David J. Gutierrez

Multi‐instrument zenith observations of noctilucent clouds over Greenland on July 30/31, 1995

Results are presented for zenith observations of a noctilucent cloud (NLC) display over the Sondrestrom atmospheric research facility near Kangerlussuaq, Greenland, on July 30/31, 1995. The observations were made with a Rayleigh lidar, which measured the NLC particle volume backscatter coefficient, and with a UV spectrograph, which measured the intensity and degree of linear polarization of solar light scattered from the NLC. The intensity and polarization measurements were made at solar depression angles of −1.8° to −4.6°. These data allowed the first simultaneous observation from the ground of the altitude and thickness of the NLC and of the radius of the NLC particles. The NLC was found to be between 86 and 84 km in altitude with a thickness of 1 to 2 km and the NLC particles had a radius at or below 0.07 μm. We also report the first observation of an NLC sublimating due to the passage of an AGW through the 85-km altitude region. These observations are generally in agreement with models of noctilucent clouds.

The ARIA I Rocket Campaign

The Atmospheric Response in Aurora (ARIA) I rocket experiment was designed to measure the energy and momentum forcing of the atmosphere during auroral disturbances and the resultant compositional and dynamical changes. It consisted of one instrumented rocket, three trimethyl aluminum chemical release rockets, and various ground-based optical instruments. The rockets were launched from Poker Flat Research Range, Alaska, in March 1992. The instrumented payload included a set of eight instruments for measuring various atmospheric and ionospheric quantities. This paper describes the contents of the program and the results of electrodynamic modeling and measurements. A substorm onset occurred approximately 4 hours before launch of the instrumented payload, giving rise to both particle and Joule heating in the vicinity of Poker Flat. By launch time, the substorm was well into recovery. We used optical measurements, electron density measurements from the Langmuir probe instrument, and model results from the Strickland electron transport code to specify latitudinal profiles of the height-integrated Pedersen conductivity. Comparison with assimilated mapping of ionospheric electrodynamics (AMIE) calculations of the Pedersen conductivities for this event indicated that AMIE located the enhanced auroral conductivity region well. However, the magnitudes of the AMIE conductivities in the enhanced region were considerably less than the measurements due to localized substorm-related particle precipitation enhancements not accounted for by AMIE. Our conductivity profiles were used in conjunction with electric field values produced by the AMIE routine to examine the atmospheric heating rates associated with the substorm. The latitudinally integrated Joule heating rate was initially less than the particle heating rate, but rapidly increased to its maximum value at the time of the substorm maximum while the particle heating rate peaked prior to substorm maximum. The particle and Joule heating were collocated during the expansion and maximum phase, but as the substorm recovered, the Joule heating moved to higher latitudes, so that by the time of launch, the two heating regions were completely separated by several degrees. The analysis indicates that the rocket was launched directly into the atmospheric region where the maximum heating had occurred.

Instrumentation on the Remote Atmospheric and Ionospheric Detection System Experiment: extreme-ultraviolet spectrometer, photometer, and near-infrared spectrometer

The Remote Atmospheric and Ionospheric Detection System experiment consists of eight instruments spanning the wavelength range from the extreme ultraviolet (55 nm) to the near infrared (800 nm) oriented to view the Earths limb from the National Oceanic and Atmospheric Administration TIROS-J spacecraft to be launched into a circular orbit in 1993. Through measurements of the natural optical emissions and scattered sunlight originating in the upper atmosphere including the mesosphere and thermosphere, state variables such as temperature, composition, density, and ion concentration of this region will be inferred. The subset of instruments fabricated or otherwise provided by the Space and Environment Technology Center (formerly Space Sciences Laboratory) at The Aerospace Corporation are described.

MAKO: a high-performance, airborne imaging spectrometer for the long-wave infrared

We report progress on a high-performance, long-wavelength infrared hyperspectral imaging system for airborne research. Based on a f/1.25 Dyson spectrometer and 128x128 arsenic doped silicon blocked impurity band array, this system has significantly higher throughput than previous sensors. An agile pointing/scanning capability permits the additional signal to be allocated between increased signal-to-noise and broader area coverage, creating new opportunities to explore LWIR hyperspectral phenomenology.

