1 r. d. gehrz astronomy and astrophysics advisory committee, october 12, 2007 sofia stratospheric...

1 Astronomy and Astrophysics Advisory Committee, October 12, 2007R. D. Gehrz

SOFIA Stratospheric Observatory

for Infrared Astronomy

R. D. Gehrz

Lead, SOFIA Community Task Force (SCTF)

Department of Astronomy, University of Minnesota


Outline

• SOFIA Science

• Description of the Observatory and Project Status

• Schedule

• Summary


Science


Key Science Topics Related to Origins

• How stars form in our galaxy and other nearby galaxies

• Chemistry, Mineralogy, and Biology

• Solar System studies

• Targets of Opportunity, for example:

– Bright Comets

– Eruptive variable stars

– Galactic and LMC/SMC classical novae

– Supernova in our galaxy or other nearby galaxies

– Eclipses and Occultations in the Solar System


SOFIA and the Chemical Evolution of the Universe


• Above 99% of the water vapor

• Transmission at 14 km >80% from 1 to 800 µm; emphasis

on the obscured IR regions

• Instrumentation: wide variety, rapidly interchangeable, state-of-the art

• Mobility: anywhere, anytime

• Twenty year design lifetime

• A near-space observatory that comes home after every flight

The Advantages of SOFIA


Unique Science Capabilities

• 8 arcmin diameter FOV allows use of very large detector arrays

• Image size is diffraction limited beyond 15 µm, making images 3 times sharper than Spitzer Space Telescope

• Because of large aperture and better detectors, sensitivity for imaging and spectroscopy will be similar to the space observatory ISO

• Ability to adapt to new technologies

• Ability to track temporal events


Expectations for Improvements in Detectors

Due to increases sensitivity and the number of pixels in large format IR detectors, the speed of measurement has doubled

every year for the last 40 years


Astrochemistry

• Most ground state molecular lines in IR or submillimeter

• Need high spectral resolution throughout which SOFIA has.

• As sensitive as CSO, but much larger wavelength range is accessible

• Light molecules: Molecular hydrogen, HD, water, other hydrides in IR and submillimeter

• The fullerene, C60, has 4 IR lines in SOFIA’s bands

CSO FTS Spectrum of ORION OMC1

Serabyn and Weisstein 1995

SOFIA is a good observatory for studyingchemistry in space


Occultation astronomy with SOFIA

Pluto occultation lightcurve observed on the KAO (1988) probes the atmosphere

• SOFIA can fly anywhere on the Earth, allowing it to position itself under the shadow of an occulting object.

• Occultation studies with SOFIA will probe the sizes, atmospheres, and possible satellites of newly discovered planet-like objects in the outer Solar system.

• The unique mobility of SOFIA opens up some hundred events per year for study compared to a handful for fixed observatories.

SOFIA will determine the properties of Dwarf Planets in and beyond the Kuiper Belt


Today over 200 extrasolar planets are known, and over 15 transit their primary star: • SOFIA will fly above the scintillating component of the atmosphere and will provide the most

sensitive freely pointing observatory for extrasolar planetary transits after HST and before JWST.

• SOFIA has instruments that can observe with high signal-to-noise the small variations in stellar flux due to a planet transit and

Provide good estimates for the mass, size and density of the planet May reveal the presence of, satellites, and/or planetary rings

Artist concept of planetary transit and the lightcurve of HD 209458b measured by HST revealing the transit signature

SOFIA will determine the properties of new extrasolar planets by use of transits with HIPO and FLITECAM working together

Extrasolar Planet Transits


Antennae GalaxiesIRAC @ 8 m (red; 160s, 4’ x 4’)HAWC Beam Sizes

Henize 206- LMC high mass star formationMIPS @ 24 mm (80s, 20’ x 20’)HAWC Fields of view (Current 12x32 array at 53, 89, 155, 216 m; Circle is total optical FOV)

NASA/JPL-Caltech/Z. Wang NASA/JPL-Caltech/V. Gorjian

Clues to the evolution of galaxies: starbursts triggered by collisions and star formation in low-metallicity environments


Atmospheric transmission around the HD line at 40,000 feet

• Deuterium in the universe is created in the Big Bang.

• Measuring the amount of cold HD (T<50K) can best be done with the ground state rotational line at 112 microns.

• A GREAT high resolution spectrometer study is possible given ISO detection

• HD traces the cold molecular hydrogen (Bergen and Hollenbach).

• HD has a much lower excitation temperature and a dipole pole moment that almost compensates for the higher abundance of molecular hydrogen.

• In the future, this technique could be used much like the HI 21cm maps but for cold molecular gas.

SOFIA will study deuterium in the galaxy using the ground state HD line at 112 microns. This will allow determination the cold molecular hydrogen abundance.

