ringed planet in the same way Pioneer 10 had done for Jupiter. (But this isn’t a story about the accomplishments of the Pioneer program; I’ll save that for another day.)

In addition to all of the data and images sent back, however, those two Pioneers also sent back a mystery. As early as 1980, it was noticed that the spacecrafts were experiencing an acceleration force toward the sun of .000000000874 m/s2 (meters per second, per second)1. To be clear, this does not mean the Pioneers are heading back towards the Sun. Pioneer 10 and 11 are cruising away from the Sun at a speed of around 132,000 kilometers per hour (82,000 miles per hour) and 175,000 kilometers (110,000 miles per hour), respectively, and this force is 10 billion times smaller than the acceleration we feel from the Earth’s gravitational pull. Nonetheless, the force is real and our instruments and techniques are precise enough to notice.

Many plausible causes were considered to explain the anomaly, including:

perturbations from the gravitational attraction of planets and smaller bodies in the solar system; radiation pressure, the tiny transfer of momentum when photons impact the spacecraft; general relativity; interactions between the solar wind and the spacecraft; possible corruption to the radio Doppler data; wobbles and other changes in Earth’s rotation; outgassing or thermal radiation from the spacecraft; and the possible influence of non-ordinary or dark matter.

In 1994, a thorough, long-term, collaborative study was undertaken to try and solve the anomaly. Initial results from that study were released in 1998, with a detailed analysis following in 2002. All known systematics were tested and calculated, yet that 8.74±1.33×10−10 m/s2 deceleration force2 remained. The origin of the anomaly was still unaccounted for, though the leading theory was that it was the result of anisotropic thermal radiation (don’t let the big words intimidate you, this just means heat was being radiated from the Pioneers in a certain direction). In 2004, another paper was published, proposing a deep space mission to solve the anomaly once-and-for-all.

But now, that expensive deep-space mission won’t be necessary, according to a paper just submitted by astrophysicist Slava Turyshev and his team of scientists and engineers, with thanks, in no small part, to The Planetary Society and its members.3

With funds provided by The Planetary Society, Turyshev and his team were able to collect and compile great volumes of data from the two Pioneer missions. The data had to come from a variety of different sources and came in any number of formats, media, and condition. According to Bruce Betts, Director of Projects at The Planetary Society:

“This was not an easy (or quick) task. These missions lasted for more than 30 years. Imagine all the people, computing formats, and hardcopy and electronic storage devices involved over that period, and you’ll start to get an idea of the problem.”

Boxes of Pioneer data tapes.

Boxes of data tapes from the Pioneer missions. Image Credit: The Planetary Society

Think of what you would have to go through if I handed you a 5.25″ floppy disk that contained… well, it couldn’t contain much compared to the amount of data we exchange today, but whatever it was, it was something you needed. Imagine trying to find the hardware to read the disk, and then the intermediary hardware and software that would be required to get the data from the disk onto one of today’s modern machines so you could even utilize it. If you consider how much technology has changed between now and floppy disks, you can only begin to imagine how much it has changed since the 1970s and how cumbersome compiling all of this data, let alone securing it, must have been. I digress.

Once Turyshev and his team were able to assemble the more-complete data picture, they were able to isolate the source of acceleration: that anisotropic thermal radiation. Again, Bruce Betts:

Why was the thermal emission from the spacecraft anisotropic and slowing the spacecraft down? First of all, because the Pioneer spacecraft were spin-stabilized and almost always pointed their big dishes towards Earth. Second of all, because two sources of thermal radiation (heat) were then on the leading side of the spacecraft. The nuclear power sources, more formally Radioisotope Thermoelectric Generators (RTG), emitted heat towards the back side of the dishes. When the dishes reflected or re-radiated this heat, it went in the direction of travel of the spacecraft. Also, the warm electronics box for the spacecraft was on the leading side of the spacecraft, causing more heat to spill that direction. Photon pressure, the same type of thing used in solar sailing, then preferentially pushed against the direction of travel, causing a tiny, but measurable, deceleration of the spacecraft – the Pioneer Anomaly.

At the end of the day, there are a few take-home lessons to be learned. First, Occam’s Razor proved itself once again (some of the suggestions to account for the Pioneer Anomaly were the need to invoke a new type of exotic physics). The second is that you can’t just apply Occam’s Razor and say that anisotropic thermal radiation is the simplest theory and therefore correct, you have to painstakingly collect all of the data needed to prove it — and more importantly, you have to have the experts that are willing to put forth the years decades of research to solve the mystery. Finally, you take in the account that this was made possible with the help of citizen scientists and those of us that contribute to furthering our understanding of the Universe, through means such as The Planetary Society4.

This new paper will undoubtedly generate more discussion about the Pioneer Anomaly and others will work to verify or disprove its results, but at this point it seems pretty safe to say that one of space physic’s mysteries is no more.

  1. 8.74±1.33×10−10 m/s2
  2. In physics, acceleration is a change in velocity over time. It does not only apply to an increase in speed. Traveling in your hot-rod sports car, as you step on the gas and race up to 100 miles per hour, you’re experiencing acceleration. When you notice a brick wall rapidly closing in from ahead of you and you stand on the brakes, you’re experiencing a negative acceleration. Acceleration is just a change from a constant velocity.
  3. Are you a member of The Planetary Society? I am. You should be, too! Sign up!
  4. Again, join!