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NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA)
Gordon J. Stacey, Cornell University (many slides borrowed from Robert Gehrz,
U. Minnesota)
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The SOFIA Observatory2.5 m telescope in a modified Boeing 747SP
aircraftOptical to millimeter-wavelengthsEmphasis on the obscured IR (30-300 m)
Joint Program between the US (80%) and Germany (20%)
First Light Will Occur in 2009Built on NASA’ Airborne Astronomy Heritage
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SOFIA Forte: the Far -Infrared
SOFIA is unique in the far-IR wavelength bands: 30 to 300 m – a region of the electromagnetic spectrum that is totally obscured by telluric water vapor for ground based observatories.
Flying at > 39,000 feet gets you above 99% of the obscuring water vapor.
Why do we do it?
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Why Study the Far -Infrared? Extinction and Energetics…
Extinction The energy for most of the radiant light in a galaxy originates in the photospheres of stars visible light. However, stars form in dusty molecular clouds.
This dust is small r ~ 0.1 m ~ wavelength of visible light scattered and absorbed (extinction)
Can’t see star formation regions in the visible must go to longer wavelengths
Effect is huge! Only one visible photon in 10 billion from the Galactic Center reaches us, but > 90% at
> 40 m reaches us!
2 m (2MASS) Image: Galactic Center ClusterOptical Image: Nearby stars
Far-IR (IRAS) Image: Warm dust
Extinction
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Far-IR = 30 µm ≤ ≤ 300 µm
10K ≤ T ≤ 100 K
The Planck Function
Wien’s Law1
12/5
2
kthce
hcF
deg m 2898max T
Energetics: What glows in the far-IR?
•Robert Gehrz, U. Minnesota
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Things Look Different at Different Wavelengths!
Cool nose
Warm eyes & ears
Cool fur10 m image of a cat
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Energetics
The same is true for stars Much of the light energy in the local Universe arrives in the far-IR bands as thermal radiation from warm dust
Example 1 – Dust: Protostars glow in the submillimeter band Stars form in the dust cores of giant
molecular clouds As the core collapses to form a
protostar, its gravitational energy is converted into kinetic energy (heat) – the core heats up.
The first glow of a protostar is in the far-IR band
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Orion Nebula: Visible and Far -IR
38 m Image: KWIC-Kuiper Airborne Observatory Harry Latvakoski, Cornell PhD
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Energetics: Gas Cooling
Example 2 – Spectral Lines -- Dominate the cooling and trace physical conditions of the gasTo form a star, gas clouds must collapseAs a cloud collapses under gravity, it heats up –
this would stop collapse unless it can cool effectively
The spectral lines in the far-IR and submillimeter bands are the primary coolants for the neutral gas that forms stars
Most important cooling lines include H2O, SO2, H2 and CO rotational lines, [CI] [CII], [OI], and [NII] fine structure lines – all of which lie in the far-IR band
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The Far -Infrared Regime is Exciting – So Why Isn’t Everyone Doing it?
14,000 feet
41,000 feet
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The History of Airborne AstronomyNASA Lear
JetObservatory
1999
2002
1967 – 1983+
“Pioneering” Airborne Astronomical Telescope – 30 cm aperture 2hr10m Flights – zip up to 45,000 feet First observations ever of many of the most important cooling
lines – hadn’t even been seen in the lab! Produced many (~20) PhDs – you are looking at the last one…
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Kuiper Airborne Observatory (KAO)
Natural Follow-on to the Lear Jet
Modified C141 Starlifter Pressurized cabin – “shirt
sleeve” environment Telescope balanced and
floated on an “air-bearing” Gyro stabilized to within < 5” 91.4 cm (36”) telescope 7.5 hr flights, 6.5 of which
above 39,000 feet Produced > 60 PhDs
Guiding done with focal plane camera and computerized feedback to torque motors on the telescope
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KAO Discoveries 1977 – Five thin rings of Uranus discovered – flight from
Perth, Australia over the Indian Ocean – mobility of telescope enables stellar occultation viewing
Unexpectedly large far-infrared luminosities of galaxies Self luminosities of Jupiter, and Saturn Discoveries of young stars being formed First strong evidence for a massive (few million) solar mass
black hole in the center of the Galaxy Water discovered in the atmosphere of Jupiter via impacts of
Comet Shoemaker-Levi (1994) 1985 – First detection of a natural interstellar infrared laser
Many of Today’s Leaders in Infrared and Submillimeter Astronomy – Particularly in Instrumentation – Cut Their Teeth
on Airborne Astronomy:
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SOFIA: The Stratospheric Observatory for Infrared Astronomy 1999
2002
20062006
2009 – 2029…
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The SOFIA Observatory
2.5 m telescope in a modified Boeing 747SP aircraft 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 Based at NASA Dryden Research Center Science Operations at NASA-Ames ~ 80-people, 20% German Deployments to the Southern Hemisphere and elsewhere >120 8-10 hour flights per year Built on NASA’ Airborne Astronomy Heritage
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Primary Mirror M1
M2
M3-1
M3-2
Focal Plane
Focal Plane Imager
Pressure bulkhead
Nasmyth tube
Spherical Hydraulic Bearing
Nasmyth: Optical Layout
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Telescope and aperture assembly
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2.7-meter (106 inch) f/1.28 Primary Mirror after final polishing
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Installing the bearing sphere
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Installation of the Secondary Mirror
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Installation of the Tertiary Mirror
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The Un-Aluminized Primary Mirror Installed
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Science Capabilities
8 arcmin diameter field of view allows use of very large detector arrays – first light cameras will have 10 times the number of pixels as those on KAO
Image size is diffraction limited beyond 15 µm, making images 3 times sharper than the best previous facilities including KAO and the Spitzer Space Telescope
Because of large aperture and better detectors, sensitivity for imaging and spectroscopy will be similar to the space observatory ISO
•Robert Gehrz, U. Minnesota
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SOFIA Airborne!
