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CT PROJECT. ESTO. An Astronomical Image Mosaic Service for the National Virtual Observatory /. Attila Bergou - JPL Bruce Berriman - IPAC Ewa Deelman - ISI John Good - IPAC Joseph C. Jacob - JPL Daniel S. Katz - JPL. Carl Kesselman - ISI

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An Astronomical Image Mosaic Service for theNational Virtual Observatory
Attila Bergou - JPL

Bruce Berriman - IPAC

Ewa Deelman - ISI

John Good - IPAC

Joseph C. Jacob - JPL

Daniel S. Katz - JPL

Carl Kesselman - ISI

Anastasia Laity - IPAC

Thomas Prince - Caltech

Gurmeet Singh - ISI

Mei-Hui Su - ISI

Roy Williams - CACR

what is montage
What is Montage?
  • Delivers custom, science grade image mosaics
    • User specifies projection, coordinates, spatial sampling, mosaic size, image rotation
    • Preserve astrometry & flux
  • Modular “toolbox” design
    • Loosely-coupled Engines for Image Reprojection, Background Removal, Co-addition
      • Control testing and maintenance costs
      • Flexibility; e.g., custom background algorithm; use as a reprojection and co-registration engine
    • Implemented in ANSI C for portability
  • Public service will be deployed on the Teragrid
    • Order mosaics through web portal
public release of montage
Public Release of Montage
  • Version 1.7.1 and User’s Guide available for download at
  • Emphasizes accuracy in photometry and astrometry
    • Images processed serially
    • Tested and validated on 2MASS 2IDR images on Linux Red Hat 8.0 (Kernel release 2.4.18-14) on a 32-bit processor
    • Tested on 10 WCS projections with mosaics smaller than 2 x 2 degrees and coordinate transformations Equ J2000 to Galactic and Ecliptic
  • Extensively tested
    • 2,595 test cases executed
    • 119 defects reported and 116 corrected
    • 3 remaining defects to be corrected in future Montage release
applications of montage
Applications of Montage
  • Large scale processing of the sky; e.g., Atlasmaker
  • Mosaics of the Infrared Sky
    • This is the age of Infrared Astronomy!
    • Infrared astronomers study regions much larger than covered by individual cameras ==> need to make mosaics to investigate star formation, redshift distribution of galaxies
    • Mosaics of the far infrared sky a primary data product of the SIRTF mission
    • Two SIRTF Legacy teams using Montage as a co-registration and mosaic engine to generate science mosaics, perform image simulations, mission planning & pipeline testing
    • Public Outreach - the wow factor!
      • Combine single color images in Photoshop
      • Example: back-lit display in NASA booth
      • See next image - Rho Ophiuchi
Rho Ophiuchi 324 2MASS images in each band => 972 imagesOn a 1 GHz Sun, mosaicking takes about 15 hours
montage the grid years
Montage: The Grid Years
  • Re-projection is slow (100 seconds for one 1024 x 512 pixel 2MASS image on a single processor 1.4 GHz Linux box), so use parallelization inherent in design
    • Grid is an abstraction - array of processors, grid of clusters, …
    • Montage has modular design - run on any environment
  • Prototype architecture for ordering a mosaic through a web portal
    • Request processed on a computing grid
    • Prototype uses the Distributed Terascale Facility (Teragrid)
      • This is one instance of how Montage could run on a grid
    • Atlasmaker is another example of Montage parallelization
montage the grid years cont
Montage: The Grid Years (cont.)
  • Prototype version of a methodology for running on any “grid environment”
    • Many parts of the process can be parallelized
    • Build a script to enable parallelization
      • Called a Directed Acyclical Graph (DAG)
      • Describes flow of data and processing
        • Describes which data are needed by which part of the job
        • Describes what is to be run and when
      • Standard tools can execute a DAG
using montage grid prototype

Teragrid Cluster



Using Montage Grid Prototype
  • Web service at JPL creates an abstract workflow description of Montage run (in XML)
  • Workflow description run through Pegasus to create concrete DAG
    • Pegasus includes transfer nodes in the concrete DAG for staging in the input image files and transferring out the generated mosaic
  • Concrete DAG submitted to Condor

Region Name,



Abstract DAG


Concrete DAG



Condor Pool

montage workflow










Final Mosaic


mProject 1

mProject 2

mProject 3


mBackground 1

mBackground 2

mBackground 3

mDiff 1 2

mDiff 2 3



a1x + b1y + c1 = 0

a2x + b2y + c2 = 0

a3x + b3y + c3 = 0

mFitplane D12

mFitplane D23


ax + by + c = 0

dx + ey + f = 0

ax + by + c = 0

dx + ey + f = 0

Montage Workflow
  • Described as abstract DAG - specifies:
    • Input, output, and intermediate files
    • Processing jobs
    • Dependencies between them
montage concrete dag single pool

Data Stage in nodes

Montage compute nodes

Data stage out nodes

Registration nodes

Montage – Concrete DAG (single pool)

Example DAG for 10 input files








montage runs on the teragrid
Montage Runs on the Teragrid
  • Test runs were done on the 1.5 degree x 1.5 degree area including M42 (Orion Nebula)
  • Required 113 input image files
  • Single pool DAG for SDSC consisted of 951 jobs
    • 117 were data transfer jobs
      • 113 for transferring the input image files
      • 3 for transferring other header files
      • 1 for transferring the final output mosaic
  • Run took 94 minutes
montage runs on the teragrid 2
Montage Runs on the Teragrid (2)
  • Using same abstract DAG for multi pool DAG at SDSC and NCSA created 1202 jobs
    • 367 were data transfer jobs
      • Some of these jobs transferred multiple files
      • 249 of these 367 were inter pool data transfer jobs
montage computations
Montage Computations
  • Building a mosaic from N 1024 x 512 pixel 2MASS images on a single processor 1.4 GHz Linux box takes roughly (N x 100) seconds
  • 98-99% of this time is in the reprojection, which can be perfectly parallelized (this doesn’t embarrass us)
  • Montage is a custom astronomical image mosaicking service that emphasizes astrometric and photometric accuracy
  • First public release, Montage_v1.7.1, available for download at the Montage website
  • A prototype Montage service has been deployed on the Teragrid; ties together distributed services at JPL, Caltech IPAC, and ISI
  • More on Montage at SC2003:
    • See ISI at ANL booth for demo of Pegasus portal running Montage on the Teragrid
    • See back-lit display of Montage images at NASA booth
  • Montage website: