Luke M. Schmidt

The MANIFEST prototyping design study

MANIFEST is a facility multi-object fibre system for the Giant Magellan Telescope, which uses ‘Starbug’ fibre positioning robots. MANIFEST, when coupled to the telescope’s planned seeing-limited instruments, GMACS, and G-CLEF, offers access to: larger fields of view; higher multiplex gains; versatile reformatting of the focal plane via IFUs; image-slicers; and in some cases higher spatial and spectral resolution. The Prototyping Design Study phase for MANIFEST, nearing completion, has focused on developing a working prototype of a Starbugs system, called TAIPAN, for the UK Schmidt Telescope, which will conduct a stellar and galaxy survey of the Southern sky. The Prototyping Design Study has also included work on the GMT instrument interfaces. In this paper, we outline the instrument design features of TAIPAN, highlight the modifications that will be necessary for the MANIFEST implementation, and provide an update on the MANIFEST/instrument interfaces.

A new path to first light for the Magdalena Ridge Observatory interferometer

The Magdalena Ridge Observatory Interferometer (MROI) was the most ambitious infrared interferometric facility conceived of in 2003 when funding began. Today, despite having suffered some financial short-falls, it is still one of the most ambitious interferometric imaging facilities ever designed. With an innovative approach to attaining the original goal of fringe tracking to H = 14th magnitude via completely redesigned mobile telescopes, and a unique approach to the beam train and delay lines, the MROI will be able to image faint and complex objects with milliarcsecond resolutions for a fraction of the cost of giant telescopes or space-based facilities. The design goals of MROI have been optimized for studying stellar astrophysical processes such as mass loss and mass transfer, the formation and evolution of YSOs and their disks, and the environs of nearby AGN. The global needs for Space Situational Awareness (SSA) have moved to the forefront in many communities as Space becomes a more integral part of a national security portfolio. These needs drive imaging capabilities ultimately to a few tens of centimeter resolution at geosynchronous orbits. Any array capable of producing images on faint and complex geosynchronous objects in just a few hours will be outstanding not only as an astrophysical tool, but also for these types of SSA missions. With the recent infusion of new funding from the Air Force Research Lab (AFRL) in Albuquerque, NM, MROI will be able to attain first light, first fringes, and demonstrate bootstrapping with three telescopes by 2020. MROI’s current status along with a sketch of our activities over the coming 5 years will be presented, as well as clear opportunities to collaborate on various aspects of the facility as it comes online. Further funding is actively being sought to accelerate the capability of the array for interferometric imaging on a short time-scale so as to achieve the original goals of this ambitious facility

Systems engineering applied to ELT instrumentation: the GMACS case

An important tool for the development of the next generation of extremely large telescopes (ELTs) is a robust Systems Engineering (SE) methodology. GMACS is a first-generation multi-object spectrograph that will work at visible wavelengths on the Giant Magellan Telescope (GMT). In this paper, we discuss the application of SE to the design of next-generation instruments for ground-based astronomy and present the ongoing development of SE products for the GMACS spectrograph, currently in its Conceptual Design phase. SE provides the means to assist in the management of complex projects, and in the case of GMACS, to ensure its operational success, maximizing the scientific potential of GMT.

Optical design for the Giant Magellan Telescope Multi-object Astronomical and Cosmological Spectrograph (GMACS): design methodology, issues, and trade-offs

We present the current optical design of GMACS, a multi-object wide field optical spectrograph currently being developed for the Giant Magellan Telescope, a member of the emerging generation of Extremely Large Telescopes (ELTs). Optical spectrographs for ELTs have unique design challenges and issues. For example, the combination of the largest practical field of view and beam widths necessary to achieve the desired spectral resolutions force the design of seeing limited ELT optical spectrographs to include aspheric lenses, broadband dichroics, and volume phase holographic gratings - all necessarily very large. We here outline details of the collimator and camera subsystems, the design methodology and trade-off analyses used to develop the collimator subsystem, the individual and combined subsystem performances and the predicted tolerances.

