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Digitized Sky Survey Update

Digitized Sky Survey Update. Brian McLean : Archive Sciences Branch / Operations and Engineering Division. DSS Distribution. DSS one of the most heavily used MAST services (~175,000+ requests/month) 9TB image data, 1TB compressed data Distributed compressed data to 15 data centers

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Digitized Sky Survey Update

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  1. Digitized Sky Survey Update Brian McLean : Archive Sciences Branch / Operations and Engineering Division

  2. DSS Distribution • DSS one of the most heavily used MAST services (~175,000+ requests/month) • 9TB image data, 1TB compressed data • Distributed compressed data to 15 data centers • Distributed compressed data to both Google and Microsoft for non-commercial use in visualization projects • Accessible via webform, VOservices & scripted url requests • Currently only provides FITS or dynamically created single colour GIF file • Started development project to create colour images from multiple bandpasses (J, F, N).

  3. Increased Interest in Visualization • Hubble Legacy Archive (EDR Release 01 August 2007) • Graphical display to visualize HST instrument footprints over DSS for context of observations. • ESO Archive Interface (Release Date TBA) • Similar to HLA but front-end to ESO archive of ground-based data. • Sky in Google Earth (Released 22 August 2007) • Browse sky using GE engine. • Combine DSS, SDSS and HST images into single layer. • Microsoft Research World-Wide Telescope (Release Date TBA) • Sky Chart UI with advanced search, collaborative capabilities and telescope control. • DSS, SDSS, 2MASS, HST, etc as separate layers • VO enabled • Increasing number of websites showing colour images constructed from DSS data.

  4. DSS Colour Representation R=IV-N, G=IIIaF, B=IIIaJ R=IIIaF, G=(IIIaJ+IIIaF)/2, B=IIIaJ

  5. DSS Colour Image Construction • Current version constructed from J & F bandpass plates. • RED (F) plate taken as reference. • Field divided into 64x64 grid of tiles each 300x300 pixels. • For each tile, the BLUE (J) image was astrometrically registered to the RED image and resampled. • A mean of the red/blue image was created for the 3rd channel. • The sky and saturation values for the red and blue plates were used to scale the 3 channel images between 0-1 and create a JPG image. • JPG image was saved with a FITS header.

  6. Image Pyramid Construction • Combine each set of 4 adjacent tiles into a single tile at half the resolution. • Repeat till entire plate is a single tile. • We have created an image pyramid at multiple scale levels • 1x = 4096 tiles • 2x = 1024 tiles • 4x = 256 tiles • 8x = 64 tiles • 16x = 16 tiles • 32x = 8 tiles • 64x = 1 tile • 5461 jpegs x 1792 fields = 9,786,112 images • Save all JPG images with updated FITS headers.

  7. DSS Colour Image Access • Loaded JPG data and FITS WCS information into SQLserver 2005 database (200GB). • Index coordinates of each tile at each scale with HTM for fast lookup. • HTM functions are compiled into DLL and bound into SQLserver for fast execution within the database. • Prototype web interface and VO SIAP service selects tiles and creates image cutout (full resolution) . • IIS webserver, ASPX pages, C# code running within .NET framework. • HLA interface (variable resolution, dynamically resamples DSS JPG to North up to overlay footprints). • C# code directly accessing SQLserver database

  8. Real-time demo(Note – DSS DB on my workstation, non-optimized debug code) • M1 http://gsss.stsci.edu/webservices/vo/SIAPgetimage.aspx?POS=83.6332083,+22.0144722&SIZE=0.25 • M3 http://gsss.stsci.edu/webservices/vo/SIAPgetimage.aspx?POS=205.5467917,+28.3754444&SIZE=0.5 • NGC 2023 http://gsss.stsci.edu/webservices/vo/SIAPgetimage.aspx?POS=85.4079167,-2.2644444&SIZE=0.75 • Coma Cluster • 1xhttp://gsss.stsci.edu/webservices/vo/SIAPgetimage.aspx?POS=194.9529167,+27.9805556&SIZE=1 • 4X http://gsss.stsci.edu/webservices/vo/SIAPgetimage.aspx?POS=194.9529167,+27.9805556&SIZE=1&SCALE=4 • SMC Plate http://gsss.stsci.edu/webservices/vo/SIAPgetimage.aspx?POS=13.1583333,-74.5&SIZE=6&SCALE=16 http://gsss.stsci.edu/webservices/vodev/webform.aspx

  9. DSS Examples Pleiedes Horsehead

  10. DSS Examples M51 NGC 253

  11. DSS Examples Omega Cen M100

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