A method to determine the temperature of an operating laser diode is to measure the wavelength emitted by the array and use the linear relationship between wavelength and temperature to infer the temperature of the laser diode bar. A unique experimental method to measure spatially and temporally resolved wavelength emitted from a laser diode array has been developed and is used to determine local temperature transients. This approach involves the non-contact rastering of a 100μm aperture over the emitting surface of the array, passing the energy from a single emitter into a spectrograph. This paper describes the design and development of the spatially and temporally resolved wavelength measurement system that is unique to any system presented in the literature. Results from a validation study of this methodology based on a comparison of wavelength and intensity maps to well-established and calibrated time and spatially averaged LDA measurement techniques and IR images are presented. In turn, preliminary results from this system show that transient laser diode emitter behavior falls into a number of distinct categories. A system that can resolve localized heating of a laser diode array both spatially and temporally can provide a wealth of information about the thermal performance of these arrays: 1) precise mapping of array temperature and relative output power, 2) precise location of hot spots and accurate measurement of the magnitude of those hot spots, and 3) variations in thermal time constants that may predict the location of packaging defects along the heat flow path from the diode bar itself to the LDA heat sink.