Wavelength and Throughput Calibration of the EUVE Spectrometer from In-Orbit Observations

The Extreme Ultraviolet Explorer was launched on June 7, 1992, into a 530 km orbit. After an initial engineering checkout period, the in-orbit calibration of the science package was accomplished over a period of 30 days. Additional calibration data continued to be taken during the all-sky survey. These calibration observations are used to check the characteristics of the spectrometer against the ground-based EUVE calibration and to confirm the feasibility of typical pointed spectroscopic observations. We describe throughput measurements of the EUVE spectrometer using a suite of continuum sources compared to the ground-based calibrations and standard models of white dwarf stars. These observations suggest that the ground-based throughput measurements are fairly representative of the in-orbit behavior of the spectrometer. The spectrometer wavelength scale and resolution have been calibrated using emission line spectra from late-type stars. In general, these observations also suggest that the in-orbit behavior of the spectrometer is very close to that expected from the ground measurements. The in-orbit calibration observations have allowed us to improve our detailed understanding of the behavior of the EUVE spectrometers. This work has been supported by NASA contracts NAS5-30180 and NAS5-29298.