Analysis of led-based solar simulator development capability for spacecraft ground testing applications

A solar simulator is one of the most difficult elements of the test equipment used during ground testing of space- crafts. The majority of modern large-size simulators are designed on the basis of the block of gas-discharge xenon lamps with air cooling using the principle of the "combined focuses". The main shortcomings of similar simulators are a low efficiency and a small resource of xenon gas-discharge lamps, high losses in the difficult optical system, complex- ity, and inconvenience of operation. The scheme of the combined simulator free from the specified shortcomings based on the high-effective light-emitting diodes in visible area of a range and additional traditional sources which can be quartz-halogen filament lamps in infrared and gas-discharge medium-pressure mercury-vapour arc lamps ultra-violet areas is offered. The LED source is structurally executed in the form of matrixes with the distributed parameters, lo- cated in the form of one or several modules in the thermal vacuum camera directly near the object of testing. Modules are supplied with the optical system forming a quasiparallel light stream, the heat insulation and the cooling system removing excess heat out of camera borders. The short comparative analysis showed advantages of the LED simulator on energy efficiency, uniformity and temporary stability of a light stream, reliability, durability and safety. The offered simulator possesses the best mass-dimensional characteristics, doesn't demand tuning and adjustment and has a num- ber of additional opportunities. The main disadvantage of LED sources is the discrepancy of the solar radiation spec- trum. Essential spectral accuracy can be reached at application in matrixes of a large number of separately power- controlled groups of white and monochrome light-emitting diodes with different length of waves and the optical system summarizing flows of groups of light-emitting diodes on a range, a corner and the area. On examples of serially pro- duced foreign LED solar simulators of a ground-level AM1,5 range the tendency of transition to LED sources is traced. It is concluded that the creation of the combined solar simulator on the basis of highly effective light-emitting diodes for ground testing of spacecrafts possessing the improved technical and operational characteristics is possible.