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  1. Work progress in Spain M. Azzaro IAA-CISC

  2. The Spain BigBOSS Consortium Institutions Consortium is led by IAA, spokesperson: F. Prada (IAA) Instrument responsible: F. Prada (IAA) Project Manager: M. Azzaro (IAA) Member institutions: IAA, IAC, UAM, ICC-UB, OA-UV A MoA will soon be signed between the Consortium, the CSIC, the Spain Ministry of Science and the LBNL. Funding Science Ministry funds for one year I+D programme for 3 years (AVS) i-LINK programme (CSIC-LBNL funds for travel expenses) More funding are needed to complete the Conceptual Design Phase Personnel F. Prada (IAA), M. Azzaro (IAA), S. Becerril (IAA), J. Sánchez (IAA), I. Morales (IAA), A. Montero (IAA), C.Vilar (UB). Possibility to hire one more mechanical engineer soon. M. Azzaro

  3. Focal plane technical requirements • The Focal plane includes the focal plate, the fiber positioners and the adapter to attach to the corrector barrel. • Normal flowdown is: • Overall science requirements definition • Error chain from Corrector i/f to fiber i/f • Error budget and error estimation • Interaction/feedback with science • Technical requirements We are here M. Azzaro

  4. Focal plate working lines This is a large, challenging item, with a complex topology and very high precision requirements. • 5549 holes (pitch 12 mm) • Spherical alignment • No pattern in location of centers • Converging Axes • Very thin wall thickness • Calculus on gravity deformations • Al-Si availability & thickness • Al-Si machineability (prototype) • Thermal behaviour M. Azzaro

  5. Fiber positioner progress Motor suitability (contact with Faulhaber) Electronics envelope estimation Anti-backlash preload system Once the basic requirements are defined and agreed, we should be ready to propose a mechanical solution. M. Azzaro

  6. Fiber-to-positioner assignment algorithm The draining algorithm is designed to maximize the number of assignments in the first few tiles, which are the relevant tiles in a real observation. In essence, the method can properly deal with objects in common areas(shared by 2 or even 3 positioners). This is not possible with other approaches such as those based on a proximity criterion (LAMOST) or a random assignment. The gain provided by the draining algorithm is ~ 2-2.5 % as compared to a random assignment for randomly distributed targets. Simulations have been carried out with 100 catalogs. M. Azzaro

  7. Fiber-to-positioner assignment algorithm Simulations with mock galaxy catalogs (Klypin et al. 2010) ~ 1.8 – 2 %improvement as compared to a random assignment. ~ 3.5 – 4.5 % for slight rotations (+/- 2o, BigBOSS) and 5 -6 % for unlimited rotations Collisions are solved optimally BigBOSS: saving several 100,000 targets, or, equivalently, ~350 sq deg (~50 tiles) M. Azzaro

  8. Critical points - We are working with a max centroid shift (fiber center to obj. center) of 10µ Is this correct (PSF light losses etc.) ?- We work with a max defocus of 30µ and a max tilt of ±0.25˚. Is this correct (light losses) ?- What is the expected accuracy of object positions on the sky?- What is the best optimizing strategy for the survey (number of objects, area, etc.) ?- What is the typical exposure time ?- Is the “nominal” wavelength halfway through BigBOSS range ?- What is the lowest elevation for observations and the time relevance of it ?BASIC SCIENTIFIC REQUIREMENTS ARE NEEDEDPROJECT SCIENTIST NEEDED M. Azzaro