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We observed lunar exospheric potassium D1 (7,698.9646 A) emissions using a high-spectral resolution Fabry-Perot spectrometer in 2014. We present the first potassium line profile measurements, which are representative of the potassium velocity distribution. Inferred temperatures are greater during the waxing gibbous phase, 1920 ± 630 K and lower at waning gibbous phase, 980 ± 200 K. Exosphere models suggest that the measured line widths are a combination of photon-stimulated desorption and impact vaporization sources. The relative potassium emission intensity decreases by ∼2.5 between lunar phases 80◦ and 30◦ and is brightest off the northwest limb near the Aristarchus crater, which is a potassium-rich surface region. Additionally, the emissions off the northern limb are brighter than the southern limb. The intensity decrease and the greater line width during the waxing gibbous versus the waning gibbous phase suggests a dawn-dusk asymmetry.

We present the first comprehensive set of lunar exospheric line width and line width derived effective temperatures as a function of lunar phase (66° waxing phase to 79° waning phase). Data were collected between November 2013 and May 2014 during six observing runs at the National Solar Observatory McMath-Pierce Solar Telescope by applying high-resolution Fabry-Perot spectroscopy (R ~ 180,000) to observe emission from exospheric sodium (5,889.9509 A, D2 line). The 3-arc min field of view of the instrument, corresponding to ~336 km at the mean lunar distance (384,400 km), was positioned at several locations off the lunar limb; only equatorial observations taken out to 950 km are presented here. We find the sodium effective temperature distribution to be approximately a symmetric function of lunar phase with respect to full Moon. Within magnetotail passage we find temperatures in the range of 2500-9000 K. For phase angles greater than 40deg we find that temperatures flatten out to ~1700 K.

A new, high-resolution field-widened spatial heterodyne spectrometer (FW-SHS) designed to observe geocoronal Balmer α (Hα, 6563 A) emission was installed at Pine Bluff Observatory (PBO) near Madison, Wisconsin. FW-SHS observations were compared with an already well-characterized dual-etalon Fabry-Perot Interferometer (PBO FPI) optimized for Hα, also at PBO. The FW-SHS is a robust Fourier transform instrument that combines a large throughput advantage with high spectral resolution and a relatively long spectral baseline (~10 times that of the PBO FPI) in a compact, versatile instrument with no moving parts. Coincident Hα observations by FW-SHS and PBO FPI were obtained over similar integration times, resolving powers (~67,000 and 80,000 at Hα) and fields of view (1.8° and 1.4°, respectively). First light FW-SHS observations of Hα intensity and temperature (Doppler width) versus viewing geometry (shadow altitude) show excellent relative agreement with the geocoronal observations previously obtained at PBO by FPI. The FW-SHS has a 640 km/s (14 A) spectral band pass and is capable of determining geocoronal Hα Doppler shifts on the order of 100 m/s with a temporal resolution on the order of minutes. These characteristics make the FW-SHS well suited for spectroscopic studies of relatively faint (~12–2 R), diffuse-source geocoronal Hα emission from Earth's upper thermosphere and exosphere and the interstellar medium in our Galaxy. Current and future FW-SHS observations extend long-term geocoronal hydrogen observation data sets already spanning three solar minima. This paper describes the FW-SHS first light performance and Hα observational results collected from observing nights across 2013 and 2014.

Geocoronal H α and H β intensity measurements using the Wisconsin H α Mapper Fabry-Perot are used to determine the intensity of the H α cascade component. From basic atomic physics and the work of Meier (1995), we show that the total cascade in geocoronal H α emission is 0.52 ± 0.03 times the geocoronal H β intensity, I(H β), for solar Lyman series excitation of geocoronal hydrogen. The results are consistent with the H α cascade measurements of Mierkiewicz et al. (2012), which were determined directly from the analysis of H α line profile measurements, and significantly narrow the range of uncertainty in the cascade measurement. Accounting for cascade is essential in determining exospheric effective temperatures and dynamics from the shape of the geocoronal H α line.

We have applied high-resolution Fabry-Perot spectroscopy to the study of the lunar sodium exosphere for the study of exospheric effective temperature and velocity variations. Observing from the National Solar Observatory McMath-Pierce Telescope, we used a dual-etalon Fabry-Perot spectrometer with a resolving power of 180,000 to measure line widths and Doppler shifts of the sodium D2 (5889.95 A) emission line. Our field of view was 360 km, and measurements were made in equatorial and polar regions from 500 km to 3500 km off the limb. Data were obtained from full moon to 3 days following full moon (waning phase) in March 2009. Measured Doppler line widths within 1100 km of the sunlit east and south lunar limbs for observations between 5 and 40 deg lunar phase imply effective temperatures ranging between 3260 +/- 190 and 1000 +/- 135 K. Preliminary line center analysis indicates velocity displacements between different locations off the lunar limb ranging between 100 and 600 m/s from the lunar rest velocity with a precision of +/-20 to +/-50 m/s depending on brightness. Based on the success of these exploratory observations, an extensive program has been initiated that is expected to constrain lunar atmospheric and surface-process modeling and help quantify source and escape mechanisms.

