SDSS Web Services

Tamás Budavári Johns Hopkins University

Coding against the UniverseCoding against the Universe

SC4DEVO-1 Tamás Budavári (JHU) 2

Outline

SDSS Primer

Technology

Web ServicesData Access

• Images• Spectra• Catalog

Higher Level

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SDSS Imaging Survey

2.5m telescopeApache Point, NM5 photometric bandsDrift scan operation

Photo pipeline100,000,000 galaxiesAutomated reductionCatalog archive server

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NGC 2068

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UGC 3214

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NGC 6070

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SDSS Spectropscopy

Two spectrographsRed and blue part

Optical fibers

640 in each bundle

Plugged manually

Automatic reduction

2D and 1D pipelines

Catalog archive server

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Developing Web Services

We chose the .NET FrameworkThe C# programming languageExtensive class library (for free)Simple and efficient database accessFast imaging and graphics routinesRapid development in Visual StudioVery easy Web Services programming

Use CVS for versioning

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Custom Tools and Packages

Wrapper for CFITSIOCFITSIO by Vivek Haridas (JHU)

Access to FITS tables and images from C#XML Web Services return FITS in attachment

Scientific PlottingUsing TeeChart LiteFast plotting of online data

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Available Web Services

SDSS Web ServicesField Finder and SIAPSDSS Image CutoutSpectrum and Filter ServicesScientific Catalog ArchiveDensityMap Services

Other Relevant ServicesNED Services WrapperCosmic Distances

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SDSS Fields and SIA

Field ImagesSearch for fields (HTM)Get all info, e.g. WCSReturns links to FITS

Simple Image Access

Wrapper on top of FieldsReturns links in VOTable

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SDSS Image Cutout

Build JPEG mosaicsFor given (RA, Dec)Arbitrary zoom levelsOverplot catalog dataOverplot geometryMapQuest like navigationList of objects

Proper WSJPEG returned in DIMEor byte array

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Spectrum Services

Public repository500,000 spectra (2B row)

Spatial search and more

Register & submit yours

Web siteOn-the-fly plotting

Building composites

Web servicesMore options and tools

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SDSS Catalog Services

CasJobsAccess to a 1TB of data80M unique galaxiesQueue system for SQLMyDB

• 500MB remote DB• Upload and extract

Web servicesWeb site interfaceCommand-line client

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SDSS DensityMap Services

A SQL query to image converterSelect x,y,f and build color coded f(x,y) image

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Other Services

Wrapper for NEDName resolver functionSearch by coordinate

Available from

Cosmic DistancesVarious distance measuresUsing ΛCDM cosmology

NED ned = new NED();ObjInfo o = ned.ObjByName(“m101”);/* Use o.ra, o.dec, etc… */

Distance d = new Distance();float z=0.1, h=0.7, m=0.3, l=0.7;float r = d.Luminosity(z,h,m,l);

http://www.voservices.org

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Consuming Web Services

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Conclusions

SDSS Web Services……provide access to scientific data and tools…are (very) easy to consume…are being used :-)

Development coordinated w/ IVOAOpen SkyQuery for federating archivesSDSS Open SkyNode