26 April 2007, L-3 Communications, Waco Texas: SOFIA takes to the air for its first test flight after completion of modifications
•Robert Gehrz, U. Minnesota
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The First Test Flight of SOFIAApril 26, 2007 at WACO, Texas
•Robert Gehrz, U. Minnesota
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SOFIA’s Instrument Complement
SOFIA is an airborne mission, with a long life-time. Therefore, unlike space missions, it supports a unique, expandable instrument suite
SOFIA covers the full IR range with imagers and low, moderate, and high resolution spectrographs
Nine instruments are under development now. Four will be available at first light in 2009
SOFIA can take fully advantage of improvements in instrument technology so that the instruments will always be state-of-the-art.
SOFIA will continue the airborne astronomy tradition of providing a platform where the next generation instrumentation scientists can be trained.
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10 0
10 1
10 2
10 3
10 4
10 5
10 6
10 7
10 8
1 10 100 1000Wavelength [µm]
Sp
ectr
al r
esol
uti
on
HIPO
FLITECAM
FORCASTHAWC
FIFI LS
EXES
CASIMIR
GREAT
SAFIREFORCAST
SOFIA Performance: Spectral Resolution of the First Generation Science Instruments
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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 λλ (µm) 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. Güsten 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 GSFC4.5-28.3
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Early Science Instruments and Observations
Working FORCAST (Cornell) instrument at Palomar in 2005
Successful lab demonstration of GREAT in July 2005
High J CO and HCN observations of Orion protostars to quantify gas cooling and density
Map the Orion Nebula at 38 µm with unprecedented angular resolution and sensitivity to investigating protostars
•Robert Gehrz, U. Minnesota
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Four First Light Instruments
Working/complete HIPO instrument in Waco on SOFIAduring Aug 2004
Working/complete
FLITECAM instrument at
Lick in 2004/5Working FORCAST instrument at Palomar in 2005
Successful lab demonstration of GREAT in July 2005
•Robert Gehrz, U. Minnesota
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START, TAXI, TAKEOFF GW 570.03000 LBS TAXI FUEL
TOTAL FUEL USED = 169,000 LBS. (24,708 Gallons)
TOTAL CRUISE TIME = 7.05 HRS.TOTAL FLIGHT TIME = 8.05 HRS
ASSUMPTIONS
ZFW 381,000 LBS.ENGINES OPERATE AT 95% MAX CONT THRUST AT CRUISE25,000 LBS. FUEL TO FIRST LEVEL OFFCLIMB TO FIRST LEVEL-OFF AT MAX CRUISE WTLANDING WITH 20,000 LBS. FUELBASED ON NASA AMI REPORT: AMI 0423 IRBASED ON 747 SP FLIGHT MANUAL TABULATED DATASTANDARD DAY PLUS 10 DEGREES CCRUISE SPEED-MACH .84
CRUISE84,000 LBS. FUEL
F.F. 20,200 LBS/HR.
CRUISE52,000 LBS.FUEL
F.F. 17,920 LBS/HR.
FL410, 4.2 HrGW 542.0
FL430, 2.9 HrGW 458.0
DESCENTGW 406.05,000 LBS. FUEL.5 HRS.
LANDINGGW 401.0 20,000 LBSFUEL
CLIMB25,000 LBS. FUEL.5 HRS.
Flight Profile 1 Performance with P&W JT9D-7J Engines: Observations - start FL410, duration 7.1 Hr
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START,TAXI,TAKEOFFGW 638.03000 LBS TAXI FUEL
TOTAL FUEL USED = 237,000 LBS. (34,650 Gallons)
TOTAL CRUISE TIME = 10.15 HRS.TOTAL FLIGHT TIME = 11.15 HRS.
