SDSS-V is the fifth generation of the Sloan Digital Sky Survey and is an ambitious follow-on to a project that has been producing ground-breaking science for two decades. SDSS-V uses two dedicated 2.5m telescopes – the SDSS telescope at Apache Point Observatory in New Mexico, and the du Pont telescope at Las Campanas Observatory in Chile – feeding BOSS and APOGEE spectrographs at each site. These survey machines generate multi-object, all-sky spectroscopy in the optical and near-IR in support of primary science programs. The new wide field corrector for the SDSS 2.5m telescope is one of several major infrastructure upgrades undertaken for SDSS-V, necessitated by the replacement of the legacy fiber plug plate system with a new robotic Fiber Positioning System (FPS), which places different requirements on the focal characteristics of the telescope. The original 2-element corrector produced a focal surface which was non-telecentric and suffered from axial color, throughput, and image quality issues when used in the H-band with the APOGEE spectrograph. We have designed and built a 3-element, all fused silica corrector which addresses the optical shortcomings in relation to the FPS. In addition, the optomechanical design required very minimal changes to the telescope interfaces and also facilitates in-situ axial adjustment of one lens element to fine-tune the as-built spherical radius of the focal surface, to match the nominal design value to which the FPS was built. This paper discusses the optical and optomechanical design details of the new wide field corrector, concluding with a brief summary of recent commissioning results.
This paper presents thermal system and imaging performance test results from the first of four near infrared cameras for the SuMIRe (Subaru Measurement of Images and Redshifts) Prime Focus Spectrograph (PFS) being developed for the Subaru Telescope. The PFS near infrared camera is a large (330 mm entrance aperture to accommodate a 275 mm collimated beam diameter) cryogenically cooled vacuum Schmidt camera with a 300 mm focal length that images dispersed light onto a 4k x 4k, 15 µm pixel, HgCdTe substrate-removed Teledyne 1.7 µm detector. The 230 kg camera contains just four optical elements: a two-element refractive corrector, a Mangin mirror, and a field flattening lens. This simple optical design produces good imaging performance considering the wide field and wavelength range, and it does so in large part due to the use of a Mangin mirror for the Schmidt primary. Thermal background, both in-band and out-of-band, is reduced to a scientifically acceptable level using cryogenically cooled optics, very black geometrically optimized baffling, and a pair of thermal rejection coatings that reject photons between the edge of the science bandpass and the detector cutoff. System operating temperature is achieved by a pair of closed-cycle cryocoolers, one dedicated to cooling the optics, and one dedicated to cooling the detector. Here we discuss the lab performance of the near infrared camera, both from the perspective of the thermal system and the optical system, including in-band and out-of-band performance.
We present the on-sky performance of the new wide field corrector for the fifth generation of the Sloan Digital Sky Survey (SDSS-V). This new three-element corrector was designed to replace the previous two-element design, which had an aspherical focal surface and was not optimized for the infrared (H-band). The purpose of the new corrector is to improve the imaging performance required for a new robotic Fiber Positioning System (FPS). For commissioning, a Focal Surface Camera (FSC) was developed and used to determine the focal surface location relative to the telescope interface, and to verify imaging performance across the 3-degree field of view of the corrector. This paper discusses the commissioning process in detail, describes how the imaging data were processed, and presents the measured image quality across the field.
PFS (Prime Focus Spectrograph), a next generation facility instrument on the Subaru telescope, is now being tested on the telescope. The instrument is equipped with very wide (1.3 degrees in diameter) field of view on the Subaru’s prime focus, high multiplexity by 2394 reconfigurable fibers, and wide waveband spectrograph that covers from 380nm to 1260nm simultaneously in one exposure. Currently engineering observations are ongoing with Prime Focus Instrument (PFI), Metrology Camera System (MCS), the first spectrpgraph module (SM1) with visible cameras and the first fiber cable providing optical link between PFI and SM1. Among the rest of the hardware, the second fiber cable has been already installed on the telescope and in the dome building since April 2022, and the two others were also delivered in June 2022. The integration and test of next SMs including near-infrared cameras are ongoing for timely deliveries. The progress in the software development is also worth noting. The instrument control software delivered with the subsystems is being well integrated with its system-level layer, the telescope system, observation planning software and associated databases. The data reduction pipelines are also rapidly progressing especially since sky spectra started being taken in early 2021 using Subaru Nigh Sky Spectrograph (SuNSS), and more recently using PFI during the engineering observations. In parallel to these instrumentation activities, the PFS science team in the collaboration is timely formulating a plan of large-sky survey observation to be proposed and conducted as a Subaru Strategic Program (SSP) from 2024. In this article, we report these recent progresses, ongoing developments and future perspectives of the PFS instrumentation.
