The Arizona Imager/Spectrograph is a set of imaging spectrographs and two-dimensional imagers for space flight. Nine nearly identical spectrographs record wavelengths from 114 to 1090 nm with resolution of 0.5 - 1.3 nm. The spatial resolution along the slit is electronically selectable and can reach 192 elements. Twelve passband imagers cover wavelengths in the 160 - 900 nm range and have fields of view from 2 degree(s) to 21 degree(s). The spectrographs and imagers rely on intensified CCD detectors to achieve substantial capability in an instrument of minimum mass and size. By use of innovative coupling techniques only two CCDs are required to record images from 12 imagers, and single CCDs record spectra from pairs of spectrographs. The fields of view of the spectrographs and imagers are coaligned, and all spectra and images can be exposed simultaneously. A scan platform can rotate the sensor head about two orthogonal axes. The Arizona Imager/Spectrograph is designed for investigations of the interaction between the Space Shuttle and its environment. It was flown on a sub-satellite deployed from and retrieved by STS-39.

Spectrometric observations (1100 A to 1800 A) of the ultraviolet radiance of Earth's atmosphere have been obtained by the Horizon Ultraviolet Program (HUP) sensor from Space Shuttle altitude at two different points in the solar cycle. Most of the radiance measurements were made during horizon scans of the earthlimb or while the HUP field of view was directed toward nadir. The expected variation of dayglow radiance with solar zenith angle (SZA) in the several spectral bands was observed. These results compare favorably to the predictions of a preliminary version of the Atmospheric Ultraviolet Radiance Integrated Code (AURIC).

The NRL's Far UV Cameras experiment flew aboard the Shuttle Orbiter on STS-39, in 1991: obtaining 105-200 nm measurements of the upper atmosphere, astronomical targets, and the Shuttle environment. Attention is presently given to observations of O2 density vs altitude in the nighttime atmosphere, the nocturnal ionosphere, Space Shuttle FUV glow, and photometry for both the stars and diffuse sources of 12 star fields at high and low galactic latitudes. The first FUV observations of the extended region of reflection nebulosity in Scorpius are included.

Since its launch in February 1990, the Low-Power Atmospheric Compensation Experiment (LACE) satellite has been used as a space-based platform from which numerous observations have been carried out using the onboard Ultraviolet Plume Instrument (UVPI). UVPI consists of two pointable, co-aligned, intensified charged-coupled-device (ICCD) cameras sharing a common telescope mount. The instrument has obtained high spatial resolution near-UV/visible images of rocket plumes, and has observed aurorae, the Earth's limb, and other features of the Earth background. A description of the instrument, the data gathered, and some selected results are presented.

The Atmospheric Ultraviolet Radiance Analyzer (AURA) has been designed to furnish global UV emissions measurements in the 115-175 nm range of sufficient sensitivity for observations of the weak emissions from the tropical arcs and the aurora from a nearly circular high-inclination orbit. Excellent S/N is obtained by AURA in the case of day airglow measurements. Two UV observation channels are available, each of which is based on a 1/8 Ebert-Fastie spectrometer and a telescope with a scanning mirror; each can furnish data in any one of three operational modes.

The UVISI instruments, comprising five spectrographic imagers and four imagers, will fly on a DoD mission in the early 1990s. We analyze, in a preliminary way, the applicability of these instruments to resolution of outstanding problems in the nature of the celestial cosmic diffuse ultraviolet background radiation.

Long-term radiometric accuracy is a fundamental requirement for the measurement of solar, terrestrial, and/or planetary atmospheric EUV emissions from space. Due to non-traceable changes of the numerous spectrometric efficiency parameters with time, long-term stability of satellite instrumentation has not been achieved in the past. One possibility to overcome these shortcomings is the use of absolute standard detectors in combination with spectrometers to recalibrate EUV spectrometers in space. The system ACES takes advantage of this approach in the wavelength range from about 1 to 180 nm at 0.4 nm to 2 nm spectral resolution. ACES is based on a combination of three spectrometers, four special double ion chambers, and one proportional counter. Specific features and experimental details are presented. The expected radiometric accuracy is better than 10 percent.

Multi-Anode Microchannel Array (MAMA) detector systems are being fabricated and tested for use in the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) and the Ultraviolet Coronagraph Spectrometer (UVCS) instruments on the ESA/NASA Solar and Heliospheric Observatory (SOHO) mission. The SOHO MAMA detector systems have formats of 360 x 1024 pixels and pixel dimensions of 25 x 25 sq microns and are optimized for operation at Extreme Ultraviolet (EUV) wavelengths between 40 and 160 nm. In this paper we report on the initial results of measurements of the performance characteristics of the first flight-configuration detector system employing the new custom Application Specific Integrated Circuits (ASICs) which are designed to improve both the dynamic range and the uniformity of response. The performance characteristics of this detector system are compared with those of earlier breadboard systems employing discrete-component electronics circuits.

