We present here preliminary results of the ASCA satellite. ASCA is equipped with X-ray telescopes that can observe the energy range up to 12 keV. There are two types of detector systems: GIS and SIS. The energy resolution of the SIS is 130 eV (FWHM at 6 keV) and can resolve emission lines clearly. For the PV phase, we planned to observe about 150 sources. Among them, there are 23 SNR's, some of which are presented here. We will be able to study the evolution of thin hot plasma in the SNRs.

Recent observations of the galactic supernova remnants the Crab Nebula, SN 1006, Cas A, and the Cygnus Loop are reviewed. New studies of the Crab Nebula suggest its progenitor may have had appreciable mass loss in the form of a circumstellar disk resulting in both a bipolar expansion and formation of the synchrotron ‘bays'. Unusually high proper motion knots near to and possibly directed away from the pulsar also have been reported. In the Cas A remnant, a NE jet of ejecta appears to be a plume of mantle material with expansion velocities up to 12000 km s-1 or nearly twice that seen in the main ejecta shell. HST observations of the sdOB star located behind SN 1006 indicate symmetrically expanding Fe II ejecta out to 8100 km s-1. Lastly, deep images of the Cygnus Loop reveal emission structures similar to those seen in 2D & 3D shocked cloud simulations.

New observations of supernova remnants in the far ultraviolet, especially in the sub-Ly α region, are changing the way we look at the interaction between blast waves and the interstellar medium. I briefly review some of the recent FUV observations of supernova remnants from the Hopkins Ultraviolet Telescope, the Voyager Ultraviolet Spectrometers, as well as IUE and HST.

Core collapse in very massive stars can lead to a central black hole that swallows the rest of the star and in less massive stars to a central neutron star and explosion. There is probably an intermediate mass range that gives an explosion and a central black hole; supernova remnants with no observable central object are candidates. The association of pulsars with Type II supernovae gives an estimate of the pulsar power to be expected in a supernova, but the uncertainty in the initial pulsar periods gives a wide range in possible powers. The relativistic wind bubble model for the Crab Nebula has steadily developed and there are now predictions regarding particle acceleration in the optical wisps. The bubble model with expansion into supernova gas can also be applied to other young pulsar nebulae.