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NASA NTRS1992

Galileo Ultraviolet Spectrometer experiment

The Galileo ultraviolet spectrometer experiment uses data obtained by the Ultraviolet Spectrometer (UVS) mounted on the pointed orbiter scan platform and from the Extreme Ultraviolet Spectrometer (EUVS) mounted on the spinning part of the orbiter with the field of view perpendicular to the spin axis. The UVS is a Ebert-Fastie design that covers the range 113-432 nm with a wavelength resolution of 0.7 nm below 190 and 1.3 nm at longer wavelengths. The UVS spatial resolution is 0.4 deg x 0.1 deg for illuminated disk observations and 1 deg x 0.1 deg for limb geometries. The EUVS is a Voyager design objective grating spectrometer, modified to cover the wavelength range from 54 to 128 nm with wavelength resolution 3.5 nm for extended sources and 1.5 nm for point sources and spatial resolution of 0.87 deg x 0.17 deg. The EUVS instrument will follow up on the many Voyager UVS discoveries, particularly the sulfur and oxygen ion emissions in the Io torus and molecular and atomic hydrogen auroral and airglow emissions from Jupiter. The UVS will obtain spectra of emission, absorption, and scattering features in the unexplored, by spacecraft, 170-432 nm wavelength region. The UVS and EUVS instruments will provide a powerful instrument complement to investigate volatile escape and surface composition of the Galilean satellites, the Io plasma torus, micro- and macro-properties of the Jupiter clouds, and the composition structure and evolution of the Jupiter upper atmosphere.

Hord, C. W.↗

NASA NTRS1973

Ultraviolet spectrometer experiment

The ultraviolet spectrometer (UVS) onboard the Apollo 17 orbiting spacecraft was used to measure emissions from the lunar atmosphere. The UVS and calibration are discussed along with the lunar atmosphere observations and lunar albedo measurements.

Fastie, W. G.↗

NASA NTRS1994

JPL Fourier transform ultraviolet spectrometer

The Fourier Transform Ultraviolet Spectrometer (FTUVS) is a new high resolution interferometric spectrometer for multiple-species detection in the UV, visible and near-IR. As an OH sensor, measurements can be carried out by remote sensing (limb emission and column absorption), or in-situ sensing (long-path absorption or laser-induced fluorescence). As a high resolution detector in a high repetition rate (greater than 10 kHz) LIF system, OH fluorescence can be discriminated against non-resonant background emission and laser scatter, permitting (0, 0) excitation.

Cageao, R. P.↗

NASA NTRS1974

Mariner 9 ultraviolet spectrometer experiment - Pressure-altitude measurements on Mars

Ultraviolet spectrometer measurements of the reflectance at 3050 A are modeled to give pressure-altitudes for Mars assuming a quiescent atmosphere. Ultraviolet light that is Rayleigh-scattered by the Mars molecular atmosphere, with allowance for uniform turbidity, is proportional to surface pressure independent of atmospheric temperature structure. All model constants except the over-all scaling factors are found by requiring ultraviolet spectrometer pressures of 47 locations on the planet to be the same when measured at different geometries. The overall scaling factor is found by intercomparison with Mariner 9 occultation pressures. Comparison with other Mars pressure-altitude measurements show deviations from the assumption of uniform turbidity to occur over the Hesperia plateau for ultraviolet measurements obtained during the 13-26 February 1972 time period.

Hord, C. W.↗

NASA NTRS1973

Task 2 of the ultraviolet spectrometer experiment S169

The far ultraviolet spectrometer for the Apollo 17 lunar scientific mission was constructed to meet the specific requirements and technical specifications as directed by the National Aeronautics and Space Administration. The Ebert Scanning Monochromator (UVS) was derived from extensive experience in the development of a variety of Ebert scanning monochromators for experiments aboard rockets and satellites. This equipment has the capability to make quantitative measurements of the composition of the lunar atmosphere as seen from the Apollo 17 CSM in lunar orbit, and to study the spectra of a number of astronomical sources during trans-earth coast.

Goss, M. E.↗

NASA NTRS1991

The Apollo 17 Ultraviolet Spectrometer - Lunar atmosphere measurements revisited

Ultraviolet resonance fluorescence of solar radiation provides the most sensitive means of detecting the expected major constituents of the tenuous daytime lunar atmosphere. Such an experiment was carried out with the Apollo 17 Ultraviolet Spectrometer in December 1972 and produced only upper limits to the number density of H, H2, O, C, N, CO, and two noble gases near the surface of the moon. The complete data set of 47 terminator crossing observations, which were not utilized in the earlier analysis, has been reexamined, and more stringent upper limits to the column emission rates for several species have been derived. These results, together with most recent values for the atomic and molecular fluorescence efficiencies, lead to more definitive limits on the content of the lunar atmosphere. The revised upper limit on atomic oxygen density allows for the possibility of comparable O/Na ratios in the atmosphere of both the moon and Mercury.

