The Giotto electron plasma experiment

Publisher Website
Google Scholar
Abstract
The RPA-Copernic plasma experiment for the Giotto mission consists of two sensors, the RPA1-EESA spectrometer and the RPA2-PICCA electrostatic mass analyser. RPA1-EESA measures the three-dimensional distributions of electrons between 10 eV and 30 keV. These electron measurements should contribute to the definition of the properties of the cometary plasma and its interaction with the solar wind. This sensor includes an electrostatic symmetric quadrispherical analyser of novel design and provides 4 pi electron measurements with high sensitivity and good energy, angular and time resolution. With a 360 degrees *4 degrees field of view and with 17 fast-counting MCP sectors, a three-dimensional distribution is obtained every 2 s (half a spin of the space probe). The experiment includes three microprocessors. They interface RPA1-EESA with RPA2-PICCA and with the spacecraft, and perform extensive onboard data processing. One of the processors is designed to sort the three-dimensional electron distribution into two-dimensional pitch angle distributions in real time. The symmetry axis of the electron momentum flux tensor is computed on board. This symmetry axis is generally aligned with the magnetic field direction.