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Virtual Observatory Topics at ADASS XII Baltimore, MD 13-17 October 2002 Vince McIntyre (ATNF, CSIRO) ANITA meeting, 2003 Jan 28/29.

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Presentation on theme: "Virtual Observatory Topics at ADASS XII Baltimore, MD 13-17 October 2002 Vince McIntyre (ATNF, CSIRO) ANITA meeting, 2003 Jan 28/29."— Presentation transcript:


2 Virtual Observatory Topics at ADASS XII Baltimore, MD October 2002 Vince McIntyre (ATNF, CSIRO) ANITA meeting, 2003 Jan 28/29

3 About the Conference ● Astronomical Data Analysis Systems & Software ● Computer system developments for astronomy ● telescope scheduling ● telescope control ● data taking formats ● data processing software ● data archiving ● archive access ● Hosted by STScI ● (CDS Strasbourg in 2003)

4 ● a whole lot less virtual than it was ● prototype web services running now, ● e.g. ● Mon: eSTAR initiative ● Tue: NRAO e2e ● Wed: Theory data ● Thu: Interop Virtual Observatory at ADASS

5 Monday: eSTAR ● Prototype robotic telescope network ● test computing infrastructure, for possible larger scale projects (e.g. Large Synoptic Survey Telescope) ● network of telescopes with: ● rapid reduction pipelines ● intelligent agents (IAs) ● Intelligent Agents ● examine the data ● request follow-up observations, as needed ● wake up astronomer

6 Monday: eSTAR ● IA architecture

7 Monday: eSTAR ● IA prototype

8 Monday: eSTAR ● Requesting observations is important - ● discovery nodes (telescopes) regulate workload by rejecting requests they have no time to fill (or because the astronomer has no allocated time) ● applies in any distributed processing system – ie computational grids. No central control bottleneck means the system can scale up hugely ● Uniform interface is important - ● From the astronomers perspective, there is no difference between a telescope and a group of federated astronomical databases – apart from the query processing time...

9 Tuesday: e2e ● e2e stands for its a data pipeline ● Exploration project ● set up VLA archive based on AIPS++ toolkit. ● Data processed in AIPS++ from visibilities to images ● Capturing observers intentions in the logfiles is critical ● Relatively simple to capture intentions ● e.g. boxes on proposal form ● Processing starts at proposal submission. Having visibilities marks the half-way point

10 Wednesday: Theory-VO ● ● typical observers task - correct an image for extinction by interstellar dust ● many versions, theoretical and observed, for different wavelength regimes ● revised over the years - one wants to be able to redo corrections on old photometry, with modern curves. ● VO should help us discover the latest (best? most widely used?)

11 Wednesday: Theory-VO ● Other examples - ● luminosity functions (stars, HII regions, planetary nebulae, galaxies) ● stellar evolution tracks & isochrones ● Small datasets, small models are important too ● A structured approach is needed, if software is going to make use of it

12 Thursday: VO interop ● Data Models important for interop & seamless scaling ● Lots of prototyping going on now ● Working demos by 3rd quarter 2003 ● Coordination site:

13 Aside: VOTable ● VOTable v1.0 published June 2002 ● VOTable: hierarchy of Metadata + Tables ● Metadata: Parameters + Infos + Descriptions + Links + Fields ● Table: list of Fields + Data ● Data: stream of Rows ● Row: list of Cells ● Cell: Primitive, or variable-length list of Primitives, or multidimensional array of Primitives

14 Aside: VOTable This is an example VOTable document This is an excerpt of the HST Guide Star Catalog, Version 1.2 (Lasker+ 1996). This version was re-reduced with PPM catalogue. Default result of GSC1.2 Server around a target Distance from target NGC40

15 Thursday: VO Web Services ● Web Services Acronyms ● SOAP - Simple Object Access Protocol ● application of XML for sending commands to a remote service (RPC) ● WSDL - Web Services Description Language ● describe what your site can do ● GLU - Generateur des Liens Uniformes ● helps maintain links between sites ● symbolic names (UCDs) generate URLs ● system of GLU servers work together to maintain links to resources

