NOVELTY - The system (100) has a light source (101) including a set of LEDs with different wavelengths, where emission spectrum of the light source complies with predetermined standard. A holding device (102) holds an object i.e. solar cell, under test. A measurement device (103) measures electrical properties of the object under test after the object under test is illuminated by the light source. A direct current supply device (104) includes a set of driving channels used to drive the LEDs with different wavelengths and to control intensity or the spectrum of the light source.    USE - Solar cell measurement system i.e. solar cell aging test system, for use during spectrum response measurement of a solar cell.    ADVANTAGE - The LEDs are arranged in an array type, so that an emission area is enlarged, thus enhancing irradiance and uniformity. The light source includes the optical integrator, which is composed of four reflection mirrors that can be a plane mirror or an embossed mirror made of aluminum, so that light with different wavelengths generated from a light source array can be mixed adequately, thus enhancing uniformity of the light on an illuminated surface or on the object. The direct current supply device includes seven driving channels for providing stable current or instantaneous current that is used to drive seven kinds of the LEDs with the different wavelengths so as to control the intensity or the spectrum of the light source generated from the light source. The system allows certain kind of the LEDs to be connected in series if the current requirement of the LEDs is similar, thus reducing a number of the channels to reduce the cost. The system allows LED chips with different wavelengths to be packaged in a single LED so as to improve density of the LED chips, so that number of LED devices can be reduced and mixing of the light can be uniform. The system uses the LEDs with different wavelengths in a solar simulator, thus obtaining accurate spectrum response curve. The system can simulate solar spectra in different conditions such as in evening or in morning without replacing filter plates to filter irradiance light.    DETAILED DESCRIPTION - The wavelengths of the LEDs are about 300 to 400 nanometers (nms), 400 to 700 nms and 700 to 1100 nms. The light source is selected from a group consisting of an optical integrator and an optical integrator array. An INDEPENDENT CLAIM is also included for a solar simulator comprising a cooling system.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic block diagram of a measurement system for a solar cell.    Solar cell measurement system (100)    Light source (101)    Holding device (102)    Measurement device (103)    Direct current supply device (104)