STScI - May 8, 20081 Destiny, The Dark Energy Space Telescope.
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Transcript of STScI - May 8, 20081 Destiny, The Dark Energy Space Telescope.
STScI - May 8, 2008 1
Destiny, The Dark Energy Space Telescope
STScI - May 8, 2008 2
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.
STScI - May 8, 2008 3
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
STScI - May 8, 2008 4
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.
STScI - May 8, 2008 5
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.
STScI - May 8, 2008 6
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)
STScI - May 8, 2008 7
Supernovae
STScI - May 8, 2008 8
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
STScI - May 8, 2008 9
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)
STScI - May 8, 2008 10
Riess et al. (2004) obtain ACS grism spectra of
z ~ 1.3 SN Ia
STScI - May 8, 2008 11
ACS Grism Images of SN2002FW (z = 1.30)
Riess et al. (2004)
STScI - May 8, 2008 12
Supernova Observations
1.Filter: locate SN & host galaxy2.Dispersed mode: spectral time series3.Difference & extract SN spectrophotometry
STScI - May 8, 2008 13
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.
STScI - May 8, 2008 14
Observing Timeline for SN Survey
Times and slews are not shown to scale
STScI - May 8, 2008 15
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
STScI - May 8, 2008 16
Supernova Types
STScI - May 8, 2008 17
Supernova Spectra
• Simultaneousspectrum & photometry = redshift & brightness
• Redshift from 615nm SiII line
• Equal precision & more accuracy than broadband filters alone
STScI - May 8, 2008 18
Light Curve Calibration
STScI - May 8, 2008 19
Supernova Light Curves
• Always get photometry around maximum light
• Sample every 5 days
STScI - May 8, 2008 20
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.
STScI - May 8, 2008 21
Supernova Survey
• Present day & ongoing surveys find hundreds
STScI - May 8, 2008 22
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
STScI - May 8, 2008 24
Weak Lensing
STScI - May 8, 2008 25
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)
STScI - May 8, 2008 26
Predicted Survey Results
Assuming a Flat Universe
STScI - May 8, 2008 27
Predicted Survey Results
Not Assuming a Flat Universe
See Knox, Song & Zhan 2006
STScI - May 8, 2008 28
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
STScI - May 8, 2008 29
Launch Around 2015
~1,500,000 km
~340,000 km~1,500,000 km
L2
STScI - May 8, 2008 30
Mission Operations / Data Flow
STScI - May 8, 2008 31
Destiny, The Dark Energy Space Telescope