For the Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) to perform high-contrast direct imaging of habitable exoplanets using a coronagraph instrument, the system must maintain extremely low system dynamic wavefront error (on the order of 10 picometers RMS over the spatial frequencies corresponding to the dark-hole region of the coronagraph) over a long time wavefront control sampling interval (typically 10 or more minutes). Meeting this level of performance requires a telescope vibration isolation system that delivers a high degree of dynamic isolation over a broad frequency range. A non-contact pointing and isolation system called the Vibration Isolation and Precision Pointing System (VIPPS) has been baselined for the LUVOIR architecture. Lockheed Martin has partnered with NASA to predict the dynamic wavefront error (WFE) performance of such a system, and mature the technology through integrated modeling, subsystem test and subscale hardware demonstration. Previous published results on LUVOIR dynamic WFE stability performance have relied on preliminary models that do not explicitly include the effects of a segmented Primary Mirror. This paper presents a study of predicted dynamic WFE performance of the LUVOIR-A architecture during steady-state operation of the coronagraph instrument, using an integrated model consisting of a segmented primary mirror, optical sensitivities, steering mirror and non-contact isolation, and control systems. The design assumptions and stability properties of the control system are summarized. Principal observatory disturbance sources included are control moment gyroscope and steering mirror exported loads. Finally, observatory architecture trades are discussed that explore tradeoffs between system performance, concept of operation and technology readiness.
The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid- and far-infrared wavelengths and offer powerful spectroscopic instruments and sensitivity three orders of magnitude better than that of Herschel, the largest telescope flown in space to date. After a 3 ½ year study, the Origins Science and Technology Definition Team will recommend to the Decadal Survey a concept for Origins with a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. A mid-infrared instrument (MISC-T) will measure the spectra of transiting exoplanets in the 2.8 – 20 μm wavelength range and offer unprecedented sensitivity, enabling definitive biosignature detections. The Far-IR Imager Polarimeter (FIP) will be able to survey thousands of square degrees with broadband imaging at 50 and 250 μm. The Origins Survey Spectrometer (OSS) will cover wavelengths from 25 – 588 μm, make wide-area and deep spectroscopic surveys with spectral resolving power R ~ 300, and pointed observations at R ~ 40,000 and 300,000 with selectable instrument modes. Origins was designed to minimize complexity. The telescope has a Spitzer-like architecture and requires very few deployments after launch. The cryo-thermal system design leverages JWST technology and experience. A combination of current-state-of-the-art cryocoolers and next-generation detector technology will enable Origins’ natural backgroundlimited sensitivity.
The Origins Space Telescope (OST) will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did the universe evolve in response to its changing ingredients? How common are life-bearing planets? To accomplish its scientific objectives, OST will operate at mid- and far-infrared wavelengths and offer superlative sensitivity and new spectroscopic capabilities. The OST study team will present a scientifically compelling, executable mission concept to the 2020 Decadal Survey in Astrophysics. To understand the concept solution space, our team studied two alternative mission concepts. We report on the study approach and describe both of these concepts, give the rationale for major design decisions, and briefly describe the mission-enabling technology.
The Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) has an optical prescription which terminates at two focal plane arrays for each module. The instrument will operate at 37K after experiencing launch loads at 293K. The focal plane array housings (FPAHs), including stray light baffles (SLBs) must accommodate all associated thermal and mechanical stresses. In addition, the stray light baffles must be installed in situ on the previously assembled flight modules. The main purpose of the FPAH SLBs is to effectively attenuate mission limiting stray light on the focal planes. This paper will provide an overview of the NIRCam stray light baffle design, mechanical and optical analysis, hardware implementation and test results.
The Near Infrared Camera (NIRCam) for the James Webb Space Telescope (JWST) has been developed over the last
several years and during the course of development, the team of engineers has overcome several technical difficulties
and discovered many things that could be improved about the design. The instrument employs a Beryllium optical
bench, mounted transmissive and reflective optics, several mechanisms and the electronics to control them. This paper
will discuss some of the technical issues encountered and the lessons learned as a result of them. These issues involve
tapping of threads in and anodic coating of Beryllium, material interfaces within mechanisms, paints and coatings of
metals, mounting of optics and general engineering practice. The issues, root causes and resolutions for problems will
be presented in addition to suggestions and recommendations for future designs.