The lunar sodium tail extends long distances due to radiation pressure on sodium atoms in the lunar exosphere. Our earlier observations measured the average radial velocity of sodium atoms moving down the lunar tail beyond Earth (i.e., near the anti-lunar point) to be $\sim 12.5$ km/s. Here we use the Wisconsin H-alpha Mapper to obtain the first kinematically resolved maps of the intensity and velocity distribution of this emission over a $15 \times 15 \deg$ region on the sky near the anti-lunar point. We present both spatially and spectrally resolved observations obtained over four nights bracketing new Moon in October 2007. The spatial distribution of the sodium atoms is elongated along the ecliptic with the location of the peak intensity drifting $3 \deg$ east along the ecliptic per night. Preliminary modeling results suggest the spatial and velocity distributions in the sodium exotail are sensitive to the near surface lunar sodium velocity distribution. Future observations of this sort along with detailed modeling offer new opportunities to describe the time history of lunar surface sputtering over several days., Comment: Accepted by Icarus April 2, 2012

Cascade contributions to geocoronal Balmer α airglow line profiles are directly proportional to the Balmer β/α line ratio and can therefore be determined with near simultaneous Balmer β observations. Due to scattering differences for solar Lyman β and Lyman γ (responsible for the terrestrial Balmer α and Balmer β fluorescence, respectively) there is an expected trend for the cascade emission to become a smaller fraction of the Balmer α intensity at larger shadow altitudes. Near coincident Balmer α and Balmer β data sets, obtained from the Wisconsin Hα Mapper (WHAM) Fabry–Perot, are used to determine the cascade contribution to the Balmer α line profile, and to show, for the first time, the Balmer β/α line ratio, as a function of shadow altitude. We show that this result is in agreement with direct cascade determinations from Balmer α line profile fits obtained independently by high resolution Fabry–Perot at Pine Bluff, WI. We also demonstrate with radiative transport forward modeling that a solar cycle influence on cascade is expected, and that the Balmer β/α line ratio poses a tight constraint on retrieved aeronomical parameters (such as hydrogen's evaporative escape rate and exobase density). Index Terms: Hydrogen Geocorona, Balmer-alpha Line Profile, Fabry–Perot Interferometry

We describe the design, development, and performance of a narrowband, all-reflective, unaliased spatial heterodyne spectrometer (SHS) that has been tested in observations at the focus of the 1.6 m main telescope of the McMath–Pierce solar telescope on Kitt Peak. The all-reflective SHS described herein is a highly robust common-path Fourier transform spectrometer without moving parts that, over a limited spectral region, combines the large field of view and high resolving power characteristic of interference spectrometers but at substantially reduced instrument size and optical tolerances. The self-scanned region of wavelength space and resolving power of the SHS are determined by the beam size, the diffraction grating groove density, the number of detector elements, and the fixed orientation of a set of pilot mirrors. The results presented here represent the first successful implementation of this reflective SHS design for field use. We discuss concepts behind the unaliased reflective SHS design and report the performance of the instrument when used to observe terrestrial airglow and absorption features, the solar spectrum, and the Jovian spectrum near λ=6300 Å, at the achieved resolving power (R=λ/δλ) of R>100,000. The results confirm that reflective SHS instruments can deliver effective interferometric performance in the visible to the far-ultraviolet wavelengths with commercial optics of moderate surface quality.

Using a newly developed spatial heterodyne spectrometer (SHS), we have obtained the first radial velocity resolved emission-line profiles of diffuse [O II] 3726 and 3729 ? emission lines from the warm (104 K) ionized component of our Galaxy's interstellar medium. These [O II] lines are a principal coolant for this widespread, photoionized gas and are a potential tracer of variations in the gas temperature resulting from unidentified heating processes that appear to be acting within the Galaxy's disk and halo. By spectrally isolating for the first time Galactic [O II] from atmospheric [O II] emission, we were able to detect interstellar [O II] out to 20? from the Galactic equator with intensities that range from tens of rayleighs near the Galactic plane to less than 1 rayleigh at high Galactic latitudes. The [O II] line profiles clearly show structure indicating emission along the lines of sight from both local and more distant interstellar gas. Comparisons of the [O II] intensities with the intensities of [N II] 6584 ? and H? 6563 ? observed with WHAM indicate that the observed variations in [N II]/H? and [O II]/H? in the diffuse interstellar gas are consistent with variations in temperature and confirm the value of the [O II] observations as a temperature diagnostic for the WIM.

Ground-based Fabry–Perot observations of the solar excited Balmer α emission line of neutral atomic hydrogen have become one of the primary means of studying the distribution and behavior of hydrogen in the thermosphere+exosphere. This first of two companion papers on “Geocoronal Hydrogen Studies Using Fabry–Perot Interferometers”, will outline the technique of Fabry–Perot spectroscopy as applied to geocoronal hydrogen. Representative high spectral resolution data sets will be discussed which will serve to highlight advances in instrumentation and in the interpretation of geocoronal Balmer α intensity and line profile observations. A second companion paper will address long-term observations of the Balmer α emission.

Long-term data sets are required to investigate sources of natural variability in the upper atmosphere. Understanding the influence of sources of natural variability such as the solar cycle is needed to characterize the thermosphere + exosphere, to understand coupling processes between atmospheric regions, and to isolate signatures of natural variability from those due to human-caused change. Multi-year comparisons of thermospheric + exospheric Balmer α emissions require cross-calibrated and well-understood instrumentation, a stable calibration source, reproducible observing conditions, separation of the terrestrial from the Galactic emission line, and consistent data analysis accounting for differences in viewing geometry. We discuss how we address these criteria in the acquisition and analysis of a mid-latitude geocoronal Balmer α column emission data set now spanning two solar cycles and taken mainly from Wisconsin and Kitt Peak, Arizona. We also discuss results and outstanding challenges for increasing the accuracy and use of these observations.

