An instrument for accurate measurement of UV-A irradiation and visible illuminance. Extra engineering effort is taken to make an accurate measurement of visible light emission from a UV-A lamp by incorporating a superior band pass filter containing only non-fluorescent filters. The instrument provides fast measurement as it offers auto ranging and concurrent measuring of visible light and UV-A irradiation. It is ergonomic and easy to use due to its light weight chassis, wireless sensor unit and compact size. Apollo 1.0 is traceable to NIST (USA’s National Institute of Standards and Technology).