Far-ultraviolet Imaging Research Articles

Far-ultraviolet imaging spectrograph and scanning grating spectrometers for the Remote Atmospheric and Ionospheric Detection System

The Remote Atmospheric and Ionospheric Detection System (RAIDS) experiment is an optical remote sensing platform consisting of eight sensors, (spectrographs, spectrometers, and photometers) covering the wavelength range 550 to 8744 Å. RAIDS employs a mechanical scan platform to view the Earth's limb and measure line-of-sight column emission from tangent altitudes from 50 to 750 km. These measurements provide vertical profiles of atmospheric dayglow and nightglow from the mesosphere to the upper regions of the F-region ionosphere. RAIDS will be flown on the National Oceanographic and Atmospheric Administration (NOAA) J weather satellite through the auspices of the U.S. Air Force Space Test Program. The RAIDS wavelength and altitude coverage allows remote sensing of the major and many minor constituents in the thermosphere and ionosphere. These measurements will be used as part of a proof of concept for remote sensing of ionospheric and neutral density profiles. The RAIDS database will be used to study composition, thermal structure, and couplings between the mesosphere, thermosphere, and ionosphere. RAIDS is a joint venture of the Naval Research Laboratory (NRL) and The Aerospace Corporation. We describe the subset of RAIDS instruments developed at NRL covering the far to near UV regions (1300 to 4000 Å).

In-Flight Performance and Preliminary Results from the Far Ultraviolet Space Telescope (Faust) Flown on ATLAS-1

In 1992 March the Far Ultraviolet Space Telescope was flown as part of the NASA ATLAS-1 mission. We describe the in-flight instrument performance and provide a preliminary view of some of the results. Twenty-two wide-field far-ultraviolet images were obtained. At this stage of our analysis, we have far-ultraviolet photometry for more than 4800 sources; the overwhelming majority of these are below the TD-1 satellite far-ultraviolet detection limit. In these images, we detect sources to a flux limit of 1×10 -14 ergs s -1 cm -2 A -1 , which is at least an order of magnitude more sensitive than the TD-1 satellite, and we have virtually complete source detections to a level of 6×10 -14 ergs s -1 cm -2 A -1

Filters for the International Solar Terrestrial Physics Mission far-ultraviolet imager

The far ultraviolet (FUV) imager for the International Solar Terrestrial Physics (ISTP) mission is designed to image four features of the aurora: O I lines at 130.4 nm and 135.6 nm and the N2 Lyman-Birge-Hopfield (LBH) bands between 140 nm - 160 nm (LBH long) and 160 nm - 180 nm (LBH long). In this paper we report the design and fabrication of narrow-band and broadband filters for the ISTP FUV imager. Narrow-band filters designed and fabricated for the O I lines have a bandwidth of less than 5 nm and a peak transmittance of 23.9 percent and 38.3 percent at 130.4 nm and 135.6 nm, respectively. Broadband filters designed and fabricated for LBH bands have the transmittance close to 60 percent. Blocking of out-of-band wavelengths for all filters is better than 5x10(exp -3) percent with the transmittance at 121.6 nm of less than 10(exp -6) percent.

Far ultraviolet remote sensing of ionospheric emissions by Polar BEAR

A few thousand far-ultraviolet images of the ionosphere have been obtained since December 1986 by the Atmospheric/Ionospheric Remote Sensor (AIRS) aboard the Polar BEAR satellite. Fast algorithms for applying automated satellite-attitude, geometric, and photometric corrections to these images were developed, and the first results are discussed. A software package that is based on these algorithms was implemented and tested. Since no attitude data is available at night (one of the two gauges is a Sun sensor), an algorithm was devised to extrapolate daytime attitude corrections to nighttime. An additional method is offered to correct satellite roll from the measured or extrapolated one based on the dayglow limbs observed at the edges of the image. Geometric rectifications include transformations to the image from the satellite coordinate system to a reference system, and from the reference system to the geographic coordinate system. Radiometric corrections include image enhancement, background airglow subtraction, and off-nadir normalization of auroral emissions. The latter two are based on theoretical calculations of column emission rates, derived by radiative transfer integrations of volume emission rates along the look direction. Results include mapping of auroral arcs in the corrected geomagnetic system, the one most applicable to auroral studies.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Far-ultraviolet spectral images of comet Halley from sounding rockets

