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The final chemical transformation and isolation in the synthesis of an active pharmaceutical ingredient (API), referred to as the Pure Step, is often chemically simple but scientifically, operation...

Since the earliest space-based observations of Earth's atmosphere, ultraviolet (UV) airglow has proven a useful resource for remote sensing of the ionosphere and thermosphere. The NASA Ionospheric Connection Explorer (ICON) spacecraft, whose mission is to explore the connections between ionosphere and thermosphere utilizes UV airglow in the typical way: an extreme-UV (EUV) spectrometer uses dayglow between 54 and 88nm to measure the density of O+, and a far-UV spectrograph uses the O 135.6nm doublet and N2 Lyman-Birge-Hopfield band dayglow to measure the column ratio of O to N2 in the upper thermosphere. Two EUV emission features, O+ 61.6 and 83.4nm, are used for the O+ retrieval; however, many other features are captured along the EUV instrument's spectral dimension. In this study, we examine the other dayglow features observed by ICON EUV and demonstrate that it measures a nitrogen feature around 87.8nm which can be used to observe the neutral thermosphere.

In near-Earth space, variations in thermospheric composition have important implications for thermosphere-ionosphere coupling. The ratio of O to N(2) is often measured using far-UV airglow observations. Taking such airglow observations from space, looking below the Earth’s limb allows for the total column of O and N(2) in the ionosphere to be determined. While these observations have enabled many previous studies, determining the impact of non-migrating tides on thermospheric composition has proved difficult, owing to a small contamination of the signal by recombination of ionospheric O(+). New ICON observations of far UV are presented here, and their general characteristics are shown. Using these, along with other observations and a global circulation model we show that during the morning hours and at latitudes away from the peak of the equatorial ionospheric anomaly, the impact of non-migrating tides on thermospheric composition can be observed. During March – April 2020, the column O/N(2) ratio was seen to vary by 3 – 4 % of the zonal mean. By comparing the amplitude of the variation observed with that in the model, both the utility of these observations and a pathway to enable future studies is shown.

In near-Earth space, variations in thermospheric composition have important implications for thermosphere-ionosphere coupling. The ratio of O to N2 is often measured using far-UV airglow observations. Taking such airglow observations from space, looking below the Earth's limb allows for the total column of O and N2 in the ionosphere to be determined. While these observations have enabled many previous studies, determining the impact of non-migrating tides on thermospheric composition has proved difficult, owing to a small contamination of the signal by recombination of ionospheric O+. New ICON observations of far UV are presented here, and their general characteristics are shown. Using these, along with other observations and a global circulation model we show that during the morning hours and at latitudes away from the peak of the equatorial ionospheric anomaly, the impact of non-migrating tides on thermospheric composition can be observed. During March - April 2020, the column O/N2 ratio was seen to vary by 3 - 4 % of the zonal mean. By comparing the amplitude of the variation observed with that in the model, both the utility of these observations and a pathway to enable future studies is shown.

The Ionospheric Connection Explorer, or ICON, is a new NASA Explorer mission that will explore the boundary between Earth and space to understand the physical connection between our world and our space environment. This connection is made in the ionosphere, which has long been known to exhibit variability associated with the sun and solar wind. However, it has been recognized in the 21st century that equally significant changes in ionospheric conditions are apparently associated with energy and momentum propagating upward from our own atmosphere. ICON's goal is to weigh the competing impacts of these two drivers as they influence our space environment. Here we describe the specific science objectives that address this goal, as well as the means by which they will be achieved. The instruments selected, the overall performance requirements of the science payload and the operational requirements are also described. ICON's development began in 2013 and the mission is on track for launch in 2017. ICON is developed and managed by the Space Sciences Laboratory at the University of California, Berkeley, with key contributions from several partner institutions.

The NASA Ionospheric Connection Explorer Extreme Ultraviolet spectrograph, ICON EUV, will measure altitude profiles of the daytime extreme-ultraviolet (EUV) OII emission near 83.4 and 61.7 nm that are used to determine density profiles and state parameters of the ionosphere. This paper describes the algorithm concept and approach to inverting these measured OII emission profiles to derive the associated $\mathrm{O}^{+}$ density profile from 150–450 km as a proxy for the electron content in the F-region of the ionosphere. The algorithm incorporates a bias evaluation and feedback step, developed at the U.S. Naval Research Laboratory using data from the Special Sensor Ultraviolet Limb Imager (SSULI) and the Remote Atmospheric and Ionospheric Detection System (RAIDS) missions, that is able to effectively mitigate the effects of systematic instrument calibration errors and inaccuracies in the original photon source within the forward model. Results are presented from end-to-end simulations that convolved simulated airglow profiles with the expected instrument measurement response to produce profiles that were inverted with the algorithm to return data products for comparison to truth. Simulations of measurements over a representative ICON orbit show the algorithm is able to reproduce hmF2 values to better than 5 km accuracy, and NmF2 to better than 12% accuracy over a 12-second integration, and demonstrate that the ICON EUV instrument and daytime ionosphere algorithm can meet the ICON science objectives which require 20 km vertical resolution in hmF2 and 18% precision in NmF2.

