We describe the Sloan Digital Sky Survey Local Volume Mapper Instrument (LVM-I) construction, testing, and initial performance. The facility is designed to produce the first integral map of thousands of degrees of the Southern sky. The map will cover spectra from bluer than [O II] to 980 nm with a dispersion of over R =Delta lambda/lambda > 4, 000 at Ha wavelength. Each spaxel will have a pitch of similar to 35 '', and the survey will be conducted using four integral field units (IFUs) with an instantaneous field of view of 530 arcmin(2). The LVM facility is designed to achieve the required sub-Rayleigh spectroscopy over large sky areas with outstanding spectrophotometric accuracy and precision. LVM-I is designed to produce this unique dataset using four siderostats on commercial mounts. The four beams are fed into 16-cm-diameter f/11.4 apochromatic objectives, and the sky is derotated with K mirrors. These telescopes produce an image of the field onto both guider cameras and a lenslet array. The array reimages the field at f/3.7 onto 107-micron-diameter fibers. Blue throughput is maximized with a short 18.5-m fiber run from the IFUs to the spectrographs. The fibers are reconfigured inside a splicing box to distribute the fibers from the four telescopes to three spectrographs. The spectrographs are near-copies of the Dark Energy Survey three-band f/1.7 spectrographs, which deliver sharp images over the entire chromatic range. Nine STA charge-coupled devices (CCDs), cooled with liquid-nitrogen dewars, are used for the survey. The LVM-I is controlled with custom Python software and distributed over various computers using power-over-ethernet networking. The system is housed in a custom enclosure with a roll-off roof to grant access to the sky. The enclosure allows all four telescopes to point all over the sky and measure the transmissivity of the atmosphere and the sky background. Some of the first-light data products are highlighted here.

New development approaches, including launch vehicles and advances in sensors, computing, and software, have lowered the cost of entry into space, and have enabled a revolution in low-cost, high-risk Small Satellite (SmallSat) missions. To bring about a similar transformation in larger space telescopes, it is necessary to reconsider the full paradigm of space observatories. Here we will review the history of space telescope development and cost drivers, and describe an example conceptual design for a low cost 6.5 m optical telescope to enable new science when operated in space at room temperature. It uses a monolithic primary mirror of borosilicate glass, drawing on lessons and tools from decades of experience with ground-based observatories and instruments, as well as flagship space missions. It takes advantage, as do large launch vehicles, of increased computing power and space-worthy commercial electronics in low-cost active predictive control systems to maintain stability. We will describe an approach that incorporates science and trade study results that address driving requirements such as integration and testing costs, reliability, spacecraft jitter, and wavefront stability in this new risk-tolerant "LargeSat" context.

An 8-inch wafer scale process was developed that provides low cost availability of back-side illuminated (BSI) imaging sensors. The process has been optimized to convert standard CMOS and CCD 6-inch or 8-inch wafers from front side illuminated (FSI) sensors to BSI sensors. The process successfully demonstrates wafer planarization, bow correction, bonding to carrier wafers, wafer thinning, re-planarization, anti-reflection coating, through silicon vias (TSVs) and back side metallization. Good wafer thinning control was obtained for a wide range of epi thicknesses varying from 4 microns to 15 microns. The thinner epi is optimized for UV and visible sensing while the thicker epi material is optimized for near-infrared (NIR) sensing. The processed wafers demonstrate backside passivation and anti-reflection (AR) coatings that optimize the QE performance in a variety of bands such as 200nm-300nm, 300nm-400nm and 400nm-900nm.

Charge coupled devices (CCDs) have been the most common high performance imaging detector for nearly all scientific and industrial imaging applications since the 1980s. In this chapter the CCD imager and its use for high performance imaging are described. The focus is on scientific and industrial applications which require quantitative measurements of the incident scene, especially in low light level conditions and when spectral information is also required. The architecture and operation of CCDs as well as their quantitative characterization and most important operational parameters are also described.

The Sloan Digital Sky Survey V (SDSS-V) is an all-sky spectroscopic survey of <6 million objects, designed to decode the history of the Milky Way, reveal the inner workings of stars, investigate the origin of solar systems, and track the growth of supermassive black holes across the Universe. The Local Volume Mapper (LVM) is a facility designed to provide a contiguous 2,500 deg2 integral-field survey over a 3.5 year period from Las Campanas Observatory in Chile. In this paper we provide an overview and status update for the LVM instrument (hereafter LVM-I). Each integral-field unit’s spaxel probes linear scales that are sub-parsec (Milky Way) to ∼10 pc (Magellanic Clouds) which is accomplished with an angular diameter of 36.900. LVM’s spectral resolution is R = λ/∆λ ∼ 4, 000 which probes velocities of 33 kms−1 (1 σ) from 365 nm to 950 nm. LVM uses four 16-cm telescopes feeding three spectrographs. One telescope carries the bulk of the science load with ∼1,800 fibers coupled to the field via a pair of lenslet arrays, two telescopes are used to measure the night sky spectra in fields that flank the science field, and a fourth telescope contemporaneously monitors bright standard stars to determine atmospheric extinction. We expect LVM-I to deliver percent-level precision on important line ratios down to a few Rayleigh. The three spectrographs are being built by Winlight corporation in France based on those for the Dark Energy Spectroscopic Instrument (DESI). In this paper we present the high-level system design of LVM-I including the lenslet-coupled fiber IFUs, telescopes, guiding+acquisition system, calibration systems, enclosures, and spectrographs.

