Search

Motivated by the ever increasing pursuit of science with the transient sky (dubbed Time Domain Astronomy or TDA), we are fabricating and will commission a new deployable tertiary mirror for the Keck I telescope (K1DM3) at the W.M. Keck Observatory. This paper presents the detailed design of K1DM3 with emphasis on the opto-mechanics. This project has presented several design challenges. Foremost are the competing requirements to avoid vignetting the light path when retracted against a sufficiently rigid system for high-precision and repeatable pointing. The design utilizes an actuated swing arm to retract the mirror or deploy it into a kinematic coupling. The K1DM3 project has also required the design and development of custom connections to provide power, communications, and compressed air to the system. This NSF-MRI funded project is planned to be commissioned in Spring 2017., 22 pages; many figures; Published in SPIE

The objective of the present study was to investigate the effects of the addition of fibre and the antioxidantN-acetylcysteine (NAC) to fat-rich diets on fetal intrauterine development in rats. A total of eighty virgin female Sprague–Dawley rats were fed a control diet, a high-fat diet (HF), a high-fat and high-fibre diet (HFF) or a high-fat NAC diet until day 19·5 of gestation. Maternal HFF consumption resulted in a significantly higher mean fetal number and placental weight than in the other groups (P P P P P

Five main belt asteroids, 2 Pallas, 129 Antigone, 409 Aspasia, 532 Herculina, and 704 Interamnia were imaged with the adaptive optics system on the 10 m Keck-II telescope in the near infrared on one night, August 16, 2006. The three axis dimensions and rotational poles were determined for Pallas, Antigone, Aspasia, and Interamnia, from their changing apparent sizes and shapes as measured with parametric blind deconvolution. The rotational pole found for Interamnia is much different from all previous work, including our own at Lick Observatory the previous month. Although images of Herculina were obtained at only two rotational phases, its rotation appears to be opposite to that predicted from the lightcurve inversion model of M. Kaasalainen, J. Torppa, and J. Piironen [2002. Icarus 159, 369–395]. A search for satellites was made in all of the asteroid images, with negative results, but three trailing stars around Herculina (200 km diameter), down to 8.9 magnitudes fainter and between 1 and 115 asteroid radii (100 to 11,500 km) from the asteroid, establishes an upper limit of 3.3 km for any object with the same albedo near Herculina.

Identification and screening of grasses with excellent drought tolerance is a desirable strategy in breeding drought-tolerant turf and forage cultivars. Not all fescue selections and cultivars may be equally drought tolerant. An Atlas fescue (Festuca mairei St. Yves) selection and three tall fescue (Festuca arundinacea Schreb.) cultivars—Barolex, Kentucky 31, and Falcon II—were subjected to increasing drought stress for a 12-week period. Soil water content (SWC), leaf elongation (LE), leaf water content (LWC), and leaf water potential (Ψw) were measured weekly, and root length (RL) and biomass (RM) were recorded after 12 weeks. The SWC declined progressively during the 12-week drought treatment for all grasses. However, for the three tall fescue cultivars, the SWC decreased at a faster rate than for Atlas fescue. This indicated that Atlas fescue extracted soil water more slowly and developed less-intensive stress than the three tall fescue cultivars. The LE, LWC, and leaf Ψw decreased in drought-treated plants of all grasses; nevertheless, the values for the Atlas fescue remained similar to control plants for a longer period of time than the values for the three tall fescue cultivars. Drought stress significantly reduced root biomass and root length of the grasses. These four Festucas avoid drought stress through changes in leaf and root morphology and probably through osmotic adjustment to maintain sufficient turgor pressure in the growing zone for leaf elongation. The slower decrease in LE, LWC, and leaf Ψw for Atlas fescue during the drought-stress period suggested greater drought tolerance and the potential value for improving this character in a breeding program.

Sustainability of agriculture is based on economic returns, environmental preservation, and sociological factors associated with quality of life. Yet, its components, except for economic return, are difficult to quantify, and their relative importance varies among economic and geographic regions. Environment-friendly agriculture adds emphasis to environmental factors and eco-friendly agriculture adds biodiversity to the environmental component. But sociological factors are very site-specific and hard to measure and value. Internationalization of agriculture puts pressure on sustainability because world trade is based on economics, and the role of private industry and the utility of most agricultural research are perceived to favor the economic component. Local people and national governments add emphasis to the environment and some to the social factors. As national economies improve, however, more emphasis by the public and national governments is placed on the environment and grows to include b...

