HST Cal. WS: July 21-23, 2010 1

HST and Astrometry in the 2010 Decade

William van AltenaYale University, New Haven, CT USA

With thanks to:Jay AndersonRolly BedinDave MonetNorbert Zacharias

Terry GirardDana CasettiElliott HorchImants PlataisTodd Henry

Fritz BenedictBarbara McArthurArt BradleyRené MéndezAndrea Ghez

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Astrometry in the 21st century• Analyze data contained in large multipurpose surveys

– SDSS, 2MASS, PanSTARRS, LSST, etc.• Extract relevant data from astrometric surveys

– UCAC, SPM, NPM• PI projects on medium to large multipurpose telescopes

– HST, 4-m telescopes, 8-10-m large telescopes• Small PI projects on dedicated astrometric telescopes

– USNO 1.5-m astrometric reflector– UCAC 0.25-m astrograph– SPM 0.50-m astrograph, etc.

• Educational use of small ground-based telescopes• Instrumentation development

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Ground vs Space Astrometry• Where ground-based Astrometry will remain important

– Ground-based parallax errors can be as low as 0.25 mas, almost as accurateas HST FGS which are about 0.20 mas.

• Beware of relying on very large “root n”

• N > 100: systematic errors may dominate

– Targets fainter than magnitude 16 can be reached, much fainter than FGS astrometry. 

– Binary stars will be done primarily by speckle interferometry from the ground. 

– Strong role for ground-based astrometry until Gaia results are available.  • After Gaia proper motions and positions will be determined from the ground using a

Gaia reference frame.

• Where space-based Astrometry will remain important– Crowded regions such as the centers of globular clusters

– Projects requiring high-precision individual observations

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HST Astrometry• Surveys

– Deep fields (1995 HDF, 1998 HDFS, 2003 HUDF)

• Crowded regions– Globular Clusters (pm membership, absolute pms

& orbits)– Magellanic Clouds (absolute pms & orbits)

• Parallaxes – Special objects (Planetary nebulae, novae, neutron

stars, …)– Cepheid Pop I and II P-L relations

• Binaries– Masses and orbits (close binaries)– Extra-Solar planets (perturbation astrometry of

nearby stars)

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Ground-based surveys current and future

• Current astrometric surveys– UCAC– NPM– SPM

• Schmidt plate scans– USNO-A2, USNO-B– SuperCosmos

• Planned astrometric surveys– URAT

• Current multipurpose surveys– SDSS and derivatives– 2MASS– Dennis– SkyMapper– PanSTARRS

• Planned multipurpose surveys– LSST

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Current Astrometric Surveys• UCAC3: U.S. Naval Observatory CCD Astrograph Catalog

– A compiled, all-sky star catalog of 100 million stars– Magnitude range 9 < R < 16– Positional errors: 15 to 20 mas for 10 < R < 14– Proper motions from early epoch SPM data (-90 to -10 deg Dec) and Schmidt plate

data– Zacharias, et al. 2009

• SPM4: Yale/San Juan Southern Proper Motion Catalog 4: (2009) • NPMx: Lick Northern Proper Motion Catalog: first epoch positions:

(2010) to be used as first-epoch positions for the UCAC4.– 103,319,647 stars and galaxies south of -20 degrees declination - SPM.– 160,000,000 stars and galaxies north of -30 degrees declination - NPM.– roughly complete to V=17.5 (all are contained in 2MASS)– precision of SPM4 positions: 30 to 150 mas– precision of SPM4 absolute proper motions: 2 to 10 mas/yr– van Altena, et al. 2009; Girard, et al. 2010

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Future Astrometric Survey• URAT: USNO Robotic Astrometric Telescope

– Magnitude range 9 < R < 16– Positional errors: 15 to 20 mas for 10 < R < 14– Proper motions from early epoch SPM data (-90 to -10 deg Dec) and

Schmidt plate data– Zacharias, et al. 2009

UCAC SPM URAT

110 megapixel CCD "superchip"20-cm astrograph 51-cm double astrograph

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Schmidt Plate Scanners

ROE SuperCOSMOS scanner

STScI Guide Star Measuring Machine

USNO PMM Measuring Machine

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• GSC 2.3 release of GSC II– 945,592,683 objects measured

on STScI PDS machines

– GSC 2.3 is a current catalog release extracted from the Guide Star Catalog II database