16 Thursday: VO Web Services ● GLU servers distribute WSDL files, so each node knows what resources are available [done] ● Each GLU site has a SOAP responder to process requests [progressing] ● GLU APIs in Java (C & Perl exist) [testing]

17 Thursday: VO Web Services ● requester sends this - jou_pick yes author Accomazzi ref_stems 2001adass

18 Thursday: VO Web Services ● this is returned (excerpt) E&db_key=AST Formatting and Retrieval Options in the Astrophysics Data System (ADS) 2002DPS E Eichhorn, G. Accomazzi, A. Grant, C. S. Kurtz, M. J. Murray, S. S. 9/ E&link_type=ABSTRACT Abstract

19 Thursday: VO Web Services ● requester code #usage: #perl author=Accomazzi jou_pick=yes ref_stems=2001adass # #use strict; use SOAP::Lite +trace; use XML::Simple; my %query = map { split(/=/,$_,2) my $response = SOAP::Lite ->uri('') ->proxy('') ->query(%query); print XMLout($response->result, noattr=>1);

20 Thursday: VO interop - VOTable ● Image Access Protocol discussion ● Proposal to use VOTable for image access service storage and transfer format ● VOTable is application of XML. ● FITS image can be part of VOTable ● details at ● Trying to define standard ● How to get it endorsed (rapidly) ● W3C? Global Grid Forum?

21 Thursday: Refactoring UCDs ● a coordinate system for astrophysics concepts UCDs - Universal Content Descriptors ● developed by SIMBAD ● Hierarchy of concepts pos_galpos pos_eq pos_gal_long pos_gal_lat pos_eq_ra pos_eq_dec ● examples "PHOT_INT-MAG_B" Integrated total blue magnitude "ORBIT_ECCENTRICITY" Orbital eccentricity "STAT_MEDIAN" Statistics Median Value "INST_QE" Detector's Quantum Efficiency

22 Thursday: Refactoring UCDs ● current set of UCDs have too few classes for precise classification (e.g. error_* UCD exists, but no way to distinguish error in R.A. vs error in Dec.) ● A tree that is too 'bushy' is also unwieldly ● Some quantity names have many independent aspects, mean different things in different contexts

23 Thursday: Refactoring UCDs ● Proposal to refactor - build up UCDs from 'atoms' in approved combinations ● e.g. POS_EQ_RA_MAIN (main RA column in a table) becomes POS_EQ_RA/MAIN, where POS_EQ_RA and MAIN are atoms that can be recognised separately in parsing ● Many 'corner cases', under discussion

24 Thursday: Data Models ● Describe (in machine-encodable terms) what you really have in the data set ● UCDs are part of this; UCDs let you know if quantities can be intercompared ● Data models let you know how you could transform a quantity for comparison ● More generally: DM for a resource tells me what questions I can ask of the resource

25 Thursday: VO interop - Data Models ● Filter Bandpass example ● Archiving a Near-IR image. ● Passband has: ● generic name: J Band ● specific name: AAO J Band ● The full name implies effective wavelength, wavelength range; ie transmission curve ● How best to express this in the metadata?

26 Thursday: VO interop - Data Models ● Do you enter filter_AAO_J-Band and have a name resolver (GLU) find and enter the transmission curve details for you? ● Or just enter the UCD and leave resolution to be done when someone looks at the image? ● Or enter filter FHWM, peak transmission etc? ● nasty cases need to be handled: ● red leak ● periodic filters ● is atmospheric transmission included?

27 Thursday: VO interop - Data Models ● Another example - data from four sources: ● AAT V-band image, FITS file ● WFPC2 multi-element FITS file ● Chandra x-ray (arrival time, position) table ● ISOCAM FITS table ● Nothing in the UCD string captures the fact these are the same kind of data – images ● Data model for each data source should allow you to infer this (or state it explicitly)

28 Recap ● UCDs describe the things you are seeking ● WSDL file from each site gives full list of services ● your local resource locator (e.g. GLU server) uses collected WSDL files to find the same UCDs in several repositories around the globe ● SOAP enquiry to (e.g.) image retrieval services at several sites ● VOTables returned as result of queries

29 The End

30 Thursday: VO interop - Data Models ● Image access protocol - scary UML diagrams

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