Division C-6 was established in 2000, but members associated with forages and grazinglands have been active in the Crop Science Society of America (CSSA) since its inception; 21 have served as President and many authored textbooks and comprehensive reference works. Complex forage and pasture mixtures were common in 1955, but shifted to monocultures in the 1960s and 1970s. Mixtures returned in the 1980s as N prices increased, broader values of legumes became known, nutritive value was better understood, and environmental issues increased. Alfalfa (Medicago sativa L.) for dairy production had strong leadership from the private sector in seed production and breeding. Tall fescue (Festuca arundinacea Schreb.) was well-adapted, conserved soil, and extended grazing in the transition zone to increase beef cow-calf production. Bermudagrass [Cynodon dactylon (L.) Pers.] benefited from vegetative propagation, conserved soil, and was improved for adaptation, yield, and nutritive value. Yield advancements, except for a few species, have been discouraging. Management benefited from advances in disease resistance, methods for assessing nutritive value, and understanding the role of endophytic fungi. Modest increases in nutritive value, coupled with improved pasture management, have increased animal performance. Emerging interests include biomass, carbon sequestration, and roles of biodiversity. Molecular techniques offer potential to better understand the plants and make genetic progress.

Alfalfa (Medicago sativa L.) growers wanting to maximize annual yields are often tempted to take an additional harvest in late autumn. Our overall objective was to determine if harvesting alfalfa an 'extra' time in late autumn impacts long-term yield and stand persistence. Averaged over five years, the net gain in yield for taking an additional harvest in late autumn was only 0.11, 0.25, and 0.40 tons/acre for alfalfa harvested every 28, 35, and 42 days during the growing season, respectively. Stand persistence was equal for all treatments. An economic analysis shows that the low net yields from a late-autumn harvest usually do not justify the added expense.

Reseeding of alfalfa is affected until autotoxic chemicals break down or are dispersed, often requiring a year or more. Bioassays of seed germination and early seedling growth, on agar medium in petri dishes, were conducted to evaluate autotoxic responses of 20 alfalfa germplasms to water-soluble extracts of alfalfa leaf tissue. Root length, 120 hr after placing imbibed seed on agar, was more sensitive to the autotoxin(s) than was hypocotyl length, germination speed, and final germination percentage. Path coefficient analyses showed variation in root length had 7-17 times more effect than variation in hypocotyl length in determining autotoxic effects on total seedling length. Although variations in seed size and germination rate were negatively associated (P < 0.05) with final root length, the autotoxin had little effect on these factors relative to that on root length. Germplasms in the control differed (P < 0.05) in root length, requiring tolerance to be evaluated as percent of control. Germplasms, as percent of control, differed significantly (P < 0.05) at extract concentrations of 1.0 and 4.0 g l(-1), but the range and LSD were more favorable for selection at 1.0 g l(-1). Root length is appropriate for genetic assessments of tolerance to the autotoxin when expressed as percent of control.

Interseeding alfalfa (Medicago sativa L.) to thicken declining alfalfa stands is seldom successful due to autotoxicity. Our objective was to characterize the lateral zone of autotoxic influence around established plants. Experiments were conducted in South Missouri in alfalfa fields of 'Apollo' [Location 1 (L1)] and 'Cody' (L2) in 1992 and 'Cimarron' (L3) in 1993. Soils were Poynor cherty silt loam (loamy-skeletal over clayey, siliceous, mesic Typic Paleudult) at L1, Ashton silt loam (fine-silty, mixed, mesic Mollic Hapludalf) at L2, and Waben very cherty silt loam (loamy-skeletal, siliceous, mesic Ultic Hapludalf) at L3. Established alfalfa was killed in May with herbicide within 2 m of selected alfalfa test plants, and then 1 yr later, Cody alfalfa was seeded within 1 m around the test plants. Granular chlorpyrifos and seed treatment metalaxyl at planting did not improve alfalfa seedling establishment or yield. Seedlings were smaller (p < 0.05) near both live and dead test plants at L1, indicating mainly autotoxicity, but at L2, yield per plant was reduced more within 25 cm from live than from dead plants, indicating competition was involved. Clipping test plants more frequently at L3 did not improve establishment and reduced seedling yield for six of eight harvests. Seedling density and dry matter yield averaged 70 and 44% (p < 0.05) of the control, respectively, within 20 to 25 cm of test plants, an area equivalent to a stand density of 8 plants m -2 . The zone of influence around established alfalfa plants involves both competition and autotoxicity and needs to be considered in replant dedsions.

