Want to stay on top of all the space news? Follow @universetoday on TwitterAn antenna array is a group of isotropic(omni-directional) radiators configured so that the currents running through them are of different amplitudes and phases. The radiators are in the EM frequency and energy. An array offers a great deal of flexibility over a single antennae because they allow for a great distance. There are a few different general types of antenna arrays. A linear array is in a straight line and a plane array is two dimensional. If you have multiple plane arrays in a group they are called a three dimensional array. An antenna array may consist of a group of isotropic radiators or it can be a group of identical radiators. In a group of identical radiators all the antennas must be share the same orientation in space. Placing the radiators in the same orientation results in either reinforcement or cancellation of the electric field intensity and insures polarization in the same direction in space.
The most common antenna array used in astronomy is the phased array. This is a group of antennas where the phases of the signals are varied so that the radiation pattern is reinforced in a desired direction and suppressed in undesired directions. This application developed in 1905. During WWII it was adapted for landing airplanes. A similar system that was developed in Germany at the same time(PESA Mammut 1) was adapted for radio astronomy. The design is also used in radar and interferometric radio antennas. Phased arrays are used in sonar, by space probes, weather research, optics, medical testing, for radio frequency identification, and human-machine interfaces.
The MESSENGER spacecraft is the first deep-space mission to use a phased-array antenna for communications. The radiating elements onboard are linearly-polarized, slotted waveguides. The antenna makes use of the X band and uses 26 radiative elements.
As you can see, the evolution of the antenna array has been extensive over the last 60 years. At one time, it was common to see a television array on every home. The simplest of arrays have always been placed on spacecraft, but MESSENGER seems to be ushering in a new era. This type of communication does not seem to be headed for extinction anytime soon.
We’ve also recorded an entire episode of Astronomy Cast all about the Electromagnetic Spectrum. Listen here, Episode 16: Across the Electromagnetic Spectrum.