The Wide-Field Infrared Transient Explorer (WINTER) is a new infrared time-domain survey instrument which will be deployed on a dedicated 1 meter robotic telescope at Palomar Observatory. WINTER will perform a seeing-limited time domain survey of the infrared (IR) sky, with a particular emphasis on identifying r-process material in binary neutron star (BNS) merger remnants detected by LIGO. As a dedicated observatory for real-time detection and rapid follow-up of infrared transient events, WINTER represents a new capability for multi-messenger astrophysics. We present the status of the WINTER instrument, including laboratory characterization and initial results from commissioning at its robotic observatory.

The Large Lenslet Array Magellan Spectrograph (LLAMAS) is a facility-class Integral Field Spectrograph slated for commissioning on the 6.5-meter Magellan Baade telescope in Fall 2022. LLAMAS' Integral Field Unit (IFU) contains a 2400-element microlens array which projects pupil images onto corresponding optical fibers for high fill factor and illumination stability. The IFU subtends a 34" x 34" sky area sampled at 0.75" pitch with ~95% fill. The fibers fan out to eight replicated spectrometers. Each spectrometer covers 350-980nm per exposure at R=2200, split over three separately optimized wavelength channels. A set of 24 thermo-electrically cooled COTS CCD cameras records data for each exposure, with heat loads transferred to a dedicated chilled water loop. We provide a status update on LLAMAS' integration and test, which is in advanced stages. Upon commissioning, LLAMAS will be available to all Magellan users, and any US investigator through NOIRLab allocation of NSF/MSIP nights.

Microelectromechanical Systems (MEMS) Deformable Mirrors (DMs) are a key technology option for adaptive optics instruments for space applications because they provide high-precision wavefront control with small formfactor, low-power devices. The Deformable Mirror Demonstration Mission (DeMi) CubeSat demonstrated a MEMS DM in space for the first time in order to raise the Technology Readiness Level (TRL) of the technology for future space applications such as high-contrast imaging of exoplanets and optical communications. The DeMi payload demonstrated a 140-actuator MEMS DM from Boston Micromachines Corporation. DM performance was measured with a Shack Hartmann wavefront sensor (SHWFS). The DeMi CubeSat began onorbit operations in July 2020 and has since met the mission goals of measuring individual actuator displacements to a precision of 12 nm and correcting wavefront errors in space to <100 nm RMS error. The DeMi mission has raised the TRL of MEMS DM technology from a 5 to a 9. This paper summarizes the DeMi payload design and the results from over a year of on-orbit operations. Individual actuator measurements from ground and space operations show the MEMS DM actuating in space with similar performance and measurement uncertainty to ground data with no dead or under-actuating actuators detected. Wavefront control experiments show the DeMi payload correcting thermal- and vibration-induced wavefront errors in space.

We present an update on our work measuring the performance and alignment of the critical-angle transmission (CAT) gratings for the proposed sounding Rocket Experiment Demonstration of a Soft X-ray Polarimeter (REDSoX) mission, as well as a possible orbital version. We built and verified a grating alignment system that could be used for REDSoX Polarimeter fabrication. The performances of the gratings were measured using the MIT polarimetry beamline. The beamline is a monochromator and has been used to measure the absolute efficiencies of not only the REDSoX prototype gratings but also the Arcus Phase A gratings. It is also capable of producing and measuring polarized soft X-rays to aid in the development and testing of future missions. Lastly, we present an update on our effort applying twisted crystals to X-ray polarimetry. Support for this work was provided in part by the NASA grant NNX15AL14G and a grant from the MIT Kavli Institute Research Investment Fund.

Microelectromechanical systems (MEMS) deformable mirrors (DMs) can provide high-precision wavefront control with a small form-factor, low power device. This makes them a key technology option for future space telescopes requiring adaptive optics for high-contrast imaging of exoplanets with a coronagraph instrument. The Deformable Mirror Demonstration Mission (DeMi) CubeSat payload is a miniature space telescope designed to demonstrate MEMS DM technology in space for the first time. The DeMi payload contains a 50-mm primary mirror, an internal calibration laser source, a 140-actuator MEMS DM from Boston Micromachines Corporation, an image plane wavefront sensor, and a Shack–Hartmann wavefront sensor (SHWFS). The key DeMi payload requirements are to measure individual actuator wavefront displacement contributions to a precision of 12 nm and correct both static and dynamic wavefront errors in space to less than 100-nm RMS error. The DeMi mission will raise the technology readiness level of MEMS DM technology from a five to at least a seven for future space telescope applications. We summarize the DeMi optical payload design, calibration, optical diffraction model, alignment, integration, environmental testing, and preliminary data from in-space operations. Ground testing data show that the DeMi SHWFS can measure individual actuator deflections on the MEMS DM to within 10 nm of interferometric calibration measurements and can meet the 12-nm precision mission requirement for actuator deflection voltages between 0 and 120 V. Payload data from throughout environmental testing show that the MEMS DM and DeMi payload survived environmental testing and provides a valuable baseline to compare with space data. Initial data from space operations show the MEMS DM actuating in space with a median agreement between individual actuator measurements from space and equivalent ground testing data of 12 nm.