Published intervals for avoiding autotoxicity when reseeding alfalfa (Medicago saliva L.) after alfalfa range from 2 wk to more than 1 yr. Intervals between killing old alfalfa stands with herbicides and reseeding alfalfa were compared in field experiments established in 1992 (Locations 1 and 2) and 1993 (Location 3) near West Plains, MO. Soils were Poynor cherty silt loam (loamy-skeletal over clayey, siliceous, mesic Typic Paleudult), Ashton silt loam (fine-silty, mixed, mesic Mollic Hapludalf), and Waben very cherty silt loam (loamy-skeletal, siliceous, mesic Ultic Hapludalf), respectively. Main plots were 18-, 12-, 6-, 0.75-, and 0.5-mo rotation intervals before a common May planting date. Subplots were insecticide and fungicide treatments at planting. Insecticide or fungicide treatment did not affect plant density or yield during the establishment year or two subsequent years. Among years, plant densities for the 0.75- and 0.5-mo rotation intervals ranged between 12 and 19.2% lower (P < 0.05) than that of the 18-mo control interval, and yields for the 6- and 0.5-mo intervals ranged between 6.3 and 10.3% lower than that of the control (P < 0.05). Although plant density of the 0.75-mo rotation interval was lower, yield was similar to the 18-mo control due to incomplete kill of old plants. Plant density and dry matter yield remained ranked according to rotation interval from the seeding year through the third year, suggesting an autoconditioning effect during establishment that was retained at the population level. A rotation interval of at least 12 mo is suggested before reseeding alfalfa after alfalfa in the lower Midwest.

The University of California Observatories will design and construct a deployable tertiary mirror (named K1DM3) for the Keck 1 telescope, which will complement technical and scientific advances in the area of time-domain astronomy. The K1DM3 device will enable astronomers to swap between any of the foci on Keck 1 in under 2 minutes, both to monitor varying sources (e.g. stars orbiting the Galactic center) and catch rapidly fading sources (e.g. supernovae, flares, gamma-ray bursts). In this paper, we report on the design development during our in-progress Preliminary Design phase. The design consists of a passive wiffle tree axial support system and a diaphragm lateral support system with a 5 arcminute field-of-view mirror. The mirror assembly is inserted into the light path with an actuation system and it relies on a kinematic mechanism for achieving repeatable, precise positioning. This project, funded by an NSF MRI grant, aspires to complete by the end of 2016.

Longitudinal elongation contributes most to leaf area expansion of grasses and its rate is known to be strongly affected by N. Our objective was to determine the effect of two N regimes (N 0 and N+) on the gradient of leaf tissue formation in meristems of two contrasting tall fescue ( Festuca arundinacea Schreb.) genotypes. Proportions of epidermal, mesophyll and vascular tissue as well as intercellular air space were determined throughout the base of actively elongating leaves. The area of leaf transverse sections nearly doubled between the ligule and the distal end of the growth zone (about 30 mm), and was mainly associated with lateral epidermal and mesophyll cell division in the proximal 5.0–7.5 mm. Further increase in transverse area was due to the formation of intercellular airspace and transverse expansion of epidermal cells. Depending on genotype and N treatment the mesophyll, epidermis, vascular bundles and air space comprised 45–54%, 20–28%, 6–9%, and 17–21%, respectively, of transverse leaf area in the distal part of the growth zone. After a slight increase close to the leaf base, the area of vascular tissue remained constant throughout the growth zone. The proportion of air space to mesophyll space was higher at N 0 than at N+ because mesophyll area was enhanced by N+ to a greater degree than by N 0 . In the genotype with slow leaf elongation, the increase in cross-sectional leaf area was due to an increase in both leaf width and leaf thickness. In the genotype which had faster leaf elongation and wider leaves, only leaf thickness was enhanced by N+.

