A novel scene-recording spectroradiometer

In this paper we describe an innovative approach to providing both a synthesised dual-beam capability and a permanent photographic record of the precise area sensed by a spectroradiometer. These advances have been achieved without modifying the spectroradiometer and may be used with a wide range of commercially-available spectroradiometers

Infrared spectroradiometer for rocket exhaust analysis

Infrared spectroradiometer measures high-resolution spectral absorption, emission, temperature, and concentration of chemical species in radically symmetric zones of the exhaust plumes of large rocket engines undergoing static firing tests. Measurements are made along predetermined lines of sight through the plume

Development of moored oceanographic spectroradiometer

Biospherical Instruments has successfully completed a NASA sponsored SBIR (Small Business Innovational Research Program) project to develop spectroradiometers capable of being deployed in the ocean for long periods of time. The completion of this project adds a valuable tool for the calibration of future spaceborne ocean color sensors and enables oceanographers to extend remote sensing optical techniques beyond the intermittent coverage of spaceborne sensors. Highlights of the project include two moorings totalling 8 months generating extensive sets of optical, biological, and physical data sets in the ocean off La Jolla, California, and a 70 day operational deployment of the resulting commercial product by the ONR and NASA sponsored BIOWATT program. Based on experience gained in these moorings, Biospherical Instruments has developed a new line of spectroradiometers designed to support the oceanographic remote sensing missions of NASA, the Navy, and various oceanographers

Estimating the irradiance spectrum from measurements in a limited number of spectral bands

Accurate measurement and characterisation of fluctuations in the irradiance environment is important for many areas of optical remote sensing. This paper describes a method of estimating spectral irradiance over the region 400 – 1000 nm from the radiance of a calibrated reference panel, measured in four narrow spectral bands (FWHM approx.10 nm). The reproducibility of the method was found to have an average root mean squared error of approximately 30 mWm-2nm-1 over the region 400 nm to 1000 nm when applied to spectra covering a range of clear sky conditions typical of mid-latitude temperate regions

Assessment of ultraviolet radiation exposures in photobiological experiments

The interfering effect of ultraviolet (UV) radiation on the natural function of biological processes is wavelength specific and the UV spectrum must be weighted with the action spectrum for the process. The UV spectral irradiance may be measured with calibrated spectroradiometers. Alternatively, the biologically effective UV may be measured with broadband devices. This paper reviews the techniques for assessing biologically effective exposures in photobiological experiments. UV meters, such as the Robertson-Berger (RB) meter, or passive dosimeters, such as polysulphone, that possess a spectral response approximating the human erythemal response can be used to estimate erythemally effective exposure or actinic exposure due to solar UV. The sensitivity of the RB meter is about 0.56 uW cm-2 and polysulphone can record an exposure of about 2mJ cm-2. For photobiological processes other than erythema these devices are not suitable to determine the exposure. In terms of these applications, a spectrum evaluator consisting of four different types of dosimeter material can be employed to evaluate the UV spectrum of the source. This method can be useful both for solar UV studies and research with UV lamps that possess radiation wavelengths shorter than 295nm. The device can be used to measure exposures where the actinic and erythemal action spectra differ significantly. It can also be used to assess exposure due to low levels of UV (about 0.01uW cm-2) caused by radiation filtered through glasses or plastic

Estimating spectral irradiance from measurements in seven spectral bands

Accurate measurement and characterisation of fluctuations in the irradiance environment is important for many areas of optical remote sensing. This paper reports a method of estimating spectral irradiance over the VNIR region (400 - 1100nm) from the radiance of a calibrated reference panel, measured in seven narrow (10nm) spectral bands. Earlier work established the potential for estimating spectral irradiance from multi-band data using a neural network technique (Milton et al., 2000). The approach described here uses linear regression analysis to regenerate the irradiance spectrum from data in seven reference wavelengths. The method was tested using data from a specially designed multiband radiometer – the INdependent SPectral IRradiance Estimator (INSPIRE). The irradiance spectrum was partitioned into a number of distinct regions within each of which the spectral irradiance was estimated from irradiance measured at one of the reference wavelengths. The precision of the method was found to be better than ±5% over most wavelengths from 400nm to 1100nm. Furthermore, the slope coefficients of the individual regression models were found to be sensitive to the sky radiance conditions, especially over the region 600-760nm, and improvement in the precision of the predicted spectrum (to within ±3%) was obtained by taking the diffuse-to-global (D:G) irradiance ratio at the time of measurement into account

A new dual-beam technique for precise measurements of spectral reflectance in the field

Field spectral measurements made using the single - beam method often include errors due to variation in illumination between measurement of the target and the reference (panel or cosine -corrected receptor). Although the dual-beam method avoids these errors, it introduces greater complexity due to the need to intercalibrate the two sensor heads used, and it is significantly more expensive. This paper describes an alternative dual-beam method which uses a neural network to estimate the complete irradiance spectrum from measurements made in 7 narrow bands. These narrow band measurements of irradiance may be made with a simple filter-based radiometer, thus avoiding the expense and complexity of a second spectroradiometer. The new technique has been tested using irradiance spectra from both continental and maritime locations

A compact spectroradiometer for solar simulator measurements

Compact spectral irradiance probe has been designed and built which uses wedge filter in conjunction with silicon cell and operational amplifier. Probe is used to monitor spectral energy distribution of solar simulators and other high intensity sources

The temporal dynamics of calibration target reflectance

A field experiment investigated the hypothesis that the nadir reflectance of calibration surface substrates (asphalt and concrete) remains stable over a range of time-scales. Measurable differences in spectral reflectance factors were found over periods as short as 30 minutes. Surface reflectance factors measured using a dual-field-of-view GER1500 spectroradiometer system showed a relationship with the relative proportion of diffuse irradiance, over periods when solar zenith changes were minimal. Reflectance measurements were collected over precise points on the calibration surfaces using a novel mobile spectroradiometer device, and uncertainty in terms of absolute reflectance was calculated as being < 0.05% within the usable range of the instrument (400-1000nm). Multi-date reflectance factors were compared using one-way ANOVA and found to differ significantly (p = 0.001). These findings illustrate the anisotropic nature of calibration surfaces, and place emphasis on the need to minimise the temporal delay in collection of field spectral measurements for vicarious calibration or empirical atmospheric correction purposes

EOS Science Poster Series: ICE- Global Ice and Snow

This poster, one in a four-part series, highlights recent images from select NASA Earth Science spacecraft and showcases related research results. The back gives a brief overview of the science and missions behind NASA's study of ICE. Educational levels: Middle school, High school, Undergraduate lower division, Undergraduate upper division, Graduate or professional