Feldman, Paul D.↗

NASA NTRS1972

Development and testing of the ultraviolet spectrometer for the Mariner Mars 1971 spacecraft

The Mariner Mars 1971 ultraviolet spectrometer is an Ebert-Fastie type of the same basic design as the Mariner Mars 1969 instrument. Light enters the instrument and is split into component wavelengths by a scanning reflection diffraction grating. Two monochrometer exit slits allow the use of two independent photomultiplier tube sensors. Channel 1 has a spectral range of 1100 to 1692 A with a fixed gain, while Channel 2 has a spectral range of 1450 to 3528 A with an automatic step gain control, providing a dynamic range over the expected atmosphere and surface brightness of Mars. The scientific objectives, basic operation, design, testing, and calibration for the Mariner Mars 1971 ultraviolet spectrometer are described. The design discussion includes those modifications that were necessary to extend the lifetime of the instrument in order to accomplish the Mariner Mars 1971 mission objectives.

Farrar, J. W.↗

NASA NTRS1980

Design and operation of the Pioneer Venus Orbiter ultraviolet spectrometer

The University of Colorado's ultraviolet spectrometer instrument carried on the Pioneer Venus Orbiter spacecraft is a 125-mm f/5 Ebert-Fastie design with a 250-mm Cassegrain telescope. The instrument has extensive logic to control the grating motor drive and to adapt the basic spectrometer to the constraints and opportunities of the mission. Success has been achieved in reconciling the conflicting requirements of spectroscopic, limb profile, and imaging observations. A description of the instrument operating techniques is given together with representative results of all three types.

Stewart, A. I. F.↗

NASA NTRS1997

Pioneer Venus Orbiter Ultraviolet Spectrometer: Operations and Data Analysis

The Ultraviolet Spectrometer investigation on the Pioneer Venus Orbiter mission was extremely successful. The instrument was designed, built and tested at CU/LASP and delivered on time and within budget. The spacecraft and its instruments were required to operate for 243 days in Venus orbit. OUVS operated successfully for a further 13 years with only minor problems. The major scientific results listed above that deal with Venus were all unexpected and significant discoveries. The Comet Halley observations came about because of a favorable alignment of Halley, the Sun, and Venus, and were an important contribution to the international study of this comet. The scientific results of the OUVS investigation are to be found in the 41 papers listed in section 4 below. OUVS data provided material for 6 PhD and one MS dissertations, listed in section 5 below.

Stewart, A. I. F.↗

NASA NTRS1980

Airglow from Jupiter's nightside and crescent - Ultraviolet spectrometer observations from Voyager 2

The Voyager Ultraviolet Spectrometer has made extensive observations of airglow from Jupiter's dark-side equatorial latitudes. The brightness of H Lyman alpha, the only emission detected, varies between 700 and 1000 rayleighs (R) as a function of longitude. The dark side of Jupiter is illuminated by sky background Lyman alpha arising from resonance scattering of the solar Lyman alpha line by the neutral hydrogen of the interstellar medium. Calculations show that resonance scattering of this sky background by hydrogen in Jupiter's thermosphere will produce about 300 R of Lyman alpha emission. The additional Lyman alpha observed is probably excited by electrons and protons precipitating at equatorial latitudes. Based on the 500-R upper limit set here on the dark-side H2 Lyman and Werner bands, and the Lyman alpha measurements, the exciting particles are thought to have a soft energy spectrum and deposit about 0.04 erg/sq cm per sec in the atmosphere. There is evidence for an asymmetrical precipitation pattern associated with the longitudinal variation in Lyman alpha emission, and a suggestion of a strong day-night difference in precipitation as well.

Mcconnell, J. C.↗

NASA NTRS1981

Preliminary observations and results obtained with the ultraviolet spectrometer and polarimeter

New observation with the Ultraviolet Spectrometer and Polarimeter (UVSP) of a number of manifestations of solar activity obtained during the first three months of Solar Maximum Mission operations are presented. Attention is given to polarimetry in sunspots, oscillations above sunspots, density diagnostics of transition-zone plasmas in active regions, and the eruptive prominence - coronal transient link.

Tandberg-Hassen, E.↗

NASA NTRS1993

A Far-Ultraviolet Study of the Cygnus Loop Using the VOYAGER Ultraviolet Spectrometers

We have used the Voyager 1 and 2 Ultraviolet Spectrometers to study the far-ultraviolet emissions from different types of shock waves in the Cygnus Loop. In the southeast and northern parts of the supernova remnant (SNR), we have measured the O(VI) lambda1035 surface brightness from the main blast wave. This value is several times below the average and more than one order of magnitude below the peak O(VI) brightness in the SNR as measured with Voyager. A simple blast wave model appears able to reproduce the observations in the southeast and the northern parts of the Cygnus Loop but can only account for 10%-15% of the total O(VI) emission from the Cygnus Loop. The brightest O(VI) and C(III) lambda977 emission is found coincident with optical filamentation and X-ray enhancements in the northeast. We interpret the observations in the northeast in terms of nonradiative and incomplete shocks whose surface area rises in the optical filamentary regions. We conclude that the bulk of the O(VI) emission from the Cygnus Loop arises from optically bright clouds within which intermediate-velocity (200 + 50 km/s) nonradiative and incomplete shocks are widespread.