The DESI Legacy Imaging Surveys are a combination of three public projects (the Dark Energy Camera Legacy Survey, the Beijing-Arizona Sky Survey, and the Mayall z-band Legacy Survey) that will jointly image approximately 14,000 deg^2 of the extragalactic sky visible from the northern hemisphere in three optical bands (g, r, and z) using telescopes at the Kitt Peak National Observatory and the Cerro Tololo Inter-American Observatory. The combined survey footprint is split into two contiguous areas by the Galactic plane. The optical imaging is conducted using a unique strategy of dynamically adjusting the exposure times and pointing selection during observing that results in a survey of nearly uniform depth. In addition to calibrated images, the project is delivering a catalog, constructed by using a probabilistic inference-based approach to estimate source shapes and brightnesses. The catalog includes photometry from the grz optical bands and from four mid-infrared bands (at 3.4, 4.6, 12 and 22 micorons) observed by the Wide-field Infrared Survey Explorer (WISE) satellite during its full operational lifetime. The project plans two public data releases each year. All the software used to generate the catalogs is also released with the data. This paper provides an overview of the Legacy Surveys project.

The Beijing–Arizona Sky Survey (BASS) is a wide-field two-band photometric survey of the northern Galactic Cap using the 90Prime imager on the 2.3 m Bok telescope at Kitt Peak. It is a four-year collaboration between the National Astronomical Observatory of China and Steward Observatory, the University of Arizona, serving as one of the three imaging surveys to provide photometric input catalogs for target selection of the Dark Energy Spectroscopic Instrument (DESI) project. BASS will take up to 240 dark/gray nights to cover an area of about 5400 deg2 in the g and r bands. The 5σ limiting AB magnitudes for point sources in the two bands, corrected for the Galactic extinction, are 24.0 and 23.4 mag, respectively. BASS, together with other DESI imaging surveys, will provide unique science opportunities that cover a wide range of topics in both Galactic and extragalactic astronomy.

For several years the University of Arizona Imaging Technology Laboratory (ITL) has developed Charge Coupled Device image sensors for the Large Synoptic Survey Telescope (LSST) project. These sensors were designed by Semiconductor Technology Associates, Inc. and then backside processed and characterized at ITL. The LSST project provided a set of specifications which the sensors must meet as well as a guideline for the acquisition and analyze process which they will use to verify sensor performance. We describe in this paper the characterization results from similar testing at ITL before shipment of the sensors. We include both electro-optical and metrology results. Specific measurements described here include dark signal, quantum efficiency, read noise, charge transfer efficiency, and charge diffusion as well as sensor flatness (and both room and operating temperatures) and absolute position.

We present and analyze the possibility of using optical u-band luminosities to estimate star-formation rates (SFRs) of galaxies based on the data from the South Galactic Cap u. band Sky Survey (SCUSS), which provides a deep u-band photometric survey covering about 5000 deg(2) of the South Galactic Cap. Based on two samples of normal star-forming galaxies selected by the. BPT diagram, we explore the correlations between u-band, H alpha, and IR luminosities by combing SCUSS data with the Sloan Digital Sky Survey and Wide-field Infrared Survey Explorer (WISE). The attenuation-corrected u-band luminosities are tightly correlated with the Balmer decrement-corrected Ha luminosities with an rms scatter of similar to 0.17 dex. The IR-corrected u luminosities are derived based on the correlations between the attenuation of u-band luminosities and WISE. 12 (or 22) mu m luminosities, and then calibrated with the Balmer-corrected Ha luminosities. The systematic residuals of these calibrations are tested against the physical properties over the ranges covered by our sample objects. We find that the best-fitting nonlinear relations are better than the linear ones and recommended to be applied in the measurement of SFRs. The systematic deviations mainly come from the pollution of old stellar population and the effect of dust extinction; therefore,. a. more detailed analysis is needed in future work.