– Positions on ICRF ACT/Tycho

– Bucciarelli, et al. 2008

• SuperCOSMOS– 1.9 billion objects

– Average J2000 positions and proper motions from 3 colors at 2 epochs

– Positions on Tycho2 and ACT

– http://surveys.roe.ac.uk/ssa/

Schmidt Plate Scans• USNO-A2

– 526,280,881 stars measured on PMM

– Average J2000 position on red and blue POSS plates

– ACT/Tycho system– Monet, et al. 1998

• USNO-B– 1 billion stars– Average J2000 positions and proper

motions from 3 colors at 2 epochs– Monet, et al. 2003

• XPM: 2MASS - USNO-A2.0– 280 million stars - whole sky– Positions and proper motions– Mag range 12 < B < 19 mag– Federov, et al. 2009

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Multipurpose Surveys• General characteristics:

– Not primarily astrometric, but huge amounts of useful data.

– New surveys should get around 10-mas per visit; lots of visits and colors.

– Surveys need much more input on astrometric needs.

– Don’t need Gaia-class accuracy for nearby stars, etc.

• Some priorities:– Develop algorithms for finding these needles in very big haystacks.

– Understand astrometric accuracy:• Regime of low signal-to-noise ratios, short exposures, fast optics, etc.

• Morphology and statistics of “reference galaxies”.

• Contribute to design and mission of LSST.

– Work on IR version of large etendue telescope+camera.

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Multipurpose Surveys• 2MASS - A large-area, deep

photometric survey• SDSS based proper motions• SDSS-USNO-B

– Covers about 3000 square degrees

– Sigma pm about 3.5 mas/yr.– Munn, et al. AJ 127, 3034, 2004 &

AJ 136, 895, 2008

• SDSS-Flagstaff 1.3-m telescope– Covers about 3000 square degrees– Proper motion accuracy about 20-

30 mas/yr with a 5-year baseline.– Munn, et al. AAS 215, 45202,

2009

• SDSS-SDSS proper motions– 300 square degree Southern

Equatorial Stripe

• Pan-STARRS 1.8-m Sky Survey– Pan-STARRS will survey the

whole sky to 24th magnitude every few days

• SkyMapper - ANU 1.35-m survey– analogous to the Sloan Digital Sky

Survey; 20,000 sq. deg. South of equator.

• LSST - Large Synoptic Survey Telescope 8.4-m primary, 6.7-m effective aperture

– Ten-year imaging survey over 20,000 square degrees south of +15 deg.

– Each pointing will be imaged 1000 times with fifteen second exposures in

– total point-source depth of r~27.5.– Gaia parallax accuracy at r = 20.5

mag and to go 4 mag fainter than Gaia

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Deep Astrometric Standards (DAS)• Large telescopes need deep and

precise reference frames for astrometric calibrations.

• Absolute astrometry at the 5 - 10 mas level and absolute proper motions good to 2 mas/yr in four 10 deg2 Galactic fields, to a depth of V=25.

• Basic reference frame is UCAC2 catalog, significantly improved by additional observations, and new VLBI positions of radio-loud and optically visible QSOs.

Platais, et al. 2006(PASP 118, 107, 2006)

Careful of LSST 15-sec exposures!

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Science in the Halo of the Galaxy• Dwarf galaxies and Globular Clusters

– The formation of the GC system: accreted from early/recent mergers of satellites and/or formed in situ?

– Orbits help to understand formation scenarios of the Galaxy and origins of GCs– Ground-based surveys & some HST provide absolute proper motions and orbits

• Casetti, et al. (2010)• Rees & Cudworth (2010)• Bellini & Bedin (2010)

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Science in the Halo of the Galaxy

• Magellanic Clouds– Ground-based pms imply

systems probably bound to Galaxy

• Vieira, et al. (2010)– HST-based pms imply systems

probably unbound• Kallivayalil, et al. (2006,

2010)

• Reference systems of galaxies & QSOs now provide the link to absolute– Gaia will be the link to

absolute in the future

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Finding Merger Remnants from Surveys• Velocity dispersion in a remnant stream

predicted Sigma v ~ ± 5 km/s (Helmi & White, 1999; Kathryn Johnston, 2006)

• 300-500 remnant streams predicted by H&W within the local 1 kpc3

• Sigv = k*Sigpm*D– 5 km/sec = 4.74* Sigpm *1000pc– Sigpm = 1 mas/yr

• Proper motions with sigpm = 0.5 mas/yr can now be determined with medium-sized telescopes in a 3-4 years to mag 21.