We present all-sky maps of two major FUV cooling lines, C IV and O VI, of highly ionized gas to investigate the nature of the transition-temperature gas. From the extinction-corrected line intensities of C IV and O VI, we calculated the gas temperature and the emission measure of the transition-temperature gas assuming isothermal plasma in the collisional ionization equilibrium. The gas temperature was found to be more or less uniform throughout the Galaxy with a value of (1.89 $\pm$ 0.06) $\times$ $10^5$ K. The emission measure of the transition-temperature gas is described well by a disk-like model in which the scale height of the electron density is $z_0=6_{-2}^{+3}$ kpc. The total mass of the transition-temperature gas is estimated to be approximately $6.4_{-2.8}^{+5.2}\times10^9 M_{\bigodot}$. We also calculated the volume-filling fraction of the transition-temperature gas, which was estimated to be $f=0.26\pm0.09$, and varies from $f\sim0.37$ in the inner Galaxy to $f\sim0.18$ in the outer Galaxy. The spatial distribution of C IV and O VI cannot be explained by a simple supernova remnant model or a three-phase model. The combined effects of supernova remnants and turbulent mixing layers can explain the intensity ratio of C IV and O VI. Thermal conduction front models and high-velocity cloud models are also consistent with our observation., Comment: 20 pages, 16 figures, Accepted to the Astrophysical Journal Supplement Series

We present the design and test results of a double-scrambler and fiber agitator system for the Keck Planet Finder (KPF) spectrograph. The mechanical agitator for modal noise suppression is constructed from two linear stages with the fibers mounted in a “W” curve. When driven back-and-forth at different rates, the stages change the position of the fiber curves, and hence vary the modes propagating through the fiber. Near-field temporal centroid shifts caused by modal-noise are reduced by a factor of 100 by the agitator, while mid-range spatial frequencies have reduced power by a factor of ∼300 in the near-field, and ∼1000 in the far-field. The scrambling system incorporates two octagonal fibers, and a scrambler consisting of two identical cemented lenses ∼20 cm apart, which exchanges the optical near- and far-fields of the fibers. The scrambler shows scrambling gains >16,000 in the near-field, and >40,000 in the far-field. The measured throughput efficiency of 99.3% of the expected maximum demonstrates that scrambler-induced focal ratio degradation (FRD) is minimal. The scrambler also serves as the feed-through into the vacuum chamber where the spectrograph is housed, thereby removing concerns about stressing the fibers, and introducing FRD, at this interface. Our illumination stabilization system, consisting of two octagonal fibers, a two lens scrambler, and a mechanical agitator, produces very homogeneous fiber output in both the near and far-fields. When coupled to the Keck Planet Finder spectrograph, this system provides illumination stability corresponding to a velocity of 0.30 m s^(−1).

The Keck Planet Finder (KPF) is a fiber-fed, high-resolution, high-stability spectrometer in development for the W.M. Keck Observatory. The instrument recently passed its preliminary design review and is currently in the detailed design phase. KPF is designed to characterize exoplanets using Doppler spectroscopy with a single measurement precision of 0.5 m s^(−1) or better; however, its resolution and stability will enable a wide variety of other astrophysical pursuits. KPF will have a 200 mm collimated beam diameter and a resolving power greater than 80,000. The design includes a green channel (445 nm to 600 nm) and red channel (600 nm to 870 nm). A novel design aspect of KPF is the use of a Zerodur optical bench, and Zerodur optics with integral mounts, to provide stability against thermal expansion and contraction effects.

We present the design, implementation, and on-ground performance measurements of the Ionospheric Connection Explorer EUV spectrometer, ICON EUV, a wide field ( $17^{\circ}\times 12^{\circ}$ ) extreme ultraviolet (EUV) imaging spectrograph designed to observe the lower ionosphere at tangent altitudes between 100 and 500 km. The primary targets of the spectrometer, which has a spectral range of 54–88 nm, are the Oii emission lines at 61.6 nm and 83.4 nm. Its design, using a single optical element, permits a imaging resolution perpendicular to the spectral dispersion direction with a large ( $12^{\circ} $ ) acceptance parallel to the dispersion direction while providing a slit-width dominated spectral resolution of $R\sim25$ at 58.4 nm. Pre-flight calibration shows that the instrument has met all of the science performance requirements.

The Ionospheric Connection Explorer (ICON) is a NASA Heliophysics Explorer Mission designed to study the ionosphere. ICON will examine the Earth's upper atmosphere to better understand the relationship between Earth weather and space-weather drivers. ICON will accomplish its science objectives using a suite of 4 instruments, one of which is the Extreme Ultraviolet Spectrograph (EUV). EUV will measure daytime altitude intensity profile and spatial distribution of ionized oxygen emissions (O+ at 83.4 nm and 61.7 nm) on the limb in the thermosphere (100 to 500 km tangent altitude). EUV is a single-optic imaging spectrometer that observes in the extreme ultraviolet region of the spectrum. In this paper, we describe instrumental performance calibration measurement techniques and data analysis for EUV. Various measurements including Lyman-α scattering, instrumental and component efficiency, and field-of-view alignment verification were done in custom high-vacuum ultraviolet calibration facilities. Results from the measurements and analysis will be used to understand the instrument performance during the in-flight calibration and observations after launch.

