Significant progress has been made in the development of the Optical Telescope Element (OTE) for the James Webb
Space Telescope (JWST) Observatory. At the time of the conference, the OTE will have been completely
assembled, including deployment testing and optics alignment and installation. This paper will discuss those
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. In 2014, a major risk reduction effort related to the Alignment, Integration, and Test (AI and T) of the segmented telescope was completed. The Pathfinder telescope includes two Primary Mirror Segment Assemblies (PMSA’s) and the Secondary Mirror Assembly (SMA) onto a flight-like composite telescope backplane. This pathfinder allowed the JWST team to assess the alignment process and to better understand the various error sources that need to be accommodated in the flight build. The successful completion of the Pathfinder Telescope provides a final integration roadmap for the flight operations that will start in August 2015.
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.
Significant progress has been made in the development of the Optical Telescope Element (OTE) for the James Webb Space Telescope (JWST) Observatory. All of the mirror assemblies are complete and delivered. The composite Primary Mirror Backplane Support Structure (PMBSS) has completed assembly and in Static Load testing. All the deployment mechanisms have completed their qualification programs. This paper will discuss the current status of all the OTE components and the plan forward to completion.
2014 marks the crystal (15th) anniversary of the launch of the Chandra X-ray Observatory, which began its existence as the Advanced X-ray Astrophysics Facility (AXAF). This paper offers some of the major lessons learned by some of the key members of the Chandra Telescope team. We offer some of the lessons gleaned from our experiences developing, designing, building and testing the telescope and its subsystems, with 15 years of hindsight. Among the topics to be discussed are the early developmental tests, known as VETA-I and VETA-II, requirements derivation, the impact of late requirements and reflection on the conservatism in the design process.
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.
Significant progress has been made in the development of the Optical Telescope Element (OTE) for the James Webb
Space Telescope (JWST) Observatory. All of the mirror assemblies are complete and through final testing. The
composite Pathfinder Primary Mirror Backplane Support Structure (PMBSS) has been completed and the flight
structure is making significant progress. This paper will discuss the current status of all the OTE components and
the plan forward to completion.
In a little under a decade, the James Webb Space Telescope (JWST) program has designed, manufactured,
assembled and tested 21 flight beryllium mirrors for the James Webb Space Telescope Optical Telescope
Element. This paper will summarize the mirror development history starting with the selection of
beryllium as the mirror material and ending with the final test results. It will provide an overview of the
technological roadmap and schedules and the key challenges that were overcome. It will also provide a
summary of the key tests that were performed and the results of these tests.
The James Webb Space Telescope (JWST) is an on axis three mirror anastigmat telescope with a primary mirror, a
secondary mirror, and a tertiary mirror. The JWST mirrors are constructed from lightweight beryllium substrates and the
primary mirror consists of 18 hexagonal mirror segments each approximately 1.5 meters point to point. Ball Aerospace
and Technologies Corporation leads the mirror manufacturing team and the team utilizes facilities at six locations across
the United States. The fabrication process for each individual mirror assembly takes approximately six years due to
limitations dealing with the number of segments and manufacturing & test facilities. The primary mirror Engineering
Development Unit (EDU) recently completed the manufacturing process with the final cryogenic performance test of the
mirror segment assembly. The 18 flight primary mirrors segments, the secondary mirror, and the tertiary mirror are all
advanced in the mirror production process with many segments through the final polishing process, coating process, final
assembly, vibration testing, and final acceptance testing. Presented here is a status of the progress through the
manufacturing process for all of the flight mirrors.
A Pathfinder of the James Webb Space Telescope (JWST) Optical Telescope Element is being developed to check out
critical ground support equipment and to rehearse integration and testing procedures. This paper provides a summary of
the baseline Pathfinder configuration and architecture, objectives of this effort, limitations of Pathfinder, status of its
development, and future plans. Special attention is paid to risks that will be mitigated by Pathfinder.
The James Webb Space Telescope (JWST) Optical Telescope Element has completed its Critical Design Review and is
well into fabrication. This paper will summarize efforts to date in the design, manufacturing and planning for integration
and testing. This will include a top level summary of mirror performance to date, hardware results, and planning status
for the integration and testing program. The future plans for manufacturing, assembly, alignment and testing will also be
summarized at a top level.
Significant progress has been made in the development of the Optical Telescope Element (OTE), one of three elements of the James Webb Space Telescope (JWST) Observatory. To achieve the 25 square meters of collecting area, JWST will employ the first segmented, deployed optical telescope, requiring a wavefront sensing and control (WFS&C) system to align and phase the telescope's optics, while operating at cryogenic temperatures. The OTE is comprised of the optical components of the three mirror anastigmat and a steering mirror, the structure to deploy and support the optics, the WFS&C system to determine the adjustments necessary to align them, the electronics to control them, and the thermal components to manage the OTE temperatures. Technology development and risk reduction hardware are being produced to address critical technical areas. Subsystem development has progressed with the successful completion of several key design reviews and significant progress on the production of the flight Primary Mirror Segment Assemblies.
The James Webb Space Telescope (JWST) conducted a phased down select for its primary mirror. Using the results of the Advanced Mirror System Demonstrator (AMSD) as a basis, the Mirror Recommendation Board (MRB) assessed the suitability for JWST of candidate mirrors in the areas of performance, schedule, cost and risk. Beryllium was selected for the JWST primary mirror. This paper summarizes the evaluation and selection process.
