In 2014, the Optical Ground Support Equipment was integrated into the large cryo vacuum chamber at Johnson Space Center (JSC) and an initial Chamber Commissioning Test was completed. This insured that the support equipment was ready for the three Pathfinder telescope cryo tests. The Pathfinder telescope which consists of two primary mirror segment assemblies and the secondary mirror was delivered to JSC in February 2015 in support of this critical risk reduction test program prior to the flight hardware. This paper will detail the Chamber Commissioning and first optical test of the JWST Pathfinder telescope.
The James Webb Space Telescope (JWST) is a 6.5m, segmented, IR telescope that will explore the first light of the universe after the big bang. 2014 is an incredible year for the Telescope Alignment, Integration, and Test portion of the program. Long awaited and planned, the two segment Pathfinder telescope will be built and the Optical Ground Support Equipment (OGSE) will be integrated into the large cryo-vacuum chamber at the Johnson Spaceflight Center. The current status of the integration equipment and the demonstrations leading up to the flight-like Pathfinder telescope will be provided as the first step to the final verification of the complex cryo test equipment. The plans and status of bringing the OGSE on-line and ready for a series of risk reduction cryo tests starting in 2015 on the Pathfinder Telescope will also be presented.
The James Webb Space Telescope (JWST) project has entered into a comprehensive integration and test (I and T) program that over the coming years will assemble and test the various elements of the observatory and verify the readiness of the integrated system for launch. Highlights of the I and T program include a sequence of cryo-vacuum tests of the Integrated Science Instrument Module (ISHvf), to be carried out at NASA's Goddard Space Flight Center (GSFC) and an end-to- end cryo-vacuum optical and thermal test - of unprecedented scale - of the telescope plus instruments at NASA's Johnson Space Center (JSC). The I and T program, as replanned for a 2018 launch readiness date, contains a number of risk-reduction features intended to maximize the prospects for success of the critical tests, leading to reduced cost and schedule risk for those activities. For the JSC test, these include enhancement of the precursor Pathfinder program, the addition of a second cryo-vacuum thermal test of the observatory's Core region, and enhancement of the subsystem level testing program for the cryo-cooler for the Mid-InfraRed Instrument (MlRl). We report here on the I and T program for JWST, focusing on the I and T path for the instruments and telescope, and on the status of the hardware and plans that support it.
KEYWORDS: Cameras, Cryogenics, Photogrammetry, James Webb Space Telescope, Distortion, Error analysis, Metrology, Calibration, Received signal strength, Optical alignment
The alignment philosophy of the James Webb Space Telescope (JWST) Integrated Science Instrument
Module (ISIM) is such that the cryogenic changes in the alignment of the science instruments (SIs) and
telescope-related interfaces are captured in an alignment error budget. The SIs are aligned to the structure's
coordinate system under ambient, clean room conditions using laser tracker and theodolite metrology. The
ISIM structure is thermally cycled and temperature-induced mechanical and structural changes are
concurrently measured to ensure they are within the predicted boundaries.
We report on the ISIM photogrammetry system and its role in the cryogenic verification of the ISIM
structure. We describe the cryogenic metrology error budget and the analysis and testing that was
performed on the ISIM mockup, a full scale aluminum model of the ISIM structure, to ensure that the
system design allows the metrology goals to be met, including measurement repeatability and distortion
introduced from the camera canister windows.
The James Webb Space Telescope (JWST) is an infrared space telescope scheduled for launch in 2013. JWST has a 6.5 meter diameter deployable and segmented primary mirror, a deployable secondary mirror, and a deployable sun-shade. The optical train of JWST consists of the Optical Telescope Element (OTE), and the Integrated Science Instrument Module (ISIM), which contains four science instruments. When the four science instruments are integrated to ISIM at NASA Goddard Space Flight Center, the structure becomes the ISIM Element. The ISIM Element is assembled at ambient cleanroom conditions using theodolite, photogrammetry, and laser tracker metrology, but it operates at cryogenic temperature, and temperature-induced mechanical and alignment changes are measured using photogrammetry. The OTE simulator (OSIM) is a high-fidelity, cryogenic, telescope simulator that features a ~1.5 meter diameter powered mirror. OSIM is used to test the optical performance of the science instruments in the ISIM Element, including focus, pupil shear, and wavefront error. OSIM is aligned to the flight coordinate system in six degrees of freedom via OSIM-internal cryogenic mechanisms and feedback from alignment sensors. We highlight optical metrology methods, introduce the ISIM and the Science Instruments, describe the ambient alignment and test plan, the cryogenic test plan, and verification of optical performance of the ISIM Element in cryo-vacuum environment.
