Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) spectrometer design and performance

The development of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) has been completed at JPL. This paper outlines the functional requirements of the spectrometer optics subsystem, and describes the spectrometer optical design. The optical subsystem performance is shown in terms of spectral modulation transfer functions, radial energy distributions, and system transmission at selected wavelengths for the four spectrometers. An outline of the spectrometer alignment is included

AVIRIS foreoptics, fiber optics and on-board calibrator

The foreoptics, fiber optic system and calibration source of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) are described. The foreoptics, based on a modified Kennedy scanner, is coupled by optical fibers to the four spectrometers. The optical fibers allow convenient positioning of the spectrometers in the limited space and enable simple compensation of the scanner's thermal defocus (at the -23 C operating temp) by active control of the fiber focal plane position. A challenging requirement for the fiber optic system was the transmission to the spectral range 1.85 to 2.45 microns at .45 numerical aperture. This was solved with custom fluoride glass fibers from Verre Fluore. The onboard calibration source is also coupled to the spectrometers by the fibers and provides two radiometric levels and a reference spectrum to check the spectrometers' alignment. Results of the performance of the assembled subsystems are presented

Optical Design of the Camera for Transiting Exoplanet Survey Satellite (TESS)

The optical design of the wide field of view refractive camera, 34 degrees diagonal field, for the TESS payload is described. This fast f/1.4 cryogenic camera, operating at -75 C, has no vignetting for maximum light gathering within the size and weight constraints. Four of these cameras capture full frames of star images for photometric searches of planet crossings. The optical design evolution, from the initial Petzval design, took advantage of Forbes aspheres to develop a hybrid design form. This maximized the correction from the two aspherics resulting in a reduction of average spot size by sixty percent in the final design. An external long wavelength pass filter was replaced by an internal filter coating on a lens to save weight, and has been fabricated to meet the specifications. The stray light requirements were met by an extended lens hood baffle design, giving the necessary off-axis attenuation

Convex Diffraction Grating Imaging Spectrometer

A 1:1 Offner mirror system for imaging off-axis objects is modified by replacing a concave spherical primary mirror that is concentric with a convex secondary mirror with two concave spherical mirrors M1 and M2 of the same or different radii positioned with their respective distances d1 and d2 from a concentric convex spherical diffraction grating having its grooves parallel to the entrance slit of the spectrometer which replaces the convex secondary mirror. By adjusting their distances d1 and d2 and their respective angles of reflection alpha and beta, defined as the respective angles between their incident and reflected rays, all aberrations are corrected without the need to increase the spectrometer size for a given entrance slit size to reduce astigmatism, thus allowing the imaging spectrometer volume to be less for a given application than would be possible with conventional imaging spectrometers and still give excellent spatial and spectral imaging of the slit image spectra over the focal plane

Optical Design of Camera for Transiting Exoplanet Survey Satellite (TESS)

No abstract availabl

Comparison of the Host Ranges and Antigenicity of Cryptosporidium parvum and Cryptosporidium wrairi from Guinea Pigs

Oocysts of a Cryptosporidium isolate from guinea pigs were not infectious for adult mice, but were infectious for two of three newborn calves and for suckling mice. However, oocysts isolated from calves or mice infected with guinea pig Cryptosporidium were not infectious for guinea pigs. Four isolates of C. parvum from calves were incapable of infecting weanling guinea pigs. Microscopic examination of tissue from the colon and cecum of suckling guinea pigs inoculated with C. parvum revealed sparse infection of some pups. These host range studies and previously described differences in 125 I-labeled oocyst surface protein profiles between Cryptosporidium sp. from guinea pigs and C. parvum suggest they are distinct species. We propose the name Cryptosporidium wrairi be retained. Studies with monoclonal antibodies indicate that C. wrairi and C. parvum are antigenically related.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75184/1/j.1550-7408.1992.tb01471.x.pd

Imaging Spectrometer Implementation on a Small Satellite Platform for Aquatic Ecosystems Science

The implementation of Imaging spectrometers with state-of-the-art performance on small satellites is challenging due to the size, weight, and power (SWaP) limitations. We have recently developed a compact form, the Chrisp Compact VNIR/SWIR Imaging Spectrometer (CCVIS), that facilitates their usage without sacrificing performance. The CCVIS enables a modular implementation that, combined with a freeform telescope, produces a wide field of view with high signal to noise ratio (SNR) performance. The targeted scientific application is the study of aquatic ecosystems. The imaging spectrometer is designed to address carbon sequestration in coastal margins and wetlands, kelp and seagrass studies, coral reefs, harmful algal blooms and hypoxia, and carbon cycling in this dynamic environment. The requirements are challenging since the high SNR, which is necessary in order to produce quality data products over water, is coupled with sufficient dynamic range in order to simultaneously record spectra from the shore area, which has elevated spectral radiance in comparison to the water. To meet these requirements, the small satellite will execute a pitchback maneuver where the imaging of the slit projected onto the surface is slowly scanned while recording focal plane array (FPA) readouts at a higher rate. The effective frame rate is determined by the time it takes to scan the projected slit one ground sample distance (GSD). This concept of operation avoids saturation over the land surface while obtaining high SNR over the water. This approach has the added benefit of measuring a range of angles during a single GSD acquisition, providing insight into the bidirectional reflectance distribution function (BRDF). One consequence of this approach is extremely large data volumes requiring a high bandwidth downlink system. Laser communications is a critical technology that enables the transfer of these large data volumes. We present a preliminary design of the imaging spectrometer based on the aquatic ecosystem requirements including the modular implementation of the CCVIS, the laser communications system, and the implementation on a ESPA-grande satellite

