An instrumented vehicle moving through the upper atmosphere or space or landing upon another celestial body in order to obtain information about the specific environment.

A biochemical substance labeled with a radioactive isotope or tagged in some other way and used to identify or isolate a gene, a gene product, or a protein.

To determine a radio interference by obtaining the relative interference level in the immediate area of a source by the use of a small, insensitive antenna in conjunction with a receiving device.

A metal rod that projects into but is insulated from a waveguide or resonant cavity; used to provide coupling to an external circuit for injection or extraction of energy or to measure the standing-wave ratio. Also known as waveguide probe.

A small tube containing the sensing element of electronic equipment, which can be lowered into a borehole to obtain measurements and data.

A small device which can be brought into contact with or inserted into a system in order to make measurements on the system; ordinarily it is designed so that it does not significantly disturb the system.