KEYWORDS: Photogrammetry, Nondestructive evaluation, Cameras, Metrology, James Webb Space Telescope, Cryogenics, Temperature metrology, Optical alignment, Space telescopes, Interfaces
The James Webb Space Telescope (JWST) is a 6.6m diameter, segmented, deployable telescope for cryogenic IR space
astronomy (~40K). The JWST Observatory architecture includes the Optical Telescope Element and the Integrated Science
Instrument Module (ISIM) element that contains four science instruments (SI) including a Guider. The ISIM structure must meet
its requirements at the ~40K cryogenic operating temperature.
The SIs are aligned to the structure's coordinate system under ambient, clean room conditions using laser tracker and theodolite
metrology. The ISIM structure is thermally cycled for stress relief and in order to measure temperature-induced mechanical,
structural changes. These ambient-to-cryogenic changes in the alignment of SI and OTE-related interfaces are an important
component in the JWST Observatory alignment plan and must be verified.
We report on the planning for and preliminary testing of a cryogenic metrology system for ISIM based on photogrammetry.
Photogrammetry is the measurement of the location of custom targets via triangulation using images obtained at a suite of digital
camera locations and orientations. We describe metrology system requirements, plans, and ambient photogrammetric
measurements of a mock-up of the ISIM structure to design targeting and obtain resolution estimates. We compare these
measurements with those taken from a well known ambient metrology system, namely, the Leica laser tracker system.
We present early results from the performance test development for the Detector Subsystem of the Near-Infrared
Spectrograph (NIRSpec). NIRSpec will be the primary near-infrared spectrograph on the James Webb Space Telescope
(JWST). The Detector Subsystem consists of a Focal Plane Assembly containing two Teledyne HAWAII-2RG arrays,
two Teledyne SIDECAR cryogenic application specific integrated circuits, and a warm Focal Plane Electronics box. The
Detector Characterization Laboratory at NASA's Goddard Space Flight Center will perform the Detector Subsystem
characterization tests. In this paper, we summarize the initial test results obtained with engineering grade components.
The James Webb Space Telescope's (JWST) Integrated Science Instrument Module (ISIM) contains the observatory's four science instruments and their support subsystems. During alignment and test of the integrated ISIM at NASA's Goddard Space Flight Center (GSFC), the Optical telescope element SIMulator (OSIM) will be used to optically stimulate the science instruments to verify their operation and performance. In this paper we present the design of two cryogenic alignment fixtures that will be used to align the OSIM to the ISIM during testing at GSFC. These fixtures, the Master Alignment Target Fixture (MATF) and the ISIM Alignment Target Fixture (IATF), will provide continuous, six degree of freedom feedback to OSIM during initial ambient alignment as well as during cryogenic vacuum testing. These fixtures will allow us to position the OSIM and detect OSIM-ISIM absolute alignment to better than 180 microns in translation and 540 micro-radians in rotation. We will provide a brief overview of the OSIM system and we will also discuss the relevance of these fixtures in the context of the overall ISIM alignment and test plan.
KEYWORDS: James Webb Space Telescope, Sensors, Spectrographs, Staring arrays, Near infrared, Space telescopes, Silicon, Infrared sensors, Infrared telescopes, Cameras
The Near Infrared Spectrograph (NIRSpec) will be the James Webb Space Telescope's (JWST's) primary near-infrared spectrograph. NIRSpec is a multi-object spectrograph with fixed-slit and integral field modes. EADS/Astrium is building NIRSpec for the European Space Agency (ESA), with NASA is providing the detector subsystem and programmable multi-aperture mask. In this paper, we summarize recent progress on the detector subsystem including tests demonstrating that JWST's Rockwell HAWAII-2RG sensor chip assemblies have achieved Technology Readiness Level 6 (TRL-6). Achieving TRL-6 is an important milestone because TRL-6 is required for flight.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.