The James Webb Space Telescope instrument suite layout: optical system engineering considerations for a large deployable space telescope

Microshutter array (MSA) subsystems were developed at NASA Goddard Space Flight Center as multiobject selectors for the Near-Infrared Spectrograph (NIRSpec) instrument on the James Webb Space Telescope (JWST). The subsystem will enable NIRSpec to simultaneously obtain spectra from >100 targets, which, in turn, increases instrument efficiency 100-fold. This system represents one of the three major innovations on the JWST that is scheduled to be launched in 2018 as the successor to the Hubble Space Telescope. Featuring torsion hinges, light shields, magnetic actuation, and electrostatic latching and addressing, microshutters are designed for the selective transmission of light with high efficiency and contrast. Complete MSA assemblies consisting of 365×171 microshutters were successfully fabricated and tested, and passed a series of critical reviews for programmable 2-D addressing, life tests, and optical contrast tests. At the final stage of the JWST MSA fabrication, we began to develop the next generation microshutter arrays (NGMSA) for future telescopes. These telescopes will require a much larger field of view than JWSTs. We discussed strategies for fabrication of a proof-of-concept NGMSA that will be modular in design and electrostatically actuated. The details of NGMSA development will be discussed in a follow-up paper.

NASA's James Webb Space Telescope (JWST) is a 6.6m diameter, segmented, deployable telescope for cryogenic IR space astronomy. The JWST Observatory architecture includes the Optical Telescope Element (OTE) and the Integrated Science Instrument Module (ISIM) element which contains four science instruments (SI), including a guider. The SIs and guider are mounted to a composite metering structure with outer envelope approximate measurements of 2.2x2.2x1.7m. These SI units are integrated to the ISIM structure and optically tested at NASA Goddard Space Flight Center as an instrument suite using an Optical telescope element SIMulator (OSIM). OSIM is a high-fidelity, cryogenic JWST simulator that features a ~1.5m diameter powered mirror. The SIs are aligned to the flight structure's coordinate system under ambient, clean room conditions using opto-mechanical metrology and customized interfaces. OSIM is aligned to the ISIM mechanical coordinate system at the cryogenic operating temperature via internal mechanisms and feedback from alignment sensors and metrology in six degrees of freedom. SI performance, including focus, pupil shear, pupil roll, boresight, wavefront error, and image quality, is evaluated at the operating temperature using OSIM. This work reports on the as-run ambient assembly and ambient alignment steps for the flight ISIM, including SI interface fixtures and customization and kinematic mount adjustment. The ISIM alignment plan consists of multiple steps to meet the "absolute" alignment requirements of the SIs and OSIM to the flight coordinate system. In this paper, we focus on key aspects of absolute, optical-mechanical alignment. We discuss various metrology and alignment techniques. In addition, we summarize our approach for dealing with and the results of ground-test factors, such as gravity.

The James Webb Space Telescope (JWST) is a large, infrared-optimized space telescope consisting of the following elements: (1) Optical telescope element (OTE) (2) Integrated science instrument module (ISIM) (3) Spacecraft (4) Sunshield The Integrated Science Instrument Module (ISIM) consists of the JWST science instruments (NIRCam, MIRI, NIRSpec), a fine guidance sensor (FGS), the ISIM Structure, and thermal and electrical subsystems. JWST's instruments are designed to work primarily in the infrared range of the electromagnetic spectrum, and the instruments and telescope operate at cryogenic temperatures (approximately 35 K for the instruments). The development and validation of a thermal distortion modeling and analysis capability for the JWST ISIM Structure was successfully completed. The modeling and analysis approach was grounded in initial constituent materials testing and benchmarked to test results at the composite bonded joint, subassembly, and fullscale flight hardware levels. Comparison of analysis predictions and test results from this series of incremental cryogenic thermal distortion tests demonstrates that the model validation goals are achieved.

