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Letter R

R is for…

NASA’s Picture Dictionary

Check out what R stands for…

Radar
Rainbow
Rehydrate
Remote Sensing
Researcher
Revolve
Robot
Robotic Arm
Rocket
Roman Numeral
Rotate
Rover

Radar

A device that sends out radio waves and picks them up again after the waves strike another object and bounce back.

A map of snowfall echo as observed by radar over Huntsvillle, Alabama. The warmer the color, the heavier the snowfall.
This weather radar has different colors to show how much snow fell in an area.
NASA

Sentences:
Radar is used to help predict weather and measure waves of the ocean.
Police officers can tell how fast a car is going by using a radar device.

Related Links:
Birds and Radar

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Rainbow

An arc or circle of colors that appears in the sky opposite the sun. A rainbow is caused by the sunlight shining through raindrops, spray or mist.

View from a mountaintop of a large rainbow with a valley in the background
Look for a rainbow when the sun comes out right after it rains.
NASA

Sentences:
The colors red, orange, yellow, green, blue, indigo and violet make up a rainbow.
A rainbow is created when sunlight passes through raindrops.

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Rehydrate

To add water to a dried item, such as food.

Assorted bags of snack food and dehydrated food
Taking the water out of foods saves room when packing for a trip into space and helps the food stay fresh.

Sentences:
Astronauts take freeze-dried food into space and rehydrate the food before eating.
When our bodies are thirsty, we must rehydrate ourselves by drinking water.

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Remote Sensing

Studying an object without coming into direct contact with it.

Artwork of the International Space Station scanning Earth with colored lines to show where the station scans
NASA can study Earth from the space station with a tool called CATS.

Sentences:
Satellites are important tools used by NASA for remote sensing.
People taking pictures from hot air balloons were the first to use remote sensing.

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Researcher

A person who studies to find out about a subject, usually to learn new facts or solve a problem.

A person with protective yellow gloves and white lab clothes, including mask and head covering, looks into a microscope
A researcher looks at a tile under a microscope.
NASA

Sentences:
NASA has researchers that study the weather.
Our teacher said that a good researcher could find answers to many problems.

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Revolve

To circle around something or move in an orbit.

Earth and Mars orbit the sun
Mars revolves around, or orbits, the sun in about 687 days. Earth is closer to the sun and revolves around it in about 365 days.
NASA

Sentences:
Earth revolves around the sun in 365 days, 5 hours, 59 minutes and 16 seconds.
The time a planet takes to revolve around the sun is called a year.

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Robot

A machine that is built to do a certain job again and again, or to do work that might be dangerous for humans.

Robot with four black legs and the three red letters JPL on its white-colored back
This robot is called RoboSimian. It was made to walk over places that would be hard for humans to walk.

Sentences:
NASA uses robots to explore other planets.
Robots are used to paint new cars.

Related Links:
Robonaut 2 Video
Robonaut 2: Introduction
R2 on Space Station

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Robotic Arm

A mechanical arm designed for grabbing, holding and moving objects.

An astronaut is anchored to a foot restraint on the International Space Station's Canadarm2
Astronaut Stephen K. Robinson rides on a robotic arm that is attached to the International Space Station.
NASA

Sentences:
The space station’s robotic arm helps astronauts lift large objects while in space.
Some factories use robotic arms to build cars.

Related Links:
Curiosity’s Robotic Arm
Robotics on the International Space Station
Dextre the Magnificent

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Rocket

A vehicle used to launch people and objects into space.

An orange and white rocket sits on the launchpad
Delta rockets have been taking NASA spacecraft into space since the 1960s.
NASA

Sentences:
NASA has used different rockets to launch humans and satellites into space.
A girl built a model rocket and tested it for her science project.

Related Links:
What is a Rocket? (Grades K-4)
What is a Rocket? (Grades 5-8)

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Roman Numeral

A letter used as a number in the very old Roman number system.

  • I equals 1
  • V equals 5
  • X equals 10
  • L equals 50
  • C equals 100
  • D equals 500
  • M equals 1,000
A round blue patch showing the space station, names of astronauts, six stars and the numerals XX
This space station patch has two Xs. They are Roman numerals that stand for the number 20.
NASA

Sentences:
Some NASA patches have Roman numerals on them.
Until 1969, NASA only used Roman numerals for missions that were a success.

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Rotate

To turn around in a circle; to spin.

A drawing of the Northern hemisphere of the globe with a curved arrow at the equator and another curved arrow at the top
Earth takes about 24 hours to rotate on its axis, which is why a day is 24 hours long.
NASA

Sentences:
Earth rotates on its axis once a day.
The second hand on the clock rotates faster than the other hands.

Related Links:
Watch Jupiter Rotate

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Rover

A vehicle for exploring the surface of a planet or moon.

An artist's drawing of one of NASA's Mars rover on the surface of Mars
An artist drew this picture of a rover exploring the surface of Mars.
NASA

Sentences:
Spirit and Opportunity are the names of two NASA rovers that have explored Mars.
The rovers have taken some very cool pictures of Mars.

Related Links:
Draw a Rover and Helicopter on Mars
Pictures of Mars

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Explore More Letters

Go Back to NASA's Picture Dictionary

NASA's Picture Dictionary – S

NASA's Picture Dictionary – T

NASA's Picture Dictionary – U

NASA's Picture Dictionary – V