The TAUVEX UV Space Telescope currently under construction by El-Op Ltd. in Israel is designed both for recording images of the sky in the UV region and to serve as the optical monitor for the SODART X-Ray Telescope being built by the Danish Space Research Institute. The two systems, together with several other experiments, will be flown on the S-R-G satellite to be launched by the CIS in 1995. TAUVEX will image a field of about 1 deg simultaneously in three spectral bands. In addition, it will record a selected object in a high-speed time-resolved mode in these bands. The concept and design of TAUVEX is described in this paper.

A new spectrally precise approach to Schumann-Runge synthesis has been devised, employing nine (9) different spectral arrays containing polynomial coefficients. The coefficients were fit to calculated cross sections obtained from a detailed Schumann-Runge model that incorporates the most recent high resolution spectroscopic data for a temperature range between 130 and 500K. This large data base is being used to reexamine the existing parameterizations of UV transmission and photolysis. In addition, it is now possible to extend atmospheric radiance codes further into the ultraviolet. Initial implementation has been accomplished for the MODTRAN code as part of the eventual development of AURIC, the Atmospheric Ultraviolet Radiance Integrated Code.

The Special Sensor Ultraviolet Spectrographic Imager (SSUSI) sensors that will be carried by USAF Defense Meteorological Satelite Program Block 5D3 satellites can measure FUV emission in five bands across the disk and onto the limb. An account is presently given of the environmental data records that are to be derived from SSUSI's dayglow disk data, as well as to projections of the disk viewing capabilities of the SSUSI system for any sum of Lyman-Birge-Hopfield bands excluding the regions around 130.4, 135.6, and 149.3 nm. The findings obtained are independent of any assumed model atmosphere.

The Atmospheric Ultraviolet Radiance Integrated Code's modules have been developed to calculate the 1000-6500 A thermospheric emission spectra and radiances of dayglow, nightglow, twilight, and electron aurora, while also accounting for solar, photoelectron, auroral electron, and chemical excitation processes as well as pure and self absorption and multiple scattering effects. An account is presently given of the overal architecture of the codes; attention is given to the design and implementation of the photoionization and electron flux modules, together with samples of the input data and generated output.

In recognition of the need for accurate collision cross-sections suitable for modeling spectroscopic observations of the planetary systems and calibrate flight instruments, NASA-JPL has determined the laboratory emission cross-sections of H, H2, N2, SO2, etc. Resonance excitation, predissociation, and non-Franck-Condon band intensity systems are determined by configuration interaction and must be taken into account in analyses of spacecraft observations. Attention is given to the application of the cross-sectional data obtained to both electron energy loss codes and models of Voyager, IUE, Galileo, and HST observations of the solar system.

A significant new application of ultraviolet sensors to remote sensing of the ionosphere and thermosphere from satellites is emerging from previous decades of UV space experimentation. This new use will be on what can be termed Global Space Weather Systems, which will have several new UV sensors in addition to the current in situ instrumentation. The technological development of UV atmospheric radiance measurements, FUV auroral imagers, and EUV solar flux measurements is traced. Challenges to current UV technology remain, including further development of the AURIC UV radiance and transmission code; use of UV stars for in-flight calibration; evaluation of occultation methods as opposed to current airglow methods; and most importantly, the necessity for ground truth validation of proposed ionospheric electron density remote sensing methods through further satellite UV airglow measurements.

We review some of the features of the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) and describe the environmental parameters that will be produced on an operational basis from this instrument's data. The associated algorithms are summarized. SSUSI consists of a scanning imaging spectrograph (SIS) whose field-of-view is scanned from horizon to horizon and a nadir-looking photometer system (NPS). The SIS produces simultaneous monochromatic images at five 'colors' in the spectral range 115nm to 180nm. The NPS consists of three photometers with filters designed to monitor the airglow at 427.8nm and 630nm and the terrestrial albedo near 630nm. SSUSI will fly on the DMSP Block 5D3 satellites S-16 through S-19. In a companion paper we provide more details on the Special Sensor Ultraviolet Spectrographic Imager (SSUSI).

Vertical perspective, mercator, and tilted perspective projection images are presented which contain calculated dayglow, nightglow, and aurora. These images are discussed in terms of their structure's sources, which encompass composition variations, solar zenith angle changes, and changes in the path length experienced on going from disk-viewing to limb-viewing. Both a global thermospheric model (MSIS-86) and a global ionospheric model (the International Reference Ionosphere) are used to respectively specify neutral composition and the profiles of OI and OII.

