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In several industrial fields, the integration of functions is a key technology to enhance the efficiency of components in terms of performance to mass/volume/cost ratio. Concerning the space industry, in the last few years the trend in spacecraft design has been towards smaller, light-weight and higher performance satellites with sophisticated payloads and instrumentation. Increasing power density figures are the common feature of such systems, constituting a challenging task for the Thermal Control System. The traditional mechanical and thermal design concepts are evidencing their limits with reference to such an emerging scenario.

Today, in several industrial fields, the integration of functions is a key technology to enhance the efficiency of components in terms of performance to mass/volume/cost/ratio. Concerning the space industry, in the last few years the trend in spacecraft design has been towards smaller, light-weight and higher performance satellites with sophisticated payloads and instrumentation. Increasing power density figures are the common feature of such systems, constituting a challenging task for the Thermal Control System. The traditional mechanical and thermal design concepts are evidencing their limits with reference to such an emerging scenario.

Several last-generation and future satellite communication systems require the use of large deployable antennas. A European product in this field is presently not available: in this frame the European Space Agency assigned a contract for the development of the Large Deployable Antenna Reflector for advanced mobile communications (LDA). The project is driven by ALENIA SPAZIO as prime contractor and system designer with the support of other companies: EGS (Russia), HTS (Switzerland), SENER (Spain), Magna (Austria). The Antenna consists of a paraboloid with 12m in projected aperture, 6.3m of focal length and located with a clearance of 3m from the focal axis. From a technical point of view, the LDA project was characterized by several challenging tasks: thermal aspects are outlined in the paper. In particular, the mathematical modeling of the reflector and the optical characterization of its reflecting mesh required particular care.

Radarsat-2 is a commercial Synthetic Aperture Radar satellite for earth observation. [1] The general stowed configuration is shown in Figure 1. In nominal operation mode, once deployed, the large SAR polarimetric Antenna (i.e. able to transmit and receive both horizontal and vertical polarisations) is inclined of about -29.8° versus the nominal direction of geodetic local surface normal (Right Looking mode). When is necessary to take images of South Pole, nominally not visible from SAR, the S/C must be rotated to the +29.8° position (Left Looking mode). During the Radarsat-2 thermal testing the S/C (PFM) was subjected to a first thermal balance/thermal cycling test in vacuum with simulation of external heat fluxes by means of I/R lamps and additional test heaters. A very complex thermal test configuration was required in order to simulate the continually varying thermal environment imposed by the S/C nominal sun-synchronous orbit and attitude.

The ARTEMIS (Advanced Relay and TEchnology MISsion) satellite represents the first element of the Data Relay and Technology Mission Programme (DRTM) developed for the European Space Agency by Alenia Aerospazio (Italy) as the prime contractor. Although using conventional design features and limited mass, power, telemetry and tele-command budgets, the thermal control of the satellite matches the demands dictated by the peculiarities of the ARTEMIS mission such as the significant overall dissipation, the wide spectrum of payload operational scenarios and the relatively unbalanced distribution of payload equipment dictated by system and payload performance considerations. This paper describes the thermal control design solutions with special regard to consideration on ground testability of the system; the analytical approach to predict on-orbit thermal response; the policy adopted in terms of margins and analytical uncertainties.

The ITALSAT telecommunication system is based on the operation of two geostationary satellites: the first (pre-operative) launched in January '91 the second (operative) to be launched in '96. The thermal design of the satellites was extensively verified by analysis and test including a Solar Simulation thermal balance on the structural-thermal model and thermal vacuum - thermal balance on flight models. Additionally, on-orbit temperature data from the protoflight model is available for equinox and solstices 24 hr. transients. The results have been statistically processed and compared with test data and correlation analysis in order to provide a reliable background for thermal control design and verification of future similar telecommunication satellites.

Italsat F1 is a communication satellite sponsored by the Italian Space Agency and developed by Alenia Spazio. The spacecraft consists with a platform, which provides all the required services, and three payloads: a global beam package, a multibeam package for domestic communication services at 20/30 GHz, and an experimental propagation package at 40/50 GHz which embraces the European continent. Italsat F1 was sent off by an Ariane IV launcher from the Kourou Space Center in French Guyana on January 16th,1991, and it has been operating since February 1991. Having gone through a complete cycle of solstices and equinoxes, Italsat experienced the extreme environmental conditions at its beginning of life. The flight data collected throughout the first year of operational life enabled a review of the spacecraft thermal performances. This paper presents an overview of in-orbit observed temperatures.

The thermal control design of the Italian Satellite (ITALSAT) has been experimentally qualified by means of a solar simulation test performed on a dedicated structural/thermal model. The test model was thermally representative of the flight unit and all the thermal hardware was flight standard. Thermal analysis in the test conditions have been performed in order to verify the thermal mathematical models of the spacecraft. The paper describes the tested spacecraft model and the test approach. Test results, correlation with predicted temperatures as well as influences of test conditions on spacecraft test temperatures are presented and discussed.