CRUISE68,000 LBS. FUEL
F.F. 21,930 LBS/HR.
CRUISE84,000 LBS. FUEL
F.F. 20,200 LBS/HR.
CRUISE52,000 LBS.FUEL
F.F. 17,920 LBS/HR.
FL390, 3.1 HrGW 610.0
FL410, 4.2 HrGW 542.0
FL430, 2.9 HrGW 458.0
DESCENTGW 406.05,000 LBS. FUEL.5 HRS.
LANDINGGW 401.020,000 LBSFUEL
CLIMB25,000 LBS. FUEL.5 HRS.
Performance with P&W JT9D-7J Engines: Observations - start FL390, duration 10.2 Hr
ASSUMPTIONS
ZFW 381,000 LBS.ENGINES OPERATE AT 95% MAX CONT THRUST AT CRUISE25,000 LBS. FUEL TO FIRST LEVEL OFFCLIMB TO FIRST LEVEL-OFF AT MAX CRUISE WTLANDING WITH 20,000 LBS. FUELBASED ON NASA AMI REPORT: AMI 0423 IRBASED ON 747 SP FLIGHT MANUAL TABULATED DATASTANDARD DAY PLUS 10 DEGREES CCRUISE SPEED-MACH .84
Flight Profile 2
•Robert Gehrz, U. Minnesota
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Example: 12.3h flight, 7h on Sgr A*
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Debris DisksProtoplanetary (debris?) dusty disks are common around young main sequence starsBut dust is only 1% (by mass) of the interstellar mediumIs there a much larger gas disk around these stars?
The high resolution spectrograph EXES on SOFIA is uniquely sensitive for probing the abundance,
kinematics, and evolution of the most abundant molecule, molecular hydrogen:
Is there only dust or also a much greater gas reservoir?What are the dynamics of these disks – dynamics
reveal gas gaps created by Jupiter mass planets. Do we (indirectly) detect any? •Robert Gehrz, U. Minnesota
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The Debris Disk of Fomalhaut
Fomalhaut at 70, 160 (Spitzer), 450, and 850 m (SCUBA) (Images are on the same scale with north up and east on the left)
FORCAST beam size is shown in red
FORCAST beam at 38 m
450 m 850 m
20 -200 20 -200
20
0
-20
FORCAST will provide the highest spatial resolution measurements to date.
•Robert Gehrz, U. Minnesota
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SOFIA Will Make Unique Contributions to Comet Science
Comets are the Rosetta Stone of the Solar System containing primordial material dating from the epoch of planet building. Water is the driving force in comets; water in comets was first discovered with the KAO Organic materials are also observable with SOFIASOFIA enables: Access to water vapor and CO2 spectral features inaccessible from the ground Observations of comet apparitions from both hemispheres•Robert Gehrz, U. Minnesota
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SOFIA flies in exceptionally stable atmosphere so that it is an excellent platform for observing extrasolar planetary transitsSOFIA’s HIPO and FLITECAM instruments, which can be mounted simultaneously, will enable observations of the small variations in stellar flux due to a planet transit to:
Provide good estimates for the mass, size and density of the planet
Reveal the presence of star spots, satellites, and/or planetary rings
Artist’s concept of planetary transit and the lightcurve of HD 209458b measured by HST revealing the transit signature
Extra-solar Planet Transits
•Robert Gehrz, U. Minnesota
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Occultation astronomy with SOFIA
Pluto occultation light-curve observed on the KAO (1989) probes the atmosphere
SOFIA can fly anywhere on the Earth, allowing it to position itself under the shadow of an occulting objectOccultations yield sizes, atmospheres, and possible satellites of Kuiper belt objects and 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 a fixed observatory, and enables study of comets, supernovae and other serendipitous objects •Robert Gehrz, U. Minnesota
One of the major discoveries of the KAO was a ring of dust and gas orbiting the very center of the Galaxy
Astronomers at ESO and Keck detected fast moving stars revealing a 4 x 106 solar mass black hole at the Galactic Center
Feeding the Black Hole in the Center of the Galaxy
The ring of dust and gas will fall into the black hole SOFIA’s angular resolution and spectrometers will tell us:
How much matter gets fed into the black hole? How much energy is released? – Will we have an outburst? What is the relationship to high energy active galactic nuclei?
KWIC-KAO: Latvakoski et al. 1999 (Cornell PhD)
•Robert Gehrz, U. Minnesota
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Summary
SOFIA is the next generation airborne observatory SOFIA promises lots of very exciting science from the
first light instruments SOFIA’s long lifetime ensures a continuing platform for
creation of state of the art instrumentation from the latest technologies – devices can be proven before being subjected to the unforgiving environment of space
Airborne astronomy is a proven path for educating the next generation of instrumentation scientists – SOFIA promises to continue this vital tradition