Europeans set infrared satellite launch.

Europeans set infrared satellite launch

Three years from now, a European Ariane rocket will boost a satellite into Earth orbit to look at hot stars, shells of dust around cool stars, possible planetary systems in formation and other sources of infrared emissions. Called the Infrared Space Observatory (ISO), it will expand on 1983 observations by the Infrared Astronomy Satellite (IRAS), a primarily U.S.-sponsored craft that took the first-ever survey of the infrared sky from above Earth's atmosphere.

Roger Bonnet, director of science programs at the European Space Agency in Paris, announced last week that the launch will take place in the spring of 1993 from the agency's space center in Kourou, French Guiana.

During the IRAS mission, only project scientists had access to the satellite. In contrast, two-thirds of ISO's observing time will be made available to the astronomical community at large. Furthermore, ISO's planners designed it to operate for 18 months, nearly twice the length of the IRAS flight.

IRAS detected infrared emissions with wavelengths no shorter than about 8 microns, whereas ISO can sense emissions as short as 2.5 microns. This should assist in searches for cooler infrared sources, such as particularly dim stars and perhaps postulated objects known as brown dwarfs. The mass of a brown dwarf is apparently so low that its self-gravity cannot create enough internal pressure to ignite thermonuclear fusion reactions, the most prominent source of starlight (see story, this page).

On the other end of the infrared spectrum, ISO should detect emissions with wavelengths as long as 200 microns, compared with 119 microns for IRAS. This may improve observations of emissions from very cold dust in the interstellar regions of the Milky Way and other galaxies, and of a 158-micron carbon spectral line valuable in understanding the physics of interstellar space.