Gary Matthews

ACCESS – A Concept Study for the Direct Imaging and Spectroscopy of Exoplanetary Systems

ACCESS is one of four medium-class mission concepts selected for study in 2008-9 by NASAs Astrophysics Strategic Mission Concepts Study program. ACCESS evaluates a space observatory designed for extreme high-contrast imaging and spectroscopy of exoplanetary systems. An actively-corrected coronagraph is used to suppress the glare of diffracted and scattered starlight to contrast levels required for exoplanet imaging. The ACCESS study considered the relative merits and readiness of four major coronagraph types, and modeled their performance with a NASA medium-class space telescope. The ACCESS study asks: What is the most capable medium-class coronagraphic mission that is possible with telescope, instrument, and spacecraft technologies available today? Using demonstrated high-TRL technologies, the ACCESS science program surveys the nearest 120+ AFGK stars for exoplanet systems, and surveys the majority of those for exozodiacal dust to the level of 1 zodi at 3 AU. Coronagraph technology developments in the coming year are expected to further enhance the science reach of the ACCESS mission concept.

Modular assembled space telescope

Abstract. We present a new approach to building a modular segmented space telescope that greatly leverages the heritage of the Hubble Space Telescope and the James Webb Space Telescope. The modular design in which mirror segments are assembled into identical panels allows for economies of scale and for efficient space assembly that make a 20-m aperture approach cost effective. This assembly approach can leverage NASA’s future capabilities and has the power to excite the public’s imagination. We discuss the science drivers, basic architecture, technology, and leveraged NASA infrastructure, concluding with a proposed plan for going forward.

ACCESS - A NASA mission concept study of an actively-corrected coronagraph for exoplanet system studies

ACCESS (Actively-Corrected Coronagraph for Exoplanet System Studies) develops the science and engineering case for an investigation of exosolar giant planets, super-earths, exo-earths, and dust/debris fields that would be accessible to a medium-scale NASA mission. The study begins with the observation that coronagraph architectures of all types (other than the external occulter) call for an exceptionally stable telescope and spacecraft, as well as active wavefront correction with one or more deformable mirrors (DMs). During the study, the Lyot, shaped pupil, PIAA, and a number of other coronagraph architectures will all be evaluated on a level playing field that considers science capability (including contrast at the inner working angle (IWA), throughput efficiency, and spectral bandwidth), engineering readiness (including maturity of technology, instrument complexity, and sensitivity to wavefront errors), and mission cost so that a preferred coronagraph architecture can be selected and developed for a medium-class mission.

The Integration and Test Program of the James Webb Space Telescope

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 NASAs 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 NASAs 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 observatorys 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.

Finding the UV-Visible Path Forward: Proceedings of the Community Workshop to Plan the Future of UV/Visible Space Astrophysics

Proceedings from Workshop held in June 2015 at NASA GSFC on the Future of UV Astronomy from Space

Architecting a revised optical test approach for JWST

It is imperative that we have high confidence that the optical performance capability of JWST is well-understood before launch. With the telescope operating at cryogenic temperatures and sporting a 6.6 meter primary mirror diameter, the optical metrology equipment required to measure the optical performance can be quite complex. The JWST Test team undertook an effort to greatly simplify the optical metrology approach, while retaining the key measurements and verification methodology. The result is a cryogenic optical test configuration and implementation using Chamber A at NASAs Johnson Space Center that uses the science instruments to help understand JWSTs optical performance.

The development of stacked core technology for the fabrication of deep lightweight UV-quality space mirrors

The 2010 Decadal Survey stated that an advanced large-aperture ultraviolet, optical, near-infrared (UVOIR) telescope is required to enable the next generation of compelling astrophysics and exoplanet science; and, that present technology is not mature enough to affordably build and launch any potential UVOIR mission concept. Under Science and Technology funding, NASA’s Marshall Space Flight Center (MSFC) and Exelis have developed a more cost effective process to make 4m class or larger monolithic spaceflight UV quality, low areal density, thermally and dynamically stable primary mirrors. A proof of concept 0.43m mirror was completed at Exelis optically tested at 250K at MSFC which demonstrated the ability for imaging out to 2.5 microns. The parameters and test results of this concept mirror are shown. The next phase of the program includes a 1.5m subscale mirror that will be optically and dynamically tested. The scale-up process will be discussed and the technology development path to a 4m mirror system by 2018 will be outlined.

Lessons we learned designing and building the Chandra telescope

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.

Cryogenic optical performance of a lightweighted mirror assembly for future space astronomical telescopes: correlating optical test results and thermal optical model

A 43cm diameter stacked core mirror demonstrator was interferometrically tested at room temperature down to 250 degrees Kelvin for thermal deformation. The 2.5m radius of curvature spherical mirror assembly was constructed by low temperature fusing three abrasive waterjet core sections between two CNC pocket milled face sheets. The 93% lightweighted Corning ULE® mirror assembly represents the current state of the art for future UV, optical, near IR space telescopes. During the multiple thermal test cycles, test results of interferometric test, thermal IR images of the front face were recorded in order to validate thermal optical model.

Ten years of Chandra: reflecting back on engineering lessons learned during the design, fabrication, integration, test, and verification of NASA's great x-ray observatory

This paper emphasizes how the Chandra telescope hardware was designed, tested, verified, and accepted for flight to benefit all future missions that must find efficient ways to drive out cost and schedule while still maintaining an acceptable level of risk. Examples of how the verification methodology mitigated risk will be provided, along with actual flight telemetry which confirms the robustness of the Chandra Telescope design and its verification methodology.