In this talk, I will present the most sensitive ultraviolet observations of Supernova
1987A to date.  Imaging spectroscopy from the HST-Cosmic Origins Spectrograph show
many narrow (FWHM ∼ 300 km/s) emission lines from the circumstellar ring, broad (FWHM
~ 10000-20000 km/s) emission lines from the reverse shock, and ultraviolet continuum
emission. The high signal-to-noise (> 40 per resolution element) Ly-alpha velocity
profile is dominated by resonant boosting of Ly-alpha photons emitted from the
circumstellar ring. The ultraviolet continuum at wavelengths > 1350A can be explained
by H I two-photon emission from circumstellar ring gas. We confirm an earlier,
tentative detection of N V 1240 emission from the reverse shock and we present the
first detections of broad He II 1640, C IV 1550, and N IV] 1486 emission lines from
the reverse shock. The helium abundance in the high-velocity material is He/H = 0.14
+/- 0.06. The N V/H-alpha line ratio requires partial ion-electron equilibration (Te≈
0.14 – 0.35 Tp). We find that the C/N abundance ratio in the gas crossing the reverse
shock is significantly lower than that in the circumstellar ring, and possible
explanations are discussed.