Abstract: A solar simulator includes a lamp array of solar lamps pivotally connected to an array frame. The array frame is rotatably and pivotally mounted on a gantry crane, the elevation and lateral position of which are adjustable relative to the position of a solar collector to be tested. The solar simulator maintains the plane of the lamp array parallel to the plane of the test device for all elevations, lateral positions and rotational positions of the lamp array, and controls tilting of the lamps relative to the array frame to any desired angle of incidence. The solar simulator is operated to control the angle of incidence of radiation received by the solar collector to be tested and to vary the distance from the array of lamps to the solar collector in such a manner that the intensity of received radiation along the surface of the test device is uniform, thereby avoiding undesirable lateral gradients in temperature along the surface of the test device.