Vancura, Olaf↗

NASA NTRS1977

Ultraviolet spectrometer experiment for the Voyager mission

An objective grating spectrometer covering the wavelength range of 500 to 1700 A with a 10-A resolution is employed for the Voyager ultraviolet spectrometer experiment. In determining the composition and structure of the atmospheres of Saturn, Jupiter and several satellites, the ultraviolet spectrometer will rely on airglow mode observations to measure radiation from the atmospheres due to resonant scattering of solar flux, and the occultation mode for assessments of the atmospheric extinction of solar or stellar radiation as the spacecraft enters shadow zones. Since it is capable of prolonged stellar observations in the 500 to 1000 A wavelength range, the spectrometer is expected to make important contributions to exploratory studies of UV sources.

Broadfoot, A. L.↗

NASA NTRS1993

(abstract) Interplanetary Lyman-alpha Observations with the Galileo Ultraviolet Spectrometer: Solar Wind Latitude Variations and Multiple Scattering at Solar Maximum

The Galileo Ultraviolet Spectrometer obtained a Lyman-alpha celestrial sphere map on 13,14 December 1990 near the first Earth encounter, with spacecraft near the interstellar wind downwind axis. The data show solar flux longitudinal and latitudinal asymmetries which are modeled with He 10830 Ssolar images. The difference between the observed brightness and a single scattering model is attributed to multiple scattering effects, which we also calculate. The data constrain the solar wind flux latitude variation at solar maximum. Other 1990-1992 Galileo Lyman-alpha data will be discussed.

solar wind ultraviolet spectrometer solar flux cel↗

NASA NTRS1977

Mariner 10 ultraviolet spectrometer - Airglow experiment

An extreme ultraviolet airglow spectrometer was flown on Mariner 10 to examine the atmosphere of Venus and Mercury. An objective grating spectrometer was used with channel electron multipliers at fixed positions in the image plane to continuously monitor the resonance-scattered emission rate of expected atomic atmospheric constituents He, H, A, Ne, O and C. A mechanical collimator placed in the entrance aperture of the spectrometer provided spectral separation of 19 A over the wavelength range from He/+/ at 304 A to C at 1657 A and provided spatial separation of 0.125 deg consistent with the spacecraft and trajectory capabilities. The calibration techniques are discussed.

Broadfoot, A. L.↗

NASA NTRS1991

On the radiometric stability of the shuttle borne solar backscatter ultraviolet spectrometer

The Shuttle Solar Backscatter Ultraviolet (SSBUV) spectrometer instrument provides regular in-orbit calibration checks on the SBUV/2 ozone/solar irradiance monitoring instruments which are being flown routinely on NOAA operational satellites. The goal of the long-term ozone monitoring program is to detect possible changes in stratospheic ozone with a two sigma accuracy of approximately 1 percent over the course of a decade. This translates into a requirement that the SSBUV instrument be calibrated to a one sigma precision of 1 percent at the wavelengths used for ozone monitoring. We have previously shown that the precision of the SSBUV calibrations is such that we can meet this requirement. Here we discuss SSBUV radiometric sensitivity changes occurring as a result of the first two Space Shuttle flights. Finally, we present and compare SSBUV solar irradiance measurements taken during these flights.

Cebula, Richard P.↗

NASA NTRS1974

Apollo 17 ultraviolet spectrometer experiment (S-169)

The scientific objectives of the ultraviolet spectrometer experiment are discussed, along with design and operational details, instrument preparation and performance, and scientific results. Information gained from the experiment is given concerning the lunar atmosphere and albedo, zodiacal light, astronomical observations, spacecraft environment, and the distribution of atomic hydrogen in the solar system and in the earth's atmosphere.

Fastie, W. G.↗

NASA NTRS1980

The Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission

The Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission spacecraft is described, including the experiment objectives, system design, performance, and modes of operation. The instrument operates in the wavelength range 1150-3600 A with better than 2 arcsec spatial resolution, raster range 256 x 256 sq arcsec, and 20 mA spectral resolution in second order. Observations can be made with specific sets of four lines simultaneously, or with both sides of two lines simultaneously for velocity and polarization. A rotatable retarder can be inserted into the spectrometer beam for measurement of Zeeman splitting and linear polarization in the transition region and chromosphere.

Woodgate, B. E.↗