Vicarious calibrations of HICO data acquired from the International Space Station.

The Hyperspectral Imager for the Coastal Ocean (HICO) presently onboard the International Space Station (ISS) is an imaging spectrometer designed for remote sensing of coastal waters. The instrument is not equipped with any onboard spectral and radiometric calibration devices. Here we describe vicarious calibration techniques that have been used in converting the HICO raw digital numbers to calibrated radiances.

Impact of signal-to-noise ratio in a hyperspectral sensor on the accuracy of biophysical parameter estimation in case II waters.

Errors in the estimated constituent concentrations in optically complex waters due solely to sensor noise in a spaceborne hyperspectral sensor can be as high as 80%. The goal of this work is to elucidate the effect of signal-to-noise ratio (SNR) on the accuracy of retrieved constituent concentrations. Large variations in the magnitude and spectral shape of the reflectances from coastal waters complicate the impact of SNR on the accuracy of estimation.

Hyperspectral Imager for the Coastal Ocean: instrument description and first images.

The Hyperspectral Imager for the Coastal Ocean (HICO) is the first spaceborne hyperspectral sensor designed specifically for the coastal ocean and estuarial, riverine, or other shallow-water areas. The HICO generates hyperspectral images, primarily over the 400-900 nm spectral range, with a ground sample distance of ≈90 m (at nadir) and a high signal-to-noise ratio. The HICO is now operating on the International Space Station (ISS).

Specular integrating tube for scattered-light spectroscopy.

A cylindrical sample cell is adapted to the problem of increasing the scattered-light signal from an optically thin liquid sample. The ends of the cylinder are coated with specularly reflecting aluminum to increase the signal by reflecting the stimulating light beam through the medium multiple times. The circumference of the cylinder is similarly coated to increase the fraction of the emitted light that is collected and sent into the slit of a spectrometer.

An analytic form for the interresponse time analysis of Shull, Gaynor, and Grimes with applications and extensions.

Shull, Gaynor and Grimes advanced a model for interresponse time distribution using probabilistic cycling between a higher-rate and a lower-rate response process. Both response processes are assumed to be random in time with a constant rate. The cycling between the two processes is assumed to have a constant transition probability that is independent of bout length.

Lambertian radiance and transmission of an integrating sphere.

The importance of Lambertian transmission, rather than total transmission, is argued and expressions for both are given. Exact expressions for output radiance are given in terms of both total sphere area and port area. A formula for choosing sphere size to give the maximum Lambertian transmission is developed.

Theoretical wave structure function when the effect of the outer scale is significant.

The wave structure function (WSF) for a plane wave, calculated from the basic Rytov theory, is usually expressed as 6.88(r/r(0))(5/3), but this does not include the effect of a finite outer scale (or of a nonzero inner scale) of turbulence. When separation distance r is only 5% of the outer scale, this expression overpredicts the WSF by a factor of approximately 2.

Fast computation of the narcissus reflection coefficient for the Herschel far-infrared/submillimeter-wave Cassegrain telescope.

Placement of a scatter cone at the center of the secondary of a Cassegrain telescope greatly reduces Nareissus reflection. To calculate the remaining Narcissus reflection, a time-consuming physical optics code/such as GRASP8 is often used to model the effects of reflection and diffraction. Fortunately, the Cassegrain geometry is sufficiently simple that a combination of theoretical analysis and Fourier propagation can yield rapid, accurate results at submillimeter wavelengths.

Photon-limited synthetic-aperture imaging for planet surface studies.

The carrier-to-noise ratio that results from phase-sensitive heterodyne detection in a photon-limited synthetic-aperture ladar (SAL) is developed, propagated through synthetic-aperture signal processing, and combined with speckle to give the signal-to-noise ratio of the resultant image. Carrier- and signal-to-noise ratios are defined in such a way as to be familiar to the optical imaging community. Design equations are presented to show that a 10-microm SAL in orbit around Mars can give centimeter-class resolution with reasonable laser power.