Lesson 3 of 5 · The far side needs a relay
The far side needs a relay
5 minute lesson · 3 checks along the way
Your goal for this lessonConnect far-side exploration to communications geometry.
In this lesson 3 sections · 3 checks
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Read & understand
Far side does not mean permanent darkness
The Moon rotates as it orbits Earth, keeping nearly the same hemisphere facing us. Both hemispheres experience sunlight and night. The far side is distinguished by its view away from Earth, which complicates direct radio communication rather than preventing sunlight from reaching it.
Check 1 of 3
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Read & understand
Reach a different part of the Moon
Chang'e 4 / Yutu-2 and Yutu-2 reached the far side in 2019. Their mission used a relay spacecraft to pass communications around the obstruction created by the Moon. Instruments, including the lander’s neutron and radiation experiment, could then study conditions from this otherwise radio-hidden surface location.
Yutu-2 leaving the Chang'e 4 / Yutu-2 lander on the lunar far side. This surface photograph is not a picture of the relay satellite. Display image resized and compressed.
Look closely
Which essential part of the mission is outside this frame?
See what to notice
The communications relay links the surface operation to Earth.
Check 2 of 3
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Read & understand
Treat communication as part of the experiment
In a fictional surface observation, the instrument works but its data are never retrieved. The measurement is not yet available to the scientific team. Relay visibility, onboard storage and transmission planning belong in the science plan, alongside what the detector can measure.
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Put it together
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