416 • Materials selection.   The material must withstand the various types of radiation present in the working  environment and avoid potential risks from electrostatic discharges produced by an  atmosphere with a high ion density. In addition, it must withstand the temperature changes occurring when its orbit passes in and out of sunlight, which range from 243 to 293K, and the maximum temperature during launch of 353K.  • Dimension and mass limits.  The mechanism must be as light as possible so that other elements can be included on the satellite. The aim is for everything to be un der 20 g. Furthermore, it must not protrude  more than 6.5 mm from the outer face of the shielding.  • Mechanical strength.  The mechanism must guarantee its structural integrity and the retention of the antennas  under the effects of knocks and vibrations. 

Adopted solutions

All the solutions proposed for each of the above problems are briefly outlined below:  • The mechanism would be built in to a single piec e that would act as a support for all the others,  which we will call the sub-chassis from here on.  • The sub-chassis would be made of a polymeric material to insulate the antenna electrically; this  would later be covered by a layer of dissipative paint.  • The sub-chassis was designed in a continuous ring shape with a C profile, so that the interior  space was available for other elements such as solar panels, cameras and so on.  • The chosen polymer was polyamide as this brings together the many features needed for subchassis operation such as acceptable resistance to radiation and ultraviolet radiation and great dimensional stability against exterior temperature changes.  • To solve the weight problem, in addition to t he material chosen for the sub-chassis, it was  decided that the attachment elements should be high strength material in order to reduce size. Finally, titanium Gr5 (Ti6Al4V) M2 nuts and bolts were chosen.  • A surrounding sheet of polyvinyl acetate wa s chosen for the retention system, a tough and  dissipative polymer to avoid static interaction with the antenna.   • This sheet shares its attachment to the su b-chassis with one of the antenna and acts as a  retainer for the antenna whilst they need to be fold ed, as it envelops them on their outer part and  keeps them within the continuous C-shaped profile described above.  • The triggering system chosen was a 0.125-W electr ical resistance with a ceramic body instead of  a Nichrome wire.    Antenna Deployment Mechanism Introduction  One of the advantages and capabilities of a satellite is the ability to collect  data in an environment that is  difficult for people to access. However, it must be able to communicate that data to areas where humans  do have access, i.e., it must have an antenna to send and receive data.  These antennas cannot be sent  into space already deployed, as this would take up t oo much room on costly spac e flights. This is where  the deployment mechanism comes into play as it  allows them to be folded during the journey and  deployed once the satellite is in orbit. The deployment mechanism is, therefore, one that is designed to integrate antenna storage before deployment plus th e deployment system and its corresponding burner  circuit, all with the smallest size and weight possible.  To achieve such integration, a modular design was proposed that would allow all the mechanisms to be fitted to a single piece, thus saving weight and space, and keeping things simple. The base for this modular attachment system was called the sub-chassis, as the satellite itself was regarded as the prime  chassis. The antenna, the re tention mechanism and the burner circuit ar e attached to it and it also acts as  NASA/CP-2010-216272