JWST will be used to help understand the shape and chemical composition of the universe, and the evolution of galaxies, stars and planets. With a 6.5 meter primary mirror, the Observatory will observe red shifted light from the early history of the universe, and will see objects 400 times fainter than those seen from large ground-based telescopes or the current generation of space-based infrared telescopes. NASA Goddard Space Flight Center (GSFC) manages JWST with contributions from a number of academic, government, and industrial partners. The contract to build the space-based Observatory for JWST was awarded to the Northrop Grumman Space Technology (NGST)/Ball/Kodak/ATK team.
The Next Generation Space Telescope will be the premier instrument for astrophysical research a decade from now. This paper describes the reference concept for the observatory being studied by a prime contractor team led by TRW and Ball Aerospace. We give an overview of the space segment of the mission, and the rationale for its heliocentric orbit at the Sun-Earth L2 Lagrangian point. At the time of this meeting many details of the engineering design are still open for trade studies. We highlight a few whose resolution will have implications for the scientific performance of the observatory, and for which preferences and recommendations from the scientific community are welcomed.
The prelaunch calibration of AXAF encompasses many aspects of the telescope. In principle, all that is needed is the complete point response function. This is, however, a function of energy, off-axis angle of the source, and operating mode of the facility. No single measurement would yield the entire result. Also, any calibration made prior to launch will be affected by changes in conditions after launch, such as the change from one g to zero g. The reflectivity of the mirror and perhaps even the detectors can change as well, for example by addition or removal of small amounts of material deposited on their surfaces. In this paper, we give a broad view of the issues in performing such a calibration, and discuss how they are being addressed in prelaunch preparation of AXAF. As our title indicates, we concentrate here on the total throughput of the observatory. This can be thought of as the integral of the point response function, i.e. the encircled energy, out to the largest practical solid angle for an observation. Since there is no standard x-ray source in the sky whose flux is well known to the approximately 1% accuracy we are trying to achieve, we must do this calibration on the ground. We also must provide a means for monitoring any possible changes in this calibration from prelaunch until on-orbit operation can transfer the calibration to a celestial x-ray source whose emission is stable. In the paper, we analyze the elements of the absolute throughput calibration, which we call the effective area. We review the requirements for calibrations of components or subsystems of the AXAF facility, including the mirror, detectors, and gratings. We show how it is necessary to have an absolute calibrated detection system available during the prelaunch calibrations to measure the flux in the x-ray beam used for calibrating AXAF. We show how it is necessary to calibrate this ground-based detection system at standard man-made x-ray sources, such as electron storage rings. We present the status of all these calibrations, with indications of the measurements remaining to be done, even though the measurements on the AXAF flight optics and detectors will have been completed by the time this paper is presented. We evaluate progress toward the goal of making 1% measurements of the absolute x-ray flux from astrophysical sources, so that comparisons can be made with their emission at other wavelengths, in support of observations such as the Sunyaev-Zeldovitch effect, which can give absolute distance measurements independent of the traditional distance measuring techniques in astronomy.
The Verification Engineering Test Article-I (VETA-I) was an assembly which held the largest pair of Advanced X-ray Astrophysics Facility (AXAF) mirror elements (1.2 meter diameter). The X-ray performance of this mirror pair, as held in the VETA-I, was tested in September 1991 at the Marshall Space Flight Center (MSFC) X-ray Calibration Facility (XRCF). Alignment of the optical elements to each other, and to the test facility axis, was required in order to execute the test. This paper will describe the VETA-I, its alignment requirements, and the hardware and procedures used to bring it into alignment.
The concept, implementation, and performance of the motion detection system (MDS) designed as a diagnostic for X-ray ground testing for AXAF are described. The purpose of the MDS is to measure the magnitude of a relative rigid body motion among the AXAF test optic, the X-ray source, and X-ray focal plane detector. The MDS consists of a point source, lens, centroid detector, transimpedance amplifier, and computer system. Measurement of the centroid position of the image of the optical point source provides a direct measure of the motions of the X-ray optical system. The outputs from the detector and filter/amplifier are digitized and processed using the calibration with a 50 Hz bandwidth to give the centroid's location on the detector. Resolution of 0.008 arcsec has been achieved by this system. Data illustrating the performance of the motion detection system are also presented.
The energy bandwidth and total throughput of a grazing incidence optics system is a strong function of the X-ray reflectivity of the surface coating. In support of the Advanced X-ray Astrophysics Facility (AXAF), studies are underway to evaluate and characterize the reflectivity of potential AXAF coatings. Here we report on results obtained for Au, Ir, and Ni coatings produced by electron-beam evaporation, evaporation with ion-assist, and sputtering. Effects of coating thickness and deposition angle have been evaluated at 6.4 and 8.1 keV; the highest reflectivities are those of the thinner, about 200 A vs about 700 A, coatings. While considerable variations exist, the best Ir samples have higher reflectivity than any of the Au coatings. Data results have been compared with models for theoretical reflectivity, particularly with regard to the effective density of the coatings. Independent measurements of the coating densities have been carried out for comparison with the reflectivity results.