PFS (Prime Focus Spectrograph), a next generation facility instrument on the Subaru telescope, is a very wide- field, massively multiplexed, and optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed in the 1.3 degree-diameter field of view. The spectrograph system has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously deliver spectra from 380nm to 1260nm in one exposure. The instrumentation has been conducted by the international collaboration managed by the project office hosted by Kavli IPMU. The team is actively integrating and testing the hardware and software of the subsystems some of which such as Metrology Camera System, the first Spectrograph Module, and the first on-telescope fiber cable have been delivered to the Subaru telescope observatory at the summit of Maunakea since 2018. The development is progressing in order to start on-sky engineering observation in 2021, and science operation in 2023. In parallel, the collaboration is trying to timely develop a plan of large-sky survey observation to be proposed and conducted in the framework of Subaru Strategic Program (SSP). This article gives an overview of the recent progress, current status and future perspectives of the instrumentation and scientific operation.
PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed, optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed over the 1.3 deg field of view. The spectrograph has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure at a resolution of ~ 1.6-2.7Å. An international collaboration is developing this instrument under the initiative of Kavli IPMU. The project recently started undertaking the commissioning process of a subsystem at the Subaru Telescope side, with the integration and test processes of the other subsystems ongoing in parallel. We are aiming to start engineering night-sky operations in 2019, and observations for scientific use in 2021. This article gives an overview of the instrument, current project status and future paths forward.
The Double Asteroid Redirection Test (DART) is a spacecraft that will impact the smaller body of the binary asteroid Didymos. As a technology demonstration, this will be the first time a kinetic impactor is used to perturb the motion of a near earth object. This technique could someday be used to deflect a dangerous asteroid on a future collision course with Earth. As the only instrument aboard DART, the Didymos Reconnaissance and Asteroid Camera for OpNav (DRACO) serves two purposes. First, DRACO provides images to the Small-body Maneuvering Autonomous Real-Time Navigation (SMARTNav) algorithm, allowing the spacecraft to precisely locate and impact the target. In its final moments, DRACO will also characterize the impact site by providing high resolution, scientific imagery of the surface. Derived from the Long Range Reconnaissance Imager (LORRI) on New Horizons, the telescope is a 208 mm aperture, f/12.6, catadioptric Ritchey-Chrétien, with a 0.29 degree field of view. A lightweight opto-mechanical structure, with low CTE mirror substrates and a composite baffle tube, maintains telescope focus in the low temperature environment of deep space. At the focal plane is a 2560 by 2160 pixel, panchromatic, front-side illuminated complementary metal oxide semiconductor (CMOS) image sensor, with digital output, global shutter, and low read noise. A highly integrated focal plane electronics (FPE) module controls the sensor and relays data to the spacecraft.
PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed, optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed over the 1.3 deg field of view. The spectrograph has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure at a resolution of ~1.6 - 2.7Å. An international collaboration is developing this instrument under the initiative of Kavli IPMU. The project is now going into the construction phase aiming at undertaking system integration in 2017-2018 and subsequently carrying out engineering operations in 2018-2019. This article gives an overview of the instrument, current project status and future paths forward.
