The 825-1110 angstroms EUV spectrum of Venus

On 15 August 1994 we launched the EUVS sounding rocket payload to observe the 825-1110 angstrom region of Venus's far ultraviolet airglow spectrum. The EUVS telescope/spectrograph obtained good data at five times higher spectral resolution than was previously available in the far ultraviolet. We present these data and compare our results to those obtained by the Galileo UVS and Venera 11/12 UV spectrophotometers. We identify several new spectral emission features, including both singly ionized nitrogen and molecular nitrogen in Venus's spectrum. We also see evidence for electron-impact-induced emission from CO. Finally, the EUVS data indicate that the "Ar" emissions detected in Venus's far ultraviolet spectrum by Venera 11/12 spectrophotometers are in fact not due to argon, thus eliminating the discrepancy between in situ and remote sensing measurements.

Centroid position measurements and subpixel sensitivity variations with the MAMA detector

Initial measurements of the position sensitivity of a visible-light multi-anode microchannel array (MAMA) detector show that centroid calculations for image spots are accurate to better than 0.04 pixels even with sources that are essentially delta functions at the photocathode. Subpixel sensitivity variations of 10-15% are typically found for pixels in the array. Variations as large as 30% are possible in the worst conditions. These variations limit the photometric accuracy of the detector when very small scale features are observed. The photometric accuracy and the position sensitivity of the detector appear to be limited by cross-coupling effects within the anode array. Initial measurements with more recent designs of the detector show that most or all of this cross-coupling has been eliminated. We will report on the position sensitivity of the newer detectors when they become available for testing.

Thomson parabola ion analyzer for laser-plasma studies

A compact, flexible design for a parallel-fields ion analyzer is presented. Accurate ion velocity and charge state measurements can be obtained over a wide range without the need for calibration sources. Etchable cellulose-nitrate foil is used to record individual ion tracks.