71 research outputs found
The Locus Algorithm II: A robust software system to maximise the quality of fields of view for Differential Photometry
We present the software system developed to implement the Locus Algorithm, a
novel algorithm designed to maximise the performance of differential photometry
systems by optimising the number and quality of reference stars in the Field of
View with the target. Firstly, we state the design requirements, constraints
and ambitions for the software system required to implement this algorithm.
Then, a detailed software design is presented for the system in operation.
Next, the data design including file structures used and the data environment
required for the system are defined. Finally, we conclude by illustrating the
scaling requirements which mandate a high-performance computing implementation
of this system, which is discussed in the other papers in this series
The Locus Algorithm IV: Performance metrics of a grid computing system used to create catalogues of optimised pointings
This paper discusses the requirements for and performance metrics of the the
Grid Computing system used to implement the Locus Algorithm to identify optimum
pointings for differential photometry of 61,662,376 stars and 23,779 quasars.
Initial operational tests indicated a need for a software system to analyse the
data and a High Performance Computing system to run that software in a scalable
manner. Practical assessments of the performance of the software in a serial
computing environment were used to provide a benchmark against which the
performance metrics of the HPC solution could be compared, as well as to
indicate any bottlenecks in performance. These performance metrics indicated a
distinct split in the performance dictated more by differences in the input
data than by differences in the design of the systems used. This indicates a
need for experimental analysis of system performance, and suggests that
algorithmic complexity analyses may lead to incorrect or naive conclusions,
especially in systems with high data I/O overhead such as grid computing.
Further, it implies that systems which reduce or eliminate this bottleneck such
as in-memory processing could lead to a substantial increase in performance
The Locus Algorithm III: A Grid Computing system to generate catalogues of optimised pointings for Differential Photometry
This paper discusses the hardware and software components of the Grid
Computing system used to implement the Locus Algorithm to identify optimum
pointings for differential photometry of 61,662,376 stars and 23,799 quasars.
The scale of the data, together with initial operational assessments demanded a
High Performance Computing (HPC) system to complete the data analysis. Grid
computing was chosen as the HPC solution as the optimum choice available within
this project. The physical and logical structure of the National Grid computing
Infrastructure informed the approach that was taken. That approach was one of
layered separation of the different project components to enable maximum
flexibility and extensibility
A catalogue of Locus Algorithm pointings for optimal differential photometry for 23 779 quasars
ABSTRACT
This paper presents a catalogue of optimized pointings for differential photometry of 23 779 quasars extracted from the Sloan Digital Sky Survey (SDSS) Catalogue and a Score for each indicating the quality of the Field of View (FoV) associated with that pointing. Observation of millimagnitude variability on a time-scale of minutes typically requires differential observations with reference to an ensemble of reference stars. For optimal performance, these reference stars should have similar colour and magnitude to the target quasar. In addition, the greatest quantity and quality of suitable reference stars may be found by using a telescope pointing which offsets the target object from the centre of the FoV. By comparing each quasar with the stars which appear close to it on the sky in the SDSS Catalogue, an optimum pointing can be calculated, and a figure of merit, referred to as the ‘Score’ is calculated for that pointing. Highly flexible software has been developed to enable this process to be automated and implemented in a distributed computing paradigm, which enables the creation of catalogues of pointings given a set of input targets. Applying this technique to a sample of 40 000 targets from the fourth SDSS quasar catalogue resulted in the production of pointings and Scores for 23 779 quasars based on their magnitudes in the SDSS r-band. This catalogue is a useful resource for observers planning differential photometry studies and surveys of quasars to select those which have many suitable celestial neighbours for differential photometry
Nimbus-7 ERB Solar Analysis Tape (ESAT) user's guide
Seven years and five months of Nimbus-7 Earth Radiation Budget (ERB) solar data are available on a single ERB Solar Analysis Tape (ESAT). The period covered is November 16, 1978 through March 31, 1986. The Nimbus-7 satellite performs approximately 14 orbits per day and the ERB solar telescope observes the sun once per orbit as the satellite crosses the southern terminator. The solar data were carefully calibrated and screened. Orbital and daily mean values are given for the total solar irradiance plus other spectral intervals (10 solar channels in all). In addition, selected solar activity indicators are included on the ESAT. The ESAT User's Guide is an update of the previous ESAT User's Guide (NASA TM 86143) and includes more detailed information on the solar data calibration, screening procedures, updated solar data plots, and applications to solar variability. Details of the tape format, including source code to access ESAT, are included
Abstracts and classification of graduate studies, submitted at Boston University, on the slow learning child
Thesis (M.A.)--Boston Universit
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