Experiment layout and signal handling.

The instrument comprises two spherically shaped probes mounted on two booms of about 0.67 m length. The booms are mounted at 15 degrees angle to the spin plane on the outer edges of two of the solar panels giving a probe to probe distance of about 2.9 meters. The probes and booms are designed and qualified by the IRF-U.

The electronics is built by IRF-U and integrated into the box of the Electric field experiment supplied by the Royal Institute of Technology in Stockholm (KTH). The probe signals will be fed to the electronics via tri-axial cables.

A common processor, EMMA system unit, for control of LINDA, the Electric Field Experiment, the Magnetometer and the Star camera as well as the interface to the Astrid System Unit (ASU) is designed by the Royal Institute of Technology (KTH). Also the power supply converter (DC/DC) is designed by KTH.

All signals will be filtered by low-pass filters to avoid aliasing effects.
 

Electronics.

The electronics is allocated on two printed circuit boards and contains preamplifiers for each of the probes, low pass filters for bandwidth limitations, analogue to digital conversion, a XILINX circuit used for calculation of the dn/n ratio.

A mass memory of 12 Mbytes, common for all experiments controlled by the EMMA system unit, is also allocated in the electronics box and can be used for storage of data sampled during times when the satellite is not visible from any of the two ground stations.
 

Booms and probes.

There are two identical deployable booms for LINDA, one for each of the probes. The booms are made of two sections with a hinge and the material is aluminium tubes of 6 mm outer diameter. The hinges and the retaining mechanisms are made of dural-aluminium and Titanium. The Titanium parts have a surface treatment of Titanium Nitride (TiN) in order to have a non-stick surface finish. In stowed position the booms are folded along the outer rim of the outermost solar panels. The retaining mechanisms contains two holders for each of the booms and the releas mechanisms are activated by the release of the solar panels.


Figure: "Top" view of S/C with solar panels and LINDA booms deployed (Wire booms excluded).


 


The probes are spherically shaped with 10 mm diameter. They are made of Titanium with a surface treatment of Titanium-Nitride (TiN) which has proven to have excellent properties for a good contact to the plasma. Between the probes and the outer end of the booms there are thin Stubs of 5 cm length on which the potential is regulated to be the same as the probe bias voltage. This is to minimise the influence of photoelectrons on the measured probe current. The rest of the booms are connected to the satellite ground.