Interpolation errors in UV-visible spectroscopy for stratospheric sensing: implications for sensitivity, spectral resolution, and spectral range

Analyzing the effect of synthetic scene resolution, sampling interval, and signal-to-noise ratio on hyperspectral imaging sensor simulations

Sensor simulation modeling is an important tool for the design of new earth imaging systems. As the input of the model, the characteristics of the synthetic spectral scene image data cube (SSSIDC) play an important role in the accuracy of the simulation. Based on a general sensor simulation model, the effects of SSSIDC resolution, sampling interval (SI), and signal-to-noise ratio (SNR) on simulated data are analyzed. Analysis shows that the simulated data characteristics are a function of the model parameters and the SSSIDC characteristics. The results can be used for evaluating the errors of simulated data, giving criteria for scene image synthesis, and designing appropriate model parameters for expected simulation. Simulation experiments are included to demonstrate the discussed analysis, with the results showing that the analysis is valid.

Undersampling correction for array detector-based satellite spectrometers

Array detector-based instruments are now fundamental to measurements of ozone and other atmospheric trace gases from space in the ultraviolet, visible, and infrared. The present generation of such instruments suffers, to a greater or lesser degree, from undersampling of the spectra, leading to difficulties in the analysis of atmospheric radiances. We provide extended analysis of the undersampling suffered by modern satellite spectrometers, which include the Global Ozone Monitoring Experiment, Scanning Imaging Absorption Spectrometer for Atmospheric Chartography, Ozone Monitoring Instrument, and Ozone Mapping and Profiler Suite. The analysis includes basic undersampling, the effects of binning into separate detector pixels, and the application of high-resolution Fraunhofer spectral data to correct for undersampling in many useful cases.

Long-path measurement of atmospheric NO2 with an obstruction flashlight and a charge-coupled-device spectrometer

A novel method of differential optical absorption spectroscopy (DOAS) is proposed and demonstrated to monitor the concentration of atmospheric pollutant gas. In contrast to conventional DOAS measurements with continuous light sources, the present method relies on white flashlights such as aviation obstruction lights that are generally installed on tall constructions. A simple detection system is devised by means of a telescope and a compact CCD spectrometer. A path length of 5.5 km allows us to measure atmospheric NO2 concentration with a detection limit of approximately 1 part per billion. We also discuss the possibility of deriving the aerosol optical thickness through the horizontal atmosphere from this pulsed DOAS measurement.

Differential optical absorption spectroscopy instrument for stratospheric balloonborne trace-gas studies

A newly developed UV-visible instrument for differential optical absorption spectroscopic measurements of atmospheric trace gases from balloon platforms is described. Direct solar light at daytime in the near-ultraviolet (320.6-422.6-nm) and the visible (417.6-670.7-nm) spectral ranges can be simultaneously analyzed for the atmospheric column abundances or profiles of O(3), NO(2), NO(3), BrO, OClO, O(4), H(2)O, and possibly other species (HNO(2), IO, CH(2)O). Compared with previously used balloonborne UV-visible spectrometers, the instrument has the superior properties of low mass (42 kg), low power consumption (30 W), decreased spectral drift that is caused by temperature and pressure changes, low detector dark current, and low spectrometer stray light. The three last-named characteristics are achieved by enclosure of the entire spectrometer in a pressurized and thermostated container and by inclusion of separately thermostated photodiode array detectors. The optical setup is simplified to reduce its weight. The spectral stray light is reduced by suppression of the higher-order and zero-order grating reflections by use of light traps and in the UV by addition of a dispersive prism preanalyzer. The major instrumental design characteristics and the instrumental performance as tested in the laboratory and during several stratospheric balloon flights are reported.