In this paper we evaluate the possibility of detecting, for the first time, the surface magnetic field of Jupiter (∼1 bar level) by observing the change of linear polarization induced by the Hanle effect on the H Lyman-alpha (Lyα) emission line of the planet. We find that, indeed, the Hanle effect, which results from the interaction between a local magnetic field and the atomic polarization induced by absorption of anisotropic radiation, is sensitive to relatively weak values of the strength of the magnetic fields expected on planets. First, we show that for the Lyα emission backscattered by atomic H in the presence of a magnetic field, the Hanle effect is polarizing. This new result is in total contrast to the depolarizing effect predicted and observed for emission lines scattered at right angles in solar prominences. Additionally, to estimate the polarization rate for the case of Jupiter, we have considered three magnetic field models: a dipole field for reference, an O 4 based model [Connerney, J.E.P., 1981. The magnetic field of Jupiter—A generalized inverse approach. J. Geophys. Res. 86, 7679–7693], and finally, an O 6 based model [Khurana, K.K., 1997. Euler potential models of Jupiter's magnetospheric field. J. Geophys. Res. 102, 11295–11306]. In all models, we show that for the jovian backscattered Lyα line, the Hanle effect does enhance the Lyα linear polarization; the polarization rate may exceed 2% at specific regions of the jovian disc, making detection possible either remotely or from an orbiter around Jupiter. In general, depending on the instrumental sensitivity and the observing strategy used, we show that accurate mapping of the linear polarization rate at the planetary surface (thermosphere) or off-disc (corona) may provide a rather accurate estimate of the jovian total magnetic field strength on large area scales.

Spatial heterodyne spectrographs combine high spectral resolution with large etendue in a compact instrument. This combination makes them useful for studies of extended diffuse sources requiring velocity resolution or the separation of closely packed emission lines, while their small size makes them suitable for platforms ranging from ground-based observatories to satellites. Improvements in optical element and detector capabilities have expanded opportunities for SHS in the VUV, where its combination of size, resolution, and etendue have not been available. Here we discuss the basics of the SHS technique and how an instrument may be designed to study various emission line sources in the solar system.

We report long-slit spectroscopic mapping of the η Carinae nebula obtained using the Space Telescope Imaging Spectrograph. The observations reveal the presence of a previously unknown bipolar emission nebula (roughly ±2'' along its major axis) embedded within the well-known and larger Homunculus Nebula. A preliminary analysis suggests that this embedded nebula may have originated from a minor eruption event circa 1890, 50 years after the formation of the larger Homunculus.

The University of Wisconsin—Madison and NASA—Goddard conducted a comprehensive multi-wavelength observing campaign of coma emissions from comet Hale-Bopp, including OH 3080 A, [0 I] 6300 A, H2O+ 6158 A, H Balmer-α 6563 A, NH2 6330 A, [C I] 9850 A CN 3879 A, C2 5141 A, C3 4062 A, C I 1657 A, and the UV and optical continua. In this work, we concentrate on the results of the H2O daughter studies. Our wide-field OH 3080 A measured flux agrees with other, similar observations and the expected value calculated from published water production rates using standard H2O and OH photochemistry. However, the total [O I] 6300 A flux determined spectroscopically over a similar field-of-view was a factor of 3 – 4 higher than expected. Narrow-band [O I] images show this excess came from beyond the H2O scale length, suggesting either a previously unknown source of [O I] or an error in the standard OH + v → O(1 D) + H branching ratio. The Hale-Bopp OH and [O I] distributions, both of which were imaged to cometocentric distances > 1 x 106 km, were more spatially extended than those of comet Halley (after correcting for brightness differences), suggesting a higher bulk outflow velocity. Evidence of the driving mechanism for this outflow is found in the Hα line profile, which was narrower than in comet Halley (though likely because of opacity effects, not as narrow as predicted by Monte-Carlo models). This is consistent with greater collisional coupling between the suprathermal H photodissociation products and Hale-Bopp’s dense coma. Presumably because of mass loading of the solar wind by ions and ions by the neutrals, the measured acceleration of H2O+ down the ion tail was much smaller than in comet Halley. Tailward extensions in the azimuthal distributions of OH 3080 A, [O I], and [C I], as well as a Doppler asymmetry in the [O I] line profile, suggest ion-neutral coupling. While the tailward extension in the OH can be explained by increased neutral acceleration, the [O I] 6300 A and [C I] 9850 A emissions show 13% and > 200% excesses in this direction (respectively), suggesting a non-negligible contribution from dissociative recombination of CO+ and/or electron collisional excitation. Thus, models including the effects of photo-and collisional chemistry are necessary for the full interpretation of these data.

Coronagraphic imaging of the nearest Herbig Be star with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope, Ks (2.15 ?m) imaging with ADONIS at the 3.6 m telescope at La Silla, and mid-infrared imaging with OSCIR using the 4 m Blanco Telescope at Cerro Tololo Inter-American Observatory confirm the detection of the disk reported by Pantin et al. and map the disk out to 5'' (~515 AU) in the optical and at Ks. While the source is unresolved at 10 and 18 ?m, it can be traced to 15 at 11.7 ?m. We confirm the change in the radial dependence of the disk surface brightness near 27 seen at 1.6 ?m by Augereau et al. at Ks. No such break in the power law is seen in the optical. The STIS data reveal spiral dark lane structure, making HD 100546 the third near?zero-age main-sequence Herbig Ae/Be star with structure more than 100 AU from the star. We also optically detect a low surface brightness envelope extending 10'' (1000 AU) from the star, in addition to nebulosity, which is probably associated with DC 292.6-7.9. The survival of the envelope through essentially the entire pre?main-sequence lifetime of the star, coupled with the absence of physical companions within 1500 AU of the star, suggests that envelope lifetimes owe more to the star-forming environment than to mass-loss activity from the Herbig Ae/Be star.

Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) observations of Io acquired in 1997 [Roesler et al., 1999] provided the first simultaneous spatially resolved measurements of emission from neutral sulfur and oxygen, the dominant atomic species in Io's exospheric corona. Previous measurements of Io's corona relied primarily on sunlight resonantly scattered from sodium, a trace element in Io's atmosphere, and required measurement during mutual satellite eclipses to obtain the necessary spatial resolution. We present here spatial profiles of Io's extended emissions derived from observations spanning the time period from October 1997 to February 2000. The STIS Far Ultraviolet Multi-Anode Microchannel Array (FUV-MAMA) detector permits measurement of the emissions with a spatial resolution of ∼0.05 Io radii out to distances of ∼20 Io radii. Useful measurements are limited to ∼10 Io radii owing to the low signal-to-noise ratio of the extended emission features. The coronal emission profiles vary considerably in slope and intensity and are generally brighter for Io west (duskside) of Jupiter. Emission profiles obtained near western elongation are relatively symmetric about Io; profiles obtained in other orbital positions display varying degrees of asymmetry, with enhanced emissions and generally steeper slopes in the downstream direction relative to the plasma flow. The downstream-upstream profile asymmetry is thought to be caused by higher electron densities in Io's plasma wake. While the coverage of the data is limited in both Jovian System III coordinates and geocentric phase, the intensities of emission from regions both near Io and in the extended corona vary with System III longitude in a near-simultaneous fashion, suggesting local torus electron density as the probable source of this modulation. The observed ratio of oxygen to sulfur emission is relatively constant in time, perhaps reflecting the stoichiometric ratio of the SO 2 source molecules. Eclipse and posteclipse observations on February 25, 2000, show a dramatic increase in profile emission brightness and slope, suggesting a dynamic response by a sublimation-supported component of Io's SO 2 atmosphere and associated atomic species.

The Wisconsin Hα Mapper (WHAM), a remotely operable, semi-automated Fabry-Perot located at Kitt Peak Observatory, has been making an all-sky survey of interstellar hydrogen Balmer α(Hα) emissions since 1997. Using the annular summing spectroscopy technique, WHAM has acquired ∼37,000 spectra to date, spanning almost 100 nights of observations. Since all of the galactic emission spectral data contain the terrestrial Hα (6562.7 A) emission line, these measurements constitute a rich source of geocoronal data for investigating natural variability in the upper atmosphere. The WHAM observations also serve as a benchmark for comparison with future data. Analysis of the first year of WHAM data shows only small day-to-day variations after shadow altitude variations are taken into account. For example, at shadow altitudes of 2000 and 3000 km, the RMS scatter is within approximately +/− 20%; this variability is expected to be reduced with accurate accounting of the smaller-scale effects of observational slant path, zenith angle, and azimuth on the Hα intensity. This result is consistent with past midlatitude Wisconsin data sets but different from observations made by other observers and instruments at the low-latitude Arecibo site. The multiple viewing geometries of the observations provide stringent modeling constraints, useful in testing current modeling capabilities. Modeling of the WHAM data with a global nonisothermal resonance radiation transport code (lyao_rt) indicates that the signal-to-noise of the data is sufficient to determine relative variations in upper atmospheric atomic hydrogen column densities to better than 5%. This paper describes the WHAM aeronomy program and its observational scheme, analysis procedures, and results from data taken in 1997. Case study comparisons are made with past data sets and with predictions from the lyao_rt resonant radiation transport modeling code of Bishop [1999].

Balmer α intensity measurements made with a dual etalon Fabry–Perot spectrometer at Haleakala during two campaigns in 1988 are presented. The data from each campaign demonstrate night-to-night stability, despite variations in geophysical conditions. Analysis of these data using a nonisothermal Lyman β radiative transport code, updated solar Lyman β line-center flux estimates, and corrected thermospheric atomic hydrogen density profiles points to the resolution of the “factor of 2” problem. A careful reassessment of other mechanisms for upper atmospheric Balmer α excitation has also been carried out.

The first observations of Io with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) showed that the brightest ultraviolet emissions come from localized regions near Io's equator, designated “equatorial spots.” This paper presents a detailed study of the location, shape, and brightness of the equatorial spots in near-monochromatic images obtained using STIS in the first-order long-slit spectroscopy mode. This study provides evidence that the equatorial emissions are linked to the interaction between the Jovian magnetosphere and Io's atmosphere. The morphology of the equatorial spots reported here provides additional information on the nature of this complex electrodynamic interaction. We find the following principal results: the locations of the equatorial spots are correlated with the Jovian magnetic field orientation at Io, but with a relation that is not 1:1; the equatorial spots are centered 10°–30° longitude downstream from Io's sub-Jovian longitude; the brightness of the emissions in this data set is correlated with Io's distance from the plasma torus centrifugal equator; and the anti-Jovian equatorial spots are ∼20% brighter than the sub-Jovian equatorial spots.