• Detection/non-detection of streams could place limits on the validity of the lambda-CDM models of cosmology

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Measuring the orbit of Sgr streamCasetti, et al. 2010

SA 71

SA 94SA 93 SA 117

SA 116

Sgr core

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Proper Motions in theHubble Deep Field - North

Kilic, von Hippel, Winget &

Méndez, Ap J accepted.

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Globular Cluster Proper Motion Membership• HST imaging cameras enable us to determine precise relative proper motions.

• This enables us to separate the cluster members from the field stars and therefore “clean” the CMDs. In some cases it is possible to study the internal dynamics of the clusters.

• Proper motion precision of 0.25 mas/year for a 3 year baseline.

• This corresponds to ≈10 km/s at 10 kpc.

Anderson & King, 2003, “The Rotation of 47 Tuc,” AJ, 126, 772

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The First Full CMD of a Globular Cluster

• Richer et al. 2005 observed NGC6397 with 126 orbits– Discoveries

• End of WD cooling seq

• Blue hook at bottom!• End of MS?

– Limitation: field stars– Solution: proper motion

membership

• Slides courtesy of Jay Anderson

19

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Proper-Motion Cleaning PI-Rich, UCLA20.020.120.220.3

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Where are the stars centered?

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Open Cluster Membership• Low field density, so a

ground-based project for Wide-Field Imagers

• Proper motion precision now available with time baseline of 3-4 years:– igmapm ~ ± 0.5

mas/yr, or– igmav ~ ± 2.6 km/s

@ 1kpc• Very clean

separation of members from field stars for clusters with D < 1-2 kpc

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The Stellar Census and Dark Matter• Ground-based programs

– USNO Flagstaff (Dahn, et al. 2008)

• Special objects with parallax precision of 0.25 mas

– RECONS at CTIO (Henry)– Parallaxes with wide-field

imagers on the ground.• ±1 mas positional astrometry

can yield 0.5 mas parallax precision.

• Determine stellar density to 2% in Solar Nbhd.

• Brown dwarfs, L & T dwarfs– Detect to MI ≤ 21 at 150 pc

Courtesy of Todd Henry

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HST FGS parallaxes• HST FGS

– Stars brighter than 16th mag• Parallax precision to 0.2 mas

– Pop I Cepheid P-L calibration - 2007

– Planetary nebulae - 2009

– Pop II Cepheid P-L calibration - HST orbits approved.

• Benedict, et al. 2007, 2009

Pop I Cepheid P-L calibration

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HST FGS parallaxes of Planetary Nebulae

Benedict, et al. 2009

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Binaries:Orbits and masses.

• Binary stars. – Gravitation --> orbit.

• Semi-major axis from – ground-based speckle

interferometry – HST FGS scans

• separations down to 10-15 mas with FGS.

• Need SIZE of orbit which means we need the parallax.– Gaia and SIM will do the

job here.

N

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The And System

50 y of Solar System from 10 pc

McArthur, et al. 20104 years, from 11 pc

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Adaptive Optics

• Adaptive optics: correct for atmospheric turbulence in Infrared

• Can see through the 20 magnitudes of visual extinction

– Very small areas of the sky, say 1”

– Need a fairly bright reference star to monitor the atmosphere, so limited unless laser reference is used

• Mass of Black Hole at the Galactic center from orbital motions of the stars

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Space Satellite accuracy projections

Gaia and SIM will determine the parallaxesGaia and SIM will determine the parallaxesthat with orbits from HST FGS, while ground-that with orbits from HST FGS, while ground-based Speckle Interferometry will define the based Speckle Interferometry will define the Mass-Luminosity relation.Mass-Luminosity relation.