We study the integral Galactic extinction and reddening based on the galaxy catalog of the South Galactic Cap u-band Sky Survey (SCUSS), where u-band galaxy number counts and u - r color distribution are used to derive the Galactic extinction and reddening respectively. We compare these independent statistical measurements with the reddening map of Schlegel et al. (SFD) and find that both the extinction and reddening from the number counts and color distribution are in good agreement with the SFD results at low extinction regions (E(B - V)(SFD) < 0.12 mag). However, for high extinction regions (E(B - V)(SFD) > 0.12 mag), the SFD map overestimates the Galactic reddening systematically, which can be approximated by a linear relation Delta E(B - V)= 0.43[ E(B - V)(SFD) - 0.12]. By combining the results from galaxy number counts and color distribution, we find that the shape of the Galactic extinction curve is in good agreement with the standard R-V = 3.1 extinction law of O'Donnell.

We present a new selection technique of producing spectroscopic target catalogues for massive spectroscopic surveys for cosmology. This work was conducted in the context of the extended Baryon Oscillation Spectroscopic Survey (eBOSS), which will use similar to 200 000 emission line galaxies (EEGs) at 0.6 < z(spec),, < 1.0 to obtain a precise baryon acoustic oscillation measurement. Our proposed selection technique is based on optical and near-infrared broad-band filter photometry. We used a training sample to define a quantity, the Fisher discriminant (linear combination of colours), which correlates best with the desired properties of the target: redshift and [OII] flux. The proposed selections are simply done by applying a cut on magnitudes and this Fisher discriminant. We used public data and dedicated SDSS spectroscopy to quantify the redshift distribution and [0111 flux of our ELG target selections. We demonstrate that two of our selections fulfil the initial eBOSS/ELG redshift requirements: for a target density' of 180 deg(-2), similar to 70% of the selected objects have 0.6 < zspec < 1.0 and only similar to 1% of those galaxies in the range 0.6 < zspec < 1.0 are expected to have a catastrophic z(spec) estimate. Additionally, the stacked spectra and stacked deep images for those two selections show characteristic features of star -forming galaxies. The proposed approach using the Fisher discriminant could, however, be used to efficiently-select other galaxy populations, based on multi-band photometry, providing that spectroscopic information is available. This technique could thus be useful for other future massive spectroscopic surveys such as PFS, DESI, and 4MOST.

The South Galactic Cap u-band Sky Survey (SCUSS) was established in 2009 in order to provide a photometric input catalog for target selection of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) project. SCUSS is an international cooperative project between National Astronomical Observatories, Chinese Academy of Sciences, and Steward Observatory at the University of Arizona, using the 90 inch (2.3m) Bok telescope on Kitt Peak. The telescope is equipped with a prime focus camera that is composed of a mosaic of four 4096 × 4096 CCDs and has a field of view of about 1 deg2. From 2009 to 2013, SCUSS performed a sky survey of an approximately 5000 deg2 field of the South Galactic Cap in u band, including the Galactic anticenter area and the SDSS-IV extended imaging area. The limiting magnitude of SCUSS is deeper than 23 mag (at a signal-to-noise ratio of 5). In this paper, we briefly describe the goals of this project, method of observations and data reduction, and we also introduce current and potential scientific activities related to the SCUSS project.

DESI (Dark Energy Spectroscopic Instrument) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations (BAO) and the growth of structure through redshift-space distortions with a wide-area galaxy and quasar redshift survey. To trace the underlying dark matter distribution, spectroscopic targets will be selected in four classes from imaging data. We will measure luminous red galaxies up to $z=1.0$. To probe the Universe out to even higher redshift, DESI will target bright [O II] emission line galaxies up to $z=1.7$. Quasars will be targeted both as direct tracers of the underlying dark matter distribution and, at higher redshifts ($ 2.1 < z < 3.5$), for the Ly-$\alpha$ forest absorption features in their spectra, which will be used to trace the distribution of neutral hydrogen. When moonlight prevents efficient observations of the faint targets of the baseline survey, DESI will conduct a magnitude-limited Bright Galaxy Survey comprising approximately 10 million galaxies with a median $z\approx 0.2$. In total, more than 30 million galaxy and quasar redshifts will be obtained to measure the BAO feature and determine the matter power spectrum, including redshift space distortions.

Based on Sloan Digital Sky Survey (SDSS) g, r and South Galactic Cap of u-band Sky Survey (SCUSS) u photometry, we develop a photometric calibration for estimating the stellar metallicity from u - g and g - r colours by using the SDSS spectra of 32 542 F-and G-type main-sequence stars, which cover almost 3700 deg(2) in the south Galactic cap. The rms scatter of the photometric metallicity residuals relative to spectrum-based metallicity is 0.14 dex when g - r < 0.4, and 0.16 dex when g - r > 0.4. Because of the deeper and more accurate magnitude of SCUSS u band, the estimate can be used up to the faint magnitude of g = 21. This application range of photometric metallicity calibration is wide enough so that it can be used to study metallicity distribution of distant stars. In this study, we select the Sagittarius (Sgr) stream and its neighbouring field halo stars in south Galactic cap to study their metallicity distribution. We find that the Sgr stream at the cylindrical Galactocentric coordinate of R similar to 19 kpc, vertical bar z vertical bar similar to 14 kpc exhibits a relative rich metallicity distribution, and the neighbouring field halo stars in our studied fields can be modelled by two-Gaussian model, with peaks, respectively, at [Fe/H] = -1.9 and -1.5.