A simple method for determining the focal ratio degradation of optical fibers has been developed. The method involves splitting the light from the test fiber and recording ring patterns that have traveled over two different, and known, optical paths. This new method will be valuable for testing many fibers as will be needed for new multiobject astronomical spectrographs.

We describe demonstrations of remarkable robustness to instrumental noises by using a multiple delay externally dispersed interferometer (EDI) on stellar observations at the Hale telescope. Previous observatory EDI demonstrations used a single delay. The EDI (also called “TEDI”) boosted the 2,700 resolution of the native TripleSpec NIR spectrograph (950-2450 nm) by as much as 10x to 27,000, using 7 overlapping delays up to 3 cm. We observed superb rejection of fixed pattern noises due to bad pixels, since the fringing signal responds only to changes in multiple exposures synchronous to the applied delay dithering. Remarkably, we observed a ~20x reduction of reaction in the output spectrum to PSF shifts of the native spectrograph along the dispersion direction, using our standard processing. This allowed high resolution observations under conditions of severe and irregular PSF drift otherwise not possible without the interferometer. Furthermore, we recently discovered an improved method of weighting and mixing data between pairs of delays that can theoretically further reduce the net reaction to PSF drift to zero. We demonstrate a 350x reduction in reaction to a native PSF shift using a simple simulation. This technique could similarly reduce radial velocity noise for future EDI’s that use two delays overlapped in delay space (or a single delay overlapping the native peak). Finally, we show an extremely high dynamic range EDI measurement of our ThAr lamp compared to a literature ThAr spectrum, observing weak features (~0.001x height of nearest strong line) that occur between the major lines. Because of individuality of each reference lamp, accurate knowledge of its spectrum between the (unfortunately) sparse major lines is important for precision radial velocimetry.

The Dark Energy Spectroscopic Instrument (DESI) is a Stage IV ground-based dark energy experiment that will be employed on the Mayall 4 m Telescope to study the expansion history of the universe. In the era of massively multiplexed fiber-fed spectrographs, DESI will push the boundaries of fiber spectroscopy with a design capable of taking 5000 simultaneous spectra over 360 to 980 nm. The instrument utilizes a suite of three-channel spectrographs, where volume-phase holographic (VPH) gratings provide dispersions. Thirty-six VPH gratings were produced and their performances were evaluated at the Lawrence Berkeley National Laboratory. We present the design and the evaluation tests for the production run of the VPH gratings, verifying the incidence angle, area-weighted efficiency, and wavefront errors (WFEs). We also present the specialized test set-up developed on-site to assess the grating performances. Measurements of the VPH gratings show high consistency in area-weighted efficiency to within an rms of 2% for the red and near-infrared and 6.2% for the blue gratings. Measured WFEs also showed high consistency per bandpass. Comprehensive evaluations show that the VPH gratings meet DESI performance requirements and have been approved for integration.

We present far ultraviolet (FUV: 912 - 1750AA) spectral imaging observations recorded with the SPEAR satellite of the interstellar OVI (1032AA), CIV (1550AA), SiIV (1394AA), SiII* (1533AA) and AlII (1671AA) emission lines originating in a 60 x 30 degree rectangular region lying close to the North Galactic Pole. These data represent the first large area, moderate spatial resolution maps of the distribution of UV spectral-line emission originating the both the highly ionized medium (HIM) and the warm ionized medium (WIM) recorded at high galactic latitudes., Comment: 5 figures

We have obtained EUV spectra between 90 and 255 \AA of the cometsC/2002 T7 (LINEAR), C/2001 Q4 (NEAT), and C/2004 Q2 (Machholz) near their perihelion passages in 2004 with the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS). We obtained contemporaneous data on Comet NEAT Q4 with the $Chandra$ X-ray Observatory ACIS instrument, marking the first simultaneous EUV and X-ray spectral observations of a comet. The total CHIPS/EUV observing times were 337 ks for Q4, 234 ks for T7, and 483 ks for Machholz and for both CHIPS and $Chandra$ we calculate we have captured all the comet flux in the instrument field of view. We set upper limits on solar wind charge exchange emission lines of O, C, N, Ne and Fe occurring in the spectral bandpass of CHIPS. The spectrum of Q4 obtained with $Chandra$ can be reproduced by modeling emission lines of C, N O, Mg, Fe, Si, S, and Ne solar wind ions. The measured X-ray emission line intensities are consistent with our predictions from a solar wind charge exchange model. The model predictions for the EUV emission line intensities are determined from the intensity ratios of the cascading X-ray and EUV photons arising in the charge exchange processes. They are compatible with the measured limits on the intensities of the EUV lines. For comet Q4, we measured a total X-ray flux of 3.7$\times 10^{-12}$ ergs cm$^{-2}$ s$^{-1}$, and derive from model predictions a total EUV flux of 1.5$\times 10^{-12}$ erg cm$^{-2}$ s$^{-1}$. The CHIPS observations occurred predominantly while the satellite was on the dayside of Earth. For much of the observing time, CHIPS performed observations at smaller solar angles than it was designed for and EUV emission from the Sun scattered into the instrument limited the sensitivity of the EUV measurements.

