New Horizons Flew by Pluto and It Was Awesome

On July 14th, 1965, scientists at NASA celebrated as Mariner 4 became the first spacecraft to successfully fly past Mars. Over the following few days, the spacecraft transmitted the first-ever up-close images of the red planet back to Earth. It was the first time human beings had ever seen the surface of another planet.

Surface of Mars, 1965

Cover of the New York Times on July 16th, 1965.
Image Credit: New York Times.

Fast forward fifty years later, to the day. On the morning of July 14th, 2015, scientists at NASA celebrated New Horizons' becoming the first-ever spacecraft to fly past Pluto. At least, that's what they'd hoped had just happened.

Pluto is so far away that, moving at the speed of light, it would take four and a half hours to travel there from Earth. For New Horizons, covering that distance took just under ten years.

And when the big moment came on July 14th, and the brave little probe made its closest approach to the surface of Pluto, nobody here on Earth knew whether or not our envoy to the former planet had been successful. We needed to wait for New Horizons to phone home—from 5.2 billion kilometers away.

Pluto from a Distance:

NASA's Cassini spacecraft, in orbit around Saturn since 2004, took this image of Pluto on July 14th, 2015, from nearly four billion kilometers away. Even at the 6th planet from the sun, Pluto is a long way off.
Image Credit: NASA/JPL-Caltech/Space Science Institute

Because of the extreme distances involved, New Horizons was pre-programmed to conduct hundreds of automated scientific observations of Pluto and its moons during the brief flyby window. The first man-made object to visit Pluto was expected to carry out a long list of complicated tasks while making history.

If all went according to plan, New Horizons would fly within 12,500 kilometers of Pluto's surface at 4:49am PST on July 14th—and thirteen hours later, at around 6:00pm PST, scientists expected to receive confirmation that everything had gone as planned. There was a lot that could potentially go wrong.

For more about the history of Pluto, check out: The Story of Pluto the Forgotten Planetoid.

Table Of Contents:

  1. Flying Into the Unknown
  2. New Horizons Phones Home
  3. The Long Wait For a Signal
  4. An Icy Mountain of Data
  5. Fifty Years of Planetary Exploration
  6. Our Place In Space

Because New Horizons would be the first-ever spacecraft to visit Pluto, there were a lot of unknowns about the Pluto system to contend with. Pre-2015, the most detailed data we had on Pluto came from the Hubble telescope, an instrument floating five billion kilometers away. 

When New Horizons launched from Earth back in 2006, Pluto hadn't yet been demoted to a 'dwarf planet'. And astronomers had yet to discover two of its moons—Kerberos (discovered in 2011) and Styx (discovered in 2012)—bringing the total to five. That means that, six years after New Horizons left Earth and three years before it arrived, we realized that Pluto had more moons than the first four planets in our solar system combined (Mars has two, Earth has one, Venus and Mercury are floating solo).

And that's a lot of objects for New Horizons to accidentally crash into. To complicate things even further, Pluto and its moon Charon are sometimes classified as a double-planet system because of their strange 'dance' around a central point in space, imaged here:

The Pluto-Charon System

Pluto and Charon orbit a central point in space in between the two of them, unlike every other planet and moon in our solar system. This also sort-of makes it the first double-planet system ever explored.

There was the chance that the complex 'dance' of Pluto and Charon could kick an unexpected amount of debris into the path of New Horizons. And, traveling at a speed of 16 kilometers per second, even hitting something as tiny as a grain of sand could be catastrophic for the probe.

But when all was said and done, the harrowing wait for a signal from beyond Pluto eventually came to an end.

For the duration of the Pluto encounter, New Horizons remained in a communications-blackout phase in order to focus on gathering scientific data. This was necessary because the probe wasn't equipped with a movable communications array—in order to establish contact with NASA, the entire spacecraft needs to be rotated so that the array can point towards Earth at a precise angle. 

This means that, while New Horizons is communicating or sending data back to Earth, it's not able to make any scientific observations because its instruments aren't able to freely point at Pluto or any other object. And since the spacecraft was programmed to utilize every possible moment of its short Pluto flyby window to conduct scientific observations, it was rendered unable to communicate with Earth until well after the flyby had already occurred.

But all of this was by design. In order to make New Horizons the fastest spacecraft ever launched from Earth, it was made to be as light and as durable as possible. This meant making a few sacrifices—sacrifices which ultimately produced amazing results:

The Most Detailed Image of Pluto, 2015

Pluto's 'Heart' is clearly visible in this image sent back by New Horizons.

Earth is approximately 150 million kilometers from the Sun, a unit we refer to as 1 AU (one astronomical unit). Pluto is over five billion kilometers from the Sun, at 35 AU. And while light from the sun takes about eight minutes to reach us here on Earth, it takes more than four and a half hours for that same light to reach Pluto.