Most assessments of allelopathy involve bioassays. Our objective was to improve the sensitivity of an alfalfa (Medicago sativa L.) seedling bioassay for evaluating genetic tolerance to autotoxic leaf extracts. In a petri dish assay on imbibed seed, light inhibited hypocotyl elongation of controls and increased root elongation. Root growth was sensitive to the autotoxin in both light and darkness. An agar medium gave better root growth of controls and lower standard errors than did filter paper when petri dishes were placed on edge to encourage downward root growth or were placed flat where roots grew laterally. Hypocotyl growth was not very sensitive to the autotoxic chemical(s) on either agar or paper medium when the plate was flat, because the hypocotyl arched upward to escape contact with the extract. Hypocotyl growth was sensitive in a rolled paper towel treatment held vertically because the hypocotyl remained in continuous contact with the extract. On agar plates placed flat, 50% inhibition of root length occurred at an extract concentration that was about 8% of that needed for 50% inhibition of germination at 36 and 48 h. Root growth was stimulated up to 15% above controls at very low concentrations of leaf extract. Root length at 120 h was the best indicator of autotoxic effects of alfalfa leaf extracts. We evaluated 17 germplasms and three cultivars of alfalfa for root growth response to the autotoxic chemical and found a twofold range (P < 0.05) in tolerance.

A rotation interval is recommended between alfalfa (Medicago sativa L.) stands to avoid negative effects of autotoxicity. Differences in soil properties such as texture can strongly influence allelopathic expression in plants and may explain the large variation in research results and recommended rotation intervals among states. A laboratory experiment was conducted to determine the influence of soil texture on alfalfa autotoxicity. Alfalfa extracts were passed though leaching columns filled with topsoil of either Sarpy fine sandy loam (mixed, mesic Typic Udipsamments) or Carlow silty clay loam (fine, smectitic, mesic Vertic Endoaquolls) and fractions were collected. Control columns for each soil were leached with distilled water only. Sequential fractions were added to 50 alfalfa seed in petri dishes. Radicle length and percentage germination were measured after 3 d. Active fractions reduced radicle growth more than percentage germination in both soils. The autotoxic chemical or chemicals moved through the Sarpy soil faster than through the Carlow soil. Fifty percent more water was required to move the active fraction of the extract through 10-cm columns of the Carlow soil than the Sarpy soil. Maximum autotoxicity within a fraction was greater for the Sarpy soil, but the effects appeared in more fractions for the Carlow soil. The results indicate that similar amounts of the autotoxic factor in sandy soil will have a greater influence on alfalfa seedling growth than in the clay soil. Conversely, the same amount of rainfall will leach the autotoxic factor from a sandy soil while only diluting it in a clay soil. Soil texture and rain water throughput may interact to affect length of rotation intervals needed for successful reseeding of alfalfa. Field research is needed to determine if rotation intervals can be modified based on soil texture and irrigation or expected rainfall.

We aim to build a new tertiary mirror (M3) and its mount for the 10 m Keck I (K1) telescope at the W. M. Keck Observatory (WMKO) to make its full observational capabilities available for time-sensitive scientific programs.. In contrast to the existing tertiary mirror and mount, the device will rapidly deploy and rotate the mirror to any instrument at a Nasmyth focus or, as desired, stow the mirror out of the light path to permit observations at the Cassegrain focus. In this manner, the K1 deployable tertiary mirror (K1DM3) will enable observations with any of the K1 instruments on any given night, and at any given time. The K1DM3 device will be integrated within the K1 telescope control system and WMKO has committed to a new operations model that takes full advantage of this new capability.

