THE TESP ELECTRON SPECTROMETER AND CORRELATOR (F7) ON FREJA

The two-dimensional electron spectrometer on Freja consists of a 'top-hat'-type electrostatic analyzer with the addition of entrance aperture deflection plates. The field of view of the concentric-hemisphere analyzer is modified from a plane to a cone up to 25 degrees from this plane by applicaiton of bipolar high voltages to the deflection plates. Fast high-voltage sweeps allow full 10 eV-25 KeV, 500-point distribution function measurements in 32 ms. Constant-energy or limited energy-sweep modes allow time resolutions down to 1 ms. A set of electronics combines the electron data with F4 wave data to allow on-board calculations of cross-correlations between electron fluxes and wave electric fields. Additionally, a fast signal processor is capable of searching the electron pulse sequence from one or several channeltrons for high-frequency modulations in the electron flux.