Cold Molecular Hydrogen using HD


Classical Nova Explosions


R. D. Gehrz, et al. 2005, ApJ, in preparation [PID 124]

Spitzer Spectra of Nova V382 Vel

IRS Short-High IRS Long-High

IRS Short and Long-High Spectra: Abundances and Kinematics

H I[Ne II] [Ne V] [Ne III]

[Ne V]

[O IV] [Ne III]


SOFIA’s Instrument Complement

• As an airborne mission, SOFIA supports a unique, expandable instrument suite

• SOFIA covers the full IR range with imagers and low, moderate, and high resolution spectrographs

• 4 instruments at IOC; 9 instruments at FOC

• SOFIA can take full advantage of improvements in instrument technology

• Both Facility and PI Instruments


10 0

10 1

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1 10 100 1000

Wavelength [µm]

Sp

ectr

al r

eso

luti

on

Planetary Atmospheres

Chemistry of the cold ISMChemistry of the cold ISM

Comet MoleculesComet MoleculesDynamics of the Galactic CenterDynamics of the Galactic Center

Dynamics of collapsing protostarsDynamics of collapsing protostars

Velocity structure and gas composition in Velocity structure and gas composition in disks and outflows of YSOsdisks and outflows of YSOs

Composition/dynamics/physics of the Composition/dynamics/physics of the ISM in external galaxiesISM in external galaxies

PAH & organic moleculesPAH & organic molecules

Nuclear synthesis in supernovae in nearby galaxiesNuclear synthesis in supernovae in nearby galaxies

Composition of interstellar grainsComposition of interstellar grains

KBOs, Planet TransitsKBOs, Planet TransitsDebris Disk StructureDebris Disk Structure

Luminosity and Morphology of Star Formation Galactic and Luminosity and Morphology of Star Formation Galactic and Extra-Galactic RegionsExtra-Galactic Regions

SOFIA: Science For the Whole Community


10 0

10 1

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1 10 100 1000Wavelength [µm]

Sp

ectr

al r

esol

uti

on

HIPO

FLITECAM

FORCASTHAWC

FIFI LS

EXES

CASIMIR

GREAT

SAFIRE

SOFIA Performance: Spectral Resolution of the First Generation Science Instruments

FORCAST

SPITZER IRSIRAC

MIPS


Frequency (THz)

2005 2010 2015 2020 2025

SOFIA

30

3

0.3

Wavelength (µm)SPITZER

1000

100

10

1

Infrared Space Observatories

He

rsch

el

SA

FIR

Ground-based Observatories

JWST

?

SOFIA provides temporal continuity and wide spectral coverage, complementing other infrared observatories.


Overview


SOFIA Overview

• 2.5 m (98 inch) telescope in a modified Boeing 747SP aircraft– Optical to millimeter-wavelengths

– Emphasis on the obscured IR (30-300 m)

• Operating altitude– 39,000 to 45,000 feet (12 to 14 km)

– Above > 99% of obscuring water vapor

• Joint Program between the US (80%) and Germany (20%)

• First Light Science 2009– 20 year design lifetime

– Science Ops at NASA-Ames and Flight Ops at NASA-Dryden

– Deployments to the Southern Hemisphere and elsewhere

– >120 8-10 hour flights per year

– Built on NASA Lear/Kuiper Airborne Observatory Heritage


Primary Mirror M1

M2

M3-1

M3-2

Focal Plane

Focal Plane Imager

Pressure bulkhead

Nasmyth tube

Spherical Hydraulic Bearing

Nasmyth: Optical Layout


The Un-Aluminized Primary Mirror Installed


Four First Light Instruments

Working/complete HIPO instrument in Waco on SOFIAduring Aug 2004

Working/complete FLITECAM

instrument atLick in 2004/5

Working FORCAST instrument at Palomar in 2005

Successful lab demonstration of GREAT in July 2005


Status


SOFIA Airborne!

26 April 2007, L-3 Communications, Waco Texas: SOFIA takes to the air for its first test flight after completion of modifications


• The aircraft has flown in April 2007 and is now at NASA Dryden FRC for flight certification tests

• Early Science is expected to occur in 2009

• Two instruments have been selected for Early Science

- FORCAST: a US 5-40 μm imager

- GREAT: a German heterodyne 60 to 200 μm Spectrometer

- Both have been tested in the lab or on a telescope

Early Science with SOFIA


Summary

-Program making progress!