Wide-field ultraviolet imagery of comets provides a useful means of determining such fundamental parameters as production rates, lifetimes and outflow velocities of daughter photodissociation products in the coma. Far-ultraviolet imagery has been used to measure the production rates and outflow characteristics of hydrogen for comets Bennett1, Kohoutek2,3 and West4,5, for C and O in comet Kohoutek6, and for C, S and CS in comet West7. Ultraviolet spectroscopy has also revealed the presence of C+ ions and CO molecules8 in comet West. Other comets have been observed spectroscopically in the ultraviolet from the International Ultraviolet Explorer (IUE) spacecraft9. Here we present far-ultraviolet images of comet Halley obtained from sounding rockets launched from White Sands Missile Range, New Mexico, on 24 February and 13 March 1986. We gained direct electrographic images of the hydrogen coma of the comet at the Lyman-α wavelength (1,216 A), and objective spectra containing images of the coma at the oxygen (1,304 A), carbon (1,561 and 1,657 A) and sulphur (1,814 A) resonance multiplets. Analysis of the Lyman-α images yields hydrogen atom production rates of l.9 × 1030 s−1 and 1.4 × 1030 s−1 for the two observations. Images of oxygen, carbon and sulphur emissions obtained with the objective grating spectrograph are presented for the first set of observations and preliminary production rates are derived for these elements.

THE S 201 FAR-ULTRAVIOLET IMAGING SURVEY : A SUMMARY OF RESULTS AND IMPLICATIONS FOR FUTURE SURVEYS.

ABSTRACT The results from all-sky surveys with the S201 FUV camera/spectrograph from the moon during the Apollo 16 mission are summarized with respect to implications for future UV all-sky surveys. The scans provided imagery of 10 fields, each 20 deg in diameter, in the wavelength ranges 1050-1600 A and 1250-1600 A. Best detection thresholds were obtained with 10 and 30 min exposures at 1400 A. Only 7 percent sky coverage was recorded, and then only down to 11th mag. A Mark II camera may be flown on the Shuttle on the Spartan 3 mission, as may be an all-reflector Schmidt telescope. An additional 20 percent of the sky will be mapped and microchannel intensification will increase the diffuse source sensitivity by two orders of magnitude. Several objects sighted with the S201 will be reviewed with the Mark II.

The S201 far-ultraviolet imaging survey. III - A field in Sagittarius

Far-ultraviolet imagery of a 20 deg diameter field in Sagittarius, centered near (1950) R.A. 18 h 34 m, decl. -30 deg 25 arcmin, was obtained by the S201 far-ultraviolet camera during the Apollo 16 mission. In a 10-minute exposure covering the 1250-1600 A wavelength range, 1034 star images are detectable, with a limiting ultraviolet magnitude of about 10. Most of these objects are identified with early-type stars listed in the Smithsonian Astrophysical Observatory Star Catalog, the Catalog of Stellar Identifications, or both, but 203 objects remain unidentified or are identified with late-type stars. The photometric measurements appear to be in reasonable agreement with those of the International Ultraviolet Explorer for stars in common, and with expectations for A0 stars. A detailed photometric study was made of the Messier 8 region, and it is concluded that dust-scattered starlight contributes about half of the total radiation observed from the central region of M8.

The S201 far-ultraviolet imaging survey. II - A field in Cygnus

view Abstract Citations (14) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The S201 far-ultraviolet imaging survey. II. A field in Cygnus. Carruthers, G. R. ; Page, T. Abstract Far-ultraviolet imagery of a region in Cygnus, a 20 deg diameter field centered near (1950) R. A. 21 h 31.2 m decl. +37 deg 25 arcmin, was obtained by the S201 far-ultraviolet camera during the Apollo 16 mission. In a 10 minute exposure covering the 1250-1600 A wavelength range (effective wavelength 1400 A), 730 star images can be detected, corresponding to a limiting ultraviolet magnitude of about m (1400) = 10. Assuming nominal interstellar extinction values in this region near the galactic plane, this result corresponds to the detection of A0 V stars to a distance of 300 pc and of B0 V stars to 1500 pc. Uncertainties in spectral classification and interstellar extinction for individual objects are probably more significant than calibration or measurement errors. Most of the objects detected are identified with stars in the Smithsonian Astrophysical Observatory Star Catalog (1966), or the Catalog of Stellar Identifications (1979) or both, but 87 objects remain unidentified (or are identified with late-type stars). Publication: The Astrophysical Journal Supplement Series Pub Date: February 1984 DOI: 10.1086/190930 Bibcode: 1984ApJS...54..271C Keywords: Astronomical Photography; Cygnus Constellation; Early Stars; Ultraviolet Astronomy; A Stars; Astronomical Catalogs; B Stars; Data Reduction; Far Ultraviolet Radiation; MOON; REMOTE SENSING; IMAGERY; ULTRAVIOLET; WAVELENGTHS; APOLLO 16; PHOTOGRAPHIC OBSERVATIONS; PROCEDURE; ANALYSIS; MAGNITUDE; DATA; SPECTRA; CLASSIFICATION; Astronomy; Miscellaneous full text sources ADS | data products SIMBAD (577) Related Materials (2) Part 1: 1983ApJS...53..623C Part 3: 1984ApJS...55..101C