Through use of a new bacteriophage assay capable of detecting a single viral plaque-forming unit (PFU), viral leakage through multiple replicates of several types of latex condoms has been evaluated. Stocks were used that had been preserved from a previous large study in which viral leakage had been assessed preliminarily in several brands. In the present research, much larger numbers of replicates--on the order of magnitude of 100 condoms per brand--were used. Leakage was demonstrated in single production lots of each of seven brands of condoms. With one notable exception, percent leakage ranged from 0.9 to 22.8%; 100% of the specimens of one profoundly flawed brand leaked. All test condoms were subjected to conditions intended to model these prevailing during coitus. Because the condoms used in this study were aged, current stocks of two widely sold brands were tested for comparison. Of these, 11.8% of one brand leaked, 25.7% of the other. The relevance of the results, which gave a high, albeit physiologically appropriate, challenge to the test brands, is discussed--so too is the significance to condom users of results deriving from a leakage assay of exquisitely high sensitivity.In California and Utah, researchers used the standard Airburst Test and the Tensile and Elongation Test to determine the stability of multiple replicates of several types of aged latex condoms (100 condoms/brand) from each brand of remaining stocks from an original National Institutes of Health-sponsored study. They used current stocks of lubricated and nonlubricated Trojan brands as controls. They physically stressed each condom as much as it would be during coitus just before ejaculation before submitting it to the 2 tests. They used a new bacteriophage assay, which can detect a single viral plaque-forming unit (PFU), to detect any leakage. The bacteriophage oX174 was used as a surrogate for HIV-1 and other viruses of sexually transmitted diseases. Each of the brands of condoms experienced some leakage. All of the Protex Contracept Plus condoms leaked. As for the remaining brands, the leakage rate varied from 0.9% to 22.8%. The Ramses Non-Lubricated condom, the original Mentor condom, and the LifeStyles Conture had the lowest percentage of condoms that leaked viral particles (0.9%, 4%, and 6.3%, respectively). Their leakage rates were lower than those of the 2 current stocks (25.7% for the lubricated Trojan controls and 11.8% for the nonlubricated Trojan controls). None of the leakages in the 3 brands were visibly detectable. Test conditions were intentionally demanding: a much smaller viral particle than HIV-1 (25% the diameter of HIV-1, close to the size of some hepatitis viruses), the enveloped and spherical shape of which enhances the potential for its passage through small holes, presence of a potent surface active agent, a longer test period than most coital acts (30 minutes), a constant pressure head during the test period, a high titer of virus and large volume of viral suspension with the condom. These results should be considered in the proper perspective.

The active control systems of segmented mirror telescopes are vulnerable to a malfunction of a few (or even one) of their segment edge sensors, the effects of which can propagate through the entire system and seriously compromise the overall telescope image quality. Since there are thousands of such sensors in the extremely large telescopes now under development, it is essential to develop fast and efficient algorithms that can identify bad sensors so that they can be removed from the control loop. Such algorithms are nontrivial; for example, a simple residual-to-the-fit test will often fail to identify a bad sensor. We propose an algorithm that can reliably identify a single bad sensor and we extend it to the more difficult case of multiple bad sensors. Somewhat surprisingly, the identification of a fixed number of bad sensors does not necessarily become more difficult as the telescope becomes larger and the number of sensors in the control system increases.

We investigate a new metric, the normalized point source sensitivity (PSSN), for characterizing the seeing-limited performance of large telescopes. As the PSSN metric is directly related to the photometric error of background limited observations, it represents the efficiency loss in telescope observing time. The PSSN metric properly accounts for the optical consequences of wave front spatial frequency distributions due to different error sources, which differentiates from traditional metrics such as the 80% encircled energy diameter and the central intensity ratio. We analytically show that multiplication of individual PSSN values due to individual errors is a good approximation for the total PSSN when various errors are considered simultaneously. We also numerically confirm this feature for Zernike aberrations as well as for the numerous error sources considered in the error budget of the Thirty Meter Telescope (TMT) using a ray optics simulator. Additionally, we discuss other pertinent features of the PSSN, including its relations to Zernike aberration, RMS wave front error, and central intensity ratio.

The Thirty Meter Telescope (TMT) Project will design and build a thirty-meter diameter telescope for research in astronomy at optical and infrared wavelengths. TMT is a partnership between the University of California, Caltech, and the Association of Canadian Universities for Research in Astronomy (ACURA). The $80 million TMT design and development phase is fully funded and Preliminary Design is in progress. An additional $300 million has been pledged towards early TMT construction which will commence in 2009. We include a high level description of the design of the telescope and its planned adaptive optics and science instrumentation. The schedule of key milestones for completing the design and construction is summarized.

The out-of-plane degrees of freedom (piston, tip, and tilt) of each of the 492 segments in the Thirty Meter Telescope primary mirror will be actively controlled using three actuators per segment and two edge sensors along each intersegment gap. We address two important topics for this system: edge sensor design, and the correction of fabrication and installation errors. The primary mirror segments are passively constrained in the three lateral degrees of freedom. We evaluate the segment lateral motions due to the changing gravity vector and temperature, using site temperature and wind data, thermal modeling, and finite-element analysis. Sensor fabrication and installation errors combined with these lateral motions will induce errors in the sensor readings. We evaluate these errors for a capacitive sensor design as a function of dihedral angle sensitivity. We also describe operational scenarios for using the Alignment and Phasing System to correct the sensor readings for errors associated with fabrication and installation.

