(r4) Homework < Keck/NGAO

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*Sean Adkins*
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Request: 

Be prepared to discuss the current state of the art for low noise CCD detectors and the outlook for future performance improvements in this area.  Be prepared to discuss the status of radial geometry CCD detectors.   

Please be able to support the costing of NGAO with tools that are used for other new instrument proposals at Keck.  Be prepared to support risk assessment for various NGAO designs.  

Be able to support the NGAO retreat with interface documentation for new instruments at Keck.  This would include such areas as mechanical interfaces and clearances for Keck Nasmyth platform (coordinate with Jim Bell).  Estimated weight limits for Nasmyth platform. Vibrations guidelines for new AO instruments with current AO system. Thermal guidelines for new AO instruments with current AO system

Resources: 

ICD for Keck OSIRIS

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*Brian Bauman*
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Request: 

1) Please be prepared to consider the optical aberrations and tolerancing of several 1:1 AO relays that pass unvignetted field of view in the 3-5 arcmin range, including:

	* OAP
	* Offner
	* Ellipsoidal

We will wish to consider single and dual DM configurations with notional conjugate heights of 0km and 8km above the Keck telescope.  We are interested in feeding both contiguously sampled narrow fields, and sparsely sampled deployable IFU fields of view that may enjoy an independent 1-4 micron stroke MEMS-DM for aberration correction, per IFU channel.

-- Main.RichardDekany - 7 Apr 2006

Assume sufficient stroke can be obtained with actuator pitch as small as 3.5 mm, but that 5 mm may be more cost-effective as an existing 'standard'.  N=48 across the pupil is a good start (and if time allows, N=64 is a good 2nd choice).  Of course 5 x 47 = 235mm, while 3.5 x 63 = 220.5mm.  5 x 63 would be 315mm (largest DM to consider).  Allow yourself use of curved DM facesheets with max surface sag as much as 'a few' millimeters with these diameters.

The conjugate height for the contiguous-field DM (which we might also called a common-mode woofer) should be around 0km.

Consider the freedom of putting optical power (or cylinder) onto an entrance window to a -35 to -40C cold tank holding the relay optics and science instrument (if this is helpful).

-- Main.RichardDekany - 12 Apr 2006

2) Please be prepared to provide advice on the control of non-common-path LGS aberrations for NGAO wavefront sensors, understanding the approach taken in the current Keck AO system and that adopted by Gemini MCAO.  Although we expect WFS design to not occur until the NGAO design phase, a good understanding of the requirements, scope, and system trades necessary to reduce complexity and cost would be helpful.

3) Please be prepared to specifically comment on the aberrations induced in the Keck telescope beam (incl. field aberrations) if we were to push the Nasmyth focus down (that is, away from M3) to create greater back focal distance from the elevation ring.

Resources:

An initial .zmx file of the Keck Telescope is attached, along with earlier models created by C. Neyman (OAP) and Eric Prieto (Offner).  Please be prepared to iteratively exercise these models to provide feedback to the point design effort.

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*Jim Bell*
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Request:

Please be able to supply the team with paper copies of the left Nasmyth platform. In particular we are concerned about the space envelope near the nominal Nasmyth focus (area around elevation ring and cable wrap). One or two clear views of the space constraints should be sufficient.  

Be prepared to provide basic information about the maximum load on the platform, maximum height of a vertically mounted instrument (I understand that segment crane access could be an issue) and basic information on services available at Nasmyth such as glycol, dry nitrogen, gantry cranes, etc.  (Coordinate with Sean Adkins.) 

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*Antonin Bouchez*
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Request:

1) Please be prepared to discuss tip/tilt limitations to sky coverage fraction (in terms of XX% sky coverage available with YY milliarcseconds of tip/tilt anisoplantism error (coordinate with Chris Neyman).  Please be prepared to comment on the merits of the following concepts:

        * Visible light Shack-Hartmann and pyramid WFS (2x2 and 3x3 subaperture)
	* Infrared light Shack-Hartmann and pyramid WFS (2x2 and 3x3 subaperture)
        * Combinations of 2 visible, 2 IR, or 1 visible + 1 IR WFS
        * Fundamental limits of using all available stars' light (at visible and IR wavelengths)

2) Please be prepared to comment on the effect of centroid anisoplantism due to aliasing of coma aberrations into low-order (e.g. tip/tilt measurements).

