The Nancy Grace Roman Space Telescope project is NASA's next flagship a strophysics mission t o s tudy dark energy, dark matter, and exoplanets along with the innumerable topics that will be enabled by the infrared survey telescope's Wide Field Instrument and Coronagraph Instrument. The Wide Field Instrument contains a focal plane of 18 newly developed Teledyne H4RG-10 HgCdTe detectors. The focal plane along with Roman's ASIC for Control And Digitization of Imagers for Astronomy (ACADIA) and the focal plane electronics that power them comprise the focal plane system. Roman's focal plane completed its first s ystem l evel thermal vacuum test at NASA Goddard in 2022, when an increase in dark current compared to component level testing was observed for several detectors. Roman chartered an anomaly review board (ARB) and in collaboration with Teledyne undertook a testing program to help identify possible root cause and select from Roman's spare inventory suitable replacement detectors for devices that had significantly d egraded. A p ossible root c ause was determined by the ARB along with recommendations for how to prevent further degradation. Three detectors were replaced in Roman's focal plane, and results from the following focal plane system thermal vacuum test, implementing recommendations from the ARB, demonstrate improved dark current performance. We summarize the initial observation of the detector anomaly, present the detector testing strategy to find s uitable spares and provide evidence of root cause, share the general findings of the ARB, and show new data showing the improved dark current performance.

Next-Generation Microshutter Arrays (NGMSA) are customizable multi-aperture spectrograph slit masks manufactured by Goddard Spaceflight Center (GSFC) that have an advanced pure electrical actuation and latching mode, which is considerably more robust than the scanning magnetic actuation and electric latching method used by the first generation MSA devices on JWST’s NIRSpec. These first-generation devices were found to have an average open-to-closed contrast ratio of approximately 66,000 at visible and near-infrared wavelengths (Kutyrev et al. 2008). NGMSA have been baselined in the multi-object UV spectroscopic designs for Habitable Worlds Observatory (HWO) and other Explorer missions. Consequently, the near-UV contrast of these devices as a function of input focal ratio is of great interest. Here we present an update to the contrast evaluation apparatus first reported in Carter et al. (2021), but with an improved doublet projection and imaging optical train. Overall spherical aberration is considerably reduced, and the analysis of a prototype flight array yields significantly higher contrast than found in that initial work, emphasizing the need for high quality projection and imaging optics for precise contrast measurements. There is a clear monotonically increasing relationship between contrast and f/#. At ratios slower than f/15 we find single slit contrast ratios in excess of 100,000 using Hg emission line source at 1849 and 2537 Å and with a narrowband filtered continuum D2 lamp at 3004 Å. The contrast using a 2214 Å filter with the D2 lamp was somewhat lower (⪆ 60,000) but may have contributions from chromatic aberration in the quartz optics and out-of-band leakage in the interference filters. Requirements for enabling the measurement of NGMSA contrast in the vacuum ultraviolet below approximately 1800 Å are addressed.

We report the latest design, fabrication, and characterization results of the Next-Generation Microshutter Arrays (NGMSA) for space borne observatory applications. Our modified blade design aims to improve overall actuation torque by reducing the electrostatic force between free end of the shutter blade and the adjacent silicon frame, which generates counter torque at intermediate travel range, thus enables pure electrostatic actuation for more reliable and stable microshutter operations. This paper presents the experimental performance results of newly fabricated microshutter arrays with varying design parameters and compares the results with simulation predictions.

The Next Generation Microshutter Array (NGMSA) is an all-electrostatic actuated, programmable light transmission device used for multi-object spectroscopy. The latest NGMSA is designed to operate by applying a voltage difference between the shutter blade electrode and a single back wall electrode. We investigate the effects of different wall electrode configurations and present a bi-electrode design that allows reliable shutter actuation at a voltage difference of 70V.

