For astronomers, the universe speaks several languages. These languages are different kinds of electromagnetic radiation, which is emitted or reflected by matter in space.
Before the end of the century, US scientists hope to have four world-class ``great observatories'' in orbit simultaneously to detect these energy messages. Each observatory will monitor a different kind of radiation for about 15 years. Instruments on the facilities will be updated about every five years.
The great observatory program has been the primary goal of US astrophysicists since 1970.
Even one observatory will yield important new scientific information. But taken together, they will help scientists piece together a much more complete view of the universe.
Orbiting outside the Earth's distorting atmosphere, the observatories will have a clearer view of the heavens than even the highest earthbound observatory. Other instruments have been in space to detect various types of radiation, but the great observatories will be by far the most sensitive.
Electromagnetic radiation is energy from accelerating electric charges. It is made up of an electric wave and a magnetic wave that are perpendicular to each other and interdependent. Matter can emit this energy or electromagnetic radiation and also interact with it.
The accompanying chart details the four great observatories, launch dates, costs, and some of their capabilities.
CHART/ILLUSTRATIONS: The Four great observatories; Orbiting outside earth's distorting atmosphere, the great observatories will have a clearer view of the heavens than the highest earthbound observatory. Taken together, they will ``see'' space events in a large proportion of the electromagnetic spectrum. 1) SPACE INFRARED TELESCOPE FACILITY; Detects: low-energy waves. Observes: center of the Milky Way, material from which stars are made, residue from exploded stars. Cost: $1 billion. Launch date: not yet funded; 2) HUBBLE SPACE TELESCOPE; Detects: medium-energy waves. Observes: mature stars, planets, may see to the edge of the universe. Cost: $1.2 billion. Launch date: February 1990; 3) ADVANCED X-RAY ASTROPHYSICS FACILITY; Detects: high-energy waves given off for years after a cosmic event. Observes: the creation and death of stars (for example, supernova resulting in black holes), high-energy physics in space. Cost: $1 billion. Launch date: none; full-scale development in fiscal year 1989 budget; 4) GAMMA RAY OBSERVATORY; Detects: very high-energy waves given off immediately after a cosmic event. Observes: the creation and death of stars. Cost: $650 million. Launch date: April 1990.