Artist's impression of Venus Express. Courtesy: ESA

Science Nuggets: Plasma Instrumentation

Calibrating the Venus Express ELS


Venus Express is one of Europe's interplanetary exploration spacecraft, equiped with a similar suite of instruments to its sister mission, Mars Express. Despite being identical in design, the performance of the Venus Express ASPERA-4 Electron Spectrometer is dramatically different from the nominal response shown by the ELS on Mars Express. While the mechanical tolerances of the key electron optical elements were suspected as being different, the precise nature of the problem was unknown until a study by Collinson et al.

Image of the Mars Express ASPERA-3 instrument. The ELS instrument is aluminium cylinder mounted on the end.

The mismatch between the results of the experimental calibration and the nominal case could not be supported without a theoretical understanding of the fundamental instrument science behind the device. Through simluation of the instrument, Collison et al. showed that a combination of a misalignment of the inner hemisphere and a wider than nominal aperture could cause a variation in the response of the instrument. By varying these parameters, the resulting instrument performance in the simulation was matched to the experimental results from the ELS instrument. This good agreement between both laboratory calibration data and computer simulation gives a firm foundation for future scientific data analysis.

For more details, see:

G.A. Collinson, D. O. Kataria, A.J. Coates, S.M.E. Tsang, C.S. Arridge, G.R. Lewis, R.A. Frahm, J.D. Winningham, and S. Barabash,
Electron Optical Study of the Venus Express ASPERA-4 Electron Spectrometer (ELS) Top-Hat Electrostatic Analyser
Meas. Sci Tech (2009), (Accepted)

 

This page was last modified 6 February, 2009 by cfo[at]mssl.ucl.ac.uk, cjo[at]mssl.ucl.ac.uk