We describe the conceptual optomechanical design for GMACS, a wide-field, multi-object, moderate-resolution optical
spectrograph for the Giant Magellan Telescope (GMT). GMACS is a candidate first-light instrument for the GMT and
will be one of several instruments housed in the Gregorian Instrument Rotator (GIR) located at the Gregorian focus. The
instrument samples a 9 arcminute x 18 arcminute field of view providing two resolution modes (i.e, low resolution, R ~
2000, and moderate resolution, R ~ 4000) over a 3700 Å to 10200 Å wavelength range. To minimize the size of the
optics, four fold mirrors at the GMT focal plane redirect the full field into four individual "arms", that each comprises a
double spectrograph with a red and blue channel. Hence, each arm samples a 4.5 arcminute x 9 arcminute field of view.
The optical layout naturally leads to three separate optomechanical assemblies: a focal plane assembly, and two identical
optics modules. The focal plane assembly contains the last element of the telescope's wide-field corrector, slit-mask,
tent-mirror assembly, and slit-mask magazine. Each of the two optics modules supports two of the four instrument arms
and houses the aft-optics (i.e. collimators, dichroics, gratings, and cameras). A grating exchange mechanism, and
articulated gratings and cameras facilitate multiple resolution modes. In this paper we describe the details of the
GMACS optomechanical design, including the requirements and considerations leading to the design, mechanism
details, optics mounts, and predicted flexure performance.
We present a conceptual design for a moderate resolution optical spectrograph for the Giant Magellan Telescope (GMT).
The spectrograph is designed to make use of the large field-of-view of the GMT and be suitable for observations of very
faint objects across a wide range of optical wavelengths. We show some details of the optical and mechanical design of
the instrument.
The James Webb Space Telescope will undergo a full system test in the cryogenic vacuum chamber A at the Johnson
Spaceflight Center in order to verify the overall performance of the combined telescope and instrument suite. This will
be the largest and most extensive cryogenic test ever undertaken. Early in the test system development, it was
determined that precise position measurements of the overall hardware would enhance the test results. Various concepts
were considered before selecting photogrammetry for this metrology. Photogrammetry has been used in space systems
for decades, however cryogenic use combined with the size and the optical/thermal sensitivity of JWST creates a unique
set of implementation challenges. This paper provides an overview of the JWST photogrammetric system and mitigation
strategies for three key engineering design challenges: 1) the thermal design of the viewing windows to prevent
excessive heat leak and stray light to the test article 2) cost effective motors and mechanisms to provide the angle
diversity required, and 3) camera-flash life and reliability sufficient for inaccessible use during the number and duration
of the cryogenic tests.
The James Webb Space Telescope (JWST) is a general astrophysics mission which consists of a 6.6m diameter,
segmented, deployable telescope for cryogenic IR space astronomy (~35K). The JWST Observatory architecture
includes the Optical Telescope Element and the Integrated Science Instrument Module (ISIM) element that contains four
science instruments (SI) including a Guider.
The alignment philosophy of ISIM is such that the cryogenic changes in the alignment of the SI interfaces are captured in
the ISIM alignment error budget. The SIs are aligned to the structure's coordinate system under ambient, clean room
conditions using laser tracker and theodolite metrology. The ISIM structure is thermally cycled and temperature-induced
structural changes are concurrently measured with a photogrammetry metrology system to ensure they are within
requirements.
We compare the ISIM photogrammetry system performance to the ISIM metrology requirements and describe the
cryogenic data acquired to verify photogrammetry system level requirements, including measurement uncertainty. The
ISIM photogrammetry system is the baseline concept for future tests involving the Optical Telescope Element (OTE) and
Observatory level testing at Johnson Space Flight Center.
The FourStar infrared camera is a 1.0-2.5 μm (JHKs) near infrared camera for the Magellan Baade
6.5m telescope at Las Campanas Observatory (Chile). It is being built by Carnegie Observatories and
the Instrument Development Group and is scheduled for completion in 2009. The instrument uses four
Teledyne HAWAII-2RG arrays that produce a 10.9' × 10.9' field of view. The outstanding seeing at the
Las Campanas site coupled with FourStar's high sensitivity and large field of view will enable many
new survey and targeted science programs.
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