1. The Path to NGAO Core Science Requirements Claire Max and Liz McGrath NGAO Team Meeting September 11-12, 2008

2. 2 Outline of Talk What do we mean by "Core Science Requirements"? Suggested approaches Next steps

3. 3 What do we mean by "Core Science Requirements"? A possible definition: –A set of science requirements such that NGAO isn't worth building if these requirements can't be met –The most minimal "fish or cut bait" set of science goals for NGAO Potential problem with this definition: –As soon as we specify the minimal requirements, they will probably end up being what the B2C system is designed to meet

4. 4 What do we mean by "Core Science Requirements"? cont'd Another possible definition: The science that a final build-to-cost design will be able to accomplish We probably don’t want to decide right now, up front, on a very specific set of science questions that will be answered –e.g. a "design reference mission" as for a spacecraft Why not? Capability of NGAO at different costs is a continuous variable –Science capability at different system costs will determine how well you can do different science cases, but in most cases will not rule out a science case entirely. The function of the science team is to give continuing input on the scientific value of design trades as the "build to cost" design is developed

5. 5 What are the distinguishing features of NGAO science? Compared with current Keck AO Compared with future planned AO systems elsewhere Compared with JWST We want NGAO to contribute science capabilities that are clearly new and that will be unique

6. 6 First cut: Key Aspects of NGAO Science Capability 1.High sensitivity and sky coverage, with NIR encircled energy < 70 mas 2.Strehl  20% at 850 nm 3.Astrometric accuracy better than 150  as at K band 4.Backup NGS mode (Strehl no worse than K2 NGS) 5.IFU multiplicity (may  larger field of regard) In priority order:

7. 7 Instruments: Key NGAO Capabilities Integral field spectroscopy @ high sensitivity and sky coverage. –Design trades: Degree of multiplicity (OSIRIS plus ??? new IFUs) Strehl ratio/FWHM for each IFU Field of view for each IFU Can one of the IFUs be extended down to ~800 nm for the black holes in nearby galaxies Key Science Driver? Imaging at shorter wavelengths, and at higher Strehl (NIR and visible). –Design trades: NIR imager needs excellent astrometry; polarimetry capability Should we build both a visible imager and a NIR imager? Or should we extend the wavelength range of the NIR imager to ~800 nm?

8. 8 Recall: We categorized science cases into 2 classes 1.Key Science Drivers: –These push the limits of AO system, instrument, and telescope performance. Determine the most difficult performance requirements. 2.Science Drivers: –These are less technically demanding but still place important requirements on available observing modes, instruments, and PSF knowledge.

9. 9 Key Science Drivers (in order of distance) 1.High-redshift galaxies 2.Black hole masses in nearby AGNs 3.General Relativity at the Galactic Center 4.Planets around low-mass stars 5.Minor planets as remnants of early Solar System

10. 10 Suggested Approach Start with existing Key Science Drivers and Science Drivers Work with Keck science community (Science Advisory Team plus others) to: –Get broad agreement on the key unique attributes of NGAO, relative to other AO systems and spacecraft available at the same epoch –To the extent possible, prioritize Key Science Drivers and Science Drivers Very hard to get a group of astronomers to agree on this! Aim for as clear a statement of priorities as possible As B2C design choices become clearer, vet them with Science Advisory Team plus others to clarify costs / benefits of design decisions with respect to science

11. 11 Next Steps CEM –Take the principal design options emerging from today and tomorrow, and begin to frame the analysis of science implications Science Advisory Team –Directors complete roster of Science Advisory Team, and finish writing its charter –Convene Team and get their suggestions and buy-in for the B2C process. [Do I have the ability to convene SAT meetings? The SAT reports to the Directors, not to me. Needs clarification.] –Tackle prioritization of Science Drivers, and definition of “core science requirements” if we can agree on definition today/tomorrow