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Robotic spacecraft

By Wikipedia,
the free encyclopedia,

http://en.wikipedia.org/wiki/Robotic_spacecraft


An artist's interpretation of the MESSENGER spacecraft at Mercury
An artist's interpretation of the MESSENGER spacecraft at Mercury

A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to lower cost and lower risk factors. In addition, some planetary destinations such as Venus or the vicinity of Jupiter are too hostile for human survival, given current technology. Outer planets such as Saturn, Uranus, and Neptune are too distant to reach with current crewed spaceflight technology, so telerobotic probes are the only way to explore them.

Many artificial satellites are robotic spacecraft, as are many landers and rovers.

History

The first space mission, Sputnik 1, was an artificial satellite put into Earth orbit by the USSR on 4 October 1957. On 3 November 1957, the USSR orbited Sputnik 2, the first to carry a living animal into space – a dog.

The USA achieved its first successful space probe launch with the orbit of Explorer 1 on 31 January 1958. Explorer 1 weighed less than 14 kilograms compared to 83.6 kg and 508.3 kg for Sputniks 1 and 2 respectively. Nonetheless, Explorer 1 detected a narrow band of radiation surrounding the Earth, named the Van Allen belts after the scientist whose equipment detected it.

Only six other countries have successfully launched missions using their own vehicles: France (1965), Japan (1970), China (1970), the United Kingdom (1971), India (1981) and Israel (1988).

Most American space probe missions have been coordinated by the Jet Propulsion Laboratory, and European missions by the European Space Operations Centre, part of the European Space Agency (ESA). ESA has conducted relatively fewer space exploration missions in the past (one example is the Giotto mission, which encountered comet Halley), but have launched several interplanetary spacecraft in recent years (e.g. Rosetta space probe, Mars Express, Venus Express). ESA has, however, launched many spacecraft to carry out astronomy, and is a collaborator with NASA on the Hubble Space Telescope. There have been many successful Russian space missions. There have also been a few Japanese, Chinese and Indian missions.

Design

In spacecraft design, the United States Air Force considers a vehicle to consist of the mission payload and the bus (or platform). The bus provides physical structure, thermal control, electrical power, attitude control and telemetry, tracking and commanding.

JPL divides the "flight system" of a spacecraft into subsystems. These include:

Structure

This is the physical backbone structure. It:

  • provides overall mechanical integrity
  • ensures spacecraft components are supported and can withstand launch loads

Data handling

This is sometimes referred to as the command and data subsystem. It is often responsible for:

  • command sequence storage
  • maintaining the spacecraft clock
  • collecting and reporting spacecraft telemetry data (e.g. spacecraft health)
  • collecting and reporting mission data (e.g. photographic images)

Attitude and articulation control

This system is responsible for the spacecraft's orientation in space (attitude) and the positioning of movable parts. Attitude is controlled in order to:

  • point an antenna at Earth for communications
  • point onboard instruments for collection of data
  • adjust heating effects of sunlight
  • for guidance during propulsive maneuvers

Telecommunications

Components in the telecommunications subsystem include radio antennas, transmitters and receivers. These may be used to communicate with ground stations on Earth, or with other spacecraft.

Electrical power

The supply of electric power on spacecraft come from photovoltaic (solar) cells or from a radioisotope thermoelectric generator. Other components of the subsystem include batteries for storing power and distribution circuitry that connects components to the power sources.

Temperature control and protection from the environment

Spacecraft are often protected from temperature fluctuations with insulation. Some spacecraft use mirrors and sunshades for additional protection from solar heating. They also often need shielding from micrometeoroids and orbital debris.

Propulsion

Mechanical devices

Mechanical components often need to be moved for deployment after launch or prior to landing. In addition to the use of motors, many one-time movements are controlled by pyrotechnic devices.

Control

Robotic spacecraft use telemetry to radio back to Earth acquired data and vehicle status information. Although generally referred to as "remotely-controlled" or "telerobotic", the earliest orbital spacecraft -- such as Sputnik 1 and Explorer 1 -- did not receive control signals from Earth. Soon after these first spacecraft, command systems were developed to allow remote control from the ground. Increased autonomy is important for distant probes where the light travel time prevents rapid decision and control from Earth. Newer probes such as Cassini-Huygens and the Mars Exploration Rovers are highly autonomous and use on-board computers to operate independently for extended periods of time.

List of space probes

This is a condensed version of the more detailed List of Solar System probes.

Lunar probes

Mars probes

Venus probes

Gas giant probes

Comet and asteroid probes

Solar observation probes

Other solar system probes

See also

External links




Text from Wikipedia is available under the Creative Commons Attribution/Share-Alike License; additional terms may apply.


Published - July 2009














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