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Glass Mirror Technology for IXO Status and Plans

Glass Mirror Technology for IXO Status and Plans. Robert Petre (NASA/GSFC) for the NASA mirror development technology team. Mirror Technology Development Team.

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Glass Mirror Technology for IXO Status and Plans

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  1. Glass Mirror Technology for IXOStatus and Plans Robert Petre (NASA/GSFC) for the NASA mirror development technology team

  2. Mirror Technology Development Team M. Biskach2, P.A. Blake, K.W. Chan1, T. Evans2, M. Hong2,L. Kolos, J.M. Mazzarella2, R. McClelland2, L. Olsen2, T.T. Saha, M. Sharpe2, W.W. Zhang NASA Goddard Space Flight Center 1 University of Maryland, Baltimore County 2 Stinger Ghaffarian Technologies, Inc. M.V. Gubarev, W.D. Jones, T. Kester, S.L. O’Dell NASA Marshall Space Flight Center D. Caldwell, W. Davis, M. Freeman, W. Podgorski, P.B. Reid, S. Romaine Smithsonian Astrophysical Observatory

  3. Outline Background; basic approach Revised optical design for CV Fabrication approach & technology status Near and long term development plans 3

  4. IXO Mirror Requirements and Constraints • Effective area: • 2.5 m2 at 1.25 keV • 0.65 m2 at 6 keV • 150 cm2 at 30 keV • Angular resolution: • 5 arcsec HPD 0.2-7.0 keV • 30 arcsec HPD 7-40 keV (5 arcsec goal) • Focal length 20 m • Envelope diameter 3.3 m; mirror diameter 3.0 m 4

  5. Glass Mirror Technology Development • Developed by NASA, ESA partner institutes • SPO and SGO mirrors require similar technical resources • To attain a given effective area, SGO requires slightly less mass and smaller aperture • SPO would require lower power if it can be operated at 0 C • Considered “backup” approach for CV input • SPO has made more progress on full range of assembly scales (result of differing technology development philosophies) • SPO and SGO face a comparable number of development challenges • Final selection to be made once both technologies reach TRL-6 • Technology currently at TRL~4, to reach TRL-5 within a year 5

  6. Segmented Glass Mirrors - Overview Thermally form mirror segments using precisely shaped mandrels. Align and mount matched segment pairs into module housing. Populate 60 modules; mount and align into mirror structure. 6

  7. FMA Parameters – Revised Design • The FMA design was rescaled to reduce its size to a common OD as that of the SPO • SGO mirror can easily meet the 2.5 m2 requirement with significant technical and performance margins • Total FMA mass is reduced by 350 kg to 1,664 kg; of which 1,300 kg is the best estimate and 364 kg is contingency • Effective area at 1.25 keV: 2.74 m2, more than meeting the 2.5 m2 requirement • Heater power requirement is < 2 kW

  8. Performance of revised FMA design XMS field of view WFI field of view • Effective area is 2.74 m2 at 1.25 and 0.7 m2 at 6 keV • when quantum efficiency reduction due to detectors is considered • Vignetting at edge of WFI field is less than 20% @ 1.25 keV

  9. Segmented mandrels • Technology development thus far has utilized three full cylinder mandrel pairs with ~50 cm diameter • Fabrication of mirrors will require use of “slab” mandrels (cylinders with needed diameter are unavailable) • Four fused quartz slab mandrels are being polished to verify production chain • Their sizes: • 1408mm in diameter parabola and hyperbola • 1520mm in diameter parabola and hyperbola • Their figure will be better than 1.5”, exceeding IXO requirements • No changes needed in segment fabrication using differently shaped mandrels

  10. Mirror Segment Assembly Process 1 • Temporary Support (requirement met) • Temporarily support a mirror segment so that it can be effectively manipulated for alignment and mount • Turn flexible segment temporarily into a rigid body without introducing stresses or distortions • Segment attached to tabs using epoxy 10

  11. Mirror Segment Assembly Process - 2 • Alignment (requirement met: < 1.5 arcsec) • Segment plus temporary mount is attached to hexapod • Locate each segment to the right position • Orient it so that it is in alignment with other mirrors • Verify alignment optically (Hartmann test) 11

  12. Mirror Segment Assembly Process - 3 • Permanent Bonding (epoxy cure causing movement and distortion) • Attach or bond the mirror segment permanently to housing without introducing stress or distortion • Remove temporary mount • Repeat process for each segment pair to build up module 12

  13. Mirror Segment Assembly Process - 4 • Active mirror alignment and mouting provides alternative approach to rigidizing segments in unstressed state • Affords correction of first order errors (radius and cone angle) • Potentially relaxes focal length requirement on mandrels • Has also met alignment requirement (< 1.5 arcsec) 13

  14. X-ray measurements confirm alignment 8.7 arcsec HPD • Aligned and bonded several sets of mirror pairs on flight-like mounts and X-ray tested, achieving better than 10 arcsec HPD images • Repeated multiple times • Latest X-ray measurements of segment show 8.7 arcsec HPD, consistent with optical measurements • No evidence of reflectivity loss due to X-ray scattering • Primary source of blur is distortion introduced in permanent bonding step 14

  15. Development Error Budget and Scorecard Requirement met for contributions from mandrels, temporary bonding, and P-H alignment Verified by X-ray Test

  16. Mirror Segment Fabrication • Mandrels already meet requirement (1.5 arcsec HPD) • Substrate pairs (or mirror segments) at 4.5 arcsec HPD (for two reflections) • Already better than needed for 10 arcsec Observatory • Very close to what’s needed for 5 arcsec Observatory • Expect segments to meet5 arcsec Observatory requirement by December 2011 16

  17. Glass Technology to be Flown on NuSTAR Three mirror assemblies built and tested for the NuSTAR mission Each module contains ~2600 glass mirror segments Fully tested; Demonstrated the technology is ready for spaceflight Demonstrated segment production at higher rate and yield than needed for IXO

  18. Mirror Technology Milestones for 2011 • Available resources in 2011 have forced a scaling back of technology development program • Key milestones have been preserved: • Make mirror substrates at ~3 arcsec HPD (two reflections) level, meeting IXO requirements • Co-align and permanently bond 3 pairs of mirror segments 18

  19. Next major step: TRL-5 Demonstration To be populated with 3 pairs of parabolic and hyperbolic mirror segments; flight-like alignment and bonding To meet IXO angular resolution requirement: first 10”, then 5” To go through all environmental tests

  20. Technology Objectives for the Decade • Astro 2010 recommended a technology development program for IXO, intended to retire major technical risks, particularly for the mirror • We have developed a technology plan for the decade consistent with the Astro 2010 guidelines. Key milestones include: • Mature mirror technology to fully meet IXO performance requirements, reduce or eliminate technical performance risk (TRL-6) • Mature the technology to high level of manufacturing readiness, reduce or eliminate cost and schedule risk (MRL-6) • Develop and raise industry partners to ready mass production process to reduce overall mirror cost 20

  21. Summary • Glass segment pairs in flight-like mount have demonstrated X-ray performance of <9 arcsec HPD • Segments have been formed with 4.5 arcsec HPD • Many error budget terms (mandrel HPD, temporary mounting accuracy, alignment accuracy) already meet required level • Near term technology development plan goals include • Producing segments with the required 3.5 arcsec HPD • Achieving <5 arcsec HPD from a segment pair in a flight-like mount • Coaligning three segment pairs in flight-like mounts with HPD < 10 arcsec • A long term technology development plan, consistent with recommendations of Astro 2010, will demonstrate required performance and manufacturability of slumped glass mirrors 21

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