500  Once the antennas have been deployed and the film is attached to the  assembly and has free movement. Another reason for avoiding ESD and  earthing it, should it make contact and discharge towards an antenna.  o Mechanical interface between the resistance and the sub-chassis. The resistance  must remain in a set position during the burning time, which means there is contact between both elements. This interface, furthermore, is designed so that its characteristics stop the resistance from becoming detached after burning, even if the power cables were to become loose for any reason.  o Switch and sub-chassis. This is another of the interfaces that caused the most  headaches throughout the project. It is very important that the switch be installed at the exact point it was designed for, because in this way the trajectory of the retention wire is correct and its aperture is guaranteed together with correct deployment measurement. There have been many modifications based on the results from tests and flight prototypes.  o Nylon wire. The nylon wire is another of the more complicated interfaces as it is in  contact with the enveloping film, the antennas, the outside of the sub-chassis, the resistance, the switch, the inside of the sub-chassis and, finally, with the sub-chassis again, when it goes through the tying holes.  o Interface between the polymeric support piece for the resistance, the sub-chassis  and the shielding. This piece should leave the resistance in the correct place and fit tightly in order to avoid vibrations or shifts of position.  o Attachments. The use of different materials to make the device's parts means that  expansion gradients can appear at the areas where there are mechanical conflicts between materials depending on the temperature changes produced during orbit. This takes on greater importance at the attachment points on the sub-chassis for the antennas, where there is contact between Polyamide 12 with fiberglass and the Titanium, Aluminium and Vanadium Alloy. Some play is needed in order to avoid polymer fault.   Electrical Interfaces. All the electrical relationships between elements in the device are given  in this section:  o Burning resistance. The design must guarantee electrical separation between the  power cables to the resistance and the metallic mass of the satellite that serves as its electrical mass. At the same time the electrical connection must be guaranteed between the resistance conductors and the power cables to the antenna board. In this case by soldering.  o Switch. In the same way as for the resistance, the switch connections must be  electrically insulated to ensure perfect measurement. As with the resistance, the connection must be guaranteed with the measurement cables in the switch. Soldering is also the solution here.  o Antennas. It is clearly necessary to insulate the antennas from any electrical contact  that may exist. This is a point had also previously been studied and included in the design of the sub-chassis itself, as can be seen in the tabs.  o Connection of antennas and metallic mass. The bolt must keep the connection wire  for each antenna in contact in order to ensure perfect data transmission. At the same time, the metallic mesh of the coaxial cable for antenna connection must be kept between the shielding and the sub-chassis, i.e., earthed at all times.  o The dissipative layer of the sub-chassis and the shielding. To avoid ESD in the subchassis, it was decided to use dissipative paint on it and earth it in contact with the shielding by direct contact between the covering and the shielding.   Thermal Interface. This interface is somewhat complicated given that in one small area 4  different materials are in contact, each with distinct conductivities, distinct fusion points and distinct responsibilities in the device; these are the resistance, the sub-chassis, the shielding and a piece that acts as the resistance support and is the sub-chassis' protection against high