NASA's Great Observatories have opened up the electromagnetic spectrum from space, providing sustained access to wavelengths not accessible from the ground. Together, Hubble, Compton, Chandra, and Spitzer have provided the scientific community with an agile and powerful suite of telescopes with which to attack broad scientific questions, and react to a rapidly changing scientific landscape. As the existing Great Observatories age, or are decommissioned, community access to these wavelengths will diminish, with an accompanying loss of scientific capability. This report, commissioned by the NASA Cosmic Origins, Physics of the Cosmos and Exoplanet Exploration Program Analysis Groups (PAGs), analyzes the importance of multi-wavelength observations from space during the epoch of the Great Observatories, providing examples that span a broad range of astrophysical investigations.

We are developing a 2D programmable field masks for Mutli-Object Spectroscopy (MOS) in sparsely populated fields. The device is based on the microshutter array MEMS technology originally developed for JWST NIRSpec. A new fabrication process has been developed to actuate microshutter arrays electrostatically thus eliminating the need for the macroscopic mechanisms and improving the reliability and robustness of the device. The microshutters, made with silicon nitride membranes with a shutter pitch size of 100 μm x 200 μm, rotate on narrow torsion bars. The microshutters are actuated, latched, and addressed electrostatically by applying voltages to the electrodes on the microshutters and the adjacent walls of the array support grid. We have demonstrated the fabrication and operation of the pilot arrays and produced an integrated flight unit that was successfully used on the FORTIS (Far-UV Off Rowland-circle Telescope for Imaging and Spectroscopy) project for suborbital flight in 2019.

Excess heat capacity in a bolometric detector has the consequence of increasing or leading to multiple device time constants. The Mo/Au bilayer transition edge sensor (TES) bolometric detectors initially fabricated for the high resolution mid-infrared spectrometer (HIRMES) exhibited two response thermalization scales, one of which is a few times longer than estimates based upon the properties of the bulk materials employed in the design. The relative contribution of this settling time to the overall time response of the detectors is roughly proportional to the pixel area, which ranges between ~0.3 and 2.6 mm2. Use of laser ablation to remove sections of the silicon membranes comprising the pixels results in a detector response with a smaller contribution from the secondary time constant. Additional information about the nature of this excess heat capacity is gleaned from glancing incidence x-ray diffraction, which reveals the presence of molybdenum silicides near the silicon surface which is a consequence of the bi-layer deposition. Quantitative analysis of the concentration of excess molybdenum, estimated with secondary ion mass spectroscopy, is commensurate to the additional heat capacity needed to explain the anomalous time response of the detectors.

Next Generation Microshutter Array (NGMSA) is an electrostatically operated micro electro-mechanical system (MEMS) device for programmable spatial light filtering application. Original microshutter array (MSA), which is magnetically operated, was developed for the James Webb Space Telescope (JWST) NIRSpec multi-object spectrometer, and NGMSA inherited its design from the original MSA. Even though there has been incremental design changes in order to achieve stable electrostatic actuation, NGMSA operation still requires further study. Previous simulation efforts to model NGMSA’s actuation mechanics allowed to gain only general understanding of the behavior due to inadequate simulation and experimental methods. In this study, a novel electrostatic numerical simulation model is presented using COMSOL Multiphysics to accurately predict microshutter’s motion during actuation. The new model addresses all the issues that hinder realistic modeling. Current Microshutter Array yield and operation performance issues related to fabrication process are analyzed with this numerical model and a potential optimized design is proposed. The result shows that a few μ m shorter shutter blade allows stable electrostatic actuation as well as better tolerance to the fabrication accuracy. Also, modified blade side shape reduces undesirable asymmetrical motions which cause failed stuck shutters.

Microshutter arrays are powerful tools enabling simultaneous spectroscopy of multiple objects within a single, crowded field-of-view. This technology is currently employed on the James Webb Space Telescope, and next-generation arrays are being proposed for future flagship missions such as LUVOIR and HabEx. For these future large missions, it is important to fully characterize the performance of the next-generation microshutter arrays in the lab, particularly in the ultraviolet range not probed with JWST. To this end, we have developed a laboratory testbed to measure the contrast between opened and closed shutters achievable with these devices.