Mission Positional

accuracy

Parallax

accuracy

Proper motion

accuracy

Gaia

V < 15

V = 20

6 uas

205 uas

21 uas

275 uas

11 uas

145 uas/yr

SIM

V < 20 3 uas 4 uas 2.5 uas/yr

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Kinematics: The Future

Gaia (15 mag)

1% 10%1% 10%SIM 2.5 kpc 25 kpcSIM 2.5 kpc 25 kpcGaia 0.4 kpc 4 kpcGaia 0.4 kpc 4 kpcHipparcos 0.01 kpc 0.1 kpcHipparcos 0.01 kpc 0.1 kpc

SIM (18 mag)DistancesDistances

Proper MotionsProper Motions::

SIM ~ 2.5 uas/yrSIM ~ 2.5 uas/yr

Gaia ~ 11 uas/yrGaia ~ 11 uas/yr

Hipparcos ~ 1 mas/yrHipparcos ~ 1 mas/yr

Gaia and SIM will define Gaia and SIM will define the kinematical structure the kinematical structure of the Galaxy.of the Galaxy.

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Local Group members

• Beyond the merging satellite galaxies– Note that all of the

proper motions are predicted to be large in the context of SIM and Gaia accuracies

– 3D velocities of the LG members will provide mass estimates of the LG and dark matter

Gaia

SIM

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Summary

• The potential for Astrometry to contribute to science is greater than at any time in history!

• A desperate need exists to train young scientists in Astrometry to make the most of this exciting future.

• There is a trend, especially in the US, for diminishing support for Astrometry.

• We need to convince universities, observatories and astronomical institutes to support the education of Astrometrists (and to hire them!!)

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UCAC3: U.S. Naval Observatory CCD Astrograph Catalog

• UCAC3 is a compiled, all-sky star catalog of 100 million stars

• 8-inch USNO astrograph: south from CTIO, north from USNO Flagstaff

• Magnitude range 9 < R < 16 • Wavelength range 670 to 750 nm• Positional errors: 15 to 20 mas for 10 < R < 14• Photometric data: SuperCosmos and 2MASS• Proper motions:

– bright stars are based on about 140 catalogs, including Hipparcos and Tycho, as well as all catalogs used for the Tycho-2 proper motion construction

– faint stars are based on a re-reduction of early epoch SPM data (-90 to -10 deg Dec) plus Schmidt plate data from the SuperCosmos project

• Zacharias, et al 2009

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URAT: USNO Robotic Astrometric Telescope

• URAT successor to the UCAC• Same lens as the UCAC, but four

110 megapixel CCD "superchips" (shown right) in a mosaic to cover 28 square degrees/exposure.

• Magnitude range 9 R < 17.5 • Wavelength range 670 to 750 nm• All sky coverage to start in

Flagstaff and then move to CTIO• First light expected in 2010 in

Washington

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SPM4: Yale/San Juan Southern Proper Motion Catalog

• 47-year collaboration between the National University of San Juan, Argentina and the Yale Southern Observatory

– 103,319,647 stars and galaxies south of -20 degrees declination.

– roughly complete to V=17.5 (all are contained in 2MASS)

– precision of its positions: 30 to 150 mas– precision of absolute proper motions: 2 to 10

mas/yr – blue and visual passband photometry +

2MASS J,H,K

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SPM4: Yale/San Juan Southern Proper Motion Catalog

• 47-year collaboration between the National University of San Juan, Argentina and the Yale Southern Observatory

– 103,319,647 stars and galaxies south of -20 degrees declination.

– roughly complete to V=17.5 (all are contained in 2MASS)

– precision of its positions: 30 to 150 mas

– precision of absolute proper motions: 2 to 10 mas/yr

– blue and visual passband photometry + 2MASS J,H,K

• Girard, et al. 2009

SPM4: < -200; 102.9 million absolute proper motions

85,155 LEDA reference galaxies

SPM density of observations

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Schmidt Plate Scans - USNO• USNO-A2

– 526,280,881 stars measured on PMM

– Average J2000 position on red and blue POSS plates

– ACT/Tycho system

– Monet, et al. 1998

• USNO-B– 1 billion stars

– Average J2000 positions and proper motions from 3 colors at 2 epochs

– Monet, et al. 2003

USNO PMM Measuring Machine at Flagstaff

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Schmidt Plate Scans - STScI & Cosmos

• GSC 2.3 release of GSC II– 945,592,683 objects measured

on STScI PDS machines– GSC 2.3 is a current catalog

release extracted from the Guide Star Catalog II database

– Positions on ICRF ACT/Tycho– Bucciarelli, et al. 2008

• SuperCOSMOS– 1.9 billion objects– Average J2000 positions and

proper motions from 3 colors at 2 epochs

– Positions on Tycho2 and ACT– http://surveys.roe.ac.uk/ssa/

SuperCOSMOS scanner

Guide Star Automatic Measuring MAchine

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XPM: 2MASS - USNO-A2.0• 280 million stars - whole sky

• Mag range 12 < B < 19 mag

• Zero-point of the absolute pms uses about 1.45 million galaxies from 2MASS, about 1 mas/yr

• Systematic errors still exist that are a function of magnitude.