Imaging spectroscopy of Io in the ultraviolet (1160–1720 A) was carried out with the Space Telescope Imaging Spectrograph on HST on three dates in October 1997 and August 1998. Among the initial results was the observation of concentrated regions of Hi Lyman-α flux near the poles of Io that exhibited a morphology and temporal variability different from those of the atomic oxygen and sulfur emission regions seen near the equatorial limbs. We examine the suggestion that the primary source of Lyman-α emission is surface reflected solar radiation that penetrates the thin polar atmosphere, but is strongly absorbed by the thicker SO2 atmosphere near Io's equator. Spectral and spatial analyses lead to derived SO2 column densities that are in good agreement with those derived from earlier HST observations of Io's albedo in the 2000–2300 A wavelength range. The Lyman-α images clearly illustrate features of Io's atmosphere that have been deduced from previous observations and theoretical modeling: a non-uniformity with respect to the sub-solar point dominated by a freezing out of the SO2 near the poles and variation with both longitude and time due to the variability of the sources of the atmospheric gas. Lyman-α imaging is demonstrated to be an extremely powerful and direct way to globally map the dynamic atmosphere of Io.

Well-resolved far-ultraviolet spectroscopic images of O i , S i , and previously undetected H i Lyman-α emission from Io were obtained with the Hubble space telescope imaging spectrograph (STIS). Detected O i and S i lines (1250 to 1500 angstroms) have bright equatorial spots (up to 2.5 kilorayleighs) that shift position with jovian magnetic field orientation; limb glow that is brighter on the hemisphere facing the jovian magnetic equator; and faint diffuse emission extending to ∼20 Io radii. All O i and S i features brightened by ∼50 percent in the last two images, concurrently with a ground-based observation of increased iogenic [O i ] 6300-angstrom emission. The H i Lyman-α emission, consisting of a small, ∼2-kilorayleigh patch near each pole, has a different morphology and time variation.

The Space Telescope Imaging Spectrograph (STIS) instrument was installed on the Hubble Space Telescope (HST) during the second servicing mission, in 1997 February. Four bands cover the wavelength range of 115–1000 nm, with spectral resolving powers between 26 and 200,000. Camera modes are used for target acquisition and deep imaging. Correction for HST's spherical aberration and astigmatism is included. The 115–170 nm range is covered by a CsI MAMA (Multianode Microchannel Array) detector and the 165–310 nm range by a Cs2Te MAMA, each with a format of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cy...

We report the firstHubble Space TelescopeSpace Telescope Imaging Spectrograph (STIS) CCD spectroscopy of the bona fide brown dwarf Gliese 229B. The optical spectrum shows absorptions of Csi at 8944 Aand water vapor bands at 9300-9600 A ˚. Strong CaH, FeH, TiO, and VO bands observed in late M dwarfs are absent from the spectrum of Gliese 229B. The formation of dust grains may explain the absence of strong atomic lines and molecular bands of these refractory elements. The broad spectral coverage obtained helps resolve current spec- ulations about the presence of dust clouds in the atmosphere of cool brown dwarfs. We find the slope of the STIS/CCD spectrum and the lack of flux detected shortward of 8000 Astrongly supports the presence of dust hazes suspended in the photosphere of Gl 229B rather than a complete settling of the grains to regions below the photosphere. Subject headings: binaries: general — stars: individual (Gl 229B) — stars: low-mass, brown dwarfs

The Space Telescope Imaging Spectrograph (STIS) was successfully installed into the Hubble Space Telescope (HST) in 1997 February, during the second HST servicing mission, STS-82. STIS is a versatile spectrograph, covering the 115-1000 nm wavelength range in a variety of spectroscopic and imaging modes that take advantage of the angular resolution, unobstructed wavelength coverage, and dark sky offered by the HST. In the months since launch, a number of performance tests and calibrations have been carried out and are continuing. These tests demonstrate that the instrument is performing very well. We present here a synopsis of the results to date.

This paper reports high-accuracy measurements of geocoronal Balmer α line profiles and demonstrates that the profiles are well fit with a model which includes cascade excitation by solar Lyman series radiation from n > 3 in addition to the direct excitation of n = 3 by solar Lyman β. The increase in the signal-to-noise of our data is made possible by the use of the Fabry-Perot annular summing technique implemented at our Fabry-Perot facility at the University of Wisconsin's Pine Bluff Observatory. The new sensitivity has allowed us to make a detailed examination of line profile asymmetries and to conclude that they are compatible with predictions that of the order of 10% of the geocoronal Balmer α emission is caused by the cascade process. Cascade excitation alters the observed profile because it produces Balmer α emission along fine structure paths yielding slightly shifted wavelengths not present in direct Lyman β excitation, which is the predominant excitation mechanism for geocoronal Balmer a. We discuss how fine structure excitation affects studies of non-Maxwellian exospheric hydrogen velocity distributions and effective temperatures through Balmer α line profile measurements. In a broader context, we consider how inclusion of the cascade excited emission in future radiation models can enhance their accuracy and their potential for assisting in the isolation in the data of shorter-term solar geophysical effects and longer timescale changes in exospheric hydrogen densities.

As part of its efforts to monitor and characterize periodic variations in the Io plasma torus, the Wisconsin Space Physics group acquired Fabry-Perot spectra of [S II] λλ6716, 6731 for a 5 week period in 1988. Previous analysis showed periodicity, but, surprisingly, not at 10.2 hr—the persistent 3% subcorotational period, often called System IV, reported in other long-term torus data sets. We show here that our 1988 data exhibit a quasi-periodic intensity variation at 10.2 hr, characterized by two distinct intensity enhancements that abruptly changed in relative magnitude during the observational run. We also present perpendicular ion temperature data from the same period, showing a periodic variation anticorrelated with intensity after the aforementioned abrupt change, but no significant periodicity beforehand. This non/anticorrelation appears to eliminate the possibility that a slowly moving magnetic field enhancement is responsible for the subcorotational periodicity. Considering these and other long-term data, we suggest that the various observed subcorotational features are not themselves responsible for the 3% subcorotational period, but rather are independent features modulated or otherwise affected by a permanent, global phenomenon in the torus lagging corotation by 3%.