Pluto Integrated Camera-Spectrometer (PICS): A Low Mass, Low Power Instrument for Planetary Exploration

The concept we describe is an integrated instrument (a Pluto Integrated Camera Spectrometer, PICS) that will perform the functions of all three optical instruments required by the Pluto Fast Flyby Mission: the near-IR spectrometer, the camera, and the UV spectrometer. This integrated approach minimizes mass and power use. It also forced us early in the conceptual design to consider integrated observational sequences and integrated power management, thus ensuring compatible duty cycles (i.e. exposure times, readout rates) to meet the composite requirements for data collection, compression, and storage. Based on flight mission experience we believe that this integrated approach will result in substantial cost savings, both in reworking instrument designs during accommodation, as well as in sequence planning and integration. Finally, this integrated payload automatically yields a cohesive mission data set, optimized for correlative analysis. In our baseline concept, a single set of lightweight, multi-wavelength foreoptics is shared by an UV imaging spectrometer (160 spectral channels 10-150 nm), a two-CCD visible imaging system (simultaneously shuttered in two colors 300-500 nm and 500-1000 nm), and a near-IR imaging spectrometer (256 spectral channels 1300-2600 nm), The entire structure and optics is built from SiC, and includes an integrated radiator for thermal control. The design has no moving parts and each spectrometer covers a single octave in wavelength. For the Pluto mission, a separate port (aligned in a direction compatible with the radio occultation experiment) is provided for PICS measurement of a UV solar occultation and for spectral radiance calibration of the IR and visible subsystems. The integrated science this instrument will yield meets or exceeds all of the Priority-1A science objectives and captures many Priority-1B science objectives as well. The presentation will provide details of the PICS instrument design and describe the fabrication and testing of the integrated SiC structure and optics at SSG Inc. Final integration and test plans for the prototype will also be described

Advanced optical instruments technology

The science objectives for proposed NASA missions for the next decades push the state of the art in sensitivity and spatial resolution over a wide range of wavelengths, including the x-ray to the submillimeter. While some of the proposed missions are larger and more sensitive versions of familiar concepts, such as the next generation space telescope, others use concepts, common on the Earth, but new to space, such as optical interferometry, in order to provide spatial resolutions impossible with other concepts. However, despite their architecture, the performance of all of the proposed missions depends critically on the back-end instruments that process the collected energy to produce scientifically interesting outputs. The Advanced Optical Instruments Technology panel was chartered with defining technology development plans that would best improve optical instrument performance for future astrophysics missions. At this workshop the optical instrument was defined as the set of optical components that reimage the light from the telescope onto the detectors to provide information about the spatial, spectral, and polarization properties of the light. This definition was used to distinguish the optical instrument technology issues from those associated with the telescope, which were covered by a separate panel. The panel identified several areas for optical component technology development: diffraction gratings; tunable filters; interferometric beam combiners; optical materials; and fiber optics. The panel also determined that stray light suppression instruments, such as coronagraphs and nulling interferometers, were in need of general development to support future astrophysics needs

Small Earth Imaging Spectrometer

Advances in several key sensor technologies make it possible now to build a high performance, very compact and low cost imaging spectrometer for spacebourne terrestrial remote sensing. We describe an instrument based on a highly innovative optical design that incorporates state of the art focal plane arrays, electronics, focal plane cooling and dimensionally stable ceramics for the optical elements and structure. The instrument is optimized for viewing the earth\u27s solid surface and adjacent coastal oceans. It has very high signal-to-noise performance over the full spectral range covered, from 400 to 2450 nanometers (nm). Spectral sampling is in 200 10-nm wide, contiguous bands. The instrument combines a high spatial resolution panchromatic imaging system with a modest spatial resolution imaging spectrometer. It weighs 25 kg, requires less than 100 watts of power, and is approximately 30 by 20 by 10 cm in dimension, fitting well within the capacity of Pegasus-class small spacecraft missions. The instrument is well suited to support studies in earth system science as well as commercial remote sensing. Several applications in these areas will be highlighted to set in context the performance requirements that were used to define the sensor design and choice of sensor technologies