We report results from a multiwavelength observing campaign conducted during 2000 March on the flare star AD Leo. Simultaneous data were obtained from several ground- and space-based observatories, including observations of eight sizable flares. We discuss the correlation of line and continuum emission in the optical and ultraviolet wavelength regimes, as well as the flare energy budget, and we find that the emission properties are remarkably similar even for flares of very different evolutionary morphology. This suggests a common heating mechanism and atmospheric structure that are independent of the detailed evolution of individual flares. We also discuss the Neupert effect, chromospheric line broadening, and velocity fields observed in several transition region emission lines. The latter show significant downflows during and shortly after the flare impulsive phase. Our observations are broadly consistent with the solar model of chromospheric evaporation and condensation following impulsive heating by a flux of nonthermal electrons. These data place strong constraints on the next generation of radiative hydrodynamic models of stellar flares.

On 2000 May 5, we began a large, multiwavelength campaign to study the intermediate polar (IP) EX Hydrae. The simultaneous observations from six satellites and four telescopes were centered around a 1 million second observation with Extreme Ultraviolet Explorer (EUVE). Although EX Hya has been studied previously with EUVE, our higher signal-to-noise ratio observations present new results and challenge the current IP models. Previously unseen dips in the light curve are reminiscent of the stream dips seen in polar light curves. Also of interest is the temporal extent of the bulge dip, approximately 0.5 in phase, implying that the bulge extends over half of the accretion disk. We propose that the magnetic field in EX Hya is strong enough (a few MG) to begin pulling material directly from the outer edge of the disk, thereby forming a large accretion curtain, which would produce a very broad bulge dip. This would also result in magnetically controlled accretion streams originating from the outer edge of the disk. We also present a period analysis of the photometric data, which shows numerous beat frequencies with strong power and also intermittent and wandering frequencies, an indication that physical conditions within EX Hya changed over the course of the observation. Iron spectral line ratios give a temperature of log T = 6.5-6.9 K for all spin phases and a poorly constrained density of ne = 1010-1011 cm-3 for the emitting plasma. This paper is the first in a series detailing our results from this multiwavelength observational campaign.

We obtained EUV photometry, optical spectroscopy, and multi-color optical photometry for WX Cet during its 1998 November superoutburst. WX Cet is only the second short-period, low mass transfer CV (TOAD) to ever be observed in the EUV. Our determined superhump period is consistent with that found by Kato et al. (0.059 d) and we confirm that superhumps are grey in the optical. The optical spectra provide direct evidence that the line emission region is optically thick and our multi-wavelength photometric measurements are used to determine the inner accretion disk and boundary layer temperatures during superoutburst. Using a determined distance to WX Cet of ~130 pc, we find T$_{ID}$= 21,000K and T_{BL}~72,500K. Both values are in good agreement with that expected by models of the superoutburst continuum being produced by the inner disk and boundary layer., Accepted in PASP - July 2002 issue

We present simultaneous EUV and infrared (J,K) observations of the polar HU Aqr obtained during August 1998 when the star was in a high mass accretion state. EUV and IR light curves and EUV spectra are presented and compared with previous observations. The accretion region on the white dwarf has increased in temperature (124,000K to 240,000K) and radius (0.04 R$_{WD}$ to 0.06 R$_{WD} $) compared with previous EUV observations made during low mass accretion states. The EUV and IR photometric observations are shown to have a similar appearance as a function o f orbital phase. The EUV photometry shows rapid changes and provides evidence for mass accretion via blobs. The high state IR light curves present an asymmetric double-humped shape with J=14.8 and K=14.1. We applied an ellipsoidal model fit to the observations and the result indicates that the cause of the modulated shape is both due to ellipsoidal variations from the Roche Lobe filling secondary star and a complex flux combination probably dominated at all orbital phases by cyclotron emission. The source of maximum cyclotron emission appears to be in the accretion column high above the white dwarf surface.

High resolution broad-band spectroscopy at near-infrared wavelengths has been performed using externally dis- persed interferometry (EDI) at the Hale telescope at Mt. Palomar. The EDI technique uses a field-widened Michelson interferometer in series with a dispersive spectrograph, and is able to recover a spectrum with a resolution 4 to 10 times higher than the existing grating spectrograph. This method increases the resolution well beyond the classical limits enforced by the slit width and the detector pixel Nyquist limit and, in principle, decreases the effect of pupil variation on the instrument line-shape function. The EDI technique permits arbi- trarily higher resolution measurements using the higher throughput, lower weight, size, and expense of a lower resolution spectrograph. Observations of many stars were performed with the TEDI interferometer mounted within the central hole of the 200 inch primary mirror. Light from the interferometer was then dispersed by the TripleSpec near-infrared echelle spectrograph. Continuous spectra between 950 and 2450 nm with a resolution as high as ~27,000 were recovered from data taken with TripleSpec at a native resolution of ∼2,700. Aspects of data analysis for interferometric spectral reconstruction are described. This technique has applications in im- proving measurements of high-resolution stellar template spectra, critical for precision Doppler velocimetry using conventional spectroscopic methods. A new interferometer to be applied for this purpose at visible wavelengths is under construction.

