Glossary

Amor - is an Earth Approaching asteroid type defined by the perihelion distance, q. If an asteroid has 1.0 < q <= 1.3 AU.

Aphelion distance - with symbol Q, is the most distant point from the sun in an objects orbit. Apogee is the term for Earth orbiting objects and Apoapsis is the generic term for any orbit around any other object. 

Apollo - is an Earth Approaching asteroid or Earth Crossing asteroid whose semi-major axis, a, is greater than 1.0 AU but it's perihelion distance, q, is less than 1.0 AU. 

Argument of pericenter - with symbol ω [Greek little omega], is an orbital element which defines the orientation of the location of perihelion or pericenter of the orbit. 

Aten - is an Earth Crossing asteroid whose semi-major axis, a, is less than 1.0 AU but it's aphelion distance, Q, is greater than 1.0 AU. 

Astronomical Unit - abbreviated AU, is approximately the mean distance of Earth from the sun. The AU was fixed by the IAU at the value of 149,597,870.7 km. 

CCD - Charge Coupled Device. The detector that most observatories, including Spacewatch, use to image the sky. 

Cosmic rays - Atomic particles moving through space at near the speed of light. They are believed to be a product of supernovae or flares on the Sun. These particles pass through the telescope CCD and artificially add to the amount of light measured by a small number of pixels on the CCD. 

Eccentricity - with symbol e, is an orbital element that defines the shape of an orbit. When eccentricity is 0.0, the orbit is circular, 1.0 the orbit is parabolic. 

Ephemeris - a table of times with predicted positions for moving object 

FMO - Fast Moving Object 

Inclination - with symbol i, is an orbital element that defines how steeply the orbit is tilted with respect to the ecliptic. 

Light curve effects - how the brightness of an object changes with time (brightness variability will have a period and an amplitude, e.g. rotating asteroids may reflect light differently off of each side - but the change in reflectivity has a discernible pattern) 

Longitude of the ascending node - with symbol Ω[Greek big omega], is an orbital element that defines what direction the object is in as it is ascending through the plane of the ecliptic 

Main-belt asteroid - An asteroid which orbits in the Main Belt, usually between Mars and Jupiter. 

MPC - Minor Planet Center

NEA - near-Earth asteroid, includes both asteroids and comets. 

NEO - near-Earth object 

Orbital elements - define the shape, size and orientation of the path ("orbit") of an object around another object. The elements are the semi-major axis, eccentricity, inclination, argument of pericenter, longitude of the ascending node and time of perihelion (or alternatively, the mean anomaly and epoch). 

Perihelion distance - with symbol q, is the closest distance of an objects orbit to the sun. Perigee is the term for Earth orbiting objects and Periapsis is the generic term for any orbit around any other object. 

Pixel - a "picture element" or a single spot of light on your image. A CCD array is composed of some number of pixels. For example, the previous generation Spacewatch CCD had 2048x2048 pixels or 4,194,304 pixels. Our new mosaic camera will be composed of 4 CCDs each with 2048x4608 pixels or 4x9,437,184 = 37,748,736 pixels. 

Pixelation - An example of pixelation is a diagonal line with a stair-stepped appearance 

Semi-major axis - with symbol a, is normally measured in units of astronomical units. a is the average distance of the object from the sun (or whatever central body it orbits) and combined with the other orbital elements, allows us to classify an object and compute where it will be at other times. 

Twilight, nautical - the moment when the center of the sun is geometrically 12 degrees below the horizon 

Twilight, astronomical - the moment at which the sun no longer contributes to sky illumination (sun is 18 degrees below the horizon) 

VFMO - Very Fast Moving Object