Angular resolution

The smallest angular size that the instrument can resolve.

Anisotropy

The difference in the property of a system with changes in direction. In this case, anisotropy refers to the difference in the temperature of the cosmic microwave background radiation with direction.

Energy Spectrum

The amount of energy emitted at a specific wavelength of light. For example, the Sun emits light at many wavelengths, which can be seen by passing sunlight through a prism. The energy spectrum of sunlight is strongest at the wavelength of yellow light, thus the Sun appears yellow to our eyes.

Feed

A component that "feeds" the signal from the optical system to the amplification electronics. Also called a "feed horn" or "horn".

HEMT

High Electron Mobility Transistor. This is a particular kind of transistor that is especially appropriate for use in microwave amplifiers.

Ionized

The state in which an atom is missing on or more of its electrons, and is therefore positively charged. An ionized gas is one in which some or all of the atoms are ionized, rather than electrically neutral. The ionized electrons behave as free particles in this gas.

Kelvin

One Kelvin degree is equivalent to one Celsius degree. The difference between the two temperature scales: All motion within an atom ceases at zero Kelvin (K) -- this point is called absolute zero. Water freezes at zero degrees Celsius, which is approximately 273.16 K.

MIDEX

NASA's Mid-Class Explorer.

Sensitivity

The level of random noise in the temperature measurement.

Structure

The patterns of the distribution of matter in the universe, as probed by the cosmic microwave background radiation or observations of galaxies.

Systematic Errors

Measurement errors that are not random.

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Last updated: February 17, 1997