MegaPipe: the MegaCam image stacking pipeline at the Canadian Astronomical Data Centre

This paper describes the MegaPipe image processing pipeline at the Canadian Astronomical Data Centre. The pipeline combines multiple images from the MegaCam mosaic camera on CFHT and combines them into a single output image. MegaPipe takes as input detrended MegaCam images and does a careful astrometric and photometric calibration on them. The calibrated images are then resampled and combined into image stacks. The astrometric calibration of the output images is accurate to within 0.15 arcseconds relative to external reference frames and 0.04 arcseconds internally. The photometric calibration is good to within 0.03 magnitudes. The stacked images and catalogues derived from these images are available through the CADC website:Comment: Data available at http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/megapipe/index.htm

Space-based tests of gravity with laser ranging

Existing capabilities in laser ranging, optical interferometry and metrology, in combination with precision frequency standards, atom-based quantum sensors, and drag-free technologies, are critical for the space-based tests of fundamental physics; as a result, of the recent progress in these disciplines, the entire area is poised for major advances. Thus, accurate ranging to the Moon and Mars will provide significant improvements in several gravity tests, namely the equivalence principle, geodetic precession, PPN parameters $\beta$ and $\gamma$, and possible variation of the gravitational constant $G$. Other tests will become possible with development of an optical architecture that would allow proceeding from meter to centimeter to millimeter range accuracies on interplanetary distances. Motivated by anticipated accuracy gains, we discuss the recent renaissance in lunar laser ranging and consider future relativistic gravity experiments with precision laser ranging over interplanetary distances.Comment: 14 pages, 2 figures, 1 table. To appear in the proceedings of the International Workshop "From Quantum to Cosmos: Fundamental Physics Research in Space", 21-24 May 2006, Warrenton, Virginia, USA http://physics.jpl.nasa.gov/quantum-to-cosmos

The Color Distribution in the Edgeworth-Kuiper Belt

We have started since 1997 the Meudon Multicolor Survey of Outer Solar System Objects with the aim of collecting a large and homogeneous set of color data for Trans-Neptunian and Centaurs objects [...] We have a combined sample of 52 B-R color measurements for 8 Centaurs, 22 Classicals, 13 Plutinos, 8 Scattered objects and 1 object with unidentified dynamical class. This dataset is the largest single and homogeneous published dataset to date [...]. A strong (color) correlation with mean excitation velocity points toward a space weathering/impact origin for the color diversity. However, thorough modeling of the collisional/dynamical environment in the Edgeworth-Kuiper belt needs to be done in order to confirm this scenario. We found also that the Classical TNOs consist in the superposition of two distinct populations: the dynamically Cold Classical TNOs (red colors, low i, small sizes) and the dynamically Hot Classical TNOs (diverse colors, moderate and high i, larger sizes). [...] Our specific observation strategy [...] permitted us to highlight a few objects suspected to have true compositional and/or texture variation on their surfaces. These are 1998 HK151, 1999 DF9, 1999 OY3, 2000 GP183, 2000 OK67, and 2001 KA77 and should be prime targets for further observations [...]. Our survey has also highlighted 1998 SN165 whose colors and dynamical properties puts it in a new dynamical class distinct from the Classicals, its previously assigned dynamical class.Comment: Accepted for publication in Astronomical Journal (38 pages, inc. 11 figures

The CFEPS Kuiper Belt Survey: Strategy and Pre-survey Results

We present the data acquisition strategy and characterization procedures for the Canada-France Ecliptic Plane Survey (CFEPS), a sub-component of the Canada-France-Hawaii Telescope Legacy Survey. The survey began in early 2003 and as of summer 2005 has covered 430 square degrees of sky within a few degrees of the ecliptic. Moving objects beyond the orbit of Uranus are detected to a magnitude limit of $m_R$=23 -- 24 (depending on the image quality). To track as large a sample as possible and avoid introducing followup bias, we have developed a multi-epoch observing strategy that is spread over several years. We present the evolution of the uncertainties in ephemeris position and orbital elements as the objects progress through the epochs. We then present a small 10-object sample that was tracked in this manner as part of a preliminary survey starting a year before the main CFEPS project. We describe the CFEPS survey simulator, to be released in 2006, which allows theoretical models of the Kuiper Belt to be compared with the survey discoveries since CFEPS has a well-documented pointing history with characterized detection efficiencies as a function of magnitude and rate of motion on the sky. Using the pre-survey objects we illustrate the usage of the simulator in modeling the classical Kuiper Belt.Comment: to be submitted to Icaru

