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Space exploration
Communicating with Earth


mission control

Communication between astronauts in space and mission control, the facility on Earth that supervises their space flight, occurs in many ways. The astronauts and mission controllers can talk to each other by radio. Television pictures can travel between space vehicles and Earth. Computers, sensors, and other equipment continuously send signals to Earth for monitoring. Facsimile machines on spacecraft also can receive information from Earth.

Working in space
Once a space vehicle reaches its orbit, the crew members begin to carry out the goals of their mission. They perform a variety of tasks both inside and outside the spacecraft.

Navigation, guidance, and control. Astronauts use computerized navigation systems and make sightings on stars to determine their position and direction. On Earth, sophisticated tracking systems measure the spacecraft's location in relation to Earth. Astronauts typically use small firings of the spacecraft's rockets to tilt the vehicle or to push it in the desired direction. Computers monitor these changes to ensure they are done accurately.

Activating equipment. Much of the equipment on a space vehicle is turned off or tied down during launch. Once in space, the astronauts must set up and turn on the equipment. At the end of the mission, they must secure it for landing.

Conducting scientific observations and research.
Astronauts use special instruments to observe Earth, the stars, and the sun. They also experiment with the effects of microgravity on various materials, plants, animals, and themselves.

Docking. As a spacecraft approaches a target, such as a space station or an artificial satellite, radar helps the crew members control the craft's course and speed. Once the spacecraft reaches the correct position beside the target, it docks (joins) with the target by connecting special equipment. Such a meeting in space is called a rendezvous. A space shuttle can also use its robot arm to make contact with targets.

Maintaining and repairing equipment. The thousands of pieces of equipment on a modern space vehicle are extremely reliable, but some of them still break down. Accidents damage some equipment. Other units must be replaced when they get old. Astronauts must find out what has gone wrong, locate the failed unit, and repair or replace it.

Assembling space stations. Astronauts may serve as construction workers in space, assembling a space station from components carried up in the shuttle. On existing space stations, crews often must add new sections or set up new antennas and solar panels. Power and air connectors must be hooked up inside and outside the station.

Leaving the spacecraft. At times, astronauts must go outside the spacecraft to perform certain tasks. Working outside a vehicle in space is called extravehicular activity (EVA). To prepare for EVA, astronauts put on their space suits and move to a special two-doored chamber called an air lock. They then release the air from the air lock, open the outer hatch, and leave the spacecraft. When they return, they close the outer door and let air into the air lock. Then they open the inner door into the rest of the spacecraft, where they remove their space suits.

A space suit can keep an astronaut alive for six to eight hours. The suit is made from many layers of flexible, airtight materials, such as nylon and Teflon. It provides protection against heat, cold, and space particles. Tight mechanical seals connect the pieces of the space suit. Equipment in a backpack provides oxygen and removes carbon dioxide and moisture. A radio enables the astronaut to communicate with other crew members and with Earth. The helmet must allow good visibility while at the same time blocking harmful solar radiation. Gloves are a crucial part of the space suit. They must be thin and flexible enough for the astronaut to feel small objects and to handle tools.

Contributor: James Oberg, M.S., Spaceflight Engineer; author, UFOs and Outer Space Mysteries.
Source : World Book 2005

Space exploration
What is space?
Getting into space and back
Living in space
Meeting basic needs in space
Communicating with Earth
The dawn of the space age
Space probes
Probes to Venus
Probes to Jupiter and beyond
Probes to comets
Human beings enter space
Apollo: Mission to the moon
Exploring the moon
Returning to Earth
The International Space Station
Space shuttles
Types of shuttle missions