While visible and UV range sensors are frequently designed to see the ground, the short-wavelength region known as 'solar-blind' (below 320 nm wavelength) includes emissions originating at altitudes above 30-140 km. The solar-blind range is being investigated for remote sensing of the composition, dynamics, and energetics of the Earth atmosphere, as well as for use in passive sensor acquisition and tracking systems. An examination is presently conducted of the PSD of mid-UV images from a recently launched satellite.

The HiRES sounding rocket payload has been described in detail in previous SPIE Proceedings. Here, optical design of the toroidal grating spectrograph is presented and discussed. Ray tracing results are presented which outline the extreme ultraviolet (EUV) performance theoretically attainable with the HiRES instrument. Effects of optical system misalignment on the spectrograph image quality are investigated. Laboratory test results of two f/15 toroidal diffraction gratings using a 1 meter vacuum spectrograph and a multi-anode microchannel array detector are presented and discussed. The test toroidal gratings are fabricated using the elastic substrate replication technique from a ruled master grating with either a 3600 lines/mm or 1800 lines/mm density. EUV images of 10 25 micrometers pinholes with 250 micrometers center-to-center spacing taken with a hollow cathode discharge lamp are presented. Interferometric studies of toroidal figure accuracy as well as optical and electron microscopy investigations into surface quality are presented and discussed. It is found that the current toroidal gratings exhibit good imaging characteristics across a wide wavelength range but suffer from excessive EUV scatter and spectral ghosting.

Thinned, backside-illuminated, p-channel CCD images are under development which can exploit the surface potential in VUV applications, yielding enhanced quantum efficiency to wavelengths as short as 1100 A. The current goal is production of large-format, 5-micron pixel imagers for spectrographic and imaging VUV spaceflight experiments. Model predictions of the effect of device design on quantum efficiency, well capacity, and crosstalk are presented for such 5-micron-approaching pixel sizes.

Curved-channel microchannel plate (C-plate) improvements resulting from an ongoing NASA STIS microchannel plate (MCP) development program are described. Performance limitations of previous C-plates led to a development program in support of the STIS MAMA UV photon counter, a second generation instrument on the Hubble Space Telescope. C-plate gain, quantum detection efficiency, dark noise, and imaging distortion, which are influenced by channel curvature non-uniformities, have all been improved through use of a new centrifuge fabrication technique. This technique will be described, along with efforts to improve older, more conventional shearing methods. Process optimization methods used to attain targeted C-plate performance goals will be briefly characterized. Newly developed diagnostic measurement techniques to study image distortion, gain uniformity, input bias angle, channel curvature, and ion feedback, will be described. Performance characteristics and initial test results of the improved C-plates will be reported. Future work and applications will also be discussed.

The objective of this effort was to compare the resolution and contrast characteristics of ultraviolet imagers with and without an intensifier. This was accomplished by first observing several bar patterns in the laboratory. Then both imagers were taken outside of the laboratory during daylight conditions and observations were made of objects with limited contrast. It was found that in all the measurements the nonintensified imager performed considerably better than the intensified imager. In fact in an observation of low contrast, with the nonintensified imager it was possible to distinguish small intensity variations, whereas with the intensified imager these variations were within the noise level of the instrument. The noise level of the intensified imager was also measured with high gain and with low gain and a definite variation was found.

A program exists at NIST to calibrate radiometric sources for the spectral range from 118-350 nm. These include deuterium lamps, hollow-cathode lamps, RF-excited dimer lamps, and wall-stabilized argon arcs. Sources have been calibrated for and used by researchers in solar physics, astrophysics, atmospheric physics (ozone measurements), magnetically controlled fusion, and photobiology. The argon arcs were developed in our laboratory, and provide intense sources of both radiance and irradiance. Calibrations are performed relative to two primary sources, a wall-stabilized hydrogen arc and a 12,000 K black-body line arc, both developed in our laboratory. Also we recently have begun periodic calibrations on the NIST storage ring, SURF II, to insure consistency between our respective radiometric bases. Various sources have been calibrated for space' applications, including several which are flyable. Also, some development and testing of radiometers for semiconductor lithography were recently carried out with an intense argon arc source.

A working standard extended source of spectral radiance has been assembled and calibrated for use in the 150- to 260-nm region. The assembly consists of a 10-kw, argon arc lamp mounted to irradiate a 4-in. diameter diffuser. The reflected energy from the diffuser is utilized as a calibration source. The procedure for calibrating the spectral radiance of the diffuser is reviewed. Traceability is accomplished by the use of a standard vacuum photodiode. The total uncertainty in the calibration of the source is estimated to be +/- 15 percent.

