The Multi-object, Fiber-fed Spectrographs for the Sloan Digital Sky Survey and the Baryon Oscillation Spectroscopic Survey

We present the design and performance of the multi-object fiber spectrographs for the Sloan Digital Sky Survey (SDSS) and their upgrade for the Baryon Oscillation Spectroscopic Survey (BOSS). Originally commissioned in Fall 1999 on the 2.5 m aperture Sloan Telescope at Apache Point Observatory, the spectrographs produced more than 1.5 million spectra for the SDSS and SDSS-II surveys, enabling a wide variety of Galactic and extra-galactic science including the first observation of baryon acoustic oscillations in 2005. The spectrographs were upgraded in 2009 and are currently in use for BOSS, the flagship survey of the third-generation SDSS-III project. BOSS will measure redshifts of 1.35 million massive galaxies to redshift 0.7 and Lyα absorption of 160,000 high redshift quasars over 10,000 deg^2 of sky, making percent level measurements of the absolute cosmic distance scale of the universe and placing tight constraints on the equation of state of dark energy. The twin multi-object fiber spectrographs utilize a simple optical layout with reflective collimators, gratings, all-refractive cameras, and state-of-the-art CCD detectors to produce hundreds of spectra simultaneously in two channels over a bandpass covering the near-ultraviolet to the near-infrared, with a resolving power R = λ/FWHM ~ 2000. Building on proven heritage, the spectrographs were upgraded for BOSS with volume-phase holographic gratings and modern CCD detectors, improving the peak throughput by nearly a factor of two, extending the bandpass to cover 360 nm < λ < 1000 nm, and increasing the number of fibers from 640 to 1000 per exposure. In this paper we describe the original SDSS spectrograph design and the upgrades implemented for BOSS, and document the predicted and measured performances

Ground-Based Astronomical Instrumentation Development in the United States: A White Paper on the Challenges Faced by the US Community

This invited white paper, submitted to the National Science Foundation in January of 2020, discusses the current challenges faced by the United States astronomical instrumentation community in the era of extremely large telescopes. Some details may have changed since submission, but the basic tenets are still very much valid. The paper summarizes the technical, funding, and personnel challenges the US community faces, provides an informal census of current instrumentation groups in the US, and compares the state-of-affairs in the US with that of the European community, which builds astronomical instruments from consortia of large hard-money funded instrument centers in a coordinated fashion. With the recent release of the Decadal Survey on Astronomy and Astrophysics 2020 (Astro2020), it is clear that strong community support exists for this next generation of large telescopes in the US. Is the US ready? Is there sufficient talent, facilities, and resources in the community today to meet the challenge of developing the complex suite of instruments envisioned for two US ELTs? These questions are addressed, along with thoughts on how the National Science Foundation can help build a more viable and stable instrumentation program in the US. These thoughts are intended to serve as a starting point for a broader discussion, with the end goal being a plan that puts the US astronomical instrumentation community on solid footing and poised to take on the challenges presented by the ambitious goals we have set in the era of ELTs.Comment: 22 pages, 1 table, 0 figures. This is an invited white paper submitted to the National Science Foundation in January of 202

Growth Patterns of Shoal Grass Halodule wrightii and Manatee Grass Syringodium filiforme in the Western Gulf of Mexico

Although manatee grass is becoming increasingly abundant in Texas bays, its growth characteristics have not been measured in the western GOM. Changes in seagrass species composition can have significant community effects (Micheli et al. 2008), but the effects of a transition from shoal to manatee grass in the LM have not been extensively studied (but see Tolan et al. 1997). The goals of our study were to measure growth patterns of these two seagrass species in two locations in the western GOM that vary in salinity, epiphyte loads, and nutrient inputs

Evolving the human niche

This is the author accepted manuscript. The final version is available from the National Academy of Sciences via the DOI in this record

Visible camera cryostat design and performance for the SuMIRe Prime Focus Spectrograph (PFS)

We describe the design and performance of the SuMIRe Prime Focus Spectrograph (PFS) visible camera cryostats. SuMIRe PFS is a massively multi-plexed ground-based spectrograph consisting of four identical spectrograph modules, each receiving roughly 600 fibers from a 2394 fiber robotic positioner at the prime focus. Each spectrograph module has three channels covering wavelength ranges 380~nm -- 640~nm, 640~nm -- 955~nm, and 955~nm -- 1.26~um, with the dispersed light being imaged in each channel by a f/1.07 vacuum Schmidt camera. The cameras are very large, having a clear aperture of 300~mm at the entrance window, and a mass of $\sim$280~kg. In this paper we describe the design of the visible camera cryostats and discuss various aspects of cryostat performance

Detectors and cryostat design for the SuMIRe Prime Focus Spectrograph (PFS)

We describe the conceptual design of the camera cryostats, detectors, and detector readout electronics for the SuMIRe Prime Focus Spectrograph (PFS) being developed for the Subaru telescope. The SuMIRe PFS will consist of four identical spectrographs, each receiving 600 fibers from a 2400 fiber robotic positioner at the prime focus. Each spectrograph will have three channels covering wavelength ranges 3800 {\AA} - 6700 {\AA}, 6500 {\AA} - 10000 {\AA}, and 9700 {\AA} - 13000 {\AA}, with the dispersed light being imaged in each channel by a f/1.10 vacuum Schmidt camera. In the blue and red channels a pair of Hamamatsu 2K x 4K edge-buttable CCDs with 15 um pixels are used to form a 4K x 4K array. For the IR channel, the new Teledyne 4K x 4K, 15 um pixel, mercury-cadmium-telluride sensor with substrate removed for short-wavelength response and a 1.7 um cutoff will be used. Identical detector geometry and a nearly identical optical design allow for a common cryostat design with the only notable difference being the need for a cold radiation shield in the IR camera to mitigate thermal background. This paper describes the details of the cryostat design and cooling scheme, relevant thermal considerations and analysis, and discusses the detectors and detector readout electronics