Multiwavelength monitoring observations of the AM Her system, QS Tel, are presented, the centrepiece being a coordinated campaign with the ASCA, EUVE and HST satellites and optical observations on 1996 September 28–29. The star was initially observed in an intermediate brightness, single pole state in 1996 April by ROSAT. However two EUVE snapshots of the system in August found it in a deep low state, the light curves appearing to retain a bright and faint phase morphology although the bright interval showed significant phase drifts compared with the earlier ROSAT data. At this time, the system appeared optically bright, while polarimetry pointed to one active pole. A modest recovery of intensity, albeit accompanied by an apparently chaotic extreme ultraviolet (EUV) light curve, was subsequently recorded during the coordinated run in late September. This brightening was confirmed by a second ROSAT pointing in early October, although the EUV brightening is matched by a marked decay in its optical output. These observations, all of which found the system in a fainter EUV state than seen in 1993, add to the catalogue of accretion mode behaviour in QS Tel. However, as yet, the data base of observations does not allow us to establish whether the accretion mode is dictated by accretion-rate dependent penetration of the magnetosphere or asynchronous rotation. The ASCA spectrum obtained during the coordinated observation is adequately described by a thermal spectrum with a temperature of about 4.4 keV and an absorbing column density of less than 8×1020 cm−2. At the same time, the 1150–2600 A UV HST spectrum shows a strong, broad Lyα absorption profile which we attribute to the white dwarf. We infer an effective temperature of 16 000–19 000 K and a mass between 0.5 and 0.93 M⊙ for the white dwarf, at least some of the uncertainty arising because the profile is very probably contaminated and broadened by Zeeman features. The orbital variation seen by HST can be matched by a blackbody-like spectrum with a temperature above 24 000 K. The near UV part of the spectrum contains evidence of phase-variable cyclotron harmonics.

We present results of simultaneous superoutburst observations in the X-ray, Extreme Ultraviolet (EUV), optical, and IR bands of the tremendous outburst amplitude dwarf novae T Leonis. Near peak luminosity, a single blackbody represents a good fit to T Leo's observed continuum in the EUV spectral region, yielding a boundary layer temperature of 71,000 to 97,000K. Inclusion of the longer wavelength observations, UV to the IR, indicates that a blackbody fit is inappropriate. A single temperature fit to only the UV and red-ward data for T Leo works well, but yields a much lower temperature, near 28,000K. Using our own observations and previously obtained EUV, UV and optical (super)outburst observations for the dwarf novae U Gem and SS Cyg, the SU UMa star VW Hyi, and the TOADS, TV Crv, BC UMa, and SW UMa, we find that in all cases, high energy observations yield high temperature, small emitting regions, while fits to UV and red-ward data produce cooler temperatures from much larger emitting regions. These results are consistent with the idea that high energy data provide a direct measurement of the boundary layer while the lower energy data measure a much larger, multi-temperature region, likely to be dominated by the outburst heated inner accretion disk. High energy outburst observations show that the boundary layer temperature decreases with decreasing orbital period and UV outburst observations provide evidence for a missing or weak inner disk in the TOADs. We present a simple model of mass accretion onto the white dwarf during (super)outburst which can account for the observed correlation between temperature.

We have developed a model of the high-energy accretion region for magnetic cataclysmic variables and applied it to {\it Extreme Ultraviolet Explorer} observations of 10 AM Herculis type systems. The major features of the EUV light curves are well described by the model. The light curves exhibit a large variety of features such as eclipses of the accretion region by the secondary star and the accretion stream, and dips caused by material very close to the accretion region. While all the observed features of the light curves are highly dependent on viewing geometry, none of the light curves are consistent with a flat, circular accretion spot whose lightcurve would vary solely from projection effects. The accretion region immediately above the WD surface is a source of EUV radiation caused by either a vertical extent to the accretion spot, or Compton scattering off electrons in the accretion column, or, very likely, both. Our model yields spot sizes averaging 0.06 R$_{WD}$, or $f \sim 1 \times 10^{-3}$ the WD surface area, and average spot heights of 0.023 R$_{WD}$. Spectra extracted during broad dip phases are softer than spectra during the out-of-dip phases. This spectral ratio measurement leads to the conclusion that Compton scattering, some absorption by a warm absorber, geometric effects, an asymmetric temperature structure in the accretion region and an asymmetric density structure of the accretion columnare all important components needed to fully explain the data. Spectra extracted at phases where the accretion spot is hidden behind the limb of the WD, but with the accretion column immediately above the spot still visible, show no evidence of emission features characteristic of a hot plasma.

We present the results of simultaneous optical polarimetry and EUV spectroscopy and photometry of PQ Gem, a magnetic cataclysmic variable which shows observational properties of the strongly magnetic AM Her class, as well as the weaker field DQ Her stars. The EUV spectrum of PQ Gem is weak, showing continuum blueward of 80 A and a few possible weak emission lines due to Mg, Si, and Ne. The EUV light curve has a similar appearance to previous X-ray data obtained for PQ Gem, including a narrow "dip" feature that is modulated with the white dwarf spin period. Observed polarization variations on the spin period, modeled by a slightly modified version of that used in Potter et al., matched the optical light curve and linear polarization curve reasonably well, but not the position angle variation. The EUV properties of PQ Gem can also be understood in the context of this model.

