A Lunar Laser Ranging Retroreflector Array for the 21st Century

Abstract Over the past 40 years, the Lunar Laser Ranging Program (LLRP) to the Apollo Cube Corner (CCR) Retroreflector Arrays (ALLRRA) [1] has supplied almost all of the significant tests of General Relativity. The LLRP has evaluated the PPN parameters, addressed the possible changes in the gravitational constant and the properties of the self-energy of the gravitational field. In addition, the LLRP has provided significant information on the composition and origin of the moon. This is the only Apollo experiment that is still in operation. Initially the ALLRRAs contributed a negligible fraction of the ranging error budget. Over the decades, the ranging capabilities of the ground stations have improved by more than two orders of magnitude. Now, because of the lunar librations, the existing Apollo retroreflector arrays contribute a significant fraction of the limiting errors in the range measurements. The University of Maryland, as the Principal Investigator for the original Apollo arrays, is now proposing a new approach to the Lunar Laser Array technology [2] . The investigation of this new technology, with Professor Currie as Principal Investigator, is currently being supported by two NASA programs and by the INFN-LNF in Frascati, Italy. Thus after the proposed installation during the next lunar landing, the new arrays will support ranging observations that are a factor 100 more accurate than the current ALLRRAs. The new fundamental cosmological physics and the lunar physics [3] that this new Lunar Laser Ranging Retroreflector Array for the 21st Century (LLRRA-21) can provide will be described. In the design of the new array, there are three major challenges: (1) validate the ability to fabricate a CCR of the required specifications, which is significantly beyond the properties of current CCRs, (2) address the thermal and optical effects of the absorption of solar radiation within the CCR, reduce the transfer of heat from the CCR housing and (3) validate an accurate emplacement technique to install the CCR package on the lunar surface. The latter requires a long-term stable relation between the optical center of the array and the deep regolith, that is, below the thermally driven expansion and contraction of the regolith during the lunar day/night cycle

Report on lunar ranging at McDonald Observatory for the period February 16 to April 15, 1970

This report describes the lunar ranging activities at McDonald Observatory and the associated activities at the University of Maryland for the two-month period February 16, 1970 to April 15, 1970. During this period numerous acquisitions were obtained. A major problem was discovered and remedied. As a result, a continuing high rate of acquisition producing good data is anticipated

My Son

Fiction by Douglas M. Curri

Skeletal maturation in the dog : a roentgenographic and skeletal study of the appearance of the ossification centres and union of the epiphyses in the bones of the limbs and bodies of the vertebrae

This study was undertaken with two objectives in mind: one objective was to obtain more definite information than had previously been available about the postnatal ages at which the ossification centres appear; the other was to establish when epiphyseal union takes place, since the findings of earlier investigators did not correspond and were inconclusive for one reason or another. Lesbre (1897) had carried out the first comprehensive study of the ossification process in the dog. His work had been accepted by veterinary anatomists in general, although his findings for those epiphyses that unite after the age of seven months had not been substantiated by the findings of later investigators. Lesbre's findings were approximate and, therefore, inconclusive because they had been based on dogs whose ages had been estimated by the teeth, while those of the later investigations were inconclusive either because of the material or because of the methods of study used.The appearance of the ossification centres was studied by X-raying dogs from four breeds fit regular intervals from birth. Epiphyseal union was studied by X-raying dogs from two breeds at regular intervals, and by examining the bones in seventy skeletons, seventy-one pectoral limbs, and one pelvis from dogs of known age. These dogs came from a variety of breeds, & number of which were achondroplastic. In addition, one hundred and twenty-six skulls from dogs of known ages were examined to study the dental changes that take place between the age of three and nineteen months, since it appeared to be important to assess the value of the teeth as a guide to the estimation of age In the dog.Age periods have been established for the appearance of each of the centres that ossify after birth, and for the union of the epiphyses with their respective diephyses. For both the appearance of the centres and the union of the epiphyses, it has been noted that the chronological order of events remains constant, but that there are age variations between individuals from the same litter or breed, and to a greater extent between individuals from different breeds. Neither sex nor the single dominant character for achondroplasia appears to influence the rate of skeletal maturation.The study of epiphyseal union has provided definite evidence that after the age of seven months epiphyseal union takes place, on sn average, five to seven months earlier than stated by LesbreThe dental study has indicated that the criteria by which Lesbre probably estimated the age of the dogs that he studied were innaccurate, because the amount of wear that he expected to find on the incisor teeth at a particular age is frequently seen about six months earlier.The conclusion is that the probable explanation for the error in Lesbre's findings is that he had misestimated the age of the dogs that he studied

