Escaping our solar system; five galactic emissaries
Pioneer 10 shortly before encapsulation.
Photo: NASA/Ames Research Center
David DickinsonPublished: January 22, 2013, 1:59 pm
Seven years ago on Jan. 19, 2006, NASA's New Horizons spacecraft launched from Cape Canaveral on a dramatic mission to reach Pluto in July of 2015. Moving at 13.78 kilometres per second, New Horizons will explore Pluto and its moons on its way out of the solar system.
This represents only the fifth time that man has launched an object that is eventually bound to orbit our galaxy for millions of years, perhaps outlasting human civilization itself. These missions continue to represent an amazing amount of science and stand as a testimony of our species' aspirations to journey beyond our solar system.
As we approach the two year countdown this year to New Horizons flyby of Pluto, we thought it would be interesting to take a look at these outbound space travellers.
Pioneer 10: Launched in 1972, Pioneer 10 was the first spacecraft to fly by Jupiter headed on an escape trajectory out of the solar system. The Pioneer missions were the first of a "Grand Tour" series conceived in the 1960's to take advantage of a fortuitous alignment of the outer planets allowing for a slingshot trajectory past Jupiter and Saturn. It's amazing to think that technology at the start of the Space Age was just getting to the point in the mid-60's where travel to the outer planets was possible. The last signal from Pioneer 10 was received 10 years ago this week on January 22nd, 2003.
The "Pioneer F" plaque affixed to the spacecraft.
Pioneer 11: Launched in 1973, Pioneer 11 passed three times closer to Jupiter than Pioneer 10 and was the first spacecraft to encounter Saturn in 1979. Both spacecraft carry a 6 x 9 inch plate which describes (we hope) the location of our solar system and depicts the species that created the spacecraft to any interstellar discoverers.
Both Pioneers were also at the center of controversy for a time due to what became known as the "Pioneer Anomaly," an apparent discrepancy of the spacecraft's predicted versus actual position in space. While there was some discussion that the laws of gravity and relativity may need amending on large frames of reference, the anomaly was eventually explained as recoil due to the radiation of waste heat by the spacecraft's nuclear-powered thermoelectric generators.
An artist's conception of the Voyager 1 spacecraft.
Voyager 1: Launched in 1977, Voyager 1 is currently the most distant man-made object ever launched at over 123 A.U. (an astronomical unit is the distance from the Earth to the Sun) from the Earth and counting. This means that a signal from Voyager 1 currently takes over 34 hours to reach the Earth.
Voyager 1 encountered Jupiter in 1979 and Saturn in 1980 before a planned pass close to Saturn's large moon Titan ejected it out of the plane of the solar system. Both Voyager spacecraft carry a golden phonograph record containing sounds of Earth along with instructions and equipment to play them should they ever be discovered orbiting the galaxy.
Both spacecraft remain functional and Voyager 1 recently made the news as it began to cross the boundary into interstellar space and leave our solar system. All spacecraft in the outer solar system must use radioisotope thermoelectric generators powered by plutonium decay, as the Sun's energy is too feeble for use in exploration of the outer solar system. NASA's Juno spacecraft, launched in 2011, will be the first to use an enormous trio of solar panels to explore Jupiter starting in August 2016.
Saturn as imaged by Voyager 2.
Voyager 2: launched in 1977, Voyager 2 also explored Jupiter and Saturn and still stands as the only spacecraft to explore the planet Uranus in 1986 and Neptune in 1989. Still functioning along with Voyager 1, Voyager 2 is currently over 100 A.U.s distant in the direction of constellation Telescopium.
Voyager 2 also discovered 3 new moons orbiting Jupiter & 11 new moons of the planet Uranus during its respective fly-bys. Both spacecraft sport a state-of-the-art (for the 1970's) 62,500 kilobyte Digital Tape Recorder for data storage and transmit data at a rate of 115.2 kilobits per second.
New Horizons in NASA's Payload Hazardous Servicing Facility (note the black nuclear MMRTG to the left) at the Kennedy Space Center.
New Horizons: Launched this week in 2006, New Horizons will flyby Pluto and its system of moons in July 2015. The launch of New Horizons atop an Atlas/Centaur rocket booster was so fast that it passed the Earth's Moon after only nine hours of travel.
Curiously, although New Horizons doesn't carry an equivalent plaque or recorded greeting like the Voyager or Pioneer spacecraft, it does carry a Maryland state quarter (one wonders what an alien intelligence would make of that), and the cremated ashes of Clyde Tombaugh, the discoverer of Pluto in 1930. Also on-board, along with its battery of cameras and sensors is the Venetia Burney Student Dust Counter named after the girl who named Pluto in 1930.
Pluto's retinue of moons has grown in the past decade from massive Charon discovered in 1978 to Nix & Hydra found by the Hubble Space Telescope in 2005 and the as of yet unnamed P4 & P5, discovered after the New Horizons launch.
There are also indications that Pluto may have an atmosphere and rings as well; doubtless, the 2015 flyby of New Horizons will be sure to re-ignite the controversy surrounding the tiny world's planet-hood. A citizen science based project known as Ice Hunters seeks to find secondary trans-Neptunian Kuiper Belt Objects for the spacecraft to study after the 2015 flyby; one such possibility is Plutino 15810 (1994 JR1).
But these aren't the fastest man-made objects ever sent into space. Launched in 1976 to study the Sun, the record for the fastest man-made object goes to the Helios 2 spacecraft. Although not on an escape trajectory from our solar system, Helios 2 actually reached the highest speed ever achieved by a man-made object at 249,945 kph (149,967 mph). Keep in mind, this movement is relative to the Sun, which is also zipping around the core of our galaxy (and us along with it) once every 225-250 million years at 220 kilometres per second. Helios 2 also reached this velocity (0.02% the speed of light) while plunging towards the Sun on its elliptical orbit.
And the fastest speed ever reached by a human? That goes to the crew of Apollo 10, which reached 39,896 kph during return from lunar orbit.
It's amazing to think that these "space artifacts" might just out-live humanity itself. In his biography The First 8 Billion Miles, scientist James Van Allen jokes about how he deliberately placed a fingerprint on the Pioneer 10 spacecraft before it was encapsulated for launch, a fingerprint that may circle the galaxy for millions of years to come. You can get a look at where these spacecraft currently are as well as where they are headed on the website Heavens-Above.
Also be sure to follow New Horizons (@NewHorizons2015 on Twitter) as it heads towards its history making encounter with Pluto, now just over 2 years away!
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Science journalist, astronomy specialist, educator. Retired from the USAF in 2007 and am now a science teacher and freelance science writer. Am out stargazing on every clear night and hope to add science... read more fiction writer to my resume!View author's profile
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