Conveniently, spacecraft communicate with Earth using electromagnetic wavelengths which travel through space at about the speed of light, so 4.5 hours is also about the time it takes for a signal sent from New Horizons to reach us here on Earth. 

But because most communications are two-way, New Horizons then needs to wait for scientists at NASA to interpret the information received and formulate a response to send back to the spacecraft—plus another 4.5 hour delay before the returned signal is received. That ends up being the equivalent of (at least) a nine hour phone call just to say "Hi, how are you?" followed by the response "I'm fine, thanks. Bye."

And to slow things down even more, every time New Horizons establishes communications with NASA, it downlinks its flight and telemetry data at a rate of about 2 kilobits per second. By comparison, most high-speed internet connections on Earth send data at a rate of at least 5,000 kilobits per second. This means that information which can typically be transferred over the internet within seconds—such as a large image file—could end up taking untold hours for New Horizons to send back to Earth.

After New Horizons successfully conducted hundreds of automated scientific observations, it sent its flight data back to NASA so that flight controllers could verify the success of the mission. Just before 6:00pm PST, 4.5 hours after the signal had been sent, the signal was received—right on time. 

In a flyby that lasted just a few short days, New Horizons collected 50GB of data. And after an intensive 10-day period of exclusive data downlinking (New Horizons taking precedent over every other spacecraft trying to communicate with Earth), NASA had only received 5% of the total data stored on the spacecraft. It's expected to take 16 months before New Horizons finishes sending back all of the data it collected during a Pluto encounter which lasted only a few days. 

Pluto Through Time

Pluto is observed through time, intitially with ground-based telescopes, followed by the Hubble space telescope, and finally using New Horizons. The final image shows what appear to be mountain ranges made of ice.

Unfortunately, the recently-released images captured during the Pluto flyby are the best we're going to have for quite a while. Taking images of Pluto was only one minor aspect of New Horizons' mission, and other data that was collected using other instruments is now taking precedent until September of 2015. After all, New Horizons isn't just a high-tech space camera, it's a $700 million dollar piece of scientific equipment. 

As New Horizons now begins to focus on downlinking data that was collected by other instruments, we may soon be able to find evidence for/against Pluto harboring a sub-surface ocean, deduce the rate at which Pluto's atmosphere is collapsing, and find answers as to why the surface of Pluto has the geological features that it does. The 16 month process may even be a blessing in disguise, as we'll now get to continuously learn 'new' things about the Pluto-Charon system well through 2016. 

On July 14th of 1965, NASA's Mariner 4 probe became the first spacecraft to successfully fly past Mars and, at the same time, the first spacecraft to take up-close images of another planet. Captured using a television camera mounted underneath the probe, all of the scientific data and images of the Martian surface were stored on a 1960's tape recorder before being translated into a digital signal and beamed back to Earth.

This innovative technique allowed scientists the opportunity to study the surface geology of other worlds without ever needing to leave Earth, and without any spacecraft needing to physically return to Earth in order to deliver the images it'd taken. And ever since this first image taken of Mars showed us our first glimpse of another world, we haven't stopped. 

The Martian Surface, 1965

Mariner 4 took this picture of the Martian surface in 1965. It's one of only 22 images transmitted back to Earth by the spacecraft.
Image Credit: NASA

Although Mariner 4 took the first up-close pictures of another planet in 1965, the first up-close pictures of another object in the solar system were taken when the Soviet Luna 3 imaged the far side of the moon for the first time ever in 1959.

Even more up-close was when Ranger 7 imaged the lunar surface on a suicide mission a few years after Luna 3:

The Lunar Surface, 1964

Ranger 7 took this picture of the lunar surface on July 31st, 1964. 17 Minutes later, it smashed into the Moon at 2.6 kilometers per second.
Image Credit: NASA

The mission of Ranger 7 was to collect as much data about the lunar surface as possible. Due to the technological restrictions of the time, the best way to collect this information was to send the probe on a trajectory directly towards the surface of the moon, during which it sent as much data as possible back to Earth before impact. This sort of approach wasn't necessary with New Horizons

Pluto's Surface, 2015

New Horizons took this picture of Pluto's surface on July 14th, 2015. Scientists are still trying to figure out how and why these 'icy plains' exist.

However, Mars wasn't the first planet visited by a man-made probe. In 1961, the Soviet Union's Venera 1 probe became the first spacecraft to fly past Venus, and the first spacecraft ever to fly past another planet. Although Venera 1 didn't include any photography system and lost contact with Earth just before the flyby of Venus occurred, its trajectory brought it to within 100,000 kilometers of the Venusian surface, making it the first man-made object to enter into the vicinity of another planet.