We present an overview of the James Webb Space Telescope (JWST) Advanced Deep Extragalactic Survey (JADES), an ambitious program of infrared imaging and spectroscopy in the GOODS-S and GOODS-N deep fields, designed to study galaxy evolution from high redshift to cosmic noon. JADES uses about 770 hr of Cycle 1 guaranteed time largely from the Near-Infrared Camera (NIRCam) and Near-Infrared Spectrograph (NIRSpec) instrument teams. In GOODS-S, in and around the Hubble Ultra Deep Field and Chandra Deep Field South, JADES produces a deep imaging region of ∼42 arcmin 2 with over 100 hr of exposure time spread over nine NIRCam filters, including two medium-band filters. This is extended at medium depth in GOODS-S and GOODS-N with NIRCam imaging of ∼167 arcmin 2 , averaging 25 hr of exposure over 8–10 filters. In both fields, we conduct extensive NIRSpec multiobject spectroscopy, including two deep pointings of 55 hr exposure time, 14 medium pointings of ∼12 hr, and 15 shallower pointings of ∼4 hr, targeting over 5000 Hubble Space Telescope– and JWST-detected faint sources with five low-, medium-, and high-resolution dispersers covering 0.6–5.3 μ m. Finally, JADES extends redward via coordinated parallels with the JWST Mid-Infrared Instrument, featuring ∼10 arcmin 2 with 43 hr of exposure at 7.7 μ m and thrice that area with 1.4–6.8 hr of exposure at 12.8 and 15 μ m. For nearly 30 yr, the GOODS-S and GOODS-N fields have been developed as the premier deep fields on the sky; JADES is now providing a compelling start on JWST's legacy in these fields.

The Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) is one of the four science instruments to be installed into the Integrated Science Instrument Module (ISIM) on JWST. NIRCam's requirements include operation at 37 Kelvin to produce high-resolution images in two wave bands encompassing the range from 0.6 microns to 5 microns. In addition, NIRCam is to be used as a metrology instrument during the JWST observatory commissioning on orbit, during the precise alignment of the observatory's multiple-segment primary mirror. This paper will present the optical analyses performed in the development of the NIRCam optical system. The Compound Reflectance concept to specify coating on optics for ghost image reduction is introduced in this paper.

One of the key components for James Webb Space Telescope (JWST) to meet its science goals is the second Lagrange point (L2) environment. This 'operationally friendly' environment provides JWST a dark, cold, and stable orbit to view the first starlight of the Universe. The environment assists the science instruments with passive cooling, limited stray light, and large contact times with Earth to increase the efficiency of the JWST. Now that JWST is moving into the design/construction phase, we are finding that the initial concepts now require a more detailed examination. We are finding that L2 has some issues that impact cost and operational friendliness. This paper will address some of these L2 environment challenges currently being reviewed: cosmic ray environment, communications, and orbit maintenance and determination. To address the above L2 environment concerns, the JWST spacecraft and science planning system requires adjustment to the onboard 'event driven' planning. As the spacecraft buildup continues, the challenges of communicating from L2 will be met so that JWST will see the first starlight in the Universe. The communication items will be covered in other papers during this conference.

The Near Infrared Camera (NIRCam) for NASA's James Webb Space Telescope (JWST) is one of the four science instruments installed into the Integrated Science Instrument Module (ISIM) on JWST intended to conduct scientific observations over a five year mission lifetime. NIRCam's requirements include operation at 32 to 37 K to produce high resolution images in two wave bands encompassing the range from λ = 0.6 to 5.0 microns. In addition NIRCam is used as a metrology instrument for the JWST observatory, providing critical data for alignment of the observatory's multiple-segment 6.3 meter primary mirror. JWST is scheduled for launch and deployment in 2012. This paper is an overview of the NIRCam instrument's optical hardware and performance. Detailed discussions of specific subassemblies will be presented in other papers in the same conference.

The next generation of large space telescopes, including ATLAST, SAFIR, IXO and Generation-X will require the development of key technologies to enable their development at an affordable cost. This includes technologies for the rapid, low cost fabrication of ultra-light weight primary mirror segments, active figure control of primary mirror segments, high speed wavefront sensing and control, highly-packageable and scalable deployment techniques, and active vibration and thermal control for light weight structural elements to supply good pointing stability. In this paper we discuss the current state-of-the-art for these technologies and roadmaps for future development in these areas.

