A study of the electrical charging of the ROSETTA orbiter: 2. Experimental tests in a laboratory plasma

Following the numerical simulation presented in the companion paper, we have performed experimental tests in a plasma simulation chamber to check the results of the numerical model and validate its capability to properly predict the electrical equilibrium of the Rosetta orbiter. Since low temperature cometary plasmas cannot be directly reproduced in such a chamber, we conducted the tests in plasmas with scaled characteristics deduced by considering similarity laws as is done in wind tunnel experiments. A mock-up of the Rosetta orbiter and solar panels was constructed with the capability of measuring collected currents over the various faces of the mock-up. These measurements included the possibility of observations on finer scales typical of ion collection as measured by ion energy analysers. This series of tests has allowed us to validate the performances and the predictions of the model presented in the companion paper.