1. Web + VO + Database Technologies = HLA Footprints STScI: Gretchen Greene, Steve Lubow, Brian McLean, Rick White and the HLA Team JHU: Alex Szalay and Tamas Budavari NVO

2. Astronomical Application Archival Research is a value added product to observation planning as well as data mining Has HST observed in this location of the sky? Which wavelength?, how long?, what instrument?, what was the exact coverage with respect to object XYZ? Show the coverage for a high level product, e.g. Hubble Deep Field, GOODS mosaics, ALL overlapping ACS exposures of a specific field I have a transient even (e.g. VOEvent notification), what is the coverage in HST? How does HST coverage compare to another observatory coverage? Large scale distributed spatial queries NVO search portal

3. HST Footprints in the HLA HLA Footprints are spatially precise geometric descriptions of the HST observed areas in the sky Current holdings include reprocessed ACS fields (~20% of the completed observations), all sky WFPC2 and STIS In transition are NICMOS, remaining ACS, FOS & GHRS Collaborations in process with NICMOS grism spectra, SPITZER…. Accessible via web client or programmatic interfaces

5. Widespread Footprint Development GALEX (STScI ) NOAO VO Portal Aladin (via APT) IVOA (International Virtual Observatory) note for Footprint Overlay specification VOServices (JHU) Sky section or image plane: pans, zooms, downloads data. The ( GALEX) MAP - (adaptable to other missions)

6. Web components Web portal built on a suite of web services (SOAP, http) using SOA Reusable components mostly in form of XML User requirements reduced significantly Network access & a browser (FIREFOX) No installation required Technologies are independent of platform and consistent with everyday lifestyle XML, XSLT processors, Javascript, ASPX Performance on the web client looks favorable accept delay or switch to server side processing for large scale requests Javascript security issues require proxy management

7. IFRAME HLA Web Portal - Footprints SQL Server Footprint DB (with HTM) IIS Web Server Javascript UI manager (state and form control) Object Parser XML Instance ASPX + JS VO Cone Search VOTable SOAP STC Web Services IFRAME VOClients GOOGLE APT SQL Server DSS DB (with HTM) RA,Dec,Radius

8. Virtual Observatory Footprints are built on IVOA standard STC XML data model (Space Time Coordinate) Regions, Convexes, Reference Frames + much much more Data Access Layer services are built on standard VO protocols Cone Search Simple Image Access (SIA) XML across the wire in VOTable or STC format VO client applications can access HLA footprint programmatic services: Datascope, Registry, Aladin, GOOGLE? IVOA note on Footprint Overlay Specification

9. Database => Performance Key Microsoft SQL Server Client development DOES NOT have to be on WINDOWS Virtualization tools (Parallels, Remote Desk Top) FreeTDS SQL scripts manage footprint computation of STC table objects/fields Build and populate the different levels of representation HTM (Hierarchical Triangulated Mesh) integrated for spatial search index Coordinate based searching Accessed via stored procedures and user defined functions Bounding circles for each region convex have htm ids

10. DB Schema STC DB Tables map to XML elements in the schema HLA Science table associates regions to science metadata tags (target, exposure, dataset, filter, PI …)

11. JHU Spherical Library Spherical geometry library Exact equations for highly accurate region definitions, leverages HTM STC elements are class types (region, convex, halfspace…) C# Assembly (SQL Server dll ) Operations for combining regions Unions (outlines) Intersections (overlaps) Mathematical Solutions Area Complex regions can be made disjoint into convexes

12. Hierarchical Representations Exposures (Level 1) Stacks (Level 1 – visualization optimization) Combined sequential exposures (Level 2) Groups (Level 3 & 4) Mosaics, weight maps, use-defined, custom constrained Fractals Performance Issues for crowded overlaps HST unique distribution sparse ALL-SKY

13. Exposure Stacks Many cases where exposures lie on top of each other (form a stack) Can reduce overhead by graphically representing exposures in a stack by a single member exposure Define stacks using coarse- grained HTM matching for aperture vertices.

14. Visualization library C# library with building canvas, frame, scaling and drawing methods using GDI DSS background image access using spherical projection and tiling algorithms ASPX is ~ html with C# class associated. ASP controls for basic web gui features Javascript for interactive mouse and cursor state Event handling between the graphics and table paging control for selection

15. Challenges Ahead Enhanced capabilities for visualization Completion of IVOA standard footprint services Community exchange of STScI Footprint schema Validation of footprint representations between existing tools (Starview/APT, HLA, external…) Development of higher level product respresentations (MOSAICS, user-defined…) Storing Region binary blob representations