• Scatter of formal proper motions for the DR5 quasars versus RA and Dec.– Proper motion accuracy: 3-4

mas/yr– North pm accuracy: 3 mas/yr– South pm accuracy: 7 mas/yr

• Federov, et al. 2009

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Large-area, deep photometric surveys

Carried out on small aperture telescopes for extragalactic studies, but very useful for astrometry: 2MASS (1.3 m), SDSS (2.5 m), INT-WFS (2.5 m) also finding lists for many other surveys, e.g. SPM4.

2MASS (Cutri et al. 2003)

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SDSS 2.5-m at Apache Point

• SDSS-I/II contains 25% of sky and includes more than 350 million objects

• The 300 square degree Southern Equatorial Stripe was scanned more than 20 times in SDSS-I and more than 40 times in the SDSS-II supernova survey.

• SDSS DR7: The final data set also includes spectra of 930,000 galaxies, 120,000 quasars, and 460,000 stars.

SDSS photometry: streams in the halo.

K. Johnston, J. Bullock

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SDSS-Based Proper Motions• SDSS-USNO-B

– Serious local systematic errors corrected using QSOs.– Covers about 3000 square degrees, i.e. the DR1 release of SDSS.– Typical proper-motion errors between SDSS-SDSS and USNO-B are

reduced by 20-30%; the systematic differences are much smaller.• Sigma pm about 3.5 mas/yr.• Munn, et al. AJ 127, 3034, 2004 & AJ 136, 895, 2008

• SDSS-Flagstaff 1.3-m telescope– Covers about 3000 square degrees to date to r = 21 mag.– Proper motion accuracy about 20-30 mas/yr with a 5-year baseline.– Munn, et al. AAS 215, 45202, 2009

• SDSS-SDSS proper motions– 300 square degree Southern Equatorial Stripe was scanned more than

20 times in SDSS-I and more than 40 times in the SDSS-II supernova survey.

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Pan-STARRS 1.8-m Sky Survey• Pan-STARRS will survey the whole

sky to 24th magnitude every few days

• Primary purpose is to detect potentially hazardous objects and to study the minor bodies in the Solar System.

• Wide-field, repetitive nature of the Pan-STARRS observations makes them ideal for determination of proper motions.– Comparison with existing catalogs– Pan-STARRS repeat observations for

high proper-motion objects

• PS1, first of 4 planned telescopes had first light on May 13, 2010. http://pan-starrs.ifa.hawaii.edu/

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SkyMapper - ANU 1.35-m survey telescope

• 1.35-m survey telescope under construction by the Australian National Univ.

• Designed to carry out the Stromlo Southern Sky Survey (S3), a multi-color, multi-epoch survey of the southern sky analogous to the Sloan Digital Sky Survey.

• 20,000 sq. deg. South of equator.

• SDSS uvgriz bandpasses to mag 21.

• Astrometry to 50 mas.http://msowww.anu.edu.au/skymapper/

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

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Large Synoptic Survey Telescope 8.4-m primary, 6.7-m effective

aperture• First light planned for 2015• Ten-year imaging survey over 20,000 square degrees south of +15 deg.

Each pointing will be imaged 1000 times with fifteen second exposures in six broad bands from 0.35 to 1.1 microns, to a total point-source depth of r~27.5.

• Proper motions from observations in Chile over a 10-yr period.• Designed to have Gaia parallax accuracy at r = 20.5 mag and to go 4 mag

fainter than Gaia• Required accuracy:

– Parallax accuracy of 1 mas at r = 22.4;– Parallax accuracy of 6 mas for red stars with 10 sigma y-band

detections;– Proper motion accuracy of 0.2 mas/yr at r = 20.5.

• Projected accuracy at r = 24.2 mag– Parallax accuracy: 3 mas– Proper motion accuracy 1 mas/yr at r = 15.

• http://www.lsst.org/lsst