From its orbit around the Earth-Sun second Lagrange point some million miles from Earth, the James Webb Space Telescope (JWST) will be uniquely suited to study early galaxy and star formation with its suite of infrared instruments. To maintain exceptional image quality using its 6.6 meter segmented primary mirror, wavefront sensing and control (WFS&C) is vital to ensure the optical alignment of the telescope throughout the mission. WFS&C design architecture includes using the Near-Infrared Camera (NIRCam) to provide imagery for ground-resident image processing algorithms which determine the optimal alignment of the telescope. There are two distinct mission phases for WFS&C, both of which use algorithms and NIRCam imagery to determine the required segment updates. For the first phase, WFS&C commissioning, the telescope is taken from its initial deployed state with each of the 18 primary mirror segments acting like independent telescopes, to its final phased state with each segment acting in concert as a part of a single mirror. The second phase, Wavefront Monitoring and Maintenance, continues for the rest of the mission. Here the wavefront quality is evaluated, and when needed, the mirror positions are updated to bring it back to an optimal configuration. This paper discusses the concept of operations for the commissioning and on-going maintenance of the telescope alignment using WFS&C.

We have repeated some of our previous measurements of the intra-pixel response of the infrared detector arrays for the Fine Guidance Sensor (FGS) instrument on the James Webb Space Telescope (JWST). This set of tests was performed on a 5 micron cutoff substrate-removed HAWAII-1RG from the new batch of devices produced for JWST. The measurements were done at wavelengths from 650 nm to 1550 nm. The results from these tests indicate that there are no significant differences in the intra-pixel response between the older JWST devices and the new ones. Modeling suggests that the primary contributor to the response profile is diffusion in the bulk detector material.

The James Webb Space Telescope (JWST) is the successor to the Hubble Space Telescope. JWST will be an infrared-optimized telescope, with an approximately 6.5 m diameter primary mirror, that is located at the Sun-Earth L2 Lagrange point. Three of JWST’s four science instruments use Teledyne HgCdTe HAWAII-2RG (H2RG) near infrared detector arrays. During 2010, the JWST Project noticed that a few of its 5 μm cutoff H2RG detectors were degrading during room temperature storage, and NASA chartered a “Detector Degradation Failure Review Board” (DD-FRB) to investigate. The DD-FRB determined that the root cause was a design flaw that allowed indium to interdiffuse with the gold contacts and migrate into the HgCdTe detector layer. Fortunately, Teledyne already had an improved design that eliminated this degradation mechanism. During early 2012, the improved H2RG design was qualified for flight and JWST began making additional H2RGs. In this article, we present the two public DD-FRB “Executive Summaries” that: (1) determined the root cause of the detector degradation and (2) defined tests to determine whether the existing detectors are qualified for flight. We supplement these with a brief introduction to H2RG detector arrays, some recent measurements showing that the performance of the improved design meets JWST requirements, and a discussion of how the JWST Project is using cryogenic storage to retard the degradation rate of the existing flight spare H2RGs.

The Segmented Telescope Control Software (STCS) uses science camera information to align and phase a deployable segmented optical telescope. It was developed the for the Next Generation Space Telescope (NGST) and has been successfully utilized on the Wavefront Control Testbed (WCT) for NGST and a portable phase retrieval camera (PPRC) system. The software provides an operating environment that will be used for the prime contractor's testbeds for NGST, and will eventually evolve into the Wavefront Sensing and Control (WFS&C) ground support software for NGST. This paper describes the engineering version of the STCS, the algorithms it incorporates, and methods of communicating with the testbed hardware.

Two-dimensional microshutter arrays are being developed at NASA Goddard Space Flight Center for the Next Generation Space Telescope (NGST) for use in the near-infrared region. Functioning as object selection devices, the microshutter arrays are designed for the transmission of light with high efficiency and high contrast. The NGST environment requires cryogenic operation at 45K. Arrays are close-packed silicon nitride membranes with a pixel size of 100 X 100 micrometers . Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with a minimized mechanical stress concentration. The mechanical shutter arrays are fabricated with MEMS technologies. The processing includes a RIE front-etch to form shutters out of the nitride membrane, an anisotropic back-etch for wafer thinning, and a deep RIE (DRIE) back-etch down to the nitride shutter membrane to form frames and to relieve shutters from the silicon substrate. Two approaches for shutter actuation have been developed. Shutters are actuated using either a combined mechanical and electrostatic force or a combined magnetic and electrostatic force. A CMOS circuit embedded in the frame between shutters allows programmable shutter selection for the first approach. A control of row and column electrodes fulfills shutter selection for the second approach.

