Adaptive measurement is a major concern when using miniature spectrometers in extreme environments, especially when the ambient temperatures and incident light intensities vary greatly. In this study, parameters, including the signal output and the relevant noise and signal-to-noise ratio (SNR) of a fiber optic spectrometry system composed of a photodiode array miniature spectrometer and external driver electronics were examined at multiple integration times from -50°C to 30°C, well below the specified operating temperature of this spectrometer. The relationships between those parameters and incident light level were also examined, at a single temperature of 0°C. Based on these examinations, temperature-induced biases in the linear operating range of the spectrometer were identified. Signal output and the relevant noise and SNR in response to different integration times, temperatures, and incident light levels were assessed separately. These assessments were then used to develop an adaptive measurement method for estimating the incident light level and setting up an optimal integration time for this spectrometer, while autonomously adapting the variation in the ambient temperature and incident light level simultaneously. This approach provides a general framework for developing an adaptive measurement algorithm for miniature spectrometers, which face tremendous variations in ambient temperature and incident light level.
Special attention should be paid during the development of the driver circuitries for miniature spectrometers when using them in extreme environments, especially when the ambient temperature changes tremendously. In this study, a driver circuitry for a miniature spectrometer is developed by providing a basic control signal and ADC circuitry. Meanwhile, temperature stability and power consumption are considered. The performance of the driver circuitry is evaluated comprehensively from −50°C to 30°C. The lower boundary is below the operating range of most electronic parts adopted. Based on these examinations, temperature dependence, linearity and conversion accuracy of the ADC circuitry are quantified. And a correction algorithm is developed to correct any deviation in the driver circuitry with an uncertainty of around ²20 Counts. The practicality of the driver circuitry is also identified. This approach provides a general framework for developing driver circuitry for miniature spectrometers which will face tremendous variations in the ambient temperature.
An irradiance profiling system was developed to obtain long-term autonomous measurements of solar irradiance above, within, and under sea ice in the Arctic. Two miniature spectrometers were adopted to sequentially sense light signals collected and transmitted by eight fiber probes deposited at different levels of the sea ice environment. Each spectrometer was aligned to each fiber probe by rotating the spectrometer to the desired angle by using a rotary spectrometer switching device. A small optical probe was developed that could be placed in an auger hole with a diameter of 5 cm and enable a high transmission rate for the light signal. The temperature dependence of the signal output was examined and evaluated over the entire operating temperature range from −50° to +30°C. A signal output correction model was proposed to correct temperature-induced biases in the system output; this was combined with the system spectral sensitivity correction to determine the absolute irradiance entering the system. The performance of the system was examined for two days during the ninth Chinese National Arctic Research Expedition by deploying it in a 185-cm-thick ice pack in the Arctic and measuring the solar irradiance distribution at different levels. The spectral shape of the measured solar irradiance above the sea ice agreed well with that measured using other commercial oceanographic spectroradiometers. The measured optical properties of the sea ice were generally comparable to those of similar ice measured using other instruments.
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