Launching a starshade to rendezvous with the Nancy Grace Roman Space Telescope would provide the first opportunity to directly image the habitable zones of nearby sunlike stars in the coming decade. A report on the science and feasibility of such a mission was recently submitted to NASA as a probe study concept. The driving objective of the concept is to determine whether Earth-like exoplanets exist in the habitable zones of the nearest sunlike stars and have biosignature gases in their atmospheres. With the sensitivity provided by this telescope, it is possible to measure the brightness of zodiacal dust disks around the nearest sunlike stars and establish how their population compares to our own. In addition, known gas-giant exoplanets can be targeted to measure their atmospheric metallicity and thereby determine if the correlation with planet mass follows the trend observed in the Solar System and hinted at by exoplanet transit spectroscopy data. In this paper we provide the details of the calculations used to estimate the sensitivity of Roman with a starshade and describe the publicly available Python-based source code used to make these calculations. Given the fixed capability of Roman and the constrained observing windows inherent for the starshade, we calculate the sensitivity of the combined observatory to detect these three types of targets and we present an overall observing strategy that enables us to achieve these objectives.

The addition of an external starshade to the Nancy Grace Roman Space Telescope will enable the direct imaging of Earth-radius planets orbiting at ∼1 AU. Classification of any detected planets as Earth-like requires both spectroscopy to characterize their atmospheres and multi-epoch imaging to trace their orbits. We consider here the ability of the Starshade Rendezvous Probe to constrain the orbits of directly imaged Earth-like planets. The target list for this proposed mission consists of the 16 nearby stars best suited for direct imaging, around which ∼10 to 15 planets are expected to be discovered. Of these planets, ∼1 to 2 will be Earth-like in mass and temperature. The field of regard for the starshade mission is constrained by solar exclusion angles, resulting in four observing windows during a two-year mission. We find that for Earth-like planets that are detected at least three times during the four viewing opportunities, their semi-major axes are measured with a median precision of 7 mas, or a median fractional precision of 3%. Habitable-zone planets can be correctly identified as such 96.7% of the time, with a false positive rate of 2.8%. If a more conservative criteria are used for habitable-zone classification (95% probability), the false positive rate drops close to zero, but with only 81% of the truly Earth-like planets correctly classified as residing in the habitable zone.

We are presenting the result of the microshutter arrays for multi-object spectroscopy. Microshutter arrays are MEMS technology devices that are 2D programmable field masks for object selection in the sparsely populated fields. This next generation microshutters are based on the first generation of the microshutter arrays developed for the James Webb Space Telescope Near-Infrared Spectrometer (JWST NIRSpec) we developed new fabrication process that allowed to build fully electrostatic microshutter arrays. The microshutter arrays based on this new development have been successfully demonstrated in the FORTIS project sounding rocket flight. We are currently in the process of expanding the fabrication process to large format microshutter arrays designed for the use on the future NASA flagship missions such as HabEx and LUVOIR.

We present the first space flight use of the electrostatically actuated Next Generation MicroShutter Array systems (NGMSA) as multiple celestial object selectors developed for NASA space telescope missions at the NASA Goddard Space Flight Center. The NGMSA assembly was installed in the Next Generation Far-ultraviolet Off Rowland-circle Telescope for Imaging and Spectroscopy (NG-FORTIS) and successfully launched recently from the White Sands Missile Range in October 2019. We started to investigate this electrostatic NGMSA technology at the late stages of James Webb Space Telescope (JWST) in 2009 to strategically align with requirements of larger field of view for future telescopes in space. The NGMSA in NG-FORTIS is a 128 X 64 programable 2-D addressing microfabricated shutter array while the current NGMSA system under development is a 736 X 384 large format. The new microshutter array (MSA) features several unique designs aiming at performance improvements: electrostatic actuation, thinned microshutters, better electrical wall insulation and anti-stiction surface coating. To ensure reliable operation in the space environment, NGMSA systems have passed a series of critical environment tests including acoustic, random vibration, life cycle of operation, thermal cycling, and optical contrast tests. The successful launch of the NG-FORTIS sounding rocket equipped with NGMSA demonstrates our NGMSA technology have achieved the highest NASA Technical Readiness Level 9 for sounding rocket space applications.