The S201 far-ultraviolet imaging survey. I - Two fields at high galactic latitude

view Abstract Citations (12) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The S 201 far-ultraviolet imaging survey. I. Two fields at high galactic latitude. Carruthers, G. R. ; Page, T. Abstract Far-ultraviolet imagery was obtained of 10 20-deg diameter fields by the S201 far-ultraviolet camera during the Apollo 16 mission. The present discussion is of two high galactic latitude fields, in Grus and Aquarius, in which exposures of up to 30 minutes duration were obtained in the 1250-1600 A wavelength range (effective wavelength 1400 A), and in which objects as faint as m(1400) = 11.8 are detected. The number versus magnitude relation for the observed objects appears to peak near m(1400) = 10, implying that relatively few such objects exist at magnitudes fainter than our sensitivity limit. Most of the stellar contribution to the ultraviolet radiation field is contributed by stars brighter than m(1400) = 6, which are mainly nearby late B and early A members of the galactic disk population. The objects fainter than m(1400) = 8, however, appear to be members of a second population of hot, subluminous objects, but further ground-based observations of these objects are needed. Publication: The Astrophysical Journal Supplement Series Pub Date: November 1983 DOI: 10.1086/190904 Bibcode: 1983ApJS...53..623C Keywords: Astronomical Photography; Early Stars; Milky Way Galaxy; Star Distribution; Ultraviolet Astronomy; A Stars; Astronomical Coordinates; Astronomical Maps; B Stars; Far Ultraviolet Radiation; Hot Stars; Stellar Magnitude; Stellar Radiation; Ultraviolet Photography; Astrophysics full text sources ADS | data products SIMBAD (23) NED (1) Related Materials (2) Part 2: 1984ApJS...54..271C Part 3: 1984ApJS...55..101C

Low Light Level Detectors for Astronomy

There is an almost bewildering variety of detectors being used for ground-based astronomical observations. Many of the detectors have advantages for particular projects. One-dimensional detectors are simple, yet suitable for spectroscopy. Other detectors offer high photometric precision and dimensional stability. Some are designed for observing only faint objects and some for bright ones. Sometimes the necessity of having a high quantum efficiency at a particular wavelength dictates the choice of detector. In reality the situation is even more chaotic. This review has not covered some of the exotic detectors that have been developed for x-ray and far-ultraviolet imaging from spacecraft. These detectors use devices such as resistive plates, multianode or crossed-wire microchannel plates, and so on. These devices have not yet seen extensive use in ground-based applications, and their future as visible light detectors remains uncertain. The reasons for the development of such a wide variety of detectors are clear. Commercially available devices are simply not capable of meeting the low light level and photometric performance capabilities needed for astronomical observations. The driving forces are the commercial and military applications for detectors, and with few exceptions there has not been sufficient funding available to mount a detector development program for astronomy. Therefore, astronomers have sought to adapt existing commercial devices to the particular problem at hand. The large number of individual efforts summarized in this review is the result. In the future, I expect the variety to diminish as one or two really good detectors become capable of performing well under the wide variety of observational conditions encountered in astronomy. Many people have proclaimed the ultimate detector to be just around the corner. This is yet to happen. However, I venture to speculate that low-noise, high-performance CCD detectors with a format of 500 by 500 or larger will emerge as the preferred astronomical detector within the next few years. I also expect photographic plates will continue to be used for the many applications requiring wide fields up to 10,000 pixels on a side. Finally, as the detectors approach the ultimate quantum limit, attention will shift away from them and toward development of the system necessary to manipulate, display, and extract the information from the 250,000 numbers that make up a 500 by 500 digital image.

Far-ultraviolet imagery of the Barnard Loop Nebula

An electrographic Schmidt camera carried on a sounding rocket has yielded far-ultraviolet (1050-2000 A and 1230-2000 A) images of the Barnard Loop Nebula and of the general background in the Orion region due to scattering of ultraviolet starlight by interstellar dust particles. The total intensity in the Barnard Loop region agrees well with OAO-2 measurements, but the discrete Loop structure contributes only some 15% of the total. The measurements are consistent with a relatively high albedo for the dust grains in the far-ultraviolet.