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Starship voyager

27th September 2013

By: Keith Campbell

Creamer Media Senior Deputy Editor

  

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On September 12, the US National Aeronautics and Space Agency (Nasa) announced that its scientists had concluded that the Voyager 1 space probe had left the solar system and entered interstellar space. It is, in fact, now believed to have done so more than a year ago, in August 2012. The importance of this is difficult to overstress. For the first time there is human artefact whose future is totally independent of the the fate of not merely its home world but its native star. In due course, Voyager 1 will be joined in interstellar space by its sister ship, Voyager 2, and later by Pioneer 10 and Pioneer 11, launched years earlier but since overtaken by the faster Voyagers. (The Pioneer probes were, and the Voyager craft are, operated by the Jet Propulsion Laboratory of the California Institute of technology on behalf of Nasa.)

The statistics regarding Voyager 1 are staggering. At the start of September the little ship was 18.7-billion kilometres from the Sun, which equivalates to 125.3 astronomical units (AU) – an AU is the average distance of the Earth from the Sun. It is travelling at a speed of some 3.6 AU a year, or 57 600 km/h, or 1.4 km/day. It now takes more than 17 hours for radio messages from Earth to reach the spaceship. In other words, it is 17 light hours from home.

Also at the beginning of this month, Voyager 2 was 15.3-billion kilometres, or 102.6 AU, from the Sun and moving at about 3.3 AU a year. Voyager 2 was actually launched first, on August 20 1977, followed by Voyager 1 on September 5. The two craft are headed in different directions – Voyager 1 is climbing above the ecliptic plane (the plane in which most of the Solar System's planets, including Earth, orbit the Sun) at an inclination of some 35 ˚, while Voyager 2 is diving below the ecliptic plane at an angle of about 48 ˚. In the year 40 272, Voyager 1 will come within 1.7 light years of the star AC+79 3888 in the constellation of Ursa Minor, while some 40 000 years from now Voyager 2 will come within 1.7 light years of the star Ross 248, in the constellation of Andromeda (not to be confused with the Andromeda galaxy).

It must be stressed that Voyager is a live programme, now known as the Voyager Interstellar Mission. Both spacecraft still operational. Some systems, most notably their cameras, were shut down years ago because they were no longer needed and in order to save energy for those instruments that were still useful. Each Voyager still has a functioning magnetic field instrument, a low energy charged particle instrument, a cosmic ray instrument and a plasma wave instrument (PWI). In addition, Voyager 1 also has a functioning ultraviolet spectrometer subsystem and Voyager 2 an operational plasma instrument (not to be confused with the PWI). These instruments supply data to five science teams, which are engaged in research into magnetic fields, low energy charged particles, cosmic rays, plasma and plasma waves. Powered by plutonium, the two craft are expected to be operational for another ten to 12 years. In sharp contrast the two Pioneers are long dead.

The original mission of both Voyagers was to explore the great gas giants of Jupiter and Saturn, with particular emphasis on Saturn’s rings, as well as the larger moons of these huge planets. Voyager 2 was then tasked with exploring Uranus and Neptune as well (Voyager 1’s trajectory, designed to allow it to pass behind Saturn’s rings and closely by the major moon Titan, made such an option impossible for this craft.) Voyager 2 is still the only space probe to visit the outer two gas giants. It discovered the rings around Neptune and provided much data on the rings of Uranus (which were only discovered, from Earth, in 1977). Between the, these two craft explored all four of our system’s gas giant planets, their rings systems, magnetic fields and 48 of their moons. They were originally designed to last five years – they are still working after 36 years!

For comparison, Pioneer 10 was launched in 1972, explored Jupiter and then continued to supply data on the outer regions of the Solar System. Designed to last 21 months, it actually ended its science mission in 1997, after nearly 25 years. Thereafter, it continued to send telemetry (data on how it and its systems were performing) until January 2003, when its radioisotope power source finally failed. It was the first human artefact to cross the orbit of Pluto. It is now headed for the region of the star Aldebaran, which it should reach in more than two million years. Its sister ship, Pioneer 11, was launched in 1973, and explored both Jupiter and Saturn. It send its last transmission to Earth in 1995. The Pioneers were much simpler, cheaper and slower than the subsequent Voyagers, but blazed the trail for their more sophisticated and faster successors.

The fact that the Voyagers are still operational makes their crossing into interstellar space really special. Firstly, it is the very scientific data that Voyager 1 has sent back that has allowed researchers on Earth to determine the fact of its exit from our system, instead of having to make pretty arbitrary guesses. Second, because it is live, Voyager 1 has become our first starship, actively exploring interstellar space. Of course, by starship standards, it is moving slowly, but it is still, now, a starship, a craft operating between the stars. In due course, Voyager 2 will join it. A new era of exploration has begun.

Even after they die, they and the now derelict Pioneers are set to massively outlast all human structures and artefacts made before them. Quite literally, they should outlast the pyramids. They could endure for millions of years. They could even outlive the Earth itself.

Edited by Martin Zhuwakinyu
Creamer Media Senior Deputy Editor

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