The lunar surface: visualizing changes

This research project attempted to create a method of comparison between the imagery from the Lunar Orbiter program (from the mid 1960\u27s) with that of the Clementine mission (of the mid 1990\u27s). The premise behind this research is that if any new surface features developed over the course of the past thirty years, they could be found by doing such a digitial comparison. There are many implication that such research could have on the future. Being that the moon is currently the most thouroughly studied celestial body, the use of doing such a comparison between databases of imagery would prove to be useful on ly for the moon. But in the future, such techniques could be applied to a variety of imagery. In the specific case of the lunar surface, it is important to know of things that develop on the surface (either volcanically or due to an impact) because it is the closest indicator of what may be happening at the earth\u27s outermost layer of atmosphere. Previously, these large databases had been collected, but not much had been done with the imagery. This research has been able to create a procedure in which such imagery from the Clementine satellite could be compared to imagery from the Lunar Orbiter program. This procedure is a bit involved because of the way that both of these databases of imagery are being archived. The Orbiter images exist as photographic negatives and the Clementine images exist on CDs as written in the PDS (Planetary Data Systems) format. This procedure is thus easy for the Orbiter imagery, which only needs to be obtained and then scanned. The Clementine image needs to be obtained and put through four programs: NasaView, Adobe Photoshop, Erdas Imagine, and an IDL (Interactive Data Language) code. Using the region of the lunar surface around the crater Aristarchus, digital comparisons yielded that there was no evidence that the lunar surface had changed. It did however prove that the major differences that were seen were due to inherent differences in the images and due to the sun\u27s illumination angle on the crater. Therefore, it seems logical to conclude that in order to obtain better results (that may translate into actual changes in lunar surface) it may be better to try to minimize the differences in image structure and resolution along with trying to correct for different illumination angles

Non-Gaussianities in Multifield Inflation: Superhorizon Evolution, Adiabaticity, and the Fate of fnl

We explore the superhorizon generation of large fnl of the local form in two field inflation. We calculate the two- and three-point observables in a general class of potentials which allow for an analytic treatment using the delta N formalism. Motivated by the conservation of the curvature perturbation outside the horizon in the adiabatic mode and also by the observed adiabaticity of the power spectrum, we follow the evolution of fnl^{local} until it is driven into the adibatic solution by passing through a phase of effectively single field inflation. We find that although large fnl^{local} may be generated during inflation, such non-gaussianities are transitory and will be exponentially damped as the cosmological fluctuations approach adiabaticity.Comment: v3: Typos corrected, minor changes to match published version, references added, 18 pages, 1 figure. v2: Changed sign of fnl to match WMAP convention, minor changes throughout, references added, 18 pages, 1 figure. v1: 17 pages, 1 figur

High Contrast L' Band Adaptive Optics Imaging to Detect Extrasolar Planets

We are carrying out a survey to search for giant extrasolar planets around nearby, moderate-age stars in the mid-infrared L' and M bands (3.8 and 4.8 microns, respectively), using the Clio camera with the adaptive optics system on the MMT telescope. To date we have observed 7 stars, of a total 50 planned, including GJ 450 (distance about 8.55pc, age about 1 billion years, no real companions detected), which we use as our example here. We report the methods we use to obtain extremely high contrast imaging in L', and the performance we have obtained. We find that the rotation of a celestial object over time with respect to a telescope tracking it with an altazimuth mount can be a powerful tool for subtracting telescope-related stellar halo artifacts and detecting planets near bright stars. We have carried out a thorough Monte Carlo simulation demonstrating our ability to detect planets as small as 6 Jupiter masses around GJ 450. The division of a science data set into two independent parts, with companions required to be detected on both in order to be recognized as real, played a crucial role in detecting companions in this simulation. We mention also our discovery of a previously unknown faint stellar companion to another of our survey targets, HD 133002. Followup is needed to confirm this as a physical companion, and to determine its physical properties.Comment: 8 pages, 4 figure

Machine Learning Classification of SDSS Transient Survey Images

We show that multiple machine learning algorithms can match human performance in classifying transient imaging data from the Sloan Digital Sky Survey (SDSS) supernova survey into real objects and artefacts. This is a first step in any transient science pipeline and is currently still done by humans, but future surveys such as the Large Synoptic Survey Telescope (LSST) will necessitate fully machine-enabled solutions. Using features trained from eigenimage analysis (principal component analysis, PCA) of single-epoch g, r and i-difference images, we can reach a completeness (recall) of 96 per cent, while only incorrectly classifying at most 18 per cent of artefacts as real objects, corresponding to a precision (purity) of 84 per cent. In general, random forests performed best, followed by the k-nearest neighbour and the SkyNet artificial neural net algorithms, compared to other methods such as na\"ive Bayes and kernel support vector machine. Our results show that PCA-based machine learning can match human success levels and can naturally be extended by including multiple epochs of data, transient colours and host galaxy information which should allow for significant further improvements, especially at low signal-to-noise.Comment: 14 pages, 8 figures. In this version extremely minor adjustments to the paper were made - e.g. Figure 5 is now easier to view in greyscal