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Destiny, The Dark Energy Space Telescope

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Science Goals & Overview

• Determine the expansion history of the Universe to 1% accuracy in z = 0.1 bins over the last 1010 yr.

• Constrain Dark Energy equation of state parameters w0 to 0.05 and wa to 0.20.

• Destiny is a Stage IV dark energy program.

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DESTINY Fact Sheet

• 1.65m telescope at L2• H2RG FPA• SN1a survey over > 3°2

• WL survey 1000°2

• NIR imaging 0.85 m < 1.7 m

• Imaging Spectrograph with ~ 75

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A Brief History of Destiny• Astronomical community recognizes the potential of dark energy space probes.

• NASA & DOE propose a generic Joint Dark Energy Mission

• Initial Destiny concept for JDEM proposed in 2003. Wins initial concept study. LMCO & LANL partners.

• NASA creates general “Beyond Einstein” program for astrophysical missions: Con-X, LISA, CMB probes, etc. Includes JDEM .

• Destiny wins 1 of 3 JDEM concept studies in 2006. NRC BEPAC recommends JDEM for first BE start in 2007.

• Probable JDEM call in September 2008 for 2009 start.

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DESTINY Philosophy

• Complete heritage - Well understood technology in a unique configuration.

• Use the minimal instrument required• Do only in space what must be done in space - leverage ground based observations.

• All spectra all the time. Complete spectro- photometric time series on all SN events.

• Highly automated survey - no time critical operations.

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Destiny Science Team

PI: Tod R. Lauer (NOAO)

Matthew Beasley (Colorado)Chris Burns (OCIW)Kenneth Carpenter (GSFC)Doug Clowe (Ohio U)Ian Dellantonio (Brown)Megan Donahue (MSU)Olivier Dore (Toronto)Chris Fassnacht (UC Davis)Wendy Freedman (OCIW)Chris Fryer (LANL)Peter Garnavich (notre Dame)Jay Holberg (Arizona)Aimee Hungerford (LANL)Robert Kirshner (Harvard) Lori Lubin (UC Davis)

Deputy PI: Dominic Benford (GSFC)

Sangeeta Malhotra (ASU)Tom Matheson (NOAO)Phillip Pinto (Arizona)Nor pirzkal (STScI)Marc Postman (STScI)James Rhoads (ASU)Yong-Seon Song (Chicago)George Sonneborn (GSFC)Sumner Starrfield (ASU)Nicholas Suntzeff (TAMU)Frank Timmes (ASU)Thomas Vestrand (LANL)Mike Warren (LANL)Rogier Windhorst (ASU)Robert Woodruff (LMCO)Ann Zabludoff (Arizona)

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Supernovae

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Why go to high redshifts?

Dark energy can be detected at low redshift, but precise constraints on the DE Eos requires measurements over both the acceleration and deceleration epochs.

SpaceGround

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NIR available only in space

Crucial near-infrared observations are impossible from the ground for the required photometric accuracy

• Sky is very bright in NIR: >100x brighter than in visible

• Sky is not transparent in NIR: absorption due to water is very strong and extremely variable

Data from Gemini Observatory & ATRAN: Lord (1992)

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Riess et al. (2004) obtain ACS grism spectra of

z ~ 1.3 SN Ia

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ACS Grism Images of SN2002FW (z = 1.30)

Riess et al. (2004)

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Supernova Observations

1.Filter: locate SN & host galaxy2.Dispersed mode: spectral time series3.Difference & extract SN spectrophotometry

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Supernovae Survey Schema

Survey area is a contiguousMosaic of Destiny FOVs.Orientation rolls by 90º every 3 months.Dithering will fill in chipgaps and ensure Nyquist sampling.

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Observing Timeline for SN Survey

Times and slews are not shown to scale

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Preliminary Operations Times for SN Survey

Times and slews are not shown to scale

d h m s frame 15:00 m:s 15 00 dither &settle 0:10 0 10 15:10 m:s 15 10 3 x 15:10 = 45:30 m:s 45 30 gap fill & settle 1:00 1 00 46:30 m:s 46 30 4 x 46:30 = 3:06 h:m 3 06 step &settle 1:00 m:s 1 00 acq guide stars 5:00 5 00 switch to filter 0:00 m:s 0 00 6:00 m:s 6 00 image 1:40 m:s 1 40 dither &settle 0:10 0 10 1:50 m:s 1 50 3 x 1:50 = 5:30 m:s 5 30 gap fill & settle 1:00 1 00 6:30 m:s 6 30

d h m s 4 x 6:30 = 26:00 m:s 26 00 0:26 + 0:06 + 3:06 = 3:38 h:m 3 38 16 x 3:38 = 2:10:08 d:h:m 2 10 08 n-s slew & settle 0:30 h:m 0 30 2:10:38 d:h:m 2 10 38 36 x 2:10:38 = 87:22:48 d:h:m 87 22 48 roll slew & settle 0:30 h:m 0 30 momentum 0:30 0 30 stationkeep 2:00 2 00 calibration 2:00 2 00 standard star (64x) 4:00 4 00 9:00 h:m 9 00 available for recovery 3:08:42 d:h:m 3 08 42 8 x 91:07:30 d:h:m = 2:00 y 2 00

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Supernova Types

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Supernova Spectra

• Simultaneousspectrum & photometry = redshift & brightness

• Redshift from 615nm SiII line

• Equal precision & more accuracy than broadband filters alone

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Light Curve Calibration

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Supernova Light Curves

• Always get photometry around maximum light

• Sample every 5 days

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Sn Photometric Calibration

• Obtain high fidelity external and internal flats in ground tests.

• Monitor with internal flats on orbit, plus field stars.• Absolute photometric calibration with DA white Dwarfs.• Sn spectra isolated with differencing. Ad hoc spectral

flat extracted from data cube of monochromatic flats.

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Supernova Survey

• Present day & ongoing surveys find hundreds

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Supernova Survey

• Present day & ongoing surveys find hundreds

• Destiny will find >3000 SN in 2 yrs.

• Most at z~1; requires 3.2 deg2 survey area

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Weak Lensing

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Dark Energy equation of state: w=p/ (w=-1 for )modifies:• angular-diameter distance• growth rate of structure• power spectrum on large scales

w can be measured from the lensing power spectrum

Dark Energy and Weak Lensing

a(t)

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Predicted Survey Results

Assuming a Flat Universe

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Predicted Survey Results

Not Assuming a Flat Universe

See Knox, Song & Zhan 2006

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Observatory• Lockheed

Spacecraft bus• Goodrich Optical

Telescope Assembly• GSFC Science

Instrument, Teledyne FPA

• GSFC Instrument Outer BaffleDestiny Observatory

Destiny OTA + Science Instrument Destiny Optics

Spacecraft BusFixed Solar Array

Instrument Radiators

Outer BaffleAssembly

Goodrich OTA GSFC Science Instrument

1.65m primary mirror

Telescope Optical Bench

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Launch Around 2015

~1,500,000 km

~340,000 km~1,500,000 km

L2

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Mission Operations / Data Flow

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Destiny, The Dark Energy Space Telescope