Nitrogen Tetroxide. Also abbreviated NTO.

The direction from a spacecraft directly down toward the center of a planet. Opposite the zenith.

National Aerospace Laboratory of Japan.

National Aeronautics and Space Administration.

National Space Development Agency (Japan).

The distance spanned by one minute of arc in latitude, defined internationally as 1,852 meters (6,076.1033 feet).

Eighth planet from the Sun, a gas giant or Jovian planet.

Atomic particles having approximately the same mass as a hydrogen atom; very penetrating.

That force which gives a mass of 1 kilogram an acceleration of 1 meter per second per second; equal to 100,000 dynes.

Nickel Cadmium.

A liquid oxidizer that reacts spontaneously with hydrazine. Also see IRFNA and IWFNA.

A liquid oxidizer that reacts spontaneously with hydrazine.

Weakly-luminous clouds, seen at night at heights of about 50 miles (80 km) above the Earth.

Communications mode wherein a spacecraft generates its downlink frequency independent of any uplink frequency.

North American Air Defense Command (USA).

A cover on the nose of a rocket or spacecraft which jettisons before insertion into orbit.

The projecting aperture at the end of a combustion chamber serving as an outlet for the exhaust gases.

National Research Council (USA).

Nitrogen Tetroxide. Also abbreviated N₂O₄.

The central body of a comet.