The Deformable Mirror Demonstration Mission (DeMi) is a 6U CubeSat that will operate and characterize the onorbit performance of a Microelectromechanical Systems (MEMS) deformable mirror (DM) with both an image plane and a Shack-Hartmann wavefront sensor (SHWFS). Coronagraphs on future space telescopes will require precise wavefront control to detect and characterize Earth-like exoplanets. High-actuator count MEMS deformable mirrors can provide wavefront control with low size, weight, and power. The DeMi payload will characterize the on-orbit performance of a 140 actuator MEMS DM with 5.5 μm maximum stroke, with a goal of measuring individual actuator wavefront displacement contributions to a precision of 12 nm. The payload is designed to measure low order aberrations to λ/10 accuracy and λ/50 precision, and correct static and dynamic wavefront phase errors to less than 100 nm RMS. The thermal stability of the payload is key to maintaining the errors below that threshold. To decrease mismatches between coefficients of thermal expansion, the payload structure is made out of a single material, aluminum 7075. The gap between the structural components of the payload was filled with a thermal gap filler to increase the temperature homogeneity of the payload. The fixture that holds the payload into the bus is a set of three titanium flexures, which decrease the thermal conductivity between the bus and the payload while providing flexibility for the payload to expand without being deformed. The mounts for the optical components are attached to the main optical bench through kinematic coupling to allow precision assembly and location repeatability. The MEMS DM is controlled by miniaturized high-voltage driver electronics. Two cross-strapped Raspberry Pi 3 payload computers interface with the DM drive electronics. Each Raspberry Pi is paired to read out one of the wavefront sensor cameras. The DeMi payload is ~4.5U in volume, 2.5 kg in mass, and is flying on a 6U spacecraft built by Blue Canyon Technologies. The satellite launch was on February 15, 2020 onboard a Northrop Grumman Antares rocket, lifting off from the NASA Wallops Flight Facility. We present the mechanical design of the payload, the thermal considerations and decisions taken into the design, the manufacturing process of the flight hardware, and the environmental testing results.

The Large Lenslet Array Magellan Spectrograph (LLAMAS) is an Integral Field Unit (IFU) spectrograph under construction as a facility instrument for the 6.5-meter Magellan Telescopes. For each pointing, LLAMAS delivers 2400 optical spectra (λ =350-970nm) over a 37”x37” celestial solid angle with a resolution of 2000 through a densely packed microlens+fiber array and replicated low-cost spectrographs. One of our main science goals is to study circumgalactic gas through Lyα emission. To achieve the required signal-to-noise ratio for these observations, LLAMAS must minimize stray light reaching the detector: diffuse scattered light must stay below 0.25% of sky flux and ghost images must not exceed 0.1% of the source signal. We present a non-sequential ray tracing analysis of a simplified LLAMAS model using Photon Engineering’s FRED Optical Engineering Software. We focus on stray light resulting from the volume phase holographic grating and from focal ratio degradation of the fibers. The analysis feeds into a discussion of the design and fabrication of baffles to mask the primary sources of stray light. Additionally, we develop a backup system of mounting rings inside of the cameras where pre-made baffles can be quickly added as needed. Finally, we report on the laboratory performance of a 2-camera LLAMAS prototype featuring the aforementioned stray light interventions.

