nasa’s stratospheric observatory for infrared astronomy (sofia)

Universities Space Research Association

CommunicationsIntegrated Systems

NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA)

Gordon J. Stacey, Cornell University (many slides borrowed from Robert Gehrz,

U. Minnesota)


CommunicationsIntegrated Systems 2

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



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?



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



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



Things Look Different at Different Wavelengths!

Cool nose

Warm eyes & ears

Cool fur10 m image of a cat



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



Orion Nebula: Visible and Far -IR

38 m Image: KWIC-Kuiper Airborne Observatory Harry Latvakoski, Cornell PhD



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



The Far -Infrared Regime is Exciting – So Why Isn’t Everyone Doing it?

14,000 feet

41,000 feet



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…



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



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:



SOFIA: The Stratospheric Observatory for Infrared Astronomy 1999

2002

20062006

2009 – 2029…



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



Primary Mirror M1

M2

M3-1

M3-2

Focal Plane

Focal Plane Imager

Pressure bulkhead

Nasmyth tube

Spherical Hydraulic Bearing

Nasmyth: Optical Layout



Telescope and aperture assembly



2.7-meter (106 inch) f/1.28 Primary Mirror after final polishing



Installing the bearing sphere



Installation of the Secondary Mirror



Installation of the Tertiary Mirror



The Un-Aluminized Primary Mirror Installed



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




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 First Test Flight of SOFIAApril 26, 2007 at WACO, Texas




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.



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



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



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




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




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




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.


F.F. 21,930 LBS/HR.


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




Example: 12.3h flight, 7h on Sgr A*



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



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.




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



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




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)




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

nasa’s stratospheric observatory for infrared astronomy (sofia)

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