Tweet Based on inputs from ROMAP co-principal investigator Hans-Ulrich Auster from the Technische Universität Braunschweig, Germany. Data collected by ROMAP, the Rosetta Lander Magnetometer and Plasma Monitor onboard Philae, is being used to help reconstruct the trajectory of the lander to its final landing site on Comet 67P/Churyumov-Gerasimenko. As we described in an earlier blog post, magnetic fields can be used for this task because both the lander and the orbiter generate small magnetic fields of their own due to the electronic circuits inside the spacecraft. These magnetic fields create perturbations in the data that are normally removed in order to analyse the purely natural magnetic fields from the comet and the solar wind. But during the descent of the lander, these perturbations were measured in order to monitor what was happening to the lander as it slowly dropped towards the surface of 67P/C-G. “Any motion of Philae in a magnetic field – even if it is small – can be seen by field changes in the measured magnetic field direction,” explains ROMAP co-principal investigator Hans-Ulrich Auster from the Technische Universität Braunschweig, Germany. ROMAP timeline The scientists have now been able to use ROMAP data to reconstruct the chain of events that took place on 12 November as follows: -       Separation was confirmed as a decay in the magnetic field perturbation as the distance between Philae and the orbiter increased; at this point the lander was spinning at a rate of about 1 rotation per 5 minutes; -       The landing gear was deployed successfully, accompanied by a change in the spin rate to 1 rotation per 8.5 minutes; -       The ROMAP boom was deployed successfully and a magnetic field decay was measured corresponding to the increased distance of the ROMAP sensor with respect to its original position on the lander; -       During the seven-hour descent, all measurements […]