Download Science in the news – Voyager`s 11 billion mile

Science in the news – Voyager’s 11 billion mile journey
Name: ...............................................................
Date: ..................................................................
Read the article from The Week magazine ‘Voyager’s 11 billion mile journey’. The Voyager 1
spacecraft was launched on the 5th September 1977. Together with Voyager 2, which was
launched on the 20th August 1977, they were designed to conduct close-up studies of Jupiter and
Saturn and were built to last 5 years. When the article was published on the 30th March 2013
they were still going and about to leave the solar system.
Answer the following questions:
1. a. How far had Voyager 1 travelled since it was launched?
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1. b. Calculate the average speed of the spacecraft in km/s. (1 mile = 1.6 km)
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The Voyager mission took advantage of the geometric arrangement of the planets in the late
1970’s and the 1980’s. This arrangement of Jupiter, Saturn, Uranus and Neptune shown below
only occurs every 175 years and it allowed the spacecraft to accomplish the four planet tour in the
minimum amount of time.
Image adapted from image courtesy NASA/JPL-Caltech
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Science in the news – Voyager’s 11 billion mile journey
2.
a. Which planets did Voyager 1 visit?
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b. Voyager 2 visited all four planets; draw its path on the diagram.
c. What do you notice about the Voyager launch dates and their journeys? Why are their
flight paths so different?
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3. Using data from the table below explain why this arrangement of Jupiter, Saturn, Uranus and
Neptune rarely occurs.
Orbital period (Earth
years)
Jupiter
Saturn
Uranus
Neptune
11.86
29.46
84.01
164.8
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4. What was the advantage of launching Voyager when the planets were in this arrangement?
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The voyager spacecraft are equipped to carry out 10 different experiments. The results of the
experiments are sent back to Earth using a spacecraft radio. Radio waves travel at the speed of
light (approx. 300 000 000 m/sec). In 2013 Voyager 1 is approximately 18 500 000 000 km
from Earth and getting further away all of the time.
5. How long does it take a radio transmission of data from Voyager 1 to reach the Earth?
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Science in the news – Voyager’s 11 billion mile journey
Voyager spacecraft cannot use solar panels for producing electricity for the on-board systems in
the same way as satellites orbiting the Earth.
6. Explain why Solar panels cannot be used on the voyager missions.
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Instead, each of the spacecraft is powered by a radioisotope thermoelectric generator (RTG) that
converts heat produced by the natural radioactive decay of plutonium to electricity.
7. How do you think the electricity is used aboard the spacecraft?
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Science in the news – Voyager’s 11 billion mile journey
Much of what we know about the outer planets and their moons is as a result of the Voyager
missions since the data would have been impossible to collect from Earth. Now Voyager is
beginning to leave our solar system and it is sending back data from interstellar space.
Some of the instruments have had to be turned off to save power. However, there are some
instruments that will continue to send back data for perhaps another 30 years.
8. Why do you think it has been necessary to save power?
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The Voyager spacecraft are carrying a number of objects that were thought to be representative of
humanity in 1977.
9. Looking at the article, which items would you include from the original inventory if a similar
mission were launched today? What other items might you include to make them more relevant
today?
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(Source: http://voyager.jpl.nasa.gov/index.html)
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Science in the news – Voyager’s 11 billion mile journey
Teaching notes and answers
The resource is based around the article ‘Voyager’s 11 billion mile journey’ from p.19 of The Week
magazine (issue 913, 30 March 2013). The magazine page can be downloaded from
www.teachitprimary.co.uk. For further background information go to
voyager.jpl.nasa.gov/index.html (weblink available at time of publication).
Answers
1 a)
b)
2 a)
b)
11 billion miles
11 billion miles x 1.6 = 17.6 billion km = 17 600 000 000 km
36 years = 36 x 365.25 x 24 x 60 x60 s = 1 136 073 600 s
speed = distance ÷ time
= 17 600 000 000 km ÷ 1 136 073 600 s
= 15.5 km/s
Jupiter and Saturn
Image courtesy NASA/JPL-Caltech
c)
Voyager 2 was launched 2 weeks before Voyager 1. Voyager 1 reached Jupiter and Saturn
before Voyager 2. Voyager 2 took full advantage of the unusual alignment of the planets
and had a trajectory that enabled it to reach all 4 planets even though it was slower.
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Science in the news – Voyager’s 11 billion mile journey
Cont.
3.
Each planet has a different length of orbit.
Taking Jupiter and Saturn as examples, Jupiter completes roughly 2.5 orbits for each orbit
of Saturn. If Jupiter and Saturn start at a position in line and on the same side from the
Sun, by the time Saturn has completed one orbit, Jupiter will be on the opposite side of the
Sun.
4.
This arrangement allows Voyager to swing from one planet to the next without the need of
large on-board propulsion systems. The flyby of each planet increases its velocity enough to
deliver it to its next destination and also decreases journey times.
5.
Time = distance ÷ speed
Ensure that all data is in the same units.
Time = 18 500 000 000 000 m ÷ 300 000 000 m/sec = 61667 seconds
(just over 17 hours)
6.
Voyager travels too far away from the Sun and there will be insufficient light energy for
the solar panels to produce enough electricity.
7.
The electricity powers the spacecraft instruments, computers, radio and other systems.
8.
The instruments rely on a generator using plutonium as its fuel source. Plutonium decays
and releases heat energy and has a half-life of 87.7 years (238Pu). In other words after 87.7
years half of the Plutonium will have decayed and the efficiency of the battery will be at
half of its original value. This is not enough to power all of the instruments.
9.
Pupils’ own answers. This provides a good opportunity to discuss the immense technological
advances since 1977.
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