GMACS: a wide-field, moderate-resolution spectrograph for the Giant Magellan Telescope

We discuss the latest developments of a spectrograph for the Giant Magellan Telescope. The instrument is designed to provide high throughput, moderate resolution, optical spectra for the telescope and be capable of flexible and rapid reconfiguration. The focal plane can be populated with custom slit masks or multiple fibers, allowing for observations of multiple objects simultaneously.

The optomechanical design of the Giant Magellan telescope multi-object astronomical and cosmological spectrograph (GMACS)

We describe the optical design of GMACS, a multi-object wide field optical spectrograph currently being developed for the Giant Magellan Telescope (GMT). Optical spectrographs for the emerging generation of Extreme Large Telescopes (ELTs) have unique design issues. For example, the combination of both the largest field of view practical and beam widths achieving the desired spectral resolutions force the design of seeing limited ELT optical spectrographs to include large refractive elements, which in turn requires a compromise between the optical performance, manufacturability, and operability. We outline the details of the GMACS optical design subsystems, their individual and combined optical performance, and the preliminary flexure tolerances. Updates to the detector specifications, field acquisition/alignment optics, and optical considerations for active flexure control are also discussed. The resulting design meets the technical instrument requirements generated from the GMACS science requirements, is expected to satisfy the available project budget, and has an acceptable level of risk for the subsystem manufacture and assembly.

Electronics prototypes for the Giant Magellan telescope multi-object astronomical and cosmological spectrograph (GMACS)

We describe the current electronics prototypes for the Flexure Compensation System (FCS) and the Slit Mask Exchange Mechanism (SMEM) for GMACS, a wide-field, multi-object, moderate-resolution optical spectrograph for the Giant Magellan Telescope (GMT). We discuss the details of the FCS and SMEM prototypes, how the prototypes relate to the preliminary conceptual designs of these systems, and what information the prototypes give that can be applied to the final design, as well as the possible next steps for each prototype.

Development of TCal: a mobile spectrophotometric calibration unit for astronomical imaging systems

We describe TCal, a mobile spectrophotometric calibration system that will be used to characterize the throughput as a function of wavelength of imaging systems at observatories around the world. TCal measurements will enhance the science return from follow-up observations of imaging surveys such as LSST (Large Synoptic Survey Telescope) and DES (Dark Energy Survey) by placing all tested imaging systems on a common photometric baseline. TCal uses a 1 nm bandpass tunable light source to measure the instrumental response function of imaging systems from 300 nm to 1100 nm, including the telescope, optics, filters, windows, and the detector. The system is comprised of a monochromator-based light source illuminating a dome flat field screen monitored by calibrated photodiodes, which allows determination of the telescope throughput as a function of wavelength. This calibration will be performed at 1-8m telescopes that expect to devote time towards survey follow-up. Performing the calibration on these telescopes will reduce systematic errors due to small differences in bandpass, making follow-up efforts more precise and accurate.

Wide-field multi-object spectroscopy with MANIFEST

MANIFEST is a multi-object fibre facility for the Giant Magellan Telescope that uses ‘Starbug’ robots to accurately position fibre units across the telescope’s focal plane. MANIFEST, when coupled to the telescope’s planned seeinglimited instruments, offers access to larger fields of view; higher multiplex gains; versatile focal plane reformatting of the focal plane via integral-field-units; image-slicers; and in some cases higher spatial and spectral resolution. The TAIPAN instrument on the UK Schmidt Telescope is now close to science verification which will demonstrate the feasibility of the Starbug concept. We are now moving into the conceptual development phase for MANIFEST, with a focus on developing interfaces for the telescope and for the instruments.

Characterization of the reflectivity of various black materials II

We report on an expanded catalog of total and specular reflectance measurements of various common (and uncommon) materials used in the construction and/or baffling of optical systems. Total reflectance is measured over a broad wavelength range (250 nm < λ < 2500 nm) that is applicable to ultraviolet, visible, and near-infrared instrumentation. Characterization of each samples specular reflection was measured using a helium-neon laser in two degree steps from near normal to grazing angles of incidence. The total and specular reflection measurements were then used to derive the specular fraction of each material.