The Near Infrared Camera for the James Webb Space Telescope is designed to operate at a temperature of 37K. The
instrument must be assembled and aligned at room temperature. The optical design is refractive and incorporates several
different lens materials in addition to several mirrors which make an athermal design very difficult. All of the instrument
components are designed so that the instrument can come into alignment at 37K after assembly at room temperature. The
methods to predict alignment shifts are presented in this paper.
The Near Infrared Camera (NIRCam) Optical Bench Assembly (OBA) is a I-220H beryllium adhesively-bonded
structure designed to operate at 35K. To support design activities, an adhesive testing program was performed, with
particular emphasis on adhesive allowables at 35K. The geometries of the samples were designed to emulate the
structural features of the OBA. The testing program is described, test data presented, and the results applied to the NIRCam OBA.
The Near Infrared Camera (NIRCam) is the primary imaging instrument on the James Webb Space Telescope. The
primary structure for NIRCam is called the Optical Bench Assembly (OBA). The OBA is a bonded Beryllium structure
designed to operate at 35K. The structure has recently undergone thermal cycling to 35K followed by structural
qualification vibration testing. Analytical predictions were made of the structural performance during vibration. These
predictions closely matched the actual performance. This paper summarizes the build and assembly of the OBA, and
focuses on the qualification thermal and structural testing of the OBA. The qualification testing is described and pre-test
analysis is presented and compared with test results.
The Near Infrared Camera (NIRCam) instrument for NASA's James Webb Space Telescope (JWST) has an optical
prescription which employs several mirrors, some of which are powered and some of which are flats that aid in
packaging. Two distinct designs for the mirrors and their mounts have been developed such that different requirements
for mass, packaging and induced wavefront error can be met. The instrument will operate at 37K after experiencing
launch loads at ~293K and the mounts must accommodate all associated thermal and mechanical stresses. Two of the
mirrors needed to be redesigned after initial prototype testing of one of the designs. This paper will provide an update
on the design and analysis status for all the mirrors including results of the initial prototype testing.
The Near Infrared Camera is the primary imaging instrument on the James Webb Space Telescope. This instrument operates in the wavelength range of 0.6 to 5 microns and at a temperature of 35K. Two mirror-image optical paths or modules are utilized to provide two adjacent fields of view for science observations and redundancy for the purpose of wavefront sensing. All optical components are supported and aligned by an Optical Bench Assembly consisting of two benches mounted back to back. Each optical bench is a closed back Beryllium structure optimized for mass and stiffness. The closed back structure is achieved by bonding two machined parts together at the midplane of the structure. Each bench half is an open back structure consisting of a facesheet with machined ribs optimized to provide stiffness and to support along primary load paths. The two benches are integrated with optical components separately and are subsequently joined by bolts and pins to form the Optical Bench Assembly. The assembly is then mounted to interface struts, which are used to mount the instrument within the Integrated Science Instrument Module for integration into the JWST observatory. The design of the Optical Bench Assembly is describing including trade studies and analysis results.
The Near Infrared Camera (NIRCam) 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. I-220H beryllium was chosen as the optical bench material for NIRCam based on its high specific stiffness, relatively high thermal conductivity, low CTE at cryogenic temperatures, and overall thermal stability at cryogenic temperatures. Beryllium has cryogenic heritage, but development of a structural bonded joint that could survive cryogenic temperatures was required. This paper will describe the trade studies performed in which bonded, I-220H beryllium was selected.
A sensitivity evaluation of mounting 100mm optics using elastomer or bipod flexures was completed to determine the relative effects of geometry, structure, material, thermal and vibration environment as they relate to optical distortion. Detailed analysis was conducted using various finite element-modeling methods. Parts were built and the results were verified by conducting brassboard tests.
What makes this evaluation noteworthy is the two vastly different approaches, and how they both exhibited athermal properties and minimized optical distortion. Materials were carefully selected while the geometry and structure were optimized through analytical iteration.
The elastomeric optical mount consists of 12 equally spaced pads of RTV placed around the circumference of the optic. These pads were sized to maximize stiffness and minimize surface deformations. The surrounding material was appropriately selected in order to contribute to an athermal design.
The bipod flexure optical mount uses three flexures cut from a single piece of material. Each flexure is a bipod oriented to comply radially with changes in temperature. This design is monolithic and uses conventional epoxy at the optical interface. The result is a very stiff athermal design.
This paper covers both opto-mechanical designs, as well as analytical results from computer modeling and brassboard tests.