Evidence for a colour dependence in the size distribution of main belt asteroids

We present the results of a project to detect small (~1 km) main-belt asteroids with the 3.6 meter Canada-France-Hawaii Telescope (CFHT). We observed in 2 filters (MegaPrime g' and r') in order to compare the results in each band. Owing to the observational cadence we did not observe the same asteroids through each filter and thus do not have true colour information. However strong differences in the size distributions as seen in the two filters point to a colour-dependence at these sizes, perhaps to be expected in this regime where asteroid cohesiveness begins to be dominated by physical strength and composition rather than by gravity. The best fit slopes of the cumulative size distributions (CSDs) in both filters tend towards lower values for smaller asteroids, consistent with the results of previous studies. In addition to this trend, the size distributions seen in the two filters are distinctly different, with steeper slopes in r' than in g'. Breaking our sample up according to semimajor axis, the difference between the filters in the inner belt is found to be somewhat less pronounced than in the middle and outer belt, but the CSD of those asteroids seen in the r' filter is consistently and significantly steeper than in g' throughout. The CSD slopes also show variations with semimajor axis within a given filter, particularly in r'. We conclude that the size distribution of main belt asteroids is likely to be colour dependent at kilometer sizes and that this dependence may vary across the belt.Comment: 28 pages, 5 figures, submitted to the Astronomical Journa

A Cryogenic Test Set-Up for the Qualification of Pre-Series Test Cells for the LHC Cryogenic Distribution Line

Three pre-series Test Cells of the LHC Cryogenic Distribution Line (QRL) [1], manufactured by three European industrial companies, will be tested in the year 2000 to qualify the design chosen and verify the thermal and mechanical performances. A dedicated test stand (170 m x 13 m) has been built for extensive testing and performance assessment of the pre-series units in parallel. They will be fed with saturated liquid helium at 4.2 K supplied by a mobile helium dewar. In addition, LN2 cooled helium will be used for cool-down and thermal shielding. For each of the three pre-series units, a set of end boxes has been designed and manufactured at CERN. This paper presents the layout of the cryogenic system for the pre-series units, the calorimetric methods as well as the results of the thermal calculation of the end box test

Hunting for planets in the HL Tau disk

Recent ALMA images of HL Tau show gaps in the dusty disk that may be caused by planetary bodies. Given the young age of this system, if confirmed, this finding would imply very short timescales for planet formation, probably in a gravitationally unstable disk. To test this scenario, we searched for young planets by means of direct imaging in the L'-band using the Large Binocular Telescope Interferometer mid-infrared camera. At the location of two prominent dips in the dust distribution at ~70AU (~0.5") from the central star we reach a contrast level of ~7.5mag. We did not detect any point source at the location of the rings. Using evolutionary models we derive upper limits of ~10-15MJup at <=0.5-1Ma for the possible planets. With these sensitivity limits we should have been able to detect companions sufficiently massive to open full gaps in the disk. The structures detected at mm-wavelengths could be gaps in the distributions of large grains on the disk midplane, caused by planets not massive enough to fully open gaps. Future ALMA observations of the molecular gas density profile and kinematics as well as higher contrast infrared observations may be able to provide a definitive answer.Comment: Accepted for publication on ApJ Letter

Co-phasing the Large Binocular Telescope: status and performance of LBTI/PHASECam

The Large Binocular Telescope Interferometer is a NASA-funded nulling and imaging instrument designed to coherently combine the two 8.4-m primary mirrors of the LBT for high-sensitivity, high-contrast, and high-resolution infrared imaging (1.5-13 um). PHASECam is LBTI's near-infrared camera used to measure tip-tilt and phase variations between the two AO-corrected apertures and provide high-angular resolution observations. We report on the status of the system and describe its on-sky performance measured during the first semester of 2014. With a spatial resolution equivalent to that of a 22.8-meter telescope and the light-gathering power of single 11.8-meter mirror, the co-phased LBT can be considered to be a forerunner of the next-generation extremely large telescopes (ELT).Comment: 8 pages, 5 figures, SPIE Conference proceeding