peking university astronomy symposium 10/17/2010

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Peking University Astronomy Symposium 10/17/2010 Large Synoptic Survey Telescope

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Sciences and Challenges with LSST Hu Zhan National Astronomical Observatories Chinese Academy of Sciences. Peking University Astronomy Symposium 10/17/2010. Large Synoptic Survey Telescope. US Astro2010 Decadal Survey. Data = Discovery Space A new mode of astronomy research: data mining - PowerPoint PPT Presentation

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Page 1: Peking University Astronomy Symposium 10/17/2010

Peking University Astronomy Symposium10/17/2010

Large Synoptic Survey Telescope

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Data = Discovery SpaceA new mode of astronomy research: data mining

a new breed: keyboard astronomer

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• 8.4-meter primary• 10 deg2 FOV• 3 billion pixels• 0.2”/pixel• 0.3–1.1 µm ugrizy• 15-s exposures• 8 hours/field total• 30 TB/night• 200 PB total• Median seeing 0.7”

Key Missions: 1.Dark energy/matter 2.Solar system3.Optical transients 4.Galactic map

First light ~ 2016/2017(funding start +4 years)

20,000 deg2

u 25.8 mag g 27.0 mag r 27.2 mag i 27.0 mag z 25.7 mag y 24.4 mag

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A sample of• Billions of galaxies• Millions of SNe• 105 galaxy clusters

arXiv:0805.2366

Huge discovery space

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Deep Wide Survey: 20,000 square degrees

Northern Ecliptic: 3300 square degrees ~2.1 pairs per lunation

Deep-Drilling: ~100 square degrees more frequent visits

Galactic Plane: 1700 square degrees to uniform depth of u: 26.1 g: 26.5 r: 26.1 i: 25.6 z: 24.9 y: 23.5

South Pole: 700 square degrees to a uniform depth of u: 25.5 g: 26.4 r: 26.0 i: 25.3 z: 25.0 y:23.4

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Bandwidth2.5 Gbps avg, 10 Gbps peak

Data Archive Center

NCSA, Champaign, IL

100 to 250 TFLOPS, 75 PB

Data Access CentersUS (2) Chile (1)

45 TFLOPS, 87 PB

Base CampCerro Pachon, La

Serena, Chile25 TFLOPS, 150 TB

8Lots of science work has to be done at the data

center.

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Must secure 1/3 of operations cost from international and private partners.

Operations Cost: 36.7M 2009 USD

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• Brookhaven National Laboratory • California Institute of Technology • Carnegie Mellon University• Chile • Columbia University• Cornell University • Drexel University• Google Inc. • Harvard-Smithsonian Center for

Astrophysics • IN2P3 Labs France• Johns Hopkins University • Kavli Institute for Particle Astrophysics and

Cosmology at Stanford University • Las Cumbres Observatory Global Telescope

Network, Inc. • Lawrence Livermore National Laboratory • Los Alamos National Laboratory

• National Optical Astronomy Observatory• Princeton University • Purdue University • Research Corporation for Science Advancement • Rutgers University• Space Telescope Science Institute• SLAC National Accelerator Laboratory • The Pennsylvania State University • The University of Arizona • University of California, Davis • University of California, Irvine • University of Illinois at Urbana-Champaign• University of Pennsylvania • University of Pittsburgh • University of Washington• Vanderbilt University

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LSST Science Book:http://www.lsst.org/lsst/scibook

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12Marana, Arizona, Aug 9-13, 2010

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Orbital inclination and ellipticity of 88000 asteroids from SDSS. The actual color difference is much smaller. 37 families are found.

Through long-term monitoring, LSST will provide precise measurements of orbital parameters as well as photometry and time-domain info of millions of asteroids, significantly improving knowledge about solar system.

Parker et al. 2008 13

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Upper left: simulation of Milky Way stellar streams and LSST observable range (main seq. ~ 100 kpc, RR Lyrae ~ 300 kpc). Right: SDSS data.

Left: structure of the MW from 2.5M stars well observed by SDSS. LSST will reach 200M stars and can study the MW structure within 100 kpc.

Ivezic et al. 2008

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SDSS z = 0.1

MUSYC UVR 29.5mag/sq”

Comparable to LSST SB limit

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“The acceleration of the Universe is, along with dark matter, the observedphenomenon that most directly demonstrates that our theories of fundamental particles and gravity are either incorrect or incomplete. Most experts believe that nothing short of a revolution in our understanding of fundamental physics will be required to achieve a full understanding of the cosmic acceleration.” – the Dark Energy Task Force, a joint committee to advise DoE, NASA, & NSF on futuredark energy research.

HEPAP

NRC

NSTC

WIMP? (SUSY: neutralino? gravitino?)Axion?

Cosmological Constant? Quintessence? Modified Gravity?Back reaction? Brane world? Landscape?

TRgRG 821

NRC

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• automated data quality assessment & discovery• scalability of machine learning and mining algorithms• development of grid-enabled parallel mining algorithms• designing a robust system for brokering classifications • multi-resolution methods for exploration• visual data mining algorithms• indexing of multi-attribute multi-dimensional databases• rapid querying of petabyte databases

Many surveys face the same challenges!

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detectionbackgrounddeblendingastrometryphotometryPSFshapeclassificationtime sequenceredshiftextinctionmaskselectionstackingcorrelation… 19

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• Transient detection: minimizing ||frame1-kernelframe2||. If we do not consider how to obtain the kernel, just the convolution part would cost at least 2× (several)2×3×109 floating point operations (FPOs). A 3GHz CPU could barely process once within the exposure time of 15s, even if at its theoretical peak performance . The actual demand is several 104 FPOs per pixel, so LSST will need ~20TFLOPS on site to process data in real time. The hardware part is fairly easy.

• To process LSST 2000×2000 exposures (3×109 pixels each) once, even if just one FPO per pixel, it would take a 100TFLOPS computer 120s. With all the complex processing, the LSST data archive center needs ~200 TFLOPS capacity. The hardware requirement is moderate.

• Desktop I/O: 6GB÷100MB/s = 60s; 8 years for 4×106 exposures.

• Correlation functions of billions of objects…

• Parameter fitting/minimization in high-dimensional space…

The software challenge is daunting!20

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Must understand the system performance and systematics!

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LSST will soon simulation ~50TB of images, taking ~2M CPU hours. 22

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• Compelling sciences, broad impact…Note: rights to lead key projects will be competed for.

• Discovering the unexpectedInvaluable aspect of surveys: discovery space.

• New trend: data intensive astronomy

• Small investment, 100% dataLimited only by computing & network resources

• Accessible to all levels of expertise• Highly complementary to future large telescopes

Targets

• Share the same data challenges of other survey projectsDome A, Chinese Space Station Telescope…

• Anyone in the US: resource-limited free data access; nonmembers outside the US: no data access.

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Policy is being reformulated.Roughly three parts Construction share:

$465M x GDP/USGDP x Astro fraction by start. Operations share:

$420M x GDP/ AllGDP x Astro fraction. Data access and computation share:

Impact on $16M / year

Early MoU will receive discounts. Must pay operations share.

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• Questions?

• Interests?

• Suggestions?

• Resources?

• Actions?

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