-Aircraft structural modifications complete-Telescope installed, several instruments tested on ground observatories-Completed first flight and ferry flight to NASA Dryden-Full envelope flight testing (closed door) has started.-Several subsystems will be installed spring/summer 08 (Door motor drive, coated primary mirror) -First science in ’09

- SOFIA will be one of the primary facilities for far-IR and sub-millimeter astronomy for many years


Schedule


SOFIA Schedule (Major Milestones)

• First Re-Flight Occurred April ’07

• Door Drive Delivered Winter ’07

• Open Door Flights at DFRC Fall ’08

• First Science ‘09

• Next Instrument call ‘10


US General Observer Opportunities

• First call for science proposals in ’09

• Future calls every 12 months

• First General Observers 2010

• Expect ~ 20 General Observer science flights

• Shared risk with Instrument PI’s

• Open Observatory with Facility Instruments


Next Call For New Instruments

• The next call for instruments will be at first Science ~FY10

• There will be additional calls every 3 years

• There will be one new instrument or upgrade per year

• Approximate funding for new instruments $8 M/yr


Summary• SOFIA has unique spectral and temporal coverage

– Unique high-resolution spectroscopy: 28 < l < 150 μm

– (l/10 μm) arc-sec image quality, unique for 30 < l < ~60 μm

– Unique ability to obtain coverage of transient events

– Unique long operating lifetime

• SOFIA will increase its unique complement of capabilities in the future and will be a test-bed of technologies for future Far-IR missions

– State-of-the-art large format IR detector arrays

– Polarimeteric imaging and spectroscopy

• SOFIA is a hands-on Far-IR observatory

– Will train future mission scientists and instrumentalists

• SOFIA is on track for first science in 2009


Appendix


The Initial SOFIA Instrument Complement

• HIPO: High-speed Imaging Photometer for Occultation

• FLITECAM: First Light Infrared Test Experiment CAMera

• FORCAST: Faint Object InfraRed CAmera for the SOFIA Telescope

• GREAT: German Receiver for Astronomy at Terahetz Frequencies

• CASIMIR: CAltech Submillimeter Interstellar Medium Investigations Receiver

• FIFI-LS: Field Imaging Far-Infrared Line Spectrometer

• HAWC: High-resolution Airborne Wideband Camera

•EXES: Echelon-Cross -Echelle Spectrograph

•SAFIRE: Submillimeter And Far InfraRed Experiment


SOFIA’s 9 First Generation Instruments

* Listed in approximate order of expected in-flight commissioning % Operational (August 2004) § Uses non-commercial detector/receiver technology

Science

Instrument * Type Resolution PI Institution

HIPO % fast imager 0.3 - 1.1 filters E. Dunham Lowell Obs.FLITECAM % imager/grism 1.0 - 5.5 filters/R~2E3 I. McLean UCLAFORCAST imager/(grism?) 5.6 - 38 filters/(R~2E3) T. Herter Cornell U.GREAT ¤ heterodyne

receiver158 - 187, 110 - 125, 62 - 65

R ~ 1E4 - 1E8 R. Gsten MPIfR

CASIMIR ¤ heterodyne receiver

250 -264, 508 -588

R ~ 1E4 -1E8 J. Zmuidzinas CalTech

FIFI LS ¤ imaging grating spectrograph

42 - 110, 110 - 210

R ~1E3 - 2E3 A. Poglitsch MPE

HAWC ¤ imager 40 - 300 filters D. A. Harper Yerkes Obs.EXES imaging echelle

spectrograph5 - 28.5 R ~ 3E3 - 1E5 J. Lacy U. Texas Austin

SAFIRE ¤ F-P imaging spectrometer

150 - 650 R ~ 1E3 - 2E3 H. Moseley NASA GSFC

4.5-28.3


Science Objectives

• Major Science Programs for SOFIA:

– Origin of stars and planetary systems– Planetary bodies that make up our Solar System– Life-cycle of dust and gas in galaxies– Composition of the molecular universe– Role of star formation and black hole activity in the energetics of luminous galaxies

• SOFIA has a unique suite of instruments that cover a wide range of wavelengths at a wide range of spectral resolution.

• SOFIA will be continuously upgraded with new instrumentation and will serve as an important technology development platform for future space missions.

• SOFIA is a highly visible icon for education and public outreach and will immerse educators in the scientific process.


Learjet-KAO Instrumentalists and their Contributions


Great Observatory Operations Costs for FY 08

Observatory Ops Costs Annual Operating Hours

Cost per Hour

HST $105M 4400 (50%) $24K

Chandra $77M 6400 (75%) $10K

Spitzer $81M 7680 (90%) $12K

SOFIA $80M (est) 960/768

(Total/NASA)

$104K

CONCLUSIONS

• SOFIA’s total operating costs are comparable to those of the other Great Observatories

• SOFIA has fewer operating hours (it’s an airplane)

•SOFIA’s costs include servicing missions with new focal plane instruments every few years


Courtesy of Gary Melnick

1 r. d. gehrz astronomy and astrophysics advisory committee, october 12, 2007 sofia stratospheric...

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