Page 54 - Curriculum Visions Dynamic Book

From Pioneer to Cassini
The journey that caught everyone’s imagination was the voyage of two identical probes that were sent to investigate the outer planets. It still fascinates us, for these probes, having completed their original tasks, have continued their journeys and are now beyond the solar system, carrying with them messages from our world in the form of golden disks. They have truly earned the title they were given—Voyager.
Two identical Voyager spacecraft, each with a mass of 815 kilograms, were designed for journeys in which there would be no possibility of repair. They had to be entirely reliable and built to last many years of journey. The communications system, for example, had a complete backup just in case one failed.
Each spacecraft communicates with Earth using a high-gain radio antenna 3.7 metres in diametre that
is always facing toward the Earth. The 23-watt radio transmitters are able to send signals over a distance
of 1 billion kilometres.
Pioneer
 The Pioneer probes were mainly sent
to other parts of the solar system. In 1965 Pioneer 6 orbited the Sun to find out what space was like close to the Sun. From it important information was gathered about solar winds and cosmic rays.
In 1972 Pioneer 10 was the first spacecraft to travel through the asTeroid belT. Later it flew by Jupiter, discovering its vast magnetism. In 1973 Pioneer 11 went close to Jupiter and then on to Saturn in September 1979. Its photographs showed two additional rings around the planet.
In 1978 Pioneers Venus 1 and 2 orbited Venus, the second probe making radar images that allowed scientists to see the whole planet’s landscape for the first time.
The Pioneers were the first of the space probes that continued into deep space. Pioneer’s last, very weak signal was received on January 23, 2003, only because its power source had given out and was no longer sending enough power to the transmitter. Pioneer 10 is now over 12 billion km away. Pioneer 10 will continue to travel in the direction of the red star Aldebaran, which forms the eye of Taurus (the Bull). Aldebaran is about 68 light-years away, and it will take Pioneer over 2 million years to reach it.
The Pioneer 11 mission ended on September 30, 1995, when the last transmission from the space probe was received. The Earth’s motion had carried it out of the range of the spacecraft antenna. The space probe is headed toward the constellation of Aquila (the Eagle). Pioneer
11 will pass near one of the stars in the constellation in about four million years.
Power source (radioisotope thermoelectric generator) converts heat from decay of plutonium source into electricity.
Communications antennae
Scientific instruments
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