Astronomy and solar physics: measurement of the solar spectral irradiance from 200 to 3000 nanometers.

The solar spectrum experiment on Spacelab 1 measured 98 percent of the sun's total energy output. It improved the absolute accuracy of solar irradiance data, especially in the ultraviolet and infrared regions. In order to detect any variation in the spectrum on future shuttle flights, the data were obtained in a radiation scale that can be preserved with high precision over many years. The instrument performance and preliminary data reduction are described.

Deuterium lamp as a UV continuum source from 160 nm to 320 nm for space applications.

The deuterium gas discharge lamp is a continuum radiation source for the 160-320 nm wavelength range. A special model has been developed to meet space requirements. The lamps under investigation withstood heavy shock and vibration, were operated in a vacuum, and their radiant output was monitored in a zero gravity environment. No changes in their characteristics were found.

The synchrotron radiation of the 6-GeV DESY machine as a fundamental radiometric standard.

The characteristics of synchrotron radiation emitted by the 6-GeV DESY machine were studied in the spectral range 2200-5500 A. For this purpose, the synchrotron radiation was compared photoelectrically with the radiation of standardized sources in a nearly differential manner. These sources (tungsten ribbon lamp, Krefft-Rössler uv normal) were calibrated with high accuracy against a blackbody. Good agreement was found between our experimental results and the values predicted by the theory of the synchrotron radiation derived by J. Schwinger. The relative spectral distribution was verified to within about +/-2%, and the absolute values of the theoretically predicted flux were ascertained to within about +/-15%. For the application of synchrotron radiation as a radiometric standard, in most cases only the relative spectral distribution is important. If one supposes the validity of the theory also in the far uv, and if the synchrotron radiation is calibrated in the visible by a standard source, one can give the abolute flux in the far uv. In this way it is possible to calibrate photometers or sources in the far uv in absolute units with an accuracy of about +/- 3% with the aid of the synchrotron radiation.

Transition Radiation as a Secondary Standard Source in the VUV.

The optical radiation caused by electron bombardment of metallic surfaces was tested for its use as a secondary standard source in the VUV. Aluminum of high purity was found to be a suitable target material. The reproducibility of the radiation is of the order of 4% to 2% for 0.11 < lambda < 0.15 microm and 0.15 < lambda < 0.27 microm, respectively. In the spectral region 0.17 microm to 0.27 microm, the source was calibrated absolutely by comparison with a deuterium lamp of known absolute intensity.

Quasi-monochromatic calibration source for the wavelength range from 0.22microm to 7.0microm.

This paper describes an optical system (consisting of a calibrated radiation source, a special double monochromator, and a Cassegrain telescope) that produces a quasi-monochromatic beam with known radiation power at its exit. The wavelength range extends from 0.22 microm to 7.0 microm. The spectral bandwidth may be varied within certain limits (0.0004-0.16 microm). The emerging light beam is either divergent (f/13.8) or parallel, and without any spectral structure. Some important remarks concerning the calibration procedure of the monochromator (polarization, slitwidths, etc.) are given.