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EPOXI

Two intriguing investigations -- One flight-proven spacecraft

Glossary

Glossary

Aphelion
          the point in an object's (ie, planets, comets, asteroids) orbit around the sun when it is farthest from the sun
 
AU (Astronomical Unit)
          the average distance between the Earth and sun (1 AU=1.496 X 10^8 km= 92.96 million miles)
 
Attitude Errors
          the difference between a computed or measured value and a true or theoretically correct value of the orientation of an aircraft's axes relative to a reference line or plane, such as the horizon.
 
Avionics
          a general term for the development and production of electrical equipment for use in aircraft, spacecraft, and missiles
 
Calibrate
          to determine or mark a correct value using a meter or other measuring instrument
 
CCD (Charged-Coupled Device)
          a photoelectric detector which contains thousands of light-sensitive cells that produce a certain amount of charge depending on how much light they are able to receive
 
Coma
          a bright shell of gas and dust that is given off by a comet's nucleus as it heats up under sunlight and that hides the nucleus from view
 
Degree-of-Freedom
          any of the independent modes in which a system can continuously change shape or move in space
 
Geometric Distortion
          a change in the image caused by the components of the optics, either lenses or mirrors
 
High Dispersion Spectrometer
          HDS splits light into its constituent colors with an accuracy of 1 part in 100,000
 
HRI (High Resolution Instrument)
          one of the Deep Impact telescopes, with a primary mirror diameter of 30 centimeters, that delivers light simultaneously to both the multispectral camera and an infrared spectrometer
 
Hydrazine
          a volatile liquid used for propulsive rocket fuel
 
MRI (Medium Resolution Instrument)
          one of the Deep Impact telescopes with a primary mirror diameter of 12 centimeters and a 0.6 degree field of view
 
Micron
          a unit of length equal to one millionth of a meter; also called a micrometer
 
Open Cluster
          (galactic cluster) a group of several hundred to a few thousand stars lying in the plane of the Milky Way Galaxy
 
Outgassing
          the ejection of gaseous material from the interior of a planet or comet
 
Perihelion
          the point in an object's orbit when it is nearest to the sun
 
Pixels
          the smallest element of an image, corresponding to a single displayed spot or color triad on a display, or to a single input spot from a camera
 
Planetesimals
          objects, a few kilometers long that were created during the same time the solar system was formed. These objects would either collided to form planets, or become asteroids and comets
 
Primordial Ices
          ice from the beginning of the solar system
 
Propulsion System
          a system that produces a required change in the momentum of a vehicle by changing the velocity of the fluid or propellant passing through the propulsive device or engine
 
Protoplanetary Disk
          a circumstellar disk of matter, including gas and dust, from which planets may eventually form or be in the process of forming
 
Small Magellanic Cloud
          one of two relatively small irregular galaxies that orbit the Milky Way Galaxy and are roughly 160,000 light-years away
 
Solar panel
          a structure containing solar cells that collects sunlight and converts it to electric current
 
Spatial Resolution
          a measure of a system's ability to distinguish the spatial separation (distance) of two points.
 
Spectroscopy
          the science that is concerned with the measurement of the emission and absorption spectra of light and other forms of electromagnetic radiations.
 
Topography
          the configuration of a land surface, including its relief
 
X- band
          a microwave band that extends from 8000 to 12000 megahertz used to transmit space data to back to Earth