The James Webb Space Telescope (JWST) is a large, infrared space telescope operating at Lagrange point 2. JWST is a joint effort between NASA, ESA, and CSA and was launched from the Centre Spatial Guyanais (CSG) on an Ariane 5 rocket in December 2021. The Ariane 5 payload faring (PLF), interior and Vehicle Equipment Bay membranes received multiple cleanings, detailed inspections, and verification sampling to achieve necessary cleanliness levels.Investigation of PLF cleanliness began early in the JWST program to test the Fairing Acoustic Protection (FAP) panels. Initial PLF cleaning was performed at RUAG in Switzerland prior to shipment to the launch site in collaboration with NASA and ESA. The cleaning procedure used at RUAG premises was based on heritage of the PLF cleaning procedure for ESA/Herschel-Planck and NASA/Mars2020 missions on an Atlas V launcher. The Ariane 5 fairing was packaged in a clean manner and inspected and cleaned upon arrival to CSG. Silicon wafers and particle fall out (PFO) plates were used to monitor the internal fairing cleanliness prior to encapsulation. Just after encapsulation, PFO plates and calcium fluoride (CaF2) crystals were placed inside the fairing on a specific tool door for monitoring the cleanliness inside the fairing during the ventilation phase. The fairing itself was specially sealed to protect the inner environment with just a small, doored porthole accessible via diving board for final closeout of the purge interface. Fairing cleanliness was achieved and mitigated contamination distribution upon launch.

Context. In recent years, significant growth in the amount of data available to astronomers has opened up the possibility for extensive multi-wavelength approaches. In the field of galaxy evolution, such approaches have uncovered fundamental correlations, linking the dust component of a galaxy to its star formation rate (SFR). Despite these achievements, the relation between the SFR and the dust is still challenging, with uncertainties related to the physical mechanisms linking the two. Aims. In this paper, we re-examine these correlations, paying specific attention to the intrinsic properties of the dust. Our goal is to investigate the origin of the observed scatter in low-redshift galaxies, and the ability of the James Webb Space Telescope (JWST) to explore such relations in the early Universe. Methods. We defined a sample of about 800 normal star-forming galaxies with photometries in the range of 0.15 < λ < 500 μm and analysed them with different spectral energy distribution (SED) fitting methods. With the SEDs extracted, we investigated the detection rate at different redshifts with the MId-Infrared instruments (MIRI) on board the JWST. Results. Dust luminosity (Ld) and SFR show a strong correlation, but for SFR < 2 M⊙ yr−1, the correlation scatter increases dramatically. We show that selection based on the fraction of ultraviolet (UV) emission absorbed by dust, that is, the UV extinction, greatly reduces the data dispersion. Dust masses (Md) and SFR show a weaker correlation, with a larger scatter due to the interstellar radiation field produced by stars during late evolutionary stages, which shifts the positions of the galaxies in the dust mass–SFR plane. At z = 2, more than 60% of the galaxies in the sample are detected with F770, F1000, F1280, F1500, and F1800. At higher redshifts, the detection decreases, and only 45% of z = 8 galaxies are detected with two filters. Reproducing the expected sensitivity of the Cosmic Evolution Early Release Science Survey and classifying galaxies according to their SFR and stellar mass (M*), we investigated the MIRI detection rate as a function of the physical properties of the galaxies. Fifty percent of the objects with SFR ∼ 1 M⊙ yr−1 at z = 6 are detected with F770, which decreases to 20% at z = 8. For such galaxies, only 5% of the subsample will be detected at 5σ with F770 and F1000 at z = 8, and only 10% with F770, F1000, and F1280 at z = 6. For galaxies with higher SFR, detection with these three filters will be possible up to z = 6 in ∼60% of the subsample. Conclusions. The link between dust and star formation is complex, and many aspects remain to be fully understood. The scatter between SFR and dust mass, and SFR and luminosity, decreases significantly when the analysis includes dust properties. In this context, the JWST will revolutionise the field, allowing investigation of the dust–star interplay well within the epoch of reionisation.