A Fabry-Perot annular summing spectroscopy technique has been used at the University of Wisconsin's Pine Bluff Observatory to acquire geocoronal Balmer-α line profile data with significantly improved precision and height resolution. The double-etalon Fabry-Perot interference pattern is imaged onto a Photometries PM512 charge-coupled device (CCD) chip, thus enabling light to be gathered in multiple spectral bins simultaneously. In comparison with scanning systems we used earlier, the high quantum efficiency of the CCD and the multichannel detection associated with the Fabry-Perot annular summing technique have enabled us to save a factor of about 10 in the integration time required for studies of the line profile. As a result, we are now able to both more precisely observe the line shape of the very faint (1–10 R) Balmer-α emission and obtain data using shorter integration times. Our data illustrate the scientific potential for using this technique for the study of very faint extended emission line sources. We present exospheric effective temperatures obtained from line profile data acquired during the period of 1992–1993. When these data are compared with predictions from the Anderson et al. [1987] and MSIS90 models, there are points of agreement as well as some discrepancies. Included in this paper are discussions of both technical issues associated with applying annular summing spectroscopy for geocoronal Balmer-α observations and results of data obtained using this technique.

Our interests in the general field of astrophysics lie principally in two areas: 1) the study of extremely faint emission lines from the interstellar medium, galactic halo, and intergalactic clouds, and 2) the study of neutral and ionized components of the outer atmospheres of solar system objects, including the earth. These studies require instruments of the highest possible area-solid angle product, but typically do not require extremely high spatial resolution. This paper highlights our past work in these areas, and discusses new instrumental approaches we are developing.

Scattered solar and collisionally stimulated H Ly-α emission is a proven diagnostic for the study of the Sun, comets, the interplanetary medium, planet atmospheres, and corona. Here we discuss the construction and testing of a narrow bandpass instrument designed to observe H Ly-α emission at a resolving power of R~100,000 from targets with an angular extent of ≤½ degree. The instrument is an all-reflective form of the spatial heterodyne spectrometer (SHS), a self-scanning Fourier Transform Spectrometer. It will be incorporated into the focal plane of a suborbital telescope that is scheduled for a March 2013 launch. Initial alignment and vibrational testing was performed with the instrument aligned to a visible analog line. The results showed alignment stability under vibration, but revealed several unacceptable resonances that have been corrected in the mechanical design.

[1] High spectral resolution line profile observations indicate a reproducible semi-annual variation in the geocoronal hydrogen Balmer α effective temperature. These observations were made between 08 January 2000 and 21 November 2001 from Pine Bluff Observatory (WI) with a second generation double etalon Fabry-Perot annular summing spectrometer operating at a resolving power of 80,000. This data set spans sixty-four nights of observations (1404 spectra in total) over 20 dark-moon periods. A two cluster Gaussian model fitting procedure is used to determine Doppler line widths, accounting for fine structure contributions to the line, including those due to cascade; cascade contributions at Balmer α are found to be 5 ± 3%. An observed decrease in effective temperature with increasing shadow altitude is found to be a persistent feature for every night in which a wide range of shadow altitudes were sampled. A semiannual variation is observed in the column exospheric effective temperature with maxima near day numbers 100 and 300 and minima near day numbers 1 and 200. Temperatures ranged from ∼710 to 975 K. Average MSIS model exobase temperatures for similar conditions are approximately 1.5× higher than those derived from the Balmer α observations, a difference likely due to contributions to the observed Balmer α column emission from higher, cooler regions of the exosphere.

[1] High precision observations during Solar Cycle 23 using the Wisconsin H-alpha Mapper (WHAM) Fabry-Perot quantify a factor of 1.5 ± 0.15 higher Balmer α column emission intensity during near-solar-maximum than during solar minimum conditions. An unresolved question is how does the observed solar cycle variation in the hydrogen column emission compare with that calculated from the hydrogen distribution in atmospheric models? We have compared WHAM solar minimum and near-solar-maximum column intensity observations with calculations using the thermospheric hydrogen density profile and background thermospheric conditions from the Mass Spectrometer Incoherent Scatter (NRLMSISE-00) empirical model extended to exospheric altitudes using the analytic exosphere model of Bishop (1991). Using this distribution, we apply the lyao_rt global resonance radiative transfer code of Bishop (1999) to calculate expected intensities that would be observed from the ground for the viewing conditions of the observations. The observed intensities are brighter than those calculated for the corresponding conditions, indicating that when MSIS is used as the thermospheric hydrogen distribution the derived intensities are too low. Additionally, both the observed and calculated WHAM hydrogen column emission intensities are higher for near-solar-maximum than for solar minimum conditions. There is better agreement between observations and intensities calculated using the evaporative analytic exosphere model at solar maximum, suggesting an underestimation of modeled satellite atoms at high altitudes. This result is consistent with sensitivity studies using the option for a quasi-exobase for satellite atoms to account for the creation of satellite orbits from charge exchange collisions.

In November and December 1988, we acquired 157 spectra of (S II) lambda 6731 emissions from the Io plasma torus with a Fabry-Perot interferometer at the McMath-Pierce Solar Telescope facility on Kitt Peak. A major goal of this experiment was to extend our earlier studies of intensity variations in the plasma torus. Our earlier analysis (F. L. Roesler, F. Scherb, and R. J. Oliversen, 1984, of (S III) lambda 9531 emission spectra acquired in April 1982 had shown that the intensity of torus emissions varied periodically with a period of 10.20 +/- 0.06 hr (1-sigma uncertainty level), slightly longer than Jupiter's System 3 rotational period of 9.925 hr. We present here an reanalysis of our 1982 data revealing, in addition to the 10.20-hr period, a clear secondary periodicity at 9.95 +/- 0.906 hr. By constrast, we show that our new (S II) lambda 6731 data have a single period of 10.14 +/- 0.03 hr. which is neither the System 3 period nor the proposed 'System 4' period of 10.224 hr.