Since first gaining the technological capability to launch objects into space, humanity has never stopped sending spacecraft out to explore the cosmos. When first aired in 1966, the introduction to every episode of Star Trek began with William Shatner narrating the mission of the fictional starship Enterprise:

"To explore strange new worlds, to seek out new life... to boldly go where no man has gone before." 

The TV show came after U.S. President John F. Kennedy had announced the goal of landing a man on the moon back in 1961, but before the Apollo 11 Moon landing in 1969—an interesting middle period from which to launch a TV show about space exploration in the far-flung 23rd century. But the vision of space travel presented in the TV series was precisely aligned with the values of NASA and other space exploration agencies of the time, and those core values are still prevalent to this day.

Ever since the first attempts to send a man-made object to the Moon during the 1950's, the space agencies of the world have worked towards the goal of exploring strange new worlds. Now, with the success of New Horizons, it's time to move on to the other facets of that mission—to seek out new life, and to boldly go...

Shortly after robotic spacecraft began surveying the Moon, NASA put humans on the Moon with the Apollo program—a total of twelve people stepping foot on the Moon over the course of six missions, from 1969-1972. 

Once we'd been successful sending multiple orbiters to survey Mars, we began landing robotic rovers on the Martian surface—culminating in the current Curiosity rover, soon to be joined by Mars InSight in 2016, the first mission with the primary goal of searching for present or past evidence of life on Mars. Even further, NASA has outlined its long-term plan to send humans to Mars in the 2030's. 

When the Voyager probes explored Jupiter, Saturn, Uranus, Neptune, and all of their collective moons between 1979-1989, we immediately began planning our next shot. The mark was Saturn, and the flagship-class orbiter Cassini arrived in 2004 and has been gathering data on the entire Saturn system for over a decade.

Along with that mission, Cassini's lander, Huygens, touched down on Saturn's moon Titan in 2005, becoming the most distant man-made object to softly land on another world. And based on what Cassini-Huygens discovered about Titan, we're now looking to develop a submarine-like robot to explore the liquid methane seas of Titan in the near future.

Now, with New Horizons' survey of Pluto and prying open of a new frontier in space exploration—the distant objects of the Kuiper belt—it's time to start asking: what's next?

The Dark Side of the Moon, 1959

In 1959, the Soviet Luna 3 spacecraft took the first picture of the Moon's rear. Because the Moon is tidally locked to Earth (its rotation speed matches its orbital speed of 27.3 days), we only ever see its 'front' side from Earth.
Image Credit: Soviet Luna 3 Probe

When the Soviet Union made the first successful flyby and image return of the Moon in 1959, it opened up a new frontier of possibilities. Seeing the dark side of the moon was irrevocable evidence that we'd sent something out into deep space—an object that we could control and which could send back planetary postcards. 

Ten years later, in 1969, human beings landed on the Moon. Two decades after that, and we'd sent various spacecraft to explore nearly every planet and moon in the Solar System. 

Now, contained within the 5% of the data downlinked by New Horizons so far, one particular image is set to become a classic of space exploration: 

The Dark Side of Pluto, 2015

Shortly after completing its flyby, New Horizons turned back and took this image of Pluto. Light from the sun is seen reflecting through the blueish atmosphere.

Shining from behind Pluto isn't just light from the sun, it's also the entire Solar System. No other image can better capture the fact that everything humanity has ever explored—the Earth, the Moon, all eight (or nine) planets and their 146 (or more) moons—exist locked behind that dark surface of Pluto, and that Pluto is now the most distant object that we've ever visited. 

By the numbers, this feat is even more impressive: 55 years, 9 months, and 7 days after Luna 3 took the first image from behind the Moon, New Horizons took the first image from behind Pluto. The Moon is 384,000 kilometers away; Pluto is 5,251,300,000 kilometers away (at the time of New Horizons' flyby)—that works out to a 13,675-fold performance increase over a 55 year period. 

If, over the next 55 years, we can achieve another 13,675-fold increase over the performance of New Horizons, that means we would hypothetically be visiting another object as far out as 7.59 light years from Earth—and there are five different star systems within that vicinity—by the year 2070. 

That sort of prediction is admittedly a bit far-fetched and would require rapidly inventing new propulsion technologies, but it does teach us something: that our progress in space exploration has been moving along exponentially. And instead of the next 55 years bringing about another exponential increase in distance, we'll probably see an exponential increase in infrastructure by the time 2070 rolls around.

After fifty years of planetary surveying, a new approach is now on the horizon—manned missions into deep space, human habitats on other worlds, and an endless array of challenges on our home planet that still require solutions.

Perhaps New Horizons' farewell glance at Pluto can show us that looking outward towards alien worlds is a good way of establishing a context for looking back inward, towards Earth. And now, with Pluto in our rear-view, it's time to tackle both in a big way—humanity's long-term future exists out among the stars and the planets alike, and all we need to do now is keep moving forward. 


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