Recent Science Results from The Stratospheric Observatory...

1 R. D. Gehrz

Recent Science Results from The Stratospheric

Observatory for Infrared Astronomy (SOFIA)

R. D. Gehrz

Chair, SOFIA Users Group (SUG)

Minnesota Institute for Astrophysics, University of Minnesota

This talk is at: http://www.sofia.usra.edu/Science/speakers/index.html

ASTRO 2001, December 5, 2019

http://www.sofia.usra.edu/Science/speakers/index.html

2 R. D. GehrzASTRO 2001, December 5, 2019

Outline

• SOFIA’s Heritage and Context

• Constructing the SOFIA Observatory and its Current Status

• SOFIA Science Instrumentation/Performance Specifications

• SOFIA Science Results

• SOFIA Schedule and General Investigator (GI) Opportunities

• Summary

3 R. D. Gehrz


The History of Flying Infrared Observatories

NASA Lear JetObservatory

1967

1977NASA Kuiper Airborne

Observatory (KAO)

1999

2002

20062006

1967

NASA Infrared AstronomicalSatellite (IRAS)

1995 2003

NASA Spitzer Space Telescope

NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA)

2009

1983

Science

objectives

1974

ESA Infrared Space Observatory (ISO)

4 R. D. Gehrz


SOFIA and its Companions in Space

SOFIA

HERSCHEL

JWST

2018

2009

2010

2003

(Spitzer)


SOFIA Overview

• 2.5 m telescope in a modified Boeing 747SP aircraft

– Imaging and spectroscopy from 0.3 m to 1.6 mm

– Emphasizes the obscured IR (30-300 m)

• Operational Altitude

– 39,000 to 45,000 feet (12 to 14 km)

– Above > 99.8% of obscuring water vapor

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

– First Light images were obtained on May 26, 2010

– 20 year design lifetime –can respond to changing technology

– Ops: Science at NASA-Ames; Flight at Dryden FRC (Palmdale- Site 9)

– Deployments to the Southern Hemisphere and elsewhere

– >120 8-10 hour flights per year


• Above 99.8% of the water

vapor

• Transmission at 14 km >80%

from 1 to 800 µm

• Emphasis is on the obscured

IR regions from 30 to 300 µm

The SOFIA Observing Environment

SOFIA , 10m Precipitable Water Vapor

Cerro Chajnantor, 700m Precipitable Water Vapor

E.T Young et al. 2012, ApJ, 749, L17

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Location of future cavity opening

8 R. D. Gehrz


New pressure

bulkhead


The SOFIA Observatory

E.T Young et al. 2012, ApJ, 749, L17 Door

door.mpg


SOFIA: Selecting the Aircraft

• Fuselage diameter (length not an

issue)

• Payload and loiter time at FL >410

• Cost ($13M in 1995 dollars)

The winner: Boeing 747-SP

Retrofitted with P&W JT9D-7J

engines to provide operational

margin

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SOFIA: Modeling the Aircraft

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FEM Predictions for Unmodified Aircraft

13 R. D. Gehrz


Sample Longitudinal Strain - Positive Vertical Acceleration

FEM Predicted Longitudinal Strain and Flight Test Calibrated Strain vs. Water Line

FEM Station 1990 (LHS)

100

150

200

250

300

350

400

-2500 -2000 -1500 -1000 -500 0 500 1000 1500 2000 2500

Microstrain, uin/in

Wa

ter

Lin

e, in

.

FEM

Flight Test Stringers

Flight Test Skins

FEM Validation: Pre-Modification Flight Test Data

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Modified Baseline Finite Element Model

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New 21.3 foot diameter Pressure Bulkhead

FEMBulkhead on Delivery

Bulkhead simulator used in Germany

for Telescope Assembly buildup

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Total Force is on the 21.3 Foot

Diameter Pressure Bulkhead?