The Large Lenslet Array Magellan Spectrograph (LLAMAS) is an NSF-funded facility-class Integral Field Unit (IFU) spectrograph under construction for the 6.5-meter Magellan Telescopes. It covers a 37" x 37" solid angle with 2,400 optical fibers efficiently coupled by a double-sided microlens-array, producing R = 2, 000 spectra with 0.7511 spatial resolution. Its broad passband from λ = 350 970nm offers access to line and continuum measurements over a wide range in redshift. Light is multiplexed by the IFU into 8 compact, carbon-fiber bench mounted spectrographs utilizing VPH grisms. We employed several trades on cost-performance ratio while optimizing LLAMAS’ system design including: (a) Splitting the passband between 3 fast all-refractive camera systems with modest entrance pupils, (b) limiting the fibers per unit (i.e. slit length) and building more spectrographs to leverage on production volume, and (c) using a commercial CCD camera built around a common detector (e2v 42-40) and thermoelectric + liquid cooling. To boost blue throughput and achieve high-quality sky subtraction the spectrograph cluster is mounted next to the focal plane on a folded Cassegrain port with gravity-invariant support. This also allows the instrument to deploy quickly, and be fully accessible within 10 minutes on any night, serving as a facility unit for observing astrophysical transients. A sub-sized IFU (169 fibers), mounted in a full-sized front end package with a single spectrograph (2 cameras) was delivered to Magellan in March 2020. We present as-measured laboratory performance from this prototype, though on-sky commissioning was unfortunately cancelled because of the COVID-19 pandemic. This contribution therefore focuses on subsequent design evolution and status of the full facility instrument.

The Wide-Field Infrared Transient Explorer (WINTER) is a new infrared time-domain survey instrument on a dedicated 1 meter robotic telescope at the Palomar Observatory. WINTER will perform the first seeing-limited time domain survey of the infrared (IR) sky, with a particular emphasis on identifying r-process material in binary neutron star (BNS) merger remnants detected by LIGO. We have developed and tested a custom optomechanical mounting scheme for a 6-channel tiled optical system with >90% fill factor. Here, we present the mechanical design and testing approach used in the development of WINTER.

The Wide-Field Infrared Transient Explorer (WINTER) is a new infrared time-domain survey instrument which will be deployed on a dedicated 1 meter robotic telescope at the Palomar Observatory. WINTER will perform a seeing-limited time domain survey of the infrared (IR) sky, with a particular emphasis on identifying r -process material in binary neutron star (BNS) merger remnants detected by LIGO. We describe the scientific goals and survey design of the WINTER instrument. With a dedicated trigger and the ability to map the full LIGO O4 positional error contour in the IR to a distance of 190 Mpc within four hours, WINTER will be a powerful kilonova discovery engine and tool for multi-messenger astrophysics investigations. In addition to follow-up observations of merging binaries, WINTER will facilitate a wide range of time-domain astronomical observations, all the while building up a deep coadded image of the static infrared sky suitable for survey science. WINTER's custom camera features six commercial large-format Indium Gallium Arsenide (InGaAs) sensors and a tiled optical system which covers a <1-square-degree field of view with 90% fill factor. The instrument observes in Y, J and a short-H (Hs) band tuned to the long-wave cutoff of the InGaAs sensors, covering a wavelength range from 0.9 – 1.7 microns. We present the design of the WINTER instrument and current progress towards final integration at the Palomar Observatory and commissioning planned for mid-2021.

The Deformable Mirror Demonstration Mission (DeMi) is a 6U CubeSat that will characterize the on-orbit performance of a Microelectromechanical Systems (MEMS) deformable mirror (DM) with both an image plane wavefront sensor and a Shack-Hartmann wavefront sensor (SHWFS). Coronagraphs on future space telescopes will require precise wavefront control to detect and characterize Earth-like exoplanets. High-actuator count MEMS deformable mirrors can provide wavefront control with low size, weight, and power. The DeMi payload will characterize the on-orbit performance of a 140 actuator MEMS Deformable Mirror (DM) with 5.5 mu m maximum stroke, with a goal of measuring individual actuator wavefront displacement contributions to a precision of 12 nm. The payload will be able to measure low order aberrations to lambda/10 accuracy and lambda/50 precision, and will correct static and dynamic wavefront phase errors to less than 100 nm RMS. We present an overview of the payload design, the assembly, integration, and test process, and report on the development and validation of an optical diffraction model of the payload. Launch is planned for late 2019.

Micro-Electro-Mechanical Systems (MEMS) Deformable Mirrors (DMs) enable precise wavefront control for optical systems. This technology can be used to meet the extreme wavefront control requirements for high contrast imaging of exoplanets with coronagraph instruments. MEMS DM technology is being demonstrated and developed in preparation for future exoplanet high contrast imaging space telescopes, including the Wide Field Infrared Survey Telescope (WFIRST) mission which supported the development of a 2040 actuator MEMS DM. In this paper, we discuss ground testing results and several projects which demonstrate the operation of MEMS DMs in the space environment. The missions include the Planet Imaging Concept Testbed Using a Recoverable Experiment (PICTURE) sounding rocket (launched 2011), the Planet Imaging Coronagraphic Technology Using a Reconfigurable Experimental Base (PICTURE-B) sounding rocket (launched 2015), the Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph (PICTURE-C) high altitude balloon (expected launch 2019), the High Contrast Imaging Balloon System (HiCIBaS) high altitude balloon (launched 2018), and the Deformable Mirror Demonstration Mission (DeMi) CubeSat mission (expected launch late 2019). We summarize results from the previously flown missions and objectives for the missions that are next on the pad. PICTURE had technical difficulties with the sounding rocket telemetry system. PICTURE-B demonstrated functionality at >100 km altitude after the payload experienced 12-g RMS (Vehicle Level 2) test and sounding rocket launch loads. The PICTURE-C balloon aims to demonstrate 10 - 7 contrast using a vector vortex coronagraph, image plane wavefront sensor, and a 952 actuator MEMS DM. The HiClBaS flight experienced a DM cabling issue, but the 37-segment hexagonal piston-tip-tilt DM is operational post-flight. The DeMi mission aims to demonstrate wavefront control to a precision of less than 100 nm RMS in space with a 140 actuator MEMS DM.

