1. Impact of Cost Savings Ideas on NGAO Instrumentation December 19, 2008 Sean Adkins

2. 2 NGAO Instrumentation Instrumentation plans and requirements based on the current version of the NGAO SCRD –Single Object near-IR IFS Larger FOV, improved sensitivity, diffraction limited spatial sampling –Near-IR imager, simple occulting spot coronagraph Nominal 30” FOV, pixel scale 3 times diffraction limit at Y band cut-on wavelength –Visible imager, no coronagraph 30” FOV?, pixel scale 2 or 3 times diffraction limit at 850 nm

3. 3 Single Object Near-IR IFS Issues for improving near-IR IFS performance have been identified and placed in the context of the NGAO science requirements NSF-ATI supported work will deliver trade studies of key performance and function trades followed by a preliminary design Sensitivity optimizationIdentifies, considers, and quantifies all of the factors affecting IFS sensitivity. Investigation of current OSIRIS performance to anchor sensitivity models. Considers the impact of various design choices and recommends best practices for controlling background and maximizing photon efficiency. Spatial sampling and FOVInvestigates the impact of different image slicing techniques and formats on available FOV and number of spatial samples. Gives quantitative considers factors such as spectral format, image slicer contribution to wavefront error, and detector size. Instrumental wavefront error optimization Identifies, considers, and quantifies all sources of instrumental wavefront error and their mitigation. Evaluates the impact of other design choices such as image slicing and spectrograph layout and optical design. Short wavelength cut-offInvestigates the performance of infrared arrays vs. CCDs for the 0.7 to 1.0 µm wavelengths. Considers and quantifies the design issues for an extended wavelength range, and evaluates the cost-benefit trade of one IFS covering all wavelengths vs. a separate IFS for operation below ~1 µm. Trade study reportsDocuments the results of each trade study, including the methodologies employed and the technical foundation of the study.

4. 4 Activities Work is in progress to establish an initial understanding of the impact of extending the spectral coverage of the near-IR IFU to below 850 nm Work is also in progress on the optical design and specifications for the near-IR imager Need final NGAO relay interface (optical and mechanical)

5. 5 Issues Instrumentation plans and requirements based on the current version of the NGAO SCRD NGAO SCRD is likely to have a revision based on impact of cost savings on science capability and to fold in connections to/impacts of the WMKO Strategic Plan, currently being drafted

6. 6 Instrumentation Impacts Cost savings estimates imply only ~$8M for instrumentation Essentially no funds for visible imager Revisions to SCRD, and general state of flux in the discussion imply a need to revisit instrumentation plans early in the New Year Straw proposal if instrumentation must be delivered for less than $8M –Combined near-IR imager and IFU, on axis, at the narrow field relay –Simple, but not totally free, visible imager –Future upgrade to visible imager to incorporate IFU mode, post NGAO funding