Transcript Universities Space Research Association NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) Gordon J.

Universities Space Research Association
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 Observatory
2.5 m telescope in a modified Boeing 747SP
aircraft
 Optical to millimeter-wavelengths
 Emphasis on the obscured IR (30-300 m)
Joint Program between the US (80%) and
Germany (20%)
First Light Will Occur in 2009
 Built 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!
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Extinction
Far-IR (IRAS) Image: Warm
2 m (2MASS) Image: Galactic
dust Nearby stars
Optical Image:
Center Cluster
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Energetics: What glows in the farIR?
The Planck Function
F 
2hc2
1
5
e hc / kt  1
Wien’s Law
maxT  2898m deg
Far-IR = 30 µm ≤  ≤ 300
µm
 10K ≤ T ≤ 100 K
•Robert Gehrz, U. Minnesota
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Things Look Different at Different
Wavelengths!
Warm eyes & ears
Cool nose
Cool fur
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10 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
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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 gas
 To form a star, gas clouds must collapse
 As 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 Astronomy
NASA Lear
Jet
Observatory
1967 – 1983+
1999
2002
 “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
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 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
1999
Infrared Astronomy
2009 – 2029…
2002
2006
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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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Nasmyth: Optical Layout
M2
Pressure bulkhead
Spherical Hydraulic Bearing
Nasmyth tube
Focal Plane
M3-1
M3-2
Focal Plane
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Imager
Primary Mirror M1
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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 SOFIA
April 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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Spectral resolution
SOFIA Performance: Spectral Resolution of the
First Generation Science Instruments
10
8
10
7
10
6
10
5
10
4
10
3
GREAT
CASIMIR
EXES
FLITECAM
FORCAST
10
2
10
1
10
0
HIPO
FORCAST
1
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Wavelength [µm]
FIFI LS
SAFIRE
HAWC
100
1000
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SOFIA’s 9 First Generation Instruments
Instrument *
Type
HIPO
%
FLITECAM %
FORCAST
GREAT
§
fast imager
imager/grism
imager/(grism?)
heterodyne
receiver
CASIMIR
§
FIFI LS
§
HAWC
EXES
§
SAFIRE
§
λλ (µm)
0.3 - 1.1
1.0 - 5.5
5.6 - 38
158 - 187,
110 - 125,
62 - 65
heterodyne
250 -264,
receiver
508 -588
imaging grating 42 - 110,
spectrograph
110 - 210
imager
40 - 300
imaging echelle 5 - 28.5
spectrograph
4.5-28.3
F-P imaging
150 - 650
spectrometer
Resolution
PI
Institution
filters
filters/R~2E3
filters/(R~2E3)
R ~ 1E4 - 1E8
E. Dunham
I. McLean
T. Herter
R. Güsten
R ~ 1E4 -1E8
J. Zmuidzinas CalTech
R ~1E3 - 2E3
A. Poglitsch
filters
D. A. Harper
R ~ 3E3 - 1E5 J. Lacy
R ~ 1E3 - 2E3 H. Moseley
Lowell Obs.
UCLA
Cornell U.
MPIfR
MPE
Yerkes Obs.
U. Texas
Austin
NASA GSFC
* Listed in approximate order of expected in-flight commissioning
% Operational (August 2004)
§ Uses non-commercial detector/receiver technology
Science
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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
Map the Orion Nebula at 38 µm with
High J CO and HCN observations
unprecedented angular resolution and of Orion protostars to quantify gas
sensitivity to investigating protostars
cooling and density
•Robert Gehrz, U. Minnesota
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Four First Light Instruments
Working/complete HIPO
instrument
in Waco on SOFIA
during Aug 2004
Working/comple
te FLITECAM
instrument at
Lick in 2004/5
Working
FORCAST
instrument at
Palomar in 2005
Successful lab
demonstration of
GREAT in July
2005
•Robert Gehrz, U. Minnesota
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Flight Profile 1
Performance with P&W JT9D-7J Engines:
Observations - start FL410, duration 7.1 Hr
ASSUMPTIONS
ZFW 381,000 LBS.
