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The use of the truss of the International Space Station (ISS) for the accommodation of several experiments, in the frame of the “Early opportunity for ISS utilization”, will have a lot of advantages such as the possibility of human or robotics intervention, the recovery of the experiment at the end of its life, visual inspection of the items and cost reduction with respect to an installation on a dedicated satellite. However, from the user point of view, the ISS generates a great number of disturbances and severe environmental conditions for the experiments providing constraints and affecting the performances in different areas (thermal, mechanical, and avionics). The present paper will discuss the thermal aspects (disturbances, constraints and performances) concerning three different projects, developed by Alenia Spazio Turin plant, that will be mounted on the truss of the ISS: Hexapod, Coarse Pointing Device (CPD) and Sky Polarization Observatory (SPOrt).

The Columbus laboratory module for the International Space Station (ISS) uses active thermal control for cooling of avionics and payload in the pressurized compartment. The Active Thermal Control Subsystem (ATCS) is based on a water loop rejecting waste heat to the Medium Temperature Heat Exchanger and Low Temperature Heat Exchanger on Node 2, part of the US Segment of the ISS. Flow and temperature control in the ATCS is achieved by means of the Water Pump Assembly (WPA) and the 3-Way Modulating Valve (WTMO) units. For the flow control the WPA speed is commanded so that a fixed pressure drop is maintained over the plenum with the avionics and payload branches. Adjusting the WTMO internal flow split permit the two active units to perform the CHX and plenum inlet temperature control. The WPA includes a filter and an accumulator to control the pressure in the ATCS and to compensate for leakage and temperature-dependent volume variations.