The Extreme Ultraviolet Explorer (EUVE) observatory, successfully launched on 1992 June 7, provided astronomers with the first observatory dedicated to observation in the extreme ultraviolet. The scientific objectives of EUVE include an all-sky survey in four spectral bands, a deep survey in two spectral bands, and a spectroscopic survey carried out through a NASA guest observer program. We describe here the hardware components of the four telescopes used to carry out both the all-sky survey and the deep survey, and we present the imaging and photometric performance characteristics of the instruments as determined from ground calibration and in-orbit data.

We have observed the intermediate polar EX Hydrae for 180,000 s with the Extreme Ultraviolet Explorer. The EUV flux is strongly modulated at both the binary period (98 minutes) and the white dwarf spin period (67 minutes). The secondary star eclipse is total, with a duration of 41 ± 2 s. The ingress and egress of the secondary eclipse have a duration 1013 cm-3, probably >1015 cm-3, in the EUV-emitting region.

We present EUV light curves for a number of AM Her systems observed either as guest observer targets or with the EUVE Right Angle Program. We have formed light curves for eight AM Her stars and show in our presentation the similarities and differences present. We draw some conclusions by grouping the systems by inclination, magnetic field strength, and accretion region geometry. In order to understand the physical structures responsible for the EUV emissions, we have developed a software model to generate synthetic light curves. We find that the EUV accretion regions in the systems UZ For, VV Pup, and AM Her cannot be fit with a flat spot confined to the white dwarf surface, regardless of its shape or brightness profile. Rather, a small, symmetric, raised spot is the only shape consistent with the data. The light curves for systems EF Eri, RE1149+28, AN UMa, and V834 Cen show evidence for additional structure that precedes the primary accretion region in phase. Our model indicates that a large portion of the light curve in each system is seen in absorption. Finally, in three systems, we detect a very gradual rise and fall in the EUV flux (

High-resolution broadband spectroscopy at near-infrared (NIR) wavelengths (950 to 2450 nm) has been performed using externally dispersed interferometry (EDI) at the Hale telescope at Mt. Palomar, with the TEDI interferometer mounted within the central hole of the 200-in. primary mirror in series with the comounted TripleSpec NIR echelle spectrograph. These are the first multidelay EDI demonstrations on starlight. We demonstrated very high (10×) resolution boost and dramatic (20× or more) robustness to point spread function wavelength drifts in the native spectrograph. Data analysis, results, and instrument noise are described in a companion paper (part 1). This part 2 describes theoretical photon limited and readout noise limited behaviors, using simulated spectra and instrument model with noise added at the detector. We show that a single interferometer delay can be used to reduce the high frequency noise at the original resolution (1× boost case), and that except for delays much smaller than the native response peak half width, the fringing and nonfringing noises act uncorrelated and add in quadrature. This is due to the frequency shifting of the noise due to the heterodyning effect. We find a sum rule for the noise variance for multiple delays. The multiple delay EDI using a Gaussian distribution of exposure times has noise-to-signal ratio for photon-limited noise similar to a classical spectrograph with reduced slitwidth and reduced flux, proportional to the square root of resolution boost achieved, but without the focal spot limitation and pixel spacing Nyquist limitations. At low boost (∼1×) EDI has ∼1.4× smaller noise than conventional, and at >10× boost, EDI has ∼1.4× larger noise than conventional. Readout noise is minimized by the use of three or four steps instead of 10 of TEDI. Net noise grows as step phases change from symmetrical arrangement with wavenumber across the band. For three (or four) steps, we calculate a multiplicative bandwidth of 1.8:1 (2.3:1), sufficient to handle the visible band (400 to 700 nm, 1.8:1) and most of TripleSpec (2.6:1).

High-resolution broadband spectroscopy at near-infrared wavelengths (950 to 2450 nm) has been performed using externally dispersed interferometry (EDI) at the Hale telescope at Mt. Palomar. Observations of stars were performed with the “TEDI” interferometer mounted within the central hole of the 200-in. primary mirror in series with the comounted TripleSpec near-infrared echelle spectrograph. These are the first multidelay EDI demonstrations on starlight, as earlier measurements used a single delay or laboratory sources. We demonstrate very high (10×) resolution boost, from original 2700 to 27,000 with current set of delays (up to 3 cm), well beyond the classical limits enforced by the slit width and detector pixel Nyquist limit. Significantly, the EDI used with multiple delays rather than a single delay as used previously yields an order of magnitude or more improvement in the stability against native spectrograph point spread function (PSF) drifts along the dispersion direction. We observe a dramatic (20×) reduction in sensitivity to PSF shift using our standard processing. A recently realized method of further reducing the PSF shift sensitivity to zero is described theoretically and demonstrated in a simple simulation which produces a 350× times reduction. We demonstrate superb rejection of fixed pattern noise due to bad detector pixels—EDI only responds to changes in pixel intensity synchronous to applied dithering. This part 1 describes data analysis, results, and instrument noise. A section on theoretical photon limited sensitivity is in a companion paper, part 2.

Externally dispersed interferometry (EDI) uses a hybrid spectrometer that combines a Michelson interferometer in series with a grating spectrometer. EDI provides a means of deriving spectral information at a resolution substantially higher than that provided by the grating spectrograph alone. Near IR observations have been conducted using the Triplespec spectrometer mounted on the 5m Hale telescope. Spectra have been reconstructed at a resolution of ~27000 where the resolution of Triplespec is ~2700. Progress in the development of the EDI technique is reported herein emphasizing studies related to the accuracy of the reconstructed spectra.

