variavel0=<b>JOSÉ SÉRGIO DE ALMEIDA</b> - jsergio@lit.inpe.br INPE - BRAZIL
<b>Abstract.</b> A  new  methodology, based on  the  Discrete  Ordinates Method (DOM), was developed to  analyze thermal radiation in complex geometries. Reducing the angular dependence of the thermal radiation in a number of discretized directions, information is carried from the thermal conditions and thermo-optical properties of the surfaces under study. Approximating the solution of the Equation of Transfer by iteration, heat transfer functions can be predicted at the walls and in the interior of analytical cells from a test system. An experimental set-up was built, including a number of internal boxes with arbitrary specification of size, shape and layout, simulating spacecraft subsystems undergoing a  technical situation of a  thermal  vacuum  test. Varying  the  thermal conditioning of the walls and the boxes, radiative heat flux could be produced and were measured. Taking the necessary precautions in terms of identifying and properly compensating the differences of the thermo-optical properties and the temperature between the surfaces of the radiometer and the test system, a very good correlation was obtained between the numerical thermal modeling and the laboratorial measurements, in this way simultaneously validating the proposed mathematical approximation by using the DOM and the experimental methodology for the measurement of the radiative heat flux.
<b>Keywords.</b> Thermal Radiation, Heat Flux, Discrete Ordinates Method, Spacecraft Testing.