Tomorrow morning, July 14, at 7:49 am ET, the spacecraft New Horizons makes its closest approach to Pluto in history. We'll be nearer to Pluto than New York City is to Hong Kong. Over the coming months the spacecraft will return libraries of knowledge about the mysterious planet. Here are a few things you might not know about the extraordinary probe.
1. New Horizons is the fastest spacecraft ever launched.
In 2006, an Atlas V rocket blasted New Horizons into space. By its third separation stage, the spacecraft was traveling a shade under 10 miles per second. To give some idea of its speed, it took the Apollo astronauts three days to get to the moon. New Horizons reached the same distance in nine hours.
2. Jupiter’s gravity acted as a slingshot on the probe.
A “gravity assist” involves a spacecraft flying near a planet and using that planet’s gravity to change speed or direction, as if flung by a giant slingshot. Jupiter’s gravity hurled New Horizons an extra 9,000 miles per hour, ramping up its speed to 52,000 miles per hour. While traveling through the Jovian system, New Horizons gave its instruments a test run, capturing such never-before-seen phenomena as lightning near Jupiter’s poles.
3. It is carrying the ashes of the man who discovered Pluto.
In 1930, Clyde Tombaugh, an American astronomer at the Lowell Observatory, discovered the planet that was eventually named Pluto. Tombaugh died in 1997, and New Horizons is carrying a small amount of his ashes. When the probe eventually moves beyond the Kuiper Belt, Tombaugh's ashes will be the first to travel beyond our solar system. The probe also carries a CD-ROM containing the names of 434,000 people who signed up to have their names sent to Pluto.
4. Planetary scientists consider Pluto a “science wonderland.”
That’s how the team at Johns Hopkins University’s Applied Physics Laboratory, which operates the New Horizons mission for NASA, describes the Pluto system. In addition to mapping Pluto’s geology and morphology, and analyzing its atmosphere and weather, New Horizons will study Charon, Pluto’s largest moon. By orbiting around a common center of gravity, the two worlds make up the only “binary planet” in the solar system. This is the first time we can study a new planetary class known as “ice dwarf” (the other two in our solar system being terrestrial planets and gas giants).
5. The entire mission will use less power than two 100-watt bulbs.
The energy efficient spacecraft is powered by a radioisotope thermoelectric generator (RTG), a kind of plutonium power plant. Like a big thermos bottle, the spacecraft is wrapped in thermal blankets (the gold foil seen in photographs) to hold in the heat produced by the spacecraft’s electronics, keeping them at a stable temperature. Notably, the RTG doesn’t provide propulsion. The spacecraft is still flying on the speed created by the launch and Jupiter’s gravity assist.
6. Its data is transmitted to Earth at 2 kbps.
The spacecraft uses a giant dish antenna to communicate with NASA’s Deep Space Network. It’s no trivial effort, though; the beam is only 0.3-degrees wide and has to hit Earth from Pluto and, eventually, beyond. (Considering the distances involved, New Horizons is quite the sharpshooter.) It takes four hours for data to arrive at the spacecraft, and once the flyby is complete, the probe will need a full 16 months to send all the data home.
7. There is almost zero margin for error.
The numbers are astonishing: New Horizons has traveled 3 billion miles at approximately 31,000 miles per hour (currently) and, if all goes as planned, will hit a target just 200 miles across. Because of orbital mechanics, if it is 100 seconds off course, it will not be able to gather 100 percent of the desired scientific data. Think about that: 100 seconds off course from a travel time of 9.5 years. Now that’s precision.
8. New moons mean new dangers.
In 2011, New Horizons discovered a second moon orbiting Pluto (Kerberos), and a year later a third (Styx). That’s been both exciting and worrying. These moons lack the mass and gravity to keep debris caused by planetary collisions from flying into space, where they could potentially smash into New Horizons. Debris doesn’t have to be big to be a threat: a piece the size of a grain of rice could prove catastrophic to the probe. Think of a rock hitting your windshield. Now imagine if you were driving 31,000 miles per hour.
9. The USA is the first country to explore every planet in the solar system.
NASA has been the first to launch each spacecraft that has successfully visited every planet, starting with Mariner 2 in 1962. July 14 is also the 50th anniversary of the Mariner 4 mission to Mars, the first exploration of the red planet. New Horizons completes humanity’s reconnaissance of the classical solar system.
10. The New Horizons mission does not stop with Pluto.
Once the spacecraft passes Pluto, it will have enough power and propellant to continue into the Kuiper Belt, a gigantic zone of icy bodies and mysterious small objects orbiting beyond Neptune. These objects are the building blocks of Pluto and planets like it. The new course will take New Horizons one billion miles beyond Pluto.