Retrieval Method Of Astronomical Image Time Series Subsets In Distributed Environment

Time domain astronomy is a field of astronomical phenomena with time-varying characteristics,which requires enough observations of the same target area within a certain time scale.Therefore,time series subsets retrieval plays an important role in time domain astronomy research.Astronomical observation data are stored in one or more geo-distributed data centers nowadays,the astronomical time series subsets retrieval takes several steps: firstly,download or copy astronomical original image datasets containing the target area from geo-distributed data centers to the personal server,and retrieve original astronomical image data;then,sort original astronomical image data through time and other factors;lastly,retrieve target time series subsets manually.With the development of telescope construction technology and science,the time and labor costs of manually processing the astronomical image data stored in geodistributed data centers have become increasingly high,even manual retrieval methods hardly apply to the current era.An efficient automatic time series subset retrieval is of great help to time domain astronomy research,which is a scientific problem to be solved urgently now.In this thesis,an efficient retrieval method called Geo-Distributed Astronomy Image Data Retrieval(GAIDR)is proposed.The retrieval method receives requests of astronomers,retrieves target astronomical time series data automatically and efficiently,and return time series subsets to astronomers.This method designs a multi-level masterslave storage structure and establishes related astronomical data index for efficient retrieval,including astronomical original data and astronomical replica index.In addition,a replica strategy based on GAIDR method is proposed to speed up the retrieval efficiency.This strategy reduces the size of replicas and merges replicas of the same or similar target area.At the same time,this strategy recognizes hot sub-files and replaces replicas through data access.In addition,replicas layout in the replica strategy is designed to realize the parallel retrieval according to the temporal and spatial characteristic of time domain astronomy research.In the geo-distributed environment,GAIDR method can achieve the highest replica hit ratio and the lowest average response time among all methods,and the average response time can be reduced by at least 14.07%comparing with NoDataLayout method which is the best performance methods.