near-surface antenna
11Metamaterial antenna — This Z antenna tested at the National Institute of Standards and Technology is smaller than a standard antenna with comparable properties. Its high efficiency is derived from the Z element inside the square that acts as a metamaterial, greatly… …
12Parabolic antenna — A parabolic satellite communications antenna at Erdfunkstelle Raisting, the biggest facility for satellite communication in the world, in Raisting, Bavaria, Germany. It has a Cassegrain type feed. A parabolic antenna is an antenna that uses a… …
13Beverage antenna — The Beverage Antenna is a relatively inexpensive but very effective long wire receiving antenna used by amateur radio, shortwave listening, and longwave radio DXers and military applications. Harold H. Beverage experimented with receiving… …
14Crossed field antenna — A crossed field antenna, or CFA, is a type of antenna for long and mediumwave broadcasting, patented in 1986, which was claimed to have the same efficiency as a conventional antenna but only one tenth the overall height. The invention was… …
15Apollo 15, Lunar surface — Apollo 15 Commander David Scott and Lunar Module Pilot James Irwin spent three days on the Moon and a total of 18½ hours outside the spacecraft on lunar extra vehicular activity. The mission was the first not to land in a lunar mare, instead… …
16Fractal antenna — A fractal antenna is an antenna that uses a fractal, self similar design to maximize the length, or increase the perimeter (on inside sections or the outer structure), of material that can receive or transmit electromagnetic signals within a… …
17Cassegrain antenna — In telecommunications and radar, a Cassegrain antenna is an antenna in which the feed radiator is mounted at or near the surface of a concave main reflector and is aimed at a convex secondary reflector slightly inside the focus of the main… …
18Mathematics and Physical Sciences — ▪ 2003 Introduction Mathematics Mathematics in 2002 was marked by two discoveries in number theory. The first may have practical implications; the second satisfied a 150 year old curiosity. Computer scientist Manindra Agrawal of the… …
19Mars Polar Lander — Artist depiction of Mars Polar Lander on Mars. Operator NASA / JPL Major contractors Martin Marietta …
201985 Mexico City earthquake — Mexico city Collapsed General Hospital …