HIRMES, SOFIA’s third generation science instrument, delivers spectroscopy at wavelengths between 25 and 122 um and resolving powers (RP) between 600 and 100,000. The detectors arrays are background-limited transition edge sensed bolometers. Here we focus on the development, testing, and performance of the series of 8 tunable cryogenic scanning Fabry-Perot interferometers (FPI) that deliver the imaging (RP = 2000), and the long-slit medium resolution (RP = 10,000) and high resolution (RP = 100,000) spectroscopic modes. The FPIs use free-standing metal meshes mirrors, flexible parallelogram translations stages, PZTs and/or cryomoters for displacement. and capacitive sensors for displacement measure.

After developing a magnetically actuated microshutter array sub-system, which acts as a field object selector for the James Webb Space Telescope (JWST), our team at the NASA Goddard Space Flight Center (GSFC) focused on the development of electrostatically actuated microshutter arrays – the Next Generation Microshutter Arrays (NGMSA). This letter describes the first NGMSA array that performed shutter operations for telescope imaging and spectroscopy in space. The carrier telescope, the Next-Generation Far-UV Off Rowland-circle Telescope for Imaging and Spectroscopy (NG-FORTIS) was produced by Prof. Stephan McCandliss and his team at Johns Hopkins University and launched into space successfully. [2020-0226]

The case for space-based telescopic direct imaging in reflected light to spectroscopically characterize planets around Sun-like stars is well established. A starshade as an external occulter has been shown to allow this capability. We present a novel concept for a cost-effective in-space assembled starshade to enable direct imaging spectroscopy.

The Starshade Rendezvous Probe Mission (https://smd-prod.s3.amazonaws.com/science-red/s3fs-public/atoms/files/Starshade2.pdf ) [1] will be the first space-based, high-contrast imaging mission with the potential to detect and characterize Earth-like planets in the habitable zone (HZ) around sunlike stars while at the same time exploring entire planetary systems about our nearest neighbors. Over the last two decades, astronomers have discovered and cataloged thousands of planets around other stars. Nevertheless, we have yet to find a planetary system like our own or to characterize discovered small planets to determine if they are similar to Earth. The next step in exploration is to image full planetary systems, including their HZs, and to obtain planetary spectra with enough sensitivity to determine if a planet is Earth-like. A space-based direct imaging mission to ultimately find and characterize other Earth-like planets is a long-term priority for space astrophysics [2, 3].

Micro shutter array (MSA) is a programmable optical spatial filtering device fabricated by MEMS technology, which was originally developed for James Webb Space Telescope to enable multi-object spectroscopy. Next Generation Micro Shutter Array (NGMSA) is an effort to improve JWST MSA by eliminating macroscopic actuation magnet and using electrostatic force to achieve simple and reliable instrument that can support NASA’s multiple future missions. We have been fabricating NGMSA with design inherited from JWST, however the legacy design is not friendly for electrostatic actuation because applied force direction on the moving shutter blade is different. We use COMSOL AC/DC module’s electrostatics feature to understand electrostatic force applied on an individual shutter within a range of motion and study new candidate designs. Also, structural mechanics module is used to study torsion bar’s restoration force.

The purpose of this white paper is to summarize the current landscape of astrophotonic devices and their scientific impact, highlight the key issues, and outline specific technological and organizational approaches to address these issues in the coming decade and thereby enable new discoveries as we embark on the era of extremely large telescopes.