Human Capital Development Before Age Five

This chapter seeks to set out what Economists have learned about the effects of early childhood influences on later life outcomes, and about ameliorating the effects of negative influences. We begin with a brief overview of the theory which illustrates that evidence of a causal relationship between a shock in early childhood and a future outcome says little about whether the relationship in question biological or immutable. We then survey recent work which shows that events before five years old can have large long term impacts on adult outcomes. Child and family characteristics measured at school entry do as much to explain future outcomes as factors that labor economists have more traditionally focused on, such as years of education. Yet while children can be permanently damaged at this age, an important message is that the damage can often be remediated. We provide a brief overview of evidence regarding the effectiveness of different types of policies to provide remediation. We conclude with a list of some of (the many) outstanding questions for future research. Hard-copy subscribers may access the tables for this paper here .

A Lunar Laser Ranging Retroreflector Array for the 21st Century

Abstract To date, lunar laser ranging to the Apollo retroreflector arrays, which are still operational after four decades, has produced some of the best tests of General Relativity. Since the ground Observatories have improved their accuracy by a factor of 200, the lunar hardware, due to the lunar librations, now limits the ranging accuracy. The Lunar Laser Ranging Retroreflector Array for the 21st Century program plans to deploy new packages that will improve the ranging accuracy by a factor of ten to one hundred in the next few years

Public vs. Private Provision of Charity Care? Evidence from the Expiration of Hill-Burton Requirements in Florida

This paper explores the consequences of the expiration of charity care requirements imposed on private hospitals by the Hill-Burton Act. We examine delivery care and the health of newborns using the universe of Florida births from 1989-2003 combined with hospital data from the American Hospital Association. We find that charity care requirements were binding on hospitals, but that private hospitals under obligation “cream skimmed” the least risky maternity patients. Conditional on patient characteristics, they provided less intensive maternity services but without compromising patient health. When obligations expired, private hospitals quickly reduced their charity caseloads, shifting maternity patients to public hospitals. There they received more intensive services, but did not experience improvements in health. These results suggest that public hospitals provided services less efficiently than private hospitals constrained to provide charity care.

Hubble Space Telescope Planetary Camera Images of NGC 1316

We present HST Planetary Camera V and I~band images of the central region of the peculiar giant elliptical galaxy NGC 1316. The inner profile is well fit by a nonisothermal core model with a core radius of 0.41" +/- 0.02" (34 pc). At an assumed distance of 16.9 Mpc, the deprojected luminosity density reaches \sim 2.0 \times 10^3 L_{\sun} pc$^{-3}$. Outside the inner two or three arcseconds, a constant mass-to-light ratio of $\sim 2.2 \pm 0.2$ is found to fit the observed line width measurements. The line width measurements of the center indicate the existence of either a central dark object of mass 2 \times 10^9 M_{\sun}, an increase in the stellar mass-to-light ratio by at least a factor of two for the inner few arcseconds, or perhaps increasing radial orbit anisotropy towards the center. The mass-to-light ratio run in the center of NGC 1316 resembles that of many other giant ellipticals, some of which are known from other evidence to harbor central massive dark objects (MDO's). We also examine twenty globular clusters associated with NGC 1316 and report their brightnesses, colors, and limits on tidal radii. The brightest cluster has a luminosity of 9.9 \times 10^6 L_{\sun} ($M_V = -12.7$), and the faintest detectable cluster has a luminosity of 2.4 \times 10^5 L_{\sun} ($M_V = -8.6$). The globular clusters are just barely resolved, but their core radii are too small to be measured. The tidal radii in this region appear to be $\le$ 35 pc. Although this galaxy seems to have undergone a substantial merger in the recent past, young globular clusters are not detected.Comment: 21 pages, latex, postscript figures available at ftp://delphi.umd.edu/pub/outgoing/eshaya/fornax