An Integer Linear Programming Solution to the Telescope Network Scheduling Problem

Telescope networks are gaining traction due to their promise of higher resource utilization than single telescopes and as enablers of novel astronomical observation modes. However, as telescope network sizes increase, the possibility of scheduling them completely or even semi-manually disappears. In an earlier paper, a step towards software telescope scheduling was made with the specification of the Reservation formalism, through the use of which astronomers can express their complex observation needs and preferences. In this paper we build on that work. We present a solution to the discretized version of the problem of scheduling a telescope network. We derive a solvable integer linear programming (ILP) model based on the Reservation formalism. We show computational results verifying its correctness, and confirm that our Gurobi-based implementation can address problems of realistic size. Finally, we extend the ILP model to also handle the novel observation requests that can be specified using the more advanced Compound Reservation formalism.Comment: Accepted for publication in the refereed conference proceedings of the International Conference on Operations Research and Enterprise Systems (ICORES 2015

Achieving better than 1 minute accuracy in the Heliocentric and Barycentric Julian Dates

As the quality and quantity of astrophysical data continue to improve, the precision with which certain astrophysical events can be timed becomes limited not by the data themselves, but by the manner, standard, and uniformity with which time itself is referenced. While some areas of astronomy (most notably pulsar studies) have required absolute time stamps with precisions of considerably better than 1 minute for many decades, recently new areas have crossed into this regime. In particular, in the exoplanet community, we have found that the (typically unspecified) time standards adopted by various groups can differ by as much as a minute. Left uncorrected, this ambiguity may be mistaken for transit timing variations and bias eccentricity measurements. We argue that, since the commonly-used Julian Date, as well as its heliocentric and barycentric counterparts, can be specified in several time standards, it is imperative that their time standards always be reported when accuracies of 1 minute are required. We summarize the rationale behind our recommendation to quote the site arrival time, in addition to using BJD_TDB, the Barycentric Julian Date in the Barycentric Dynamical Time standard for any astrophysical event. The BJD_TDB is the most practical absolute time stamp for extra-terrestrial phenomena, and is ultimately limited by the properties of the target system. We compile a general summary of factors that must be considered in order to achieve timing precisions ranging from 15 minutes to 1 microsecond. Finally, we provide software tools that, in principal, allow one to calculate BJD_TDB to a precision of 1 microsecond for any target from anywhere on Earth or from any spacecraft.Comment: Online BJD_TDB calculator at http://astroutils.astronomy.ohio-state.edu/time/utc2bjd.html. PASP accepted, 11 pages, 6 figures, updated to match published versio

Dual Adaptive Recumbent Trike

The DART team\u27s objective was to develop a tandem recumbent tricycle that would be economical, easy to build, and adaptable. This would involve designing, building and testing the tricycle

A novel eccentricity parameterization for transit-only models

We present a novel eccentricity parameterization for transit-only fits that allows us to efficiently sample the eccentricity and argument of periastron, while being able to generate a self-consistent model of a planet in a Keplerian orbit around its host star. With simulated fits of 330 randomly generated systems, we demonstrate that typical parameterizations often lead to inaccurate and overly precise determinations of the planetary eccentricity. However, our proposed parameterization allows us to accurately -- and often precisely -- recover the eccentricity for the simulated planetary systems with only transit data available.Comment: 10 pages, 7 figures, submitted to PAS

Double Jeopardy: Minority Stress and the Influence of Transgender Identity and Race/Ethnicity

This study assessed gender and racial/ethnic differences in gender-related discrimination and psychological distress within a sample of transgender and gender nonconforming individuals. Prior research suggests transgender individuals with multiple minority statuses experience higher psychological stress than their singly disadvantaged counterparts, and both minority race/ethnicity and transgender minorities experience more frequent and severe forms of discrimination than white and cisgender individuals. Using data from a convenience sample of 101 self-identified transgender and gender nonconforming adults recruited through LGBTQ+ organizations from across North America, I analyzed the relationship between race/ethnicity, gender-related minority stress, and psychological distress. Gender-related discrimination and gender-related victimization did not significantly differ by gender identity or race/ethnicity. However, racial/ethnic minorities reported significantly higher psychological distress than white participants. While being a racial/ethnic minority may not directly worsen one\u27s experiences with gender-related discrimination and victimization, other factors, such as experiences with race related discrimination, may contribute to disparities in mental health

High Precision Photometry of Transiting Exoplanets

In order to increase the rate of finding, confirming, and characterizing Earth-like exoplanets, the MINiature Exoplanet Radial Velocity Array (MINERVA) was recently built with the purpose of obtaining the spectroscopic and photometric precision necessary for these tasks. Achieving the satisfactory photometric precision is the primary focus of this work. This is done with the four telescopes of MINERVA and the defocusing technique. The satisfactory photometric precision derives from the defocusing technique. The use of MINERVA’s four telescopes benefits the relative photometry that must be conducted. Typically, it is difficult to find satisfactory comparison stars within a telescope’s field of view when the primary target is very bright. This issue is resolved by using one of MINERVA’s telescopes to observe the primary bright star while the other telescopes observe a distinct field of view that contains satisfactory bright comparison stars. In order to maintain time-efficiency throughout MINERVA’s survey of many bright stars, the relative photometry, analysis of defocused images and the production of light curves have been automated via software recently constructed

Analytic Approximations for Transit Light Curve Observables, Uncertainties, and Covariances

The light curve of an exoplanetary transit can be used to estimate the planetary radius and other parameters of interest. Because accurate parameter estimation is a non-analytic and computationally intensive problem, it is often useful to have analytic approximations for the parameters as well as their uncertainties and covariances. Here we give such formulas, for the case of an exoplanet transiting a star with a uniform brightness distribution. We also assess the advantages of some relatively uncorrelated parameter sets for fitting actual data. When limb darkening is significant, our parameter sets are still useful, although our analytic formulas underpredict the covariances and uncertainties.Comment: 33 pages, 14 figure