available room and taking into account technological, manufacturing and functional aspects. In particular,  four basic concepts have been studied:/g131Tropical solution: to apply the preload using three pullers hardly engaged in the satellite body.  /g131Clamp Solution: to apply the preload using four arms on the upper surface of the satellite to push  down the satellite against a preloaded pad.  /g131Equatorial Solution:  to apply the preload using four pin-pushers inserted in the equatorial holes and by using a lower supporting circular pad engaging the sphere bottom part providing a vertical support  and preload. /g131Hinge Solution: the same as solution 3 without using sliding pins but using equatorial hinged pins.  Solution n. 1 (Tropical Solution) The satellite is fastened to the SSEP structure by using three fixation points positioned at 120°. These  three points could be threaded bars screwed in the satellite for one side and fixed to the separation device on the other side. After the release, three protruding elements remain attached to the spherical  satellite. The benefits of this solution are simplicity and stiffness; simplicity means high reliability and  shorter development, manufacturing and testing time. On the other hand several disadvantages exist that lead to discard this solution:  the protrusions modify the satellite configuration by adding a small  uncertainty source in the Lense-Thirring measure, the preload application to these bars is complicated,  and finally the failure tolerance implementation is not easy (if a threated bar remains engaged no  possibility to release the satellite exists). Solution n. 2 (Clamp Solution) The Clamp Solution was designed to provide the preload using a combination of locked arms in the upper  part of the satellite and a pushing cap on the south polar region of the satellite. The clamps are used to obtain a reaction to the preload applied by the pushing cap. The clamps are blocked during the flight until the separation devices receive the separation signal. To provide enough satellite clearance, the clamps have to move when the constraint is unlocked; they are pulled back by a rotational spring inserted inside a hinge. The contact surface between the clamp and the sphere needs to have an area > 23 cm 2; which means  the clamp has the same curvature of the sphere. In order to avoid damage on the satellite surface due to vibration effects, the same surface finish has to be on the clamp interface area and the satellite. Micro  welding is prevented using a suitable material for the clamp. The most important part of this configuration  is the clamp that has to hold the satellite. In Figure 2, the main components of this solution are shown; furthermore, the mechanism in open and closed configuration is shown. The conical insert, where the separation device is positioned, is designed in order to withstand shear loads.                                   Figure 2. Clamp Solution assembly on left. Clamp de tail in the center. Clamp section in open and  closed configuration on right  The benefits of this solution were simplicity and stiffness; the main drawback is that it is not possible to  implement the failure tolerance functionality (if a clamp remains in closed configuration, the vertical force  component blocks the satellite on SSEP). Solution n. 3 (Equatorial Solution) 261