The Thirty Meter Telescope (TMT) projecthas been collecting data on“ve candidate sites since 2003. This paperdescribes the site testing portion of the TMT site selection program and the process and standards employedby it. This includes descriptions of the candidate sites, the process by which they were identi“ed, the sitecharacterization instrument suite and its calibration and the available results, which will be published shortly.Keywords: Site testing, site selection, ELTs 1. INTRODUCTION This paper provides a summary of the Thirty Meter Telescope (TMT) site testing program that was conductedto support a site selection. The principles underlying this program and the selection of candidate sites werealready described in Ref. 1. Some of them are repeated here in abbreviated or updated form in order to providethe reader with a complete and consistent picture of the process. In addition, more information about theinstruments and instrument calibrations is given and the available results are described. The results from thesite testing period will be published shortly.TMT needs to be built on the best available site in order to obtain the maximum return from its sciencepotential. Careful site testing has therefore been extremely important to TMT from the very beginning of theproject. The site testing process started in 2001/2002, in a collaboration between the AURA New InitiativesOce (NIO) and the California Extremely Large Telesco pe (CELT), with the selection of “ve candidate sites tobe studied in detail. The sites were studied via the operation of remote site monitoring stations starting in 2003.The TMT site needs to be suited for producing astronomical data of superb quality and for building andoperating an observatory of the size and complexity of TMT. Strict technical requirements as they apply toother parts of the project do not exist for the TMT site, as there are many combinations of site parametersentering the TMT site decision which may de“ne an excellent site for TMT. Instead, the site selection processinvolves measuring and predicting both the technical and programmatic properties of the sites and balancingthem so as to determine the site that best meets the TMT needs. It is not a priori obvious how to combineall the parameters to arrive at the “nal site decision. A series of steps have therefore been taken by the TMTProject to develop a method of dealing with the complexity of the TMT site selection process. These includethe development of a site ranking metric which provides a method for an objective comparison of the technicalproperties of the candidate sites and their science producing implications, the issuing of several comprehensiveintermediate reports, quarterly results update reports as well as quarterly internal and approximately annualexternal reviews. These steps have proven to be invaluable for the both the site testing team and the TMTproject and served their intended purpose of providing information to the parties involved in the site decisionand of “ne-tuning our data analysis and site comparison methodology.

This paper presents refinements to the design of the TMT primary mirror segment passive-support system that are effective in reducing gravity print-through and thermal distortion effects. First, a novel analytical method is presented for tuning the axial and lateral support systems in a manner that results in improved optical performance when subject to varying gravity fields. The method utilizes counterweights attached to the whiffletrees to cancel astigmatic and comatic errors normally resulting when the lateral support system resists transverse loads induced by gravity. Secondly, several central diaphragm designs are presented and analyzed to assess lateral-gravity and thermal distortion performance: 1) a simple flat diaphragm, 2) a stress-relieving diaphragm having a slotted outer rim and a circumferential convolution near the outside diameter, and 3) a flat diaphragm having a slotted outer rim. The latter design is chosen based on results from analytical studies which show it to have better overall optical performance in the presence of gravity and thermal environments.

The Thirty Meter Telescope (TMT) project, a partnership between ACURA, Caltech, and the University of California, is currently developing a 30-meter diameter optical telescope. The primary mirror will be composed of 492 low expansion glass segments. Each segment is hexagonal, nominally measuring 1.44m across the corners. Because the TMT primary mirror is curved (i.e. not flat) and segmented with uniform 2.5mm nominal gaps, the resulting hexagonal segment outlines cannot all be identical. All segmentation approaches studied result in some combination of shape and size variations. These variations range from fractions of a millimeter to several millimeters. Segmentation schemes for the TMT primary mirror are described in some detail. Various segmentation approaches are considered, with the goal being to minimize various measures of shape variation between segments, thereby reducing overall design complexity and cost. Two radial scaling formulations are evaluated for their effectiveness at achieving these goals. Optimal tuning of these formulations and detailed statistics of the resulting segment shapes are provided. Finally, we present the rationale used for selecting the preferred segmentation approach for TMT.

We investigate a new metric, Normalized Point Source Sensitivity (PSSN), for characterizing the seeing limited performance of the Thirty Meter Telescope. As the PSSN metric is directly related to the photometric error of background limited observations, it truly represents the efficiency loss in telescope observing time. The PSSN metric properly accounts for the optical consequences of wavefront spatial frequency distributions due to different error sources, which makes it superior to traditional metrics such as the 80% encircled energy diameter. We analytically show that multiplication of individual PSSN values due to individual errors is a good approximation for the total PSSN when various errors are considered simultaneously. We also numerically confirm this feature for Zernike aberrations, as well as for the numerous error sources considered in the TMT error budget using a ray optics simulator, Modeling and Analysis for Controlled Optical Systems. We also discuss other pertinent features of the PSSN including its relations to Zernike aberration and RMS wavefront error.

