COMMISSION 27 OF THE I. A. U.
      INFORMATION BULLETIN ON VARIABLE STARS
                   NUMBER 466

                           Konkoly Observatory
                           Budapest
                           1970 September



     NASA's SAS-A spacecraft which is intended to conduct
an all-sky survey x-rays (2-20 keV) is now scheduled for
launch early in December 1970. The instrumentation is
capable of detecting emission of about 5 x 10 -11 0 ergs/cm2-sec
   (5*10 -3 of the Crab Nebula) during a single pass across
a source. The spacecraft has limited manuevering capability
and we hope to be able to observe specified regions of the
sky during prescribed time intervals, in particular, we hope
to be able to have the spacecraft in position to view many
of the flare stars that are included in the 1970 observing
schedule published by the Working Group on Flare Stars (IBVS)
No. 416). It is our plan to devote one or two days of continuous 
observing of a given object with the two week
interval scheduled for the object. We also hope to publish
in this bulletin the exact time interval during which the
spacecraft will be viewing the object so that other observers
may be able to record data simultaneously in the optical
and radio wavelengths.
     Interested parties can obtain more information concerning 
the capability of the SAS-A experiment and our observing 
plans by writing to Herbert Gursky, who will assume
responsibility for the coordination with optical and radio
observations during the life of the SAS-A satellite.



                 R. GIACCONI, H. GURSKY,
                 E. KELLOGG, H. TANANBAUM
                    
                American Science and Engineering, Inc.
                     11 Carleton Street
                  Cambridge; Massahusetts
                         USA 02142