We present the first thermospheric wind measurements using a Doppler Asymmetric Spatial Heterodyne (DASH) spectrometer and the oxygen red-line nightglow emission. The ground-based observations were made from Washington, DC and include simultaneous calibration measurements to track and correct instrument drifts. Even though the measurements were made under challenging thermal and light pollution conditions, they are of good quality with photon statistics uncertainties between about three and twenty-nine meters per second, depending on the nightglow intensity. The wind data are commensurate with a representative set of Millstone Hill Fabry-Perot wind measurements selected for similar geomagnetic and solar cycle conditions.

We describe the design, development and performance tests of a narrow-band, high-resolution all-reflection Spatial Heterodyne Spectrometer tuned to 630nm as a step towards a FUV design that will operate at the 121nm Lyman-alpha line.

We describe laboratory and field tests of a Doppler Asymmetric Spatial Heterodyne (DASH) interferometer for upper atmospheric wind observations of the O[1D] 630 nm emission.

Reviewed will be a flight concept for a DASH optical interferometer to passively measure upper atmospheric Doppler winds, a completed laboratory DASH prototype instrument, and current field campaign results.

High-spectral-resolution scans of H2O(+) emissions from Austin 1990 V were obtained. A simple model of the ion distribution in the FOV is used to determine a lower limit phi(H2O+) to the H2O(+) ion flux away from the nucleus for each night of observations. A similar analysis is applied to previous observations of H2O(+) emissions from Comet P/Halley 1986 III. It is found that the mean ratio is phi(H2O+)/Q(H2O) is 1.2 x exp -3 for Halley (solar minimum) and 2.6 x 10 exp -3 for Austin (solar maximum).

Observations of the geocoronal Balmer α nightglow have been made from Wisconsin for more than a solar cycle with an internally consistent intensity reference to standard astronomical nebulae. These measurements were made with a double-etalon, pressure-scanned, 15-cm aperture Fabry-Perot interferometer. The resulting long time line data provides an opportunity to examine solar cycle influence on the mid-latitude exosphere and to address accompanying questions concerning the degree to which the exosphere is locally static or changing. Our exospheric Balmer α absolute intensity measurements show no statistically significant variations throughout the solar cycle when the variation with viewing geometry is removed by normalizing the data to reference exospheric model predictions by Anderson et al. However, the relative intensity dependence on solar depression angle does show a solar cycle variation. This variation suggests a possible related variation in the exospheric hydrogen density profile, although other interpretations are also possible. The results suggest that additional well-calibrated data taken over a longer time span could probe low-amplitude variations over the solar cycle and test predictions of a slow monotonic increase in exospheric hydrogen arising from greenhouse gases.

Flat field images of Comet Austin 1990 V were obtained from the morning sky, and a log of the observations is presented. Absolute intensity calibrations of the comet images are obtained along with scans of the cometary forbidden O I 6300 emission. The O(1D) distribution of the comet is found, and the OH mean lifetime at 1 AU is determined to be (1.1 +/- 0.3) 10 exp 5 s.

We describe the design, fabrication and laboratory tests of a Doppler Asymmetric Spatial Heterodyne (DASH) interferometer for upper atmospheric wind and temperature observations of the O[1D] 630 nm emission. The monolithic interferometer has no moving parts, a large etendue, relaxed fabrication and alignment tolerances and can measure multiple emission lines simultaneously. Laboratory measurements indicate that the design resolution and etendue were achieved and that thermal drifts can be determined with sufficient precision for geophysical applications.

The technique of Fabry-Perot CCD annular-summing spectroscopy, with particular emphasis on applications in aeronomy, is discussed. Parameter choices for optimizing performance by the use of a standard format CCD array are detailed. Spectral calibration methods, techniques for determining the ring pattern center, and effects imposed by limited radial resolution caused by superpixel size, variable by on-chip binning, are demonstrated. The technique is carefully evaluated experimentally relative to the conventional scanning Fabry-Perot that uses a photomultiplier detector. We evaluate three extreme examples typical of aeronomical spectroscopy using calculated signal-to-noise ratios. Predicted sensitivity gains of 10-30 are typical. Of the cases considered, the largest savings in integration time are estimated for the day sky thermospheric O(1)D case, in which the bright sky background dominates the CCD read noise. For profile measurements of faint night sky emission lines, such as exospheric hydrogen Balmer-α, long integration times are required to achieve useful signal-to-noise ratios. In such cases, CCD read noise is largely overcome. Predictions of a factor of 10-15 savings in integration time for night sky Balmer-α observations are supported by field tests. Bright, isolated night sky lines such as thermospheric O(1)D require shorter integration times, and more modest gains dependent on signal level are predicted. For such cases it appears from estimate results that the Fabry-Perot CCD annular-summing technique with a conventional rectangular format may be outperformed by a factor of 2-5 by special CCD formats or by unusual optical coupling configurations that reduce the importance of read noise, based on the ideal transmission for any additional optics used in these configurations.

