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    PR # 31078                                                                   
     SN 1993J is one of five recent supernova explosions (SNe) detected in       
      X-rays. It is observationally unprecedented, in that it is the only        
     SNe detected in the radio and in X-rays within a week of the explosio       
     n, and whose X-ray lightcurve and spectral evolution have  been caref       
     ully measured for over one year.  The observations we  propose extend       
      the lightcurve (luminosity, spectral hardness, and temperature) into       
      years. This first-of-a-kind opportunity, to follow the evolution in        
     X-rays of the shocked circumstellar matter during the first few years       
      after the explosion of a red supergiant,  should not be missed.            
                                                                                 
                                                                                 
                                                                                 
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