Design and Implementation of the HXMT Data Retrieval/Publishing System Based on the Virtual Observatory

The Virtual Observatory (VO) integrates worldwide astronomical-data resources seamlessly and transparently to meet requirements of cross-regional processing, retrieval, and publishing of astronomical data (which can be of multiple-band). Currently, many international astronomical projects have adopted VO standard protocols for developing data retrieval/publishing systems. After logging into the VO, a user can search and retrieve data of various astronomical projects by using the VO Portal. Following this trend the Hard X-ray Modulation Telescope (HXMT) Project also has adopted VO technologies in the design and implementation of the HXMT data retrieval/publishing system. This will make the system to meet the requirements of HXMT-data publishing, and to integrate HXMT data into the VO environment for international data sharing. In this paper we propose such a system, with its architecture conformed to VO specifications. It consists of a user layer, a service layer, and a resource layer. We implement the Simple Cone Search (SCS), Simple Image Access Protocol (SIAP), Simple Spectral Access Protocol (SSAP), and VOTable standard in the system. In addition, we develop the system software using the MVC mode, SSH framework, and various J2EE technologies. This makes the system easily deployable, scalable, stable, and user friendly. We have successfully constructed a prototype of the system. The prototype provides Web-service interfaces for invoking other software applications and has a user interface which is a portal website. The prototype has various functions, including those allowing retrieval, access, download, and visualization of data. Our experiments with the prototype show that the system is widely applicable in cross manipulation of astronomical data from different resources, data sharing/publishing, data search/access, and integration of heterogeneous applications. The system can benefit the development of retrieval/publishing systems for other astronomical satellite data in China.