A week after launch, the boom hosting the magnetometer instrument on the JUpiter ICy moons Explorer (JUICE) mission has been successfully deployed.
JUICE launched on 14 April 2023 , and one week later on the 21 April, the 10.6-metre boom was unfolded and the magnetometer instrument - J-MAG - was switched on. Data collected by J-MAG captured the moment of deployment.
The J-MAG instrument will be crucial for JUICE’s mission to characterise the oceans expected to be found beneath the outer icy crusts of three of Jupiter’s moons - Ganymede, Callisto and Europa - and determine whether they might be able to support life.
Although JUICE will take around eight years to get to the Jupiter system, the early deployment of the instrument is an important milestone for the feasibility of the mission.
J-MAG Principal Investigator Professor Michele Dougherty , from the Department of Physics at Imperial, said: "It was a great relief to see the successful deployment of the magnetometer boom, which was the crucial next step for the team."
J-MAG consists of three sensors - one built at Imperial College London, one built at the Technische Universität Braunschweig, Germany, and one built at the Space Research Institute, Graz in partnership with Graz University of Technology, Austria.
The Imperial and Braunschweig instruments are ’fluxgate’ sensors, which can measure the direction and strength of magnetic fields. They are labelled ’outboard’ (MAGOBS) and ’inboard’ (MAGIBS) sensors respectively, separated by about three metres with MAGOBS mounted close to the end of the 10.6 boom.
A plot of the deployment has been released today (below). It shows the magnitude of the magnetic field from the two fluxgate sensors, MAGOBS and MAGIBS, before and after the deployment. The labels OBS and IBS indicate the data from the outboard and inboard sensors respectively.
The left side of the plot shows the measurement of the local magnetic field traces before the boom deployment. The sensors are up against the side of the spacecraft and MAGOBS is located close to two spacecraft thrusters which are quite magnetic, which explains the large discrepancy in the two field magnitudes between MAGOBS and MAGIBS.
Moving to the righthand side, the traces change as the boom deployment occurs, taking approximately two seconds starting just after 14:29:38. The two field magnitudes are then at a similar level close to zero and stable, indicating that the boom has deployed the full 10.6m and both sensors are measuring the ambient solar wind field, which is very small - in the region of a few nanoTesla (nT).
For full calibration of the J-MAG instrument, the third sensor, MAGSCA, which measures the magnetic field magnitude, needs to be switched on, which will happen in the coming week. The J-MAG team will also perform detailed instrument commissioning, which will include operation in its more sensitive ranges.