Resources:

Attached is a new report from Richard Clare (future CARA postdoc) on the comparison of J, H, and K-band for WFS'ing with TMT's NFIRAOS system.  Please understand the assumptions, calculations, and differences between that case and Keck NGAO.

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*Matthew Britton*
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Request

Please consider potential strategies for uplink compensation of the sodium laser beam.  In particular, consider alternative strategies for obtaining the necessary wavefront information for correction of the uplink.  Consider pulsed sodium beam full-aperture (time-sharing) strategies, dedicated Rayleigh beacon strategies, and hill-climbing approaches to beacon concentration.  (Coordinate with Don Gavel.)

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*Jason Chin*
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Request:

1) Please be able to comment on laser transport options for NGAO.  Please document information on the state of art of optical fibers for laser transport, in particular we will need values for transmission loss, coupling loss, and maximum power that a fiber can support.     

2) Please work with Jim Bell to consider potential locations for laser installation locations.  Assume up to 3 long laser benches (each 5' x 12' long) each providing 50W of CW power (e.g. similar to Gemini MCAO) as an upper limit.  What are the infrastructure requirements (e.g. power, cooling, etc.)  Be prepared to comment on how an additional 150-300W of power might be added (someday)?
 
3) Please be able to discuss plans for KECK I laser upgrade specifically the laser launch telescope and surrounding laser diagnostics package.   We also need basic mechanical interface information about  Keck secondary including weight and space constraints.  

4) Please be able to discuss current laser trouble shooting system at Keck, current laser safety system.   

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*Rich Dekany*
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Request:

1) Please be prepared to exercise the jointly developed system-optimizing error budget spreadsheet in real-time to consider performance tradeoffs, high-order and tip/tilt error terms, sky coverage fraction.  Particularly, consider the image quality sharpening of field NGS stars under various assumptions.

2) Please obtain and make available the latest Mauna Kea Cn2(h) information available courtesy of the TMT Project Office.

3) Be prepared to comment on the state-of-the-art in macro-DM technology, including the latest iinformation from CILAS and Xinetics.  Include ROM cost estimates for mirrors having N=40 to N=64 actuators per pupil, if available.

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*Ralf Flicker*
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Request: 

Please review reconstruction algorithms for NGAO and be prepared to comment on the following points.  Is it possible to recast sparse matrix algorithms used in current NGAO simulations as a single matrix vector multiply?  For NGAO we are considering both the minimum variance estimator (MVE) and the pseudo open loop controller (PLOC).  If possible determine operation count for these reconstructors.

Assume DM formats ranging from N=32 actuators per telescope diameter up to N=64.  Be prepared to comment on scaling laws pertinent to N=128 (including, perhaps in an MOAO configuration).

Resources: 

See attached POLC LGS RTC block diagram from Brent Ellerbroek

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*Don Gavel*
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Request: 

1) Please be prepared to iteratively consider residual wavefront error due to imperfect tomographic wavefront sensing (possibly combined with fitting error) for NGAO asterisms supporting

	* Minimum on-axis WFE, with a req'ment of 70nm rms and goal of 45nm rms
	* Areally averaged WFE spanning FoV in the range of 3' - 5'

Make no a priori assumptions regarding physical WFS packaging constraints, but be prepared to comment on the degradation of WFS'ing performance for perturbations to notional asterism geometries.

2) Please be prepared to comment on the state-of-the-art in MEMS-DM technology.  Include schedule and ROM cost estimates for N=32 to N=128 actuators per pupil, if available.

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*Chris Neyman*
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Request:

1) Please document trade studies for key NGAO components using simulations, update the current NGAO narrow field (KPAO) error budget.  