Since 1981 more than 150 instrument calibrations have been performed on the radiometric instrumentation calibration beamline at the Synchrotron Ultraviolet Radiation Facility (SURF II) at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland. This 300 MeV electron storage ring operates routinely at electron currents greater than 250 mA. The spectrometer calibration beamline provides a continuum of radiation from 4 nm through the visual spectral region in the form of an intense beam with total angular divergence of 1.2 mrad. The probable uncertainty for the flux ranges from about 5 percent at 4 nm to less than 2 percent above 20 nm. The new system will radiometrically trace to SURF II, and thus is expected to reduce the calibration uncertainty for diodes in this region by a factor of five to the 1-2 percent level.

Bidirectional reflectance distribution function (BRDF) is an important quantity to describe the scattering condition from a diffuse surface. The current presentation describes the instrumentation, instrument characterization and diffuser calibration in the ultraviolet (UV) spectral region.

The Naval Research Laboratory recently completed construction of a new instrument handling facility for contamination sensitive optical space flight instruments. The solar instrument test facility includes a clean room for instrument assembly and a relatively large (1.65x104 liters) optical test and calibration vacuum chamber. The performance of each has been verified in preparation for the arrival of the Large Angle Spectrometric Coronagraph (LASCO) instrument. After vacuum conditioning, the chamber had an ultimate pressure of 8 x l0 exp -9 Torr. The chamber ambient vacuum was measured to have no partial pressure peaks greater than 10 exp -10 Torr above 55 atomic mass units as measured with a residual gas analyzer. The clean room was tested and found to be Class 10 in the instrument areas. This paper describes the A-13 clean room and vacuum tank facilities and their experimentally measured performance.

Dynamic alignment has been demonstrated as a practical approach to alignment maintenance for systems in the infrared region of the spectrum. On the basis of work done by OPTRA, this technique was introduced in commercial Fourier transform spectrometer systems in 1982 and in various forms is now available from a number of manufacturers. This paper reports on work by OPTRA to extend the basic technique to systems operating in the ultraviolet. In addition, this paper reports the preliminary results of the development of an alignment system using a laser diode in place of a gas laser normally found in dynamic alignment systems. A unique optical system and spatial heterodyne technique allows for achievement of a metrology system with characteristics that fully satisfy the requirements of an ultraviolet spectrometer system.

This paper reviews the research and design of high temperature blackbody sources for the temperature interval from 2000 K to 3000 K. Sources with large apertures are addressed specifically, as these are well suited to the important problem of spectral irradiance scale realizations.

Chemical vapor deposited (CVD) silicon carbide mirrors were exposed to bombardment by 8 km/s (5.2 eV) oxygen atoms that simulated exposure in low earth orbit for periods up to 7.5 years. The reflectances of four mirrors were measured before and after exposure at 584, 736, 1048, 1216, and 1610 angstroms and at eleven angles of incidence ranging from 5 degree(s) to 80 degree(s). The oxygen exposure reduced the normal incidence reflectances by factors of 1.5 to 4.5 in the VUV but had no effect on the visual appearance. The optical constants and thicknesses of the surface layers present on the SiC substrates were determined from reflectance measurements. This analysis indicated that before exposure the surface layers were composed of SiO_x (where x approximately equals 1.5) with thicknesses of 8 - 18 angstroms. After exposure the thicknesses had increased to 35 - 45 angstrom. There were no systematic differences in the reflectances after simulated space exposures of 1.5, 4.5, and 7.5 years. This implied that most of the growth in thickness of the SiO_x layers occurred early in the exposure and stabilized at thicknesses of 35 - 45 angstroms. The optical results were consistent with x-ray photoelectron spectroscopy of the four mirrors after oxygen exposure.

This paper will describe a new UV sensitive photoconductive detector based on gallium nitride (GaN) material. Data will be presented on devices fabricated over the past several months. These devices have a high responsivity between 200 to 360 nm with a sharp long wavelength cutoff at 360 nm. The detectors have measured gains in excess of six thousand and frequency responses of greater than 100 Hz. The devices have measured dynamic ranges of over four orders of magnitude and operate with bias voltages of 5 to 10 volts. Device designs will be shown that can be utilized in the development of a large monolithic focal plane for UV imaging.