We present the performance and recent results of the MIT polarimetry beamline. Originally designed for testing Chandra HETG gratings, the beamline has been adapted to test components for soft x-ray polarimetry applications. Since then, its monochromator capabilities have also been used to test gratings. We present results on the measured absolute efficiencies of the Arcus Phase A gratings using the B-K, O-K, and C-K emission lines. The beamline has also been used to develop tools and techniques to measure the linear polarization of soft X-rays (0.2-0.8 keV), which form the basis for a sounding rocket mission REDSoX (Rocket Experiment Demonstration of a Soft X-ray Polarimeter) and a possible orbital mission. We present our tests to align the REDSoX gratings, as well as our idea to use thin twisted crystals as a possible alternative to laterally-graded multilayer mirrors. Support for this work was provided in part by the NASA grant NNX15AL14G and a grant from the MIT Kavli Institute.

Coronagraphs on future space telescopes will require precise wavefront correction to detect Earth-like exoplanets near their host stars. High-actuator count microelectromechanical system (MEMS) deformable mirrors provide wavefront control with low size, weight, and power. The Deformable Mirror Demonstration Mission (DeMi) payload will demonstrate a 140 actuator MEMS Deformable Mirror (DM) with 5:5 μm maximum stroke. We present the flight optomechanical design, lab tests of the flight wavefront sensor and wavefront reconstructor, and simulations of closed-loop control of wavefront aberrations. We also present the compact flight DM controller, capable of driving up to 192 actuator channels at 0-250V with 14-bit resolution. Two embedded Raspberry Pi 3 compute modules are used for task management and wavefront reconstruction. The spacecraft is a 6U CubeSat (30 cm x 20 cm x 10 cm) and launch is planned for 2019.

The Giant Magellan Telescope (GMT) M1 Subsystem includesthe seven 8.4 meter M1 (Primary) Segment Mirrors and the steel mirror cell weldments which house the mirror active support and thermal control systems. The segmented nature of the primary mirror and the requirement that each of the six off-axis segment cells be interchangeable impose requirements on the range of motion and control beyond those applicable to the M1 subsystems on 6.5m and 8.4m telescopes using the structured honeycomb mirrors.The subsystem is both technically challenging to design and costly to produce. The M1 Subsystem is allocated a large fraction of the GMT natural seeing image quality budget. Support actuator tolerances, range of motion, accuracy, and precision, as well as the ability of the thermal control system to regulate the primary mirror temperature, all have a significant effect on the image quality. The authors have developed several linear models to estimate the effect of force and moment errors at the M1 Segment Active Supports and the non-uniformity of temperature across M1 segments on the delivered image quality. These results are coupled to the Wavefront Control Subsystem model and are integrated into the GMT system-level simulations to produce a final image quality budget and to quantify the effectiveness of the Wavefront Control Subsystem to compensate for M1 Subsystem error. In this paper, we present the modeling process and preliminary performance results obtained using the models.

X-ray polarimetry offers a new window into the high-energy universe, yet there has been no instrument so far that could measure the polarization of soft X-rays (about 17-80 Å) from astrophysical sources. The Rocket Experiment Demonstration of a Soft X-ray Polarimeter (REDSoX Polarimeter) is a proposed sounding rocket experiment that uses a focusing optic and splits the beam into three channels. Each channel has a set of criticalangle transmission (CAT) gratings that disperse the x-rays onto a laterally graded multilayer (LGML) mirror, which preferentially reflects photons with a specific polarization angle. The three channels are oriented at 120 deg to each other and thus measure the three Stokes parameters: I, Q, and U. The period of the LGML changes with position. The main design challenge is to arrange the gratings so that they disperse the spectrum in such a way that all rays are dispersed onto the position on the multi-layer mirror where they satisfy the local Bragg condition despite arriving on the mirror at different angles due to the converging beam from the focusing optics. We present a polarimeteric Monte-Carlo ray-trace of this design to assess non-ideal effects from e.g. mirror scattering or the finite size of the grating facets. With mirror properties both simulated and measured in the lab for LGML mirrors of 80-200 layers we show that the reflectivity and the width of the Bragg-peak are sufficient to make this design work when non-ideal effects are included in the simulation. Our simulations give us an effective area curve, the modulation factor and the figure of merit for the REDSoX polarimeter. As an example, we simulate an observation of Mk 421 and show that we could easily detect a 20% linear polarization.