The South Galactic Cap u-band Sky Survey (SCUSS) provides a deep u-band imaging of about 5000 deg2 in south Galactic cap. It is about 1.5 mag deeper than the SDSS u-band. In this article, we evaluate the capability of quasar selection using both SCUSS and SDSS data, based on considerations of the deep SCUSS u-band imaging and two-epoch u-band variability. We find that the combination of the SCUSS u-band and the SDSS griz-band allows us to select more faint quasars and more quasars at redshift around 2.2 than the selection that uses only the SDSS ugriz data. Quasars have significant u-band variabilities. The fraction of quasars with large two-epoch variability is much higher than that of stars. The selection by variability can select both low-redshift quasars with ultraviolet excess and mid-redshift (2 < z < 3.5) quasars where quasar selection by optical colors is inefficient. The above two selections are complementary and make full use of the SCUSS u-band advantages.

The South Galactic Cap u-band Sky Survey (SCUSS) is a deep u-band imaging survey in the Southern Galactic Cap, using the 90Prime wide-field imager on the 2.3m Bok telescope at Kitt Peak. The survey observations started in 2010 and ended in 2013. The final survey area is about 5000 deg2 with a median 5-sigma point source limiting magnitude of about 23.2. This paper describes the survey data reduction process, which includes basic imaging processing, astrometric and photometric calibrations, image stacking, and photometric measurements. Survey photometry is performed on objects detected both on SCUSS u-band images and in the SDSS database. Automatic, aperture, point-spread function (PSF), and model magnitudes are measured on stacked images. Co-added aperture, PSF, and model magnitudes are derived from measurements on single-epoch images. We also present comparisons of the SCUSS photometric catalog with those of the SDSS and CFHTLS.

We present the [O II] (lambda lambda 3729; 3726) luminosity function measured in the redshift range 0.1 < z < 1.65 with unprecedented depth and accuracy. Our measurements are based on medium resolution flux-calibrated spectra of emission line galaxies with the visual and near UV FOcal Reducer and low dispersion Spectrograph (FORS2) for the Very Large Telescope (VLT) of the European Southern Observatory (ESO) and with the SDSS-III/BOSS spectrograph. The FORS2 spectra and the corresponding catalog containing redshifts and line fluxes are released along with this paper. In this work we use a novel method to combine these surveys with GAMA, zCOSMOS, and VVDS, which have di ff erent target selection, producing a consistent weighting scheme to derive the [O II] luminosity function. The [O II] luminosity function is in good agreement with previous independent estimates. The comparison with two stateof- the-art semi-analytical models is good, which is encouraging for the production of mock catalogs of [O II] flux limited surveys. We observe the bright end evolution over 8.5 Gyr: we measure the decrease of log L-* from 42.4 erg/s at redshift 1.44 to 41.2 at redshift 0.165 and we find that the faint end slope flattens when redshift decreases. This measurement confirms the feasibility of the target selection of future baryonic acoustic oscillation surveys aiming at observing [OII] flux limited samples.

SCUSS is a u-band photometric survey covering about 4000 square degree of the South Galactic Cap, reaching depths of up to 23 mag. By extending around 1.5 mag deeper than SDSS single-epoch u data, SCUSS is able to probe much a larger volume of the outer halo, i.e. with SCUSS data blue horizontal branch (BHB) stars can trace the outer halo of the Milky Way as far as 100-150 kpc. Utilizing this advantage we combine SCUSS u band with SDSS DR9 gri photometric bands to identify BHB stars and explore halo substructures. We confirm the existence of the Pisces overdensity, which is a structure in the outer halo (at around 80 kpc) that was discovered using RR Lyrae stars. For the first time we are able to determine its spatial extent, finding that it appears to be part of a stream with a clear distance gradient. The stream, which is 5 degrees wide and stretches along 25 degrees, consists of 20-30 BHBs with a total significance of around 6sigma over the background. Assuming we have detected the entire stream and that the progenitor has fully disrupted, then the number of BHBs suggests the original system was similar to smaller classical or a larger ultra-faint dwarf galaxy. On the other hand, if the progenitor still exists, it can be hunted for by reconstructing its orbit from the distance gradient of the stream. This new picture of the Pisces overdensity sheds new light on the origin of this intriguing system.