Design Of Imaging Spectrometer Research Articles

Optical design of a coastal ocean imaging spectrometer

We present an optical design for an airborne imaging spectrometer that addresses the unique constraints imposed by imaging the coastal ocean region. A fast (F/1.8) wide field system (36 degrees) with minimum polarization dependence and high response uniformity is required, that covers the spectral range 350-1050 nm with 3 nm sampling. We show how these requirements can be achieved with a two-mirror telescope and a compact Dyson spectrometer utilizing a polarization-insensitive diffraction grating.

Velocity map ion imaging applied to studies of molecular fragmentation with synchrotron radiation

A novel apparatus has been employed to investigate molecular fragmentation following inner-shell photoionization by synchrotron radiation. A modified design of the velocity map imaging spectrometer, first introduced by Eppink and Parker [A.T.J.B. Eppink, D.H. Parker, Rev. Sci. Instrum. 68 (1997) 3477], provides high detection efficiency and good focusing properties for an extended interaction region, while the use of a time and position resolving anode allows electron–ion and ion–ion coincidence measurements. We discuss overall capabilities of the spectrometer and present first results for the C(1s) photoionization of CO 2. Special emphasis is placed on the analysis of time and vector correlations between ions detected in coincidence.

Assessing polarization effects for the Airborne imaging spectrometer APEX

Abstract. In the scope of hyperspectral airborne imaging spectrometer (APEX) design activities, the acceptable sensitivity of linear polarization of the spectrometer is analyzed by assessing the amount of polarization of reflected light in the atmosphere-surface system. A large number of calculations is performed for a wide variaty of viewing geometries to study the influences of aerosol models, natural surfaces and flight altitudes over the spectral range from the near-UV to the short-wave infrared (SWIR). Thereinafter the design of the imaging spectrometer is outlined accounting for these requirements and a method of partially correcting the instrument polarization sensitivity is briefly introduced. APEX design and post-processing capabilities will enable to reduce the influence of polarization sensitivity of at-sensor radiance and its higher-level products generated for most of the observation conditions.

‘Molecular photography’: velocity–map imaging of chemical events

Every chemical reaction bears its own unique fingerprint, embodied in the kinetic energy, angular distribution and rotational and vibrational motion of the newly formed reaction products. These quantities reflect the forces acting during the chemical reaction, and their measurement often provides unparalleled insight into the basic physics governing chemical reactivity. One experimental technique that has truly captured the imagination of the reaction-dynamics community is velocity-map ion imaging, which provides a visual 'snapshot' of the complete product scattering distribution in a single measurement. Originally developed to study gas-phase photodissociation, the technique is now routinely being applied to bimolecular processes, particularly inelastic and reactive scattering. This article will review recent developments in the field, using examples from studies of a range of chemical processes.

Technique for narrow-band imaging in the far ultraviolet based on aberration-corrected holographic gratings.

We have developed a new family of imaging spectrometer designs that combine the imaging power of two-element telescopes with the aberration control of first-generation holographic gratings. The resulting optical designs provide high spatial resolution over modest fields of view at selectable wavelengths. These all-reflective designs are particularly suited for narrow-band imaging below 1050 A, the wavelength below which there are no transmitting materials in the UV. We have developed designs to efficiently map the spatial distribution of UV-emitting material. This mapping capability is absent in current and future astronomical instruments but is crucial to the understanding of the nature of a variety of astrophysical phenomena. Although our examples focus on UV wavelengths, the design concept is applicable to any wavelength.

Design of pushbroom imaging spectrometers for optimum recovery of spectroscopic and spatial information

A modulation transfer function-based optimization method is described that generates optimal spectral and spatial uniformity of response from compact pushbroom imaging spectrometer designs. Such uniformity is essential for extracting accurate spectroscopic information from a pushbroom imaging spectrometer for Earth-observing remote sensing applications. Two simple and compact spectrometer design examples are described that satisfy stringent uniformity specifications.