[1] The Spatial Heterodyne Imager for Mesospheric Radicals (SHIMMER) was a high-resolution, near ultraviolet spectrometer that imaged the Earth's limb for 2.5 years between March 2007 and October 2009. The instrument used the Spatial Heterodyne Spectroscopy technique for the first time on a satellite and successfully demonstrated its capabilities. SHIMMER measured the solar resonance fluorescence of the OH A2Σ+-X2Π (0, 0) band around 309 nm, which allows the retrieval of mesospheric OH density profiles. It also measured the Rayleigh scattered background from the clear atmosphere and solar scattering from polar mesospheric cloud particles. We present details on the SHIMMER mission, the payload design, and the data analysis. A comparison between SHIMMER and concurrent Microwave Limb Sounder OH data shows good agreement between 60 and 90 km altitude for several latitudes and seasons. We also find good agreement of the SHIMMER OH densities and standard photochemical model calculations between 60 and 80 km. We find no evidence of a 25%–35% mesospheric OH deficit, previously reported using Middle Atmosphere High-Resolution Spectrograph Investigation (MAHRSI) OH data. However, independent analysis of Rayleigh scattered background signals observed by SHIMMER and MAHRSI under similar lighting conditions revealed that MAHRSI radiances are systematically smaller than SHIMMER radiances by 24%. Although this difference is well outside of the combined uncertainties for both experiments, the agreement of SHIMMER OH with Microwave Limb Sounder OH and standard photochemistry results, together with our Rayleigh scattering comparison, suggests an unidentified MAHRSI calibration problem that effectively eliminates the mesospheric OH deficit reported using MAHRSI observations.

Temperature and velocity-distribution remote-sensing of faint diffuse sources such as the interplanetary medium (IPM), comets and planetary atmospheres, is an instrumental challenge that becomes more pronounced in the ultraviolet. All-reflective Spatial-Heterodyne Spectrometers (SHS), an emerging new class of instruments that combines both high etendue and high resolving power (greater than 10 5 ), are ideally suited to these types of observations. Their all-reflective configuration and their self-compensating monolithic design enable them to operate under the tight tolerances of the ultraviolet and to survive the rigors of space launch. An in-development sounding-rocket experiment, the Hydrogen Polarimetric Explorer (HYPE), will merge an all-reflective SHS with a half-wave Brewster reflection polarimeter to obtain the first interferometric polarimetry of an ultraviolet emission line source. Its initial flight will target the IPM at the hydrogen Lyman-alpha transition (121.6nm). HYPE's novel optical configuration also combines several improvements in reflective SHS design, including true zero-path interferometry, no aliasing, and one-dimensional imaging. The optical layout and performance of the HYPE prototype will be described along with simulation results from ray-tracing computations.

The results of a project to develop a spatial heterodyne spectrometer (SHS) for a sounding rocket mission to study the Cygnus Loop, a prototypical middle-aged supernova remnant, are discussed. The goal was to obtain a radial velocity-resolved spectrum of the C IV lambdalambda1550 emission line from bright features of the Cygnus Loop, as a test for mapping the diffuse hot interstellar medium (ISM). A full Fourier-transform analysis of Cygnus Loop emission data is presented, showing lack of velocity-resolved C IV emission detection. Optics contamination is shown to be the most likely problem, and ways to eliminate this contamination for future SHS sounding rocket and satellite missions are discussed.

Operation of an all-reflection, broadband, spatial heterodyne spectrometer (SHS) is reported. This Mark 2 SHS is constructed using a custom diffraction grating and other standard optical components. The custom grating is coarse (18 grooves/mm), with a symmetric blaze that allows its simultaneous use as dispersing element and beam splitter and combiner. The grating is combined with a plane mirror and a roof mirror to form a very stable ring interferometer which has been used successfully in earlier narrowband SHS designs. Fringes from the extra grating orders in the main blaze envelope are unexpectedly found to combine constructively with the desired primary fringes of the interferometer. Elimination of ambiguity between wavelengths above and below blaze in a given order, and order separation are demonstrated using a small tilt of the plane mirror about an axis in the plane of the figure. Coverage of a factor of four in wavelength in a single CCD frame is demonstrated.

This paper describes the design and tests of an all-reflection two-beam interferometer. The interferometer consists of three reflecting diffraction gratings and two collimating mirrors. The use of only reflection optics eliminates the need for a transmitting beam splitter and compensation plate thus permitting the possibility of using the interferometer in the vacuum ultraviolet. This instrument can be used as a Fourier transform spectrometer. Obtaining the spectrum of the incident light from the interferogram is not so straightforward as with a Michelson interferometer. The method of Fourier inversion is described, and examples of interferograms taken with the instrument and the spectra obtained from the interferograms are presented. The interferometer has been tested in the visible and in the near ultraviolet at 2537 A.

The Doppler shift of light from a rapidly rotating or rapidly flowing source limits the spectroscopic resolution with which it can be studied using Fabry-Perot spectrometers that have the usual axial fringe adjustment. Because of the angular dependence of the wavenumber transmitted by the Fabry-Perot, the entrance aperture can be positioned off-axis at an angle chosen such that the wavenumber shift across the entrance aperture matches the shift presented by the source, thereby compensating for the Doppler effect. The principle can be extended to the Michelson interferometer for Fourier transform spectroscopy when the Michelson is used without field compensation. High resolution spectra obtained with a PEPSIOS spectrometer using the entire disk of Jupiter, a rapidly rotating planet, are presented as an example.

The essential features of apparatus suitable for routine mapping of pairs of wedged uncoated optical flats are described. In this method the aperture of the pair of flats is scanned in a regular pattern, and information about the spacing uniformity is derived from the interference of light reflected from the flat surfaces. Accuracies within about lambda/500 are obtained.