We describe the fiber optics systems for use in BigBOSS, a proposed massively parallel multi-object spectrograph for the Kitt Peak Mayall 4-m telescope that will measure baryon acoustic oscillations to explore dark energy. BigBOSS will include 5,000 optical fibers each precisely actuator-positioned to collect an astronomical target’s flux at the telescope prime-focus. The fibers are to be routed 40m through the telescope facility to feed ten visible-band imaging spectrographs. We report on our fiber component development and performance measurement program. Results include the numerical modeling of focal ratio degradation (FRD), observations of actual fibers’ collimated and converging beam FRD, and observations of FRD from different types of fiber terminations, mechanical connectors, and fusion-splice connections.

An optical technique called "interferometric spectral reconstruction" (ISR) is capable of increasing a spectrograph's resolution and stability by large factors, well beyond its classical limits. We have demonstrated a 6- to 11-fold increase in the Triplespec effective spectral resolution (R=2,700) to achieve R=16,000 at 4100 cm-^(1) to 30,000 at 9600 cm^(-1) by applying special Fourier processing to a series of exposures with different delays (optical path differences) taken with the TEDI interferometer and the near-infrared Triplespec spectrograph at the Mt. Palomar Observatory 200 inch telescope. The TEDI is an externally dispersed interferometer (EDI) used for Doppler radial velocity measurements on M-stars, and now also used for ISR. The resolution improvement is observed in both stellar and telluric features simultaneously over the entire spectrograph bandwidth (0.9-2.45 μm). By expanding the delay series, we anticipate achieving resolutions of R=45,000 or more. Since the delay is not continuously scanned, the technique is advantageous for measuring time-variable phenomena or in varying conditions (e.g. planetary fly-bys). The photon limited signal to noise ratio can be 100 times better than a classic Fourier Transform Spectrometer (FTS) due to the benefit of dispersion.

We describe a non-contact optical measurement method used to determine the surface flatness of a cryogenic sensor array developed for the JDEM mission. Large focal planes envisioned for future visible to near infra-red astronomical large area point-source surveys such as JDEM, WFIRST, or EUCLID must operate at cryogenic temperatures while maintaining focal plane flatness within a few 10's of μm over half-meter scales. These constraints are imposed by sensitivity conditions that demand low noise observations from the sensors and the large-field, fast optical telescopes necessary to obtain the science yield. Verifying cryogenic focal plane flatness is challenging because μm level excursions need to be measured within and across many multi-cm sized sensors using no physical contact and while situated within a high-vacuum chamber. We have used an optical metrology Shack-Hartmann scheme to measure the 36x18 cm focal plane developed for the JDEM mission at the Lawrence Berkeley National Laboratory. The focal plane holds a 4x8 array of CCDs and HgCdTe detectors. The flatness measurement scheme uses a telescope-fed micro-lens array that samples the focal plane to determine slope changes of individual sensor zones.

We analyze EUV spectra of the full solar disk from the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) spanning a period of two years. The observations were obtained via a fortuitous off-axis light path in the 140 -- 270 Angstrom passband. The general appearance of the spectra remained relatively stable over the two-year time period, but did show significant variations of up to 25% between two sets of Fe lines that show peak emission at 1 MK and 2 MK. The variations occur at a measured period of 27.2 days and are caused by regions of hotter and cooler plasma rotating into, and out of, the field of view. The CHIANTI spectral code is employed to determine plasma temperatures, densities, and emission measures. A set of five isothermal plasmas fit the full disk spectra well. A 1 -- 2 MK plasma of Fe contributes 85% of the total emission in the CHIPS passband. The standard Differential Emission Measures (DEMs) supplied with the CHIANTI package do not fit the CHIPS spectra well as they over-predict emission at temperatures below log(T) = 6.0 and above log(T) = 6.3. The results are important for cross-calibrating TIMED, SORCE, SOHO/EIT, and CDS/GIS, as well as the recently launched Solar Dynamics Observatory., Comment: 27 Pages, 13 Figures

The Cosmic Hot Interstellar Plasma Spectrometer (CHIPS) observatory launched on 12 January 2003, and was the first and only successful GSFC UNEX (NASA Goddard Spaceflight Center University Explorer class) mission. The UNEX program was conceived by the National Aeronautics and Space Administration (NASA) as a new class of Explorer mission charged with demonstrating that significant science and/or technology experiments can be performed by small satellites with constrained budgets and a limited schedule. The purpose of the observatory was to examine details of the local bubble thermal pressure, spatial distribution and ionization history. The observatory was also used to observe solar spectra, both scattered from the Lunar surface and via a fortuitous 2nd order scattering path. CHIPS confirmed that spectral features within the 90-260a band were much dimmer than was predicted by contemporary theories, and operated four years beyond its design lifetime. The observatory was placed in an extended safe-hold mode in April of 2008 for budgetary purposes. The spectrometer consisted of six spectrograph channels which delivered >λ/100 resolution spectra to a single detector. Cost constraints of UNEX led to a design based on a traditional aluminum structure, and an instrument with a large field of view (5° x 26°). All optical and optomechanical systems on the spectrometer performed flawlessly on orbit. We discuss the challenges, difficulties and lessons learned during the design, fabrication and execution stages of the mission.