I describe the design of the Thirty Meter Telescope, a project to build a ground-based thirty-meter telescope. The partners include the University of California, Caltech, the Association of Canadian Universities for Research in Astronomy (ACURA), and NSF. The Project is currently in the design and development phase and will be ready for a 2009 construction start.

The Thirty Meter Telescope project will design and build a thirty-meter diameter telescope for research in astronomy at optical and infrared wavelengths. The highly segmented primary mirror will use edge sensors to align and stabilize the relative piston, tip, and tilt degrees of freedom of the segments. We describe an edge sensor conceptual design and relate the sensor errors to the performance of the telescope as whole. We discuss the sensor calibration, installation, maintenance, and reliability.

The Thirty Meter Telescope (TMT) Project will design and build a thirty-meter diameter telescope for research in astronomy at optical and infrared wavelengths. TMT is a partnership between the University of California, Caltech, Association of Canadian Universities for Research in Astronomy (ACURA), and the Association of Universities for Research in Astronomy (AURA). The TMT design and development phase is funded and work is underway. We include a high level description of the design of the telescope and its planned adaptive optics and science instrumentation. The organizational structure of the project is summarized along with the schedule of key milestones in the design. We are carrying out key conceptual and cost reviews in 2006 and will be prepared to begin construction in 2009, with first light in 2015.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper describes the studies performed to establish a baseline conceptual design of the Segment Support Assembly (SSA) for the Thirty Meter Telescope (TMT) primary mirror. The SSA uses a combination of mechanical whiffletrees for axial support, a central diaphragm for lateral support, and a whiffletree-based remote-controlled warping harness for surface figure corrections. Axial support whiffletrees are numerically optimized to minimize the resulting gravityinduced deformation. Although a classical central diaphragm solution was eventually adopted, several lateral support concepts are considered. Warping harness systems are analyzed and optimized for their effectiveness at correcting second and third order optical aberrations. Thermal deformations of the optical surface are systematically analyzed using finite element analysis. Worst-case performance of the complete system as a result of gravity loading and temperature variations is analyzed as a function of zenith angle using an integrated finite element model.

The most common detector configuration for Shack Hartmann (SH) wavefront sensors used for adaptive optics (AO) wavefront sensing is the quad cell. Advances in detectors, such as the CCDs being developed in a project on which we are collaborators (funded by the Adaptive Optics Development Program), make it possible to use larger pixel arrays. The CCD designs incorporate improved read amplifiers and novel pixel geometries optimized for laser guide star (LGS) AO wavefront sensing. While it is likely that finer sampling of the SH spot will improve the ability of the wavefront sensor to accurately determine the spot displacement, particularly for elongated or aberrated spots such as those seen in LGS AO systems, the optimal sampling is not dependent simply on the number of pixels but must also take into account the effects of photon and detector noise. The performance of a SH wavefront sensor also depends on the performance of the algorithm used to find the spot displacement. In the literature alternatives have been proposed to the common center of mass algorithm, but these have not been simulated in detail. In this paper we will describe the results of our study of the performance of a SH wavefront sensor with a well sampled spot. We will present results for simulations of the wavefront sensor that enable us to optimize the design of the detector for varying conditions of signal to noise and spot elongation. We will also discuss the application of correlation algorithms to SH wavefront sensors and present results regarding the performance and statistics of this algorithm.

The Thirty Meter Telescope (TMT) is a collaborative project between the California Institute of Technology (CIT), the University of California (UC), the Association of Universities for Research in Astronomy (AURA), and the Association of Canadian Universities for Research in Astronomy (ACURA). The Alignment and Phasing System (APS) for the Thirty Meter Telescope will be a Shack-Hartmann type camera that will provide a variety of measurements for telescope alignment, including segment tip/tilt and piston, segment figure, secondary and tertiary figure, and overall primary/secondary/tertiary alignment. The APS will be modeled after the Phasing Camera System (PCS), which performed most, but not all, of these tasks for the Keck Telescopes. We describe the functions of the APS, including a novel supplemental approach to measuring and adjusting the segment figures, which treats the segment aberrations as global variables.