2) Document simulation of multi object AO systems (MOAO) tomography and fitting errors.  

3) Document AO sky coverage estimates for NGAO with probable detector technologies, star models and level of assumed AO correction fall off with field of view.  (coordinate with Antonin Bouchez).

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*Gustavo Rahmer*
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Request:

1) Please be prepared to discuss infrared wavefront sensor options applicable to both:

        * Small format (16x16 or 32x32) tip/tilt/focus arrays for NGS wavefront sensing
        * Larger format (128x128 or 256x256) high order wavefront sensing arrays for embedded NGS targets

2) Please be prepared to discuss the IR science detector options for a AO-assisted IR Multi-Object Spectrograph.  Use the TMT IRMOS/TiPi concept as a guideline in terms of spectral coverage, spectral resolution, dark current, and other parameters.  

3) Be ready to provide ROM cost estimates for the latest commercially available IR detector arrays in various sizes, their corresponding controllers, and other associated detector system costs.

Resources:

TMT Tipi/IRMOS Feasibility Study Report

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*Doug Summers*
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Request:

1) Please be able to estimate the impact on laser traffic control on NAGO laser systems. Please comment on US space command clearance for laser propagation and typical time lost with the current Keck II laser.  Documents current observing sequence with single LGS, AO and instrument. (Is KAON 378 up to date?)  The current AO architecture could involve as many as 13 LGS over a 5 arc minute field with (worst case) with an initial deployment of 5 laser beacons over a 2 arc minute being more probable.

2) Please prepare to comment on a strategy for development of formal software requirements, assuming the existance of a system-level functional requirements document (capturing the flow-down from the science cases.)  Be ready to estimate the ROM labor cost for the software requirements capture.

Resources:

See attached LGS-AO acquisition procedure: KAON 378

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*Viswa Velur*
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Request: 

1) Please be prepared to comment on the focus-tracking requirements for a low-order tip/tilt/focus WFS.  Using current knowledge of the variability in sodium layer height, consider the focus update rate that the LOWFS must provide.

Resources:

Attached is a technical report generated by the TMT NFIRAOS team.  Please understand the assumptions, calculations, and differences between that case and Keck NGAO.

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*Peter Wizinowich*
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Request:

Please meet with the Next Generation Keck AO science case subcommittee chairs before the point design retreat.  Use these meetings and the information from the CfAO workshop to complete the science requirements matrix (Spreadsheet).   Be prepared to discus how the implication of these requirements for the new instruments and AO architectures.     

Resources:

Science Requirements Spreadsheet:    (http://www.keck.hawaii.edu/realpublic/optics/ScienceCase/TechSciInstrmnts/ScienceCaseReqmnts033106.xls)
Science Instrument Options : 
(http://www.keck.hawaii.edu/realpublic/optics/ScienceCase/Science_Instrument_Options.xls)
NGAO Architecture Options: 
(http://www.keck.hawaii.edu/realpublic/optics/ScienceCase/NGAO%20architecture%20options%20v0_8.pdf)
Attachments
Topic attachments
I	Attachment	History	Action	Size	Date	Who	Comment
pdf	JHK_for_NGS_WFS_for_NFIRAOS.pdf	r1	manage	161.1 K	2006-04-07 - 17:13	RichardDekany	TMT NFIRAOS study
ZMX	KeckTelescope.ZMX	r1	manage	18.5 K	2006-04-07 - 16:33	RichardDekany	Keck Telescope .zmx file
ppt	POLC_LGS_RTC_block_diagram.ppt	r1	manage	50.5 K	2006-04-07 - 21:26	UnknownUser	POLC Block Diagram
pdf	Sensitivity_to_focus_from_sodium_laser_guide_star.pdf	r1	manage	135.8 K	2006-04-07 - 17:12	RichardDekany	TMT NFIRAOS study
pdf	kaon378.pdf	r1	manage	128.6 K	2006-04-07 - 21:25	UnknownUser	Keck AO Note 378
Topic revision: r4 - 2006-04-12 - RichardDekany
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