The Cosmic Hot interstellar Plasma Spectrometer (CHIPS), successfully launched on 2003 January 12, provides astronomers with an observatory dedicated to observation of the hot interstellar medium in the extreme ultraviolet. We describe here the otpical and photometric performance of the spectrograph based on calibrations of the individual components, end-to-end vacuum tests, and in-orbit observations of the Moon.

We describe the design and development of the CHIPS microchannel plate detector. The Cosmic Hot Interstellar Plasma Spectrometer will study the diffuse radiation of the interstellar medium in the extreme ultraviolet band pass of 90a to 260a. Astronomical fluxes are expected to be low, so high efficiency in the band pass, good out-of-band rejection, low intrinsic background, and minimal image non-linearities are crucial detector properties. The detector utilizes three 75mm diameter microchannel plates (MCPs) in an abutted Z stack configuration. A NaBr photocathode material deposited on the MCP top surface enhances the quantum detection efficiency. The charge pulses from the MCPs are centroided in two dimensions by a crossed-delayline (XDL) anode. A four panel thin-film filter array is affixed above the MCPs to reduce sensitivity to airglow and scattered radiation, composed of aluminum, polyimide/boron, and zirconium filter panes. The detector is housed in a flight vacuum chamber to preserve the hygroscopic photocathode, the pressure sensitive thin-film filters, and to permit application of high voltage during ground test.

The CHIPS observatory was launched on 12 January 2003, and is the first UNEX (NASA Goddard Spaceflight Center University Explorer class) mission. It is currently on-orbit and performing diffuse spectroscopy in the 90-260a wavelength band. The instrument is integrated with a custom 3-axis stabilized mini-satellite, designed for roughly one year of operation. The purpose of the observatory is examination of details of the local bubble thermal pressure, spatial distribution and ionization history. The spectrometer consists of six spectrograph channels which deliver >lambda/100 resolution spectra to a single detector. Cost constraints of UNEX led to a design based on a traditional aluminum structure, and an instrument with a large field of view (5° x 26°) for the dual purpose of increasing sensitivity in the photon-starved 90-260a band, and to reduce requirements on spacecraft pointing. All optomechanical systems on the spectrometer, including coalignment, thermal, front cover and vacuum door release are performing well on orbit. We discuss design, test and operational performance of these systems, as well as launch loads and thermal system considerations.

CHIPS is a NASA UNEX mission designed for diffuse background spectroscopy in the EUV bandpass from 90-260a. The spectrometer is optimized for peak resolution near 170 a, in order to study diffuse emissions from cooling million degree plasma. Details of local bubble thermal pressure, spatial distribution, and ionization history are the goals of CHIPS observations. We discuss the opto-mechanical design adopted to meet the throughput, signal to noise, and spectral resolution requirements within the mass, volume, and budgetary constraints of a UNEX Delta-II secondary payload. Mechanical tolerance requirements for the six spectrometer channels are discussed, along with details of the lightweight mounting scheme for CHIPS diffraction gratings, front cover slit mechanisms and thermal design. Finally, visible light and vacuum alignment techniques are discussed, as well as with methods employed to minimize stray light.

We present a status report on CHIPS, the Cosmic Hot Interstellar Plasma Spectrometer. CHIPS is the first NASA University-Class Explorer (UNEX) project. CHIPS was selected in 1998 and is now scheduled for launch in December of 2002. The grazing incidence CHIPS spectrograph will survey the sky and record spectra of diffuse emission in the comparatively unexplored wavelength band between 90 and 260 a. These data will provide important new constraints on the temperature, ionization state, and emission measure of hot plasma in the "local bubble" of the interstellar medium.

The source EUVE J1429-38.0 was discovered serendipitously by the Extreme Ultraviolet Explorer (EUVE) satellite on 1993 March 5. Optical spectroscopy confirms a cataclysmic variable-type optical counterpart for the source, showing Balmer, He I, and Ca emission, as well as strong He II emission. The optical spectrum, the apparent high/low state behavior, and possible weak cyclotron humps visible in the spectrum indicate that this star is likely to be an AM Herculis system, but the possibility of being a DQ Her, or an unlocked AM Her system, cannot be excluded. Analysis of the highly modulated EUVE photometry yields a period of 2 hr 22 minutes, which we conclude is the binary orbital period. In addition, a 57 minute period is also present. An orbital period of 2.5 hr would make EUVE J1429-38.0 only the third known AM Her system within the cataclysmic variable period gap, all three of which were discovered through EUV observations.

EUVE J2056-17.1 is one of the brightest sources in the First EUVE Source Catalog with 0.24 counts s-1 in the Deep Survey Lexan/B band. We present optical and EUV results that show this source is one of the most active late-type dwarfs. EUVE observed a large flare with energy in excess of 1035 ergs in its Lexan/B band. The quiescent optical spectrum of the source reveals strong hydrogen Balmer and Ca II H and K emission. A strong Li I 6707 A line is also present in the spectrum. We have estimated a Li abundance of log N(Li) = 2.5±0.4. The high Li abundance and the high flare activity favors an interpretation where the enhanced Li is sustained by spallation reactions.