<h2>CLUSTER EFW Electric Field in ISR2</h2>
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   <b>Electric Field in ISR2</b> is obtained from
    <a href="http://caa.estec.esa.int/caa/" TARGET=_BLANK>CAA</a> C[1-4]_CP_EFW_L3_E <br/> <br/>
      The EFW instrument measures the electric field only in the spacecraft 
    spin plane, therefore a spin-plane oriented coordinate system is best 
    suited for scientific studies involving the electric field. The ISR2 
    (Inverted Spin Reference) system, also known as DSI (Despun System 
    Inverted), is such a system. The X and Y axes are in the spin plane, 
    with X pointing as near sunward as possible and Y perpendicular to the 
    sunward direction, positive towards dusk. The Z-axis is along the 
    (negative) spacecraft spin axis, towards the north ecliptic. The 
    coordinate system is called “Inverted” because the actual spin axis of 
    Cluster is pointing towards the south ecliptic. The difference between 
    ISR2 (DSI) and the GSE (Geocentric Solar Ecliptic) is a tilt of 2° to 7° 
    of the Z-axis performed in order to avoid shading of the EFW probes by 
    the spacecraft.