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