• Altitude = 45,000 ft

• Cabin pressure altitude = 7,000 ft

• Scale Height of the atmosphere = 26,000 ft

• Presure differential = 8.63 psi

• Total for = 442,526 lb

EMD SD90GMAC Locomotive

• 6,000 Hp

• 415,000 lb

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Frame Modifications and Sill Beams

FS 1480

FS 2000

FwdUp

Lower Main Sill

ICDR #1

Upper Auxiliary Sill

ICDR # 1

Lower Auxiliary Sill

ICDR#1

Forward Bulkhead Main Frames

ICDR #1

Upper Main Sill

ICDR #1

Fwd Auxiliary Frame

ICDR #4

Aft Auxiliary Frame

ICDR #4

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Control Cables - SOFIA Re-routing

Flight Control Cables

96128500

Hydraulic Lines

(left side) 96128300

APU Fuel Line

96128210

Pitot Lines

96128400

FWD

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Control Cables

Forward

STA 1264

STA 1350

STA 1940

STA 2078

BP#1BP#2

BP#3

BP#4View Looking

Down/Fwd

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Control Cable Re-routing Details

BP#1

BP#2

Forward Bulkhead PlateSTA1394

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Door System Fairings

Forward Fairing

Lower Fairing

Aft Fairing

Fiberglass Close-outFiberglass

Close-out

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SOFIA Door System

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Studies of Cavity Acoustics: SOFIA 7% model in

Ames 14 foot Transonic Wind Tunnel

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Test Description/Conditions

• Boeing 747-SP 7% Model

• NASA ARC 14-Foot Tunnel

• Mach: 0.3<M<0.92

• Yaw: -4.5<b<4.5o

• Angle of attack: 2o<a<5o

• TA Elevation: 25o <g< 60o

Data Acquired /Design validation

• Aero-acoustics

• Telescope torque

• Pressure loads

• Boundary layer characterization

Partial External Door

7% Wind Tunnel Tests

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Dynamic Environment in the Cavity

Science

Instrument

Shear Layer at

Cavity Opening

Standing Waves Excited

by the Shear Layer

Wind in Cavity Induced

by the Shear Layer

Aircraft

Vibrations

Cabin

26 R. D. Gehrz


Major Results of 7% Wind Tunnel Tests

• Shear layer control technology developed successfully

• Shear layer control is robust and provides the quietest

cavity known for an aircraft based open port cavity

• The effect of the cavity on stability and control

characteristics will be negligible

27 R. D. Gehrz


Stability and Control Studies: SOFIA

Model in U of W Kirsten Wind Tunnel


Major Results of 3% Wind Tunnel Tests

• Drag - 8 Count Increase CD = 0.0008

• Lift - No change

• Side Force - Small Change depending on door position

• Pitching Moment - Small change ( 2%)

• Yawing Moment - No Change

• Rolling Moment - No Change


Telescope and Optical Layout

E.T Young et al. 2012, ApJ, 749, L17

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Telescope Size is Maximum forAvailable Volume

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Counter

Weight

Primary Mirror M1

M2

M3-1

M3-2

Focal

Plane

Focal Plane

Imager

Major Telescope Components

Cameras

Focal Plane

Imager

Science

Instrument

Hydraulic System

Motors

Brakes

Bearing Sphere

Forward Bulkhead

Vibration

Isolation

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Spherical Bearing

First Oil at 735 psi

The Bearing Sphere on the Nasmyth Tube

Rotation Isolation Subsystem

Ball Aerospace & Technologies Corporation, Boulder, CO, June 10, 2011ASTRO 2001, December 5, 2019

33 R. D. Gehrz


Primary Mirror photo here

2.7 M

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Telescope arrival in Waco- Sept 2002

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Unloading Telescope Pieces

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ASTRO 2001, December 5, 2019Inside aircraft just before SUA installation

38 R. D. Gehrz


Back End of the SOFIA Telescope

SOFIA Science Vision Blue Ribbon Panel Review October 24, 2008


SOFIA Airborne on July 13, 2010

First Door Open Flight Door Open 100

411260main_SOFIA_FirstDoorOpenFlight_480_DV.mov

SOFIA_OpenDoor_100.mov

40 R. D. Gehrz

• SIs cover the full IR range

with imagers and low to

high resolution

spectrographs

• 4 SIs at Initial Operations;

7 SIs at Full Operations.

• SOFIA will take advantage

of improvements in

instrument technology.

• Will support both Facility

Instruments and PI Class

Instruments

SOFIA Science Instruments


SOFIA supports a unique, expandable suite of Science Instruments (SIs)


Photometric Sensitivity and Angular resolution

SOFIA is diffraction limited

beyond 25 µm (θmin ~ λ/10 in

arcseconds) and can produce

images three times sