Astronomers plan a month on the sun.

Astronomers plan a month on the sun

Stereo images of the sun, taken jointly by a U.S. spacecraft orbiting Earth and a Soviet craft on its way to Mars, may be among the highlights of International Solar Month. Among the diverse activities planned for the elaborate program will be observations throughout September, involving researchers from at least 13 countries and facilities both in space and on the ground.

The solar month idea was born essentially out of an April 28 meeting in Bethesda, Md., between U.S. and soviet solar scientists, who were discussing the possibility of simultaneous observations with the U.S. Solar Maximum Mission satellite and one of the Soviet Union's two spacecraft now heading toward the little Martian moon Phobos (SN: 6/18/87, p.392). Both "Solar Max" and Phobos 1 carry white-light coronagraphs for photographing the sun's coronal fringes, as well as soft X-ray imaging devices that make pictures of the solar disk in a very different part of the spectrum.

Another major participant will be the Very Large Array (VLA), a vast complex of 27 radiotelescopes in Socorro, N.M. In September, the VLA's antennas will be arranged in an ideal pattern for "imaging" the full solar disk, notes Joan Schmelz of Applied Research Corp. in Landover, Md. Further restricting the time available for International Solar Month is the fact that Solar Max may be destroyed es early as 1990, as the result of reentering Earth's atmosphere. Thus, Schmelz wrote in the July 26 Eos, next month is likely to be "one of at most two opportunities" available for the VLA and Solar Max to study the sun at the same time.

In fact, she says, "I think every solar physicist in the world would admit that what we really need for solar studies are simultaneous multiwaveband observations." Aiding plans for each day's operations will be daily images from the five Earth-based observatories of the U.S. Air Force's Solar Optical Observing Network, which will form the basis for regularly updated observing guidelines to participants worldwide.

Other nations involved in International Solar Month include Canada, Australia, Japan West Germany, hungary, Poland and Italy. Some were partners in the Coronal Magnetic Structures Observing Campaign in late 1987, an intensive study of several active solar regions at different wavelengths during the rise phase of the present solar cycle.