JWST Optics Lessons Learned for Probe Missions
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In this presentation we will review the evolution of the ISIM primary structure tube topology and kinematic mount configuration to the current baseline concept. We will also show optimization procedures used and challenges resulting from complex joints under launch loads. Two additional key ISIM structure challenges of meeting thermal distortion and stability requirements and metal-composite bonded joint survivability at cryogenic temperatures are covered in other presentations.
The images in this viewgraph presentation have the following captions: 1) EDU mirror after being sawed in half; 2) EDU Delivered to Axsys; 3) Be EDU Blank Received and Machining Started; 4) Loaded HIP can for flight PM segments 1 and 2; 5) Flight Blanks 1 and 2 Loaded into HIP Can at Brush-Wellman; 6) EDU in Machining at Axsys.
I will provide a programmatic and scientific overview and update on the status and technical accomplishments of the James Webb Space Telescope project.
Contents include the following: James Webb Space Telescope/Integrated Science Instrument Module (JWST/ISIM) Overview. ISIM Thermal Verification Requirements. Emittance Test Objectives. Cryochamber Design Requirements. Cryochamber Construction. Emittance Test Sample Selection and Configuration. Error Sources and Error Mitigation. Cryochamber Operation. Cryochamber and Emittance Sample Test Results.
Finite element analysis was vital to the design and optimization of the kinematic mounts for the Near Infrared Camera (NIRCam) instrument The design had to meet dueling structural requirements driven by 12G launch loads, a survivability of bulk cool down from room temperature to 22 K, minimum first mode of 50 Hz and mass allocation constraints. Additionally the design has to meet stability and Integrated Science Instrument Module (ISIM) interfaces when cooled to 22K.
Contents include the following: JWST/ISIM introduction. Design and analysis challenges for ISIM bonded joints. JWST/ISIM joint designs. Bonded joint analysis. Finite element modeling. Failure criteria and margin calculation. Analysis/test correlation procedure. Example of test data and analysis.
This viewgraph presentation reviews the requirements, chamber location, shutter system design, stepper motor specifications, dry lubrication, control system, the environmental cryogenic function testing and the test results of the Focal Plane Array Shutter mechanism for the James Webb Space Telescope Near Infrared Spectrum Detector system. Included are design views of the location for the Shutter Mechanism, lubricant (lubricated with Molybdenum Di Sulfide) thickness, and information gained from the cryogenic testing.
The database organizations within three different NASA projects have advanced current practices by creating database synergy between the various spacecraft life cycle stakeholders and educating users in the benefits of the Consultative Committee for Space Data Systems (CCSDS) XML Telemetry and Command Exchange (XTCE) format. The combination of XML for managing program data and CCSDS XTCE for exchange is a robust approach that will meet all user requirements using Standards and Non proprietary tools. COTS tools for XTCEKML are very wide and varied. To combine together various low cost and free tools can be more expensive in the long run than choosing a more expensive COTS tool that meets all the needs. This was especially important when deploying in 32 remote sites with no need for licenses. A common mission XTCEKML format between dissimilar systems is possible and is not difficult. Command XMLKTCE is more complex than telemetry and the use of XTCEKML metadata to describe pages and scripts is needed due to the proprietary nature of most current ground systems. Other mission and science products such as spacecraft loads, science image catalogs, and mission operation procedures can all be described with XML as well to increase there flexibility as systems evolve and change. Figure 10 is an example of a spacecraft table load. The word is out and the XTCE community is growing, The f ~ sXt TCE user group was held in October and in addition to ESAESOC, SC02000, and CNES identified several systems based on XTCE. The second XTCE user group is scheduled for March 10, 2008 with LDMC and others joining. As the experience with XTCE grows and the user community receives the promised benefits of using XTCE and XML the interest is growing fast.
The James Webb Space Telescope is on track for a launch in 2013. The author reviews the status and progress on the key hardware. The first primary mirror segments are already at MSFC for cryogenic tests, the mid IR instrument (MIRI) has already had successful tests of the engineering model, and the detectors are showing excellent performance. The author also describes the scientific objectives of the mission, with emphasis on the predicted capabilities for observing planets by the transit technique and through direct imaging. Recent direct observations of planets by HST and by adaptive optics from the ground have shown that, under favorable circumstances, much can be learned.
Topics include: INtegrated Science Instrument Module (ISIM) plus Optical Telescope Element (OTE) equals OTIS, Test Assessment Task (TAT) scope, text complexity at JSC, OTIS cryo test timeline, thermal verification overview, optical verification overview, ISIM cryo test configuration at GSFC, ISIM I and T flow, ISIM cryo test timeline, and JSC activities flow.
Mirror Technology was identified as a (if not the) critical capability necessary to achieve the Level 1 science goals. A never before demonstrated space telescope capability was required: 6 to 8 meter class pri mary mirror, diffraction limited at 2 micrometers and operates at temperatures below 50K. Launch vehicle constraints placed significant architectural constraints: deployed/segmented primary mirror (4.5 meter fairing diameter) 20 kg/m2 areal density (PM 1000 kg mass) Such mirror technology had never been demonstrated - and did not exist
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