070712 Notes Thursday, Claire Max
NGAO System Architecture Meeting

Discussion of Peter's rainbow science requirements summary:

1) Think about how to specify the "pixel scale" for the IFU's
	(two pixels per slit size or whatever)
2) Think about desired 50% enclosed energy spec for the narrow
field IFU (don't duplicate dIFU)
3) Are the dIUF and NIR narrow field IFU the same in spatial
resolution?  in other features?  what specific new features 
are needed for the high strehl IFU?
4) 	Uranus as a special case (4"):
	Field of view at least 5 arc sec
	Able to do NGS wavefront sensing?
	Able to do tip-tilt sensing?
	(n.b. Neptune is 2 arc sec)

Rich discussed whether the technical field should be 120" or
180" - he's thinking that it could be important to have 180"

1) Rich: 120" may be too limiting: may preclude later desires for
80% sky coverage.  Should we specify a larger technical field
in order to cover this contingency?
2) Claire: even if we only have a 120" field, future IR detectors
will be better, so sky coverage can improve by using fainter TT
stars.  Also, if you really need 80% sky coverage you can (maybe)
live with only two TT sensors and take the hit with the null
modes.
3) Claire: what matters more than 80% sky coverage is the ability
for AO to function well at mediocre seeing conditions.  Claire
would prefer to spend the extra $ on building in robustness to
the AO system (such as more laser power and higher bandwidth).
4) Are there any architecture designs which would be precluded
by 180" but not 120"?
5) Rich: 50% sky coverage would imply 150" (easier than 180")


Rich:
Do we need to have a deployable imager with an available field
of more than 2 arc min diameter?  Keep future option open?
Do better than GSAOI on Gemini S?
Claire says no science cases are asking for this.  Rich says
future (not yet known) discoveries could require this.


Discussion of cost spreadsheet
(see revised spreadsheet)


Ranking: what would it take to vault a specific architecture 
into each of our top two choices?

Split relay:
Rich:
1) To vault the split relay into his top two, would need
better layout and model information to convince him that there
is room for the instruments, pickoffs, etc.  In short,
convince him that it all fits.
2) Convince him that open loop correction on the sky will work.
Address multiple guide star pupil registration issues.  
3) Feasibility/cost of a brand new set of two IF AO systems
(new design? MACAO cost)
4) Wants confirmation from our science community that we 
never have need for larger than 30" science field.  We sold
the NGAO proposal based on having an MCAO upgrade path that 
could give more than 30" NIR science field (e.g. the Indian
Wells design).  Will people be disappointed if we implement
the split relay, for example.  Is the 30" relay adequate?
5) Do we really need a PSF patrol camera?  What are its
specs.
6) Can the cost of 64x64 MEMS come down?  Don phone BMC
and discuss this.
Anna:
6) Figure out where the acquisition camera would go
7) Issue of rotators: registration between LOWFS and narrow 
field instruments (split relay and AM2).