The Rocket Experiment Demonstration of a Soft X-ray Polarimeter (REDSoX Polarimeter) is a sounding rocket instrument that can make the first measurement of the linear X-ray polarization of an extragalactic source in the 0.2-0.8 keV band as low as 10%. We employ multilayer-coated mirrors as Bragg reflectors at the Brewster angle. By matching the dispersion of a spectrometer using replicated optics from MSFC and critical angle transmission gratings from MIT to three laterally graded multilayer mirrors (LGMLs), we achieve polarization modulation factors over 90%. We present a novel arrangement of gratings, designed optimally for the purpose of polarimetry with a converging beam. The entrance aperture is divided into six equal sectors; pairs of blazed gratings from opposite sectors are oriented to disperse to the same LGML. The LGML position angles are 120 degrees to each other. CCD detectors then measure the intensities of the dispersed spectra after reflection and polarizing by the LGMLs, giving the three Stokes parameters needed to determine a source’s linear polarization fraction and orientation. A current grant is funding further development to improve the LGMLs. Sample gratings for the project have been fabricated at MIT and the development team continues to improve them under separate funding. Our technological approach is the basis for a possible orbital mission

During 2014 and 2015, NASA's Neutron star Interior Composition Explorer (NICER) mission proceeded success- fully through Phase C, Design and Development. An X-ray (0.2-12 keV) astrophysics payload destined for the International Space Station, NICER is manifested for launch in early 2017 on the Commercial Resupply Services SpaceX-11 flight. Its scientific objectives are to investigate the internal structure, dynamics, and energetics of neutron stars, the densest objects in the universe. During Phase C, flight components including optics, detectors, the optical bench, pointing actuators, electronics, and others were subjected to environmental testing and integrated to form the flight payload. A custom-built facility was used to co-align and integrate the X-ray "con- centrator" optics and silicon-drift detectors. Ground calibration provided robust performance measures of the optical (at NASA's Goddard Space Flight Center) and detector (at the Massachusetts Institute of Technology) subsystems, while comprehensive functional tests prior to payload-level environmental testing met all instrument performance requirements. We describe here the implementation of NICER's major subsystems, summarize their performance and calibration, and outline the component-level testing that was successfully applied.

We present a simple seeing-limited IR spectrometer design for the Giant Magellan Telescope, with continuous R = 6000 coverage from 0.87-2.50 microns for a 0:7” slit. The instrument's design is based on an asymmetric white pupil echelle layout, with dichroics splitting the optical train into yJ, H, and K channels after the pupil transfer mirror. A separate low-dispersion mode offers single-object R ~ 850 spectra which also cover the full NIR bandpass in each exposure. Catalog gratings and H2RG detectors are used to minimize cost, and only two cryogenic rotary mechanisms are employed, reducing mechanical complexity. The instrument dewar occupies an envelope of 1:8×1:5×1:2 meters, satisfying mass and volume requirements for GMT with comfortable margin. We estimate the system throughput at ~ 35% including losses from the atmosphere, telescope, and instrument (i.e. all coatings, gratings, and sensors). This optical efficiency is comparable to the FIRE spectrograph on Magellan, and we have specified and designed fast cameras so the GMT instrument will have an almost identical pixel scale as FIRE. On the 6.5 meter Magellan telescopes, FIRE is read-noise limited in the y and J bands, similar to other existing near-IR spectrometers and also to JWST/NIRSPEC. GMT's twelve-fold increase in collecting area will therefore offer gains in signal-to-noise per exposure that exceed those of moderate resolution optical instruments, which are already sky-noise limited on today's telescopes. Such an instrument would allow GMT to pursue key early science programs on the Epoch of Reionization, galaxy formation, transient astronomy, and obscured star formation environments prior to commissioning of its adaptive optics system. This design study demonstrates the feasibility of developing relatively affordable spectrometers at the ELT scale, in response to the pressures of joint funding for these telescopes and their associated instrument suites.