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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. Astronomical Application.

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web vo database technologies hla footprints

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

astronomical application
Astronomical Application

Archival Research is a value added product to observation planning as well as data mining

  • HasHST 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
hst footprints in the hla
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
widespread footprint development
Widespread Footprint Development

The (GALEX) MAP - (adaptable to other missions)

  • 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.

web components
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 platformand 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
hla web portal footprints
HLA Web Portal - Footprints

Javascript UI manager

(state and form control)

VOTable

VO Cone Search

VOClients

RA,Dec,Radius

Object Parser

XML Instance

GOOGLE

IIS Web Server

APT

ASPX + JS

IFRAME

IFRAME

SOAP STC

Web Services

SQL Server

Footprint DB

(with HTM)

SQL Server

DSS DB

(with HTM)

virtual observatory
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
database performance key
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 htmids
db schema stc
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 …)
jhu spherical library
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
hierarchical representations
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
exposure stacks
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.
visualization library
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
challenges ahead
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
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