The Cluster PEACE experiment is made up of two sensor heads called LEEA and HEEA (Low and High Energy Electrostatic Analysers), mounted on opposite sides of each of the four Cluster spacecraft (Johnstone et al (1997)). Generally LEEA scans the lower energy range and HEEA the upper range, together covering electrons with eV
keV. Over the duration of a spin (
s), LEEA and HEEA cover 4
steradians of velocity space.
The moment sums can be thought of as combinations of the low energy moments (the B (BOTTOM) moments, eV), the high energy moments (the T (TOP) moments,
keV), and the moments from where the energy scan of LEEA and HEEA overlap (which we call L1L2 and H1H2 respectively) as sketched in Figure 3.2. These separate pieces are telemetered to the ground, where we can construct moment sums covering the entire energy range by summing B, L1L2/H1H2 and T moments. The `measured' moments (subscript `m') are the raw sum of, for example B+overlap+T moments, which have not been corrected.
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