At the National Renewable Energy Laboratory (NREL), ongoing projects investigate the use of ultraviolet (UV) energy as it applies to aqueous toxic waste purification, material degradation, and terrestrial spectral solar irradiance model development. These projects require knowledge of the UV spectral distribution of natural terrestrial sunlight and artificial sources rich in UV radiation. NREL has modified instrumentation to measure terrestrial solar spectral distributions from 250 to 400 nanometers (nm) at 1 nm intervals. It uses a band width of 2 nm, and a small double monochromator and photomultiplier (1P28) detector. The modified instrument measures artificial sources in the laboratory with up to 1000 times the intensity of natural solar UV radiation. This is done using coupled multiple integrating spheres and by limiting apertures to provide appropriate signal levels. A newly acquired UV spectroradiometer with good wavelength accuracy (0.3 nm) is used to calibrate broad-band solar UV monitoring detectors outdoors and against laboratory standards. Both the metrology and research applications of these UV spectral measurements require detailed uncertainty analyses, which show that uncertainty in the measurements is a strong function of wavelength below 350 nm. The major contributors to the uncertainty are wavelength drive accuracy, passband, detector noise, and calibration source uncertainty.

A model is presented which calculates intensities of Rayleigh-scattered sunlight to large solar zenith angles (SZAs). The intensity integrand contains appropriate transmission functions and a volume emission rate profile with SZA varying along the line-of-sight. The calculation is performed for a spherically-symmetric model atmosphere and allows for limb and nonlimb viewing. We compare O I 6300 A nightglow and N2(+) 4278 A auroral signals to their Rayleigh-scattered counterparts at various SZAs beyond the terminator, addressing the major problems encountered by operational sensors when a rapid change in scattered sunlight intensity occurs at the terminator. To illustrate the effects of baffling systems, we examine three simple baffle designs being considered for a nadir-viewing photometer system to be flown on Defense Meteorological Satellite Program (DMSP) Block 5D3 satellites. The results show how far these photometers must be beyond the terminator to make good airglow and auroral measurements.

The number and variety of applications for UV curable inks, coatings, and adhesives continue to expand at a rapid pace, and pose new design challenges to increase cure efficiency, speed, and the physical properties of the cured polymer film. The latest developments in microwave powered lamps for industrial processing are presented. Among these are: (1) the selection and control of the lamp emission spectra to match the optical properties of the film and its photoinitiator, (2) sustained high power lamp operation at 6 kilowatts, and (3) the use of absorptive dichroic reflectors to mange the relative components of UV and infrared energy in the highly focused radiation delivered to surfaces being processed. The design considerations of high powered UV lamps and dichroic reflectors for them are presented.

The multi-anode microchannel array (MAMA) is a microchannel plate based photon counting detector with applications in ground-based and space-based astronomy. The detector electronics decode the position of each photon event, and the decoding algorithm that associates a given event with the appropriate pixel is determined by the geometry of the anode array. The standard MAMA detector has a spatial resolution set by the anode array of 25 microns, but the MCP pore resolution exceeds this. The performance of a new algorithm that halves the pixel spacing and improves the pixel spatial resolution is described. The new algorithm does not degrade the pulse-pair resolution of the detector and does not require any modifications to the detector tube. Measurements of the detector's response demonstrate that high resolution decoding yields a 60% enhancement in spatial resolution. Measurements of the performance of the high resolution algorithm with a 14 micron MAMA detector are also described. The parameters that control high resolution performance are discussed. Results of the application of high resolution decoding to speckle interferometry are presented.

Plumes and aerodynamic shock structures of rockets produce prominent UV and IR emissions. The extensive literature explains many aspects of the IR emission: whereas the UV emissions are less well understood and have only recently been quantified. Hypervelocity missiles in the continuum and near-continuum atmosphere produce high temperature shocklayers (i.e., 8000 K for speeds of 5 km/sec). Atmospheric molecular oxygen and nitrogen react and the products are excited to produce nitrogen oxide molecular - band radiation. Previous papers describe two rocket flight experiments that obtained in-situ radiometric UV data with onboard instruments directly viewing the shocklayer and plume regions. An example of data obtained were the well defined spectra of NO ((Gamma) ,(Beta) ) emission with signal strengths on the order of 0.0014 W/cm²sr for a rocket velocity of 5 km/sec at 70 km. This radiance was 15 times stronger than recent theoretical predictions and is observable using present detector systems. The UV radiance and background data that has been collected from these rocket flights and the LACE/UVPI satellite program implies a systems utility. In addition, a third experiment is being planned to extend the velocity to 7 km/sec. Scanning spectrometers and photometers will observe the shock plume interactions. Angular scanning is being included to define the structures of the far field plume. The area of greatest uncertainty and potential opportunity will be described in terms of the mechanistic understanding.