<title>Some design and performance features of SUMER: solar ultraviolet measurements of emitted radiation</title>

The instrument SUMER (solar ultraviolet measurements of emitted radiation) is designed to investigate structures and associated dynamical processes occurring in the solar atmosphere from the chromosphere through the transition region to the inner corona, over a temperature range from 10<SUP>4</SUP> to 2 multiplied by 10<SUP>6</SUP> K and above. The observations will be performed, on board SOHO (solar and heliospheric observatory) scheduled for launch in November 1995, by a scanning, normal-incidence telescope/spectrometer system in the wavelength range from 500 to 1610 angstrom. Spatial resolution requirements compatible with the pointing stability of SOHO are less than 1000 km corresponding to about 1-arcsec angular resolution. Doppler observations of EUV line shifts and broadenings should permit solar plasma velocity measurements down to 1 km s<SUP>-1</SUP>. We report here on some specific features of this instrument related to its pointing as well as its spatial and spectral resolution capabilities.