ENGINES OPERATE AT 95% MAX CONT THRUST AT CRUISE
25,000 LBS. FUEL TO FIRST LEVEL OFF
CLIMB TO FIRST LEVEL-OFF AT MAX CRUISE WT
LANDING WITH 20,000 LBS. FUEL
BASED ON NASA AMI REPORT: AMI 0423 IR
BASED ON 747 SP FLIGHT MANUAL TABULATED DATA
STANDARD DAY PLUS 10 DEGREES C
FL410, 4.2
CRUISE SPEED-MACH .84
GW 542.0
FL430, 2.9 Hr
GW 458.0
Hr
CRUISE
52,000 LBS.FUEL
F.F. 17,920 LBS/HR.
CRUISE
84,000 LBS. FUEL
F.F. 20,200 LBS/HR.
CLIMB
25,000 LBS.
FUEL
.5 HRS.
START, TAXI, TAKEOFF
GW 570.0
3000 LBS TAXI FUEL
TOTAL FUEL USED = 169,000 LBS.
(24,708 Gallons)
TOTAL CRUISE TIME = 7.05 HRS.
TOTAL FLIGHT TIME = 8.05 HRS
•Robert Gehrz, U. Minnesota
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DESCENT
GW 406.0
5,000 LBS. FUEL
.5 HRS.
LANDING
GW 401.0
20,000 LBS
FUEL
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Flight Profile 2
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 CRUISE
25,000 LBS. FUEL TO FIRST LEVEL OFF
CLIMB TO FIRST LEVEL-OFF AT MAX CRUISE WT
LANDING WITH 20,000 LBS. FUEL
BASED ON NASA AMI REPORT: AMI 0423 IR
BASED ON 747 SP FLIGHT MANUAL TABULATED DATA
STANDARD DAY PLUS 10 DEGREES C
FL410, 4.2
CRUISE SPEED-MACH .84
GW 542.0
GW 610.0
START,TAXI,TAKEOFF
GW 638.0
3000 LBS TAXI FUEL
GW 458.0
Hr
CRUISE
52,000 LBS.FUEL
F.F. 17,920 LBS/HR.
CRUISE
84,000 LBS. FUEL
F.F. 20,200 LBS/HR.
FL390, 3.1 Hr
CLIMB
25,000 LBS.
FUEL
.5 HRS.
FL430, 2.9 Hr
DESCENT
GW 406.0
5,000 LBS. FUEL
.5 HRS.
CRUISE
68,000 LBS. FUEL
F.F. 21,930 LBS/HR.
TOTAL FUEL USED = 237,000 LBS.
(34,650 Gallons)
TOTAL CRUISE TIME = 10.15 HRS.
TOTAL FLIGHT TIME = 11.15 HRS.
•Robert Gehrz, U. Minnesota
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LANDING
GW 401.0
20,000 LBS
FUEL
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Example: 12.3h flight, 7h on Sgr A*
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Debris Disks
Protoplanetary (debris?) dusty
disks are common around young
main sequence stars
But dust is only 1% (by mass)
of the interstellar medium
Is 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
•Robert Gehrz, U. Minnesota
we (indirectly) detect any?
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The Debris Disk of Fomalhaut
FORCAST will provide the highest spatial
resolution measurements to date.
450 m
850 m
20
0
-20
20
0
-20
20
0
-20
FORCAST beam at 38 m
 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
•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 SOFIA
SOFIA 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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Extra-solar Planet Transits
Artist’s concept of planetary transit and the lightcurve of HD 209458b
measured by HST revealing the transit signature
SOFIA flies in exceptionally stable atmosphere so that it is an
excellent platform for observing extrasolar planetary transits
SOFIA’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
•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 object
Occultations yield sizes, atmospheres, and possible
satellites of Kuiper belt objects and newly discovered planetlike 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
•Robert Gehrz, U. Minnesota
other serendipitous objects
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Feeding the Black Hole in the Center of
the Galaxy
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
KWIC-KAO: Latvakoski
et al. 1999 (Cornell PhD)
 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?
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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
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