Instrumentation on the RAIDS experiment II: extreme-ultraviolet spectrometer, photometer, and near-IR spectrometer

The RAIDS experiment consists of eight instruments spanning the wavelength range from the extreme ultraviolet (55 nm) to the near infrared (800 nm) oriented to view the Earths limb from the NOAA-J spacecraft to be launched into a circular orbit in 1993. Through measurements of the natural optical emissions and scattered sunlight origmating in the upper atmosphere including the mesosphere and thermosphere, state variables such as temperature, composition, density and ion concentration of this region will be inferred. This paper describes the subset of instruments fabricated or otherwise provided by the Space and Environment Technology Center (formerly Space Sciences Laboratory) at The Aerospace Corp. The companion to this paper describes the instruments from the Naval Research Laboratory. The Extreme Ultraviolet Spectrograph (EUVS), the three fixed filter photometers 0! (630), 0! (777), and Na (589), and the near infrared spectrometer (NIR) will be described. These are all mounted on a mechanical scan platform that scans the limb from approximately 75 to 750 km in the orbital plane of the satellite every 90 seconds.

MAGI: A New High-Performance Airborne Thermal-Infrared Imaging Spectrometer for Earth Science Applications

A new airborne facility instrument for Earth science applications is introduced. The Mineral and Gas Identifier (MAGI) is a wide-swath (programmable up to ±42° off nadir) moderate spectral resolution thermal-infrared (TIR) imaging spectrometer that spans the 7.1- to 12.7-μm spectral window in 32 uniform and contiguous channels. Its spectral resolution enables improved discrimination of rock and mineral types, greatly expanded gas-detection capability, and generally more accurate land-surface temperature retrievals. The instrument design arose from trade studies between spectral resolution, spectral range, and instrument sensitivity and has now been validated by flight data acquired with the completed sensor. It offers a potential prototype for future space-based TIR instruments, which will require much higher spectral resolution than is currently available in order to address more detailed climate, anthropogenic, and solid Earth science questions.

Mako airborne thermal infrared imaging spectrometer: performance update

The Aerospace Corporation’s sensitive Mako thermal infrared imaging spectrometer, which operates between 7.6 and 13.2 microns at a spectral sampling of 44 nm, and flies in a DeHavilland DHC-6 Twin Otter, has undergone significant changes over the past year that have greatly increased its performance. A comprehensive overhaul of its electronics has enabled frame rates up to 3255 Hz and noise reductions bringing it close to background-limited. A replacement diffraction grating whose peak efficiency was tuned to shorter wavelength, coupled with new AR coatings on certain key optics, has improved the performance at the short wavelength end by a factor of 3, resulting in better sensitivity for methane detection, for example. The faster frame rate has expanded the variety of different scan schemes that are possible, including multi-look scans in which even sizeable target areas can be scanned multiple times during a single overpass. Off-nadir scanning to ±56.4° degrees has also been demonstrated, providing an area scan rate of 33 km2/minute for a 2-meter ground sampling distance (GSD) at nadir. The sensor achieves a Noise Equivalent Spectral Radiance (NESR) of better than 0.6 microflicks (μf, 10-6 W/sr/cm2/μm) in each of the 128 spectral channels for a typical airborne dataset in which 4 frames are co-added. An additional improvement is the integration of a new commercial 3D stabilization mount which is significantly better at compensating for aircraft motions and thereby maintains scan performance under quite turbulent flying conditions. The new sensor performance and capabilities are illustrated.

Dyson spectrometers for infrared earth remote sensing

The Dyson spectrometer form is capable of providing high throughput, excellent image quality, low spatial and spectral distortions, and high tolerance to fabrication and alignment errors in a compact format with modest demands for weight, volume, and cooling resources. These characteristics make it attractive for hyperspectral imaging from a space-based platform. After a brief discussion of history and basic principles, we present two examples of Dyson spectrometers being developed for airborne applications. We conclude with a concept for an earth science instrument soon to begin development under the Instrument Incubator Program of NASAs Earth Science Technology Office.

Description of a proposed space-based high-resolution ozone imaging instrument (HIROIG)

In order to measure the effect of rocket exhaust on stratospheric ozone and aerosol profiles, it is necessary to deploy a space-based mid-UV spectrograph capable of making measurements at high spatial resolution (1 - 2 km) of the intensity and state of polarization of solar light backscattered by the atmosphere. This paper describes the design of an instrument called HIROIG (high resolution ozone imager) which is expected to be deployed in a sun synchronous orbit sometime after 1995. The instrument consists of three identical spectrographs, each one sensitive to light polarized in one direction. Each spectrograph uses a frame-transfer CCD which images the entire 270 - 370 nm spectrum at approximately equals 1 nm spectral resolution. Images re exposed, in the push broom mode, for 140 msec, providing an effective spatial resolution of better than 2 km for typical orbital velocities. The HIROIG field of view is 1000 km cross-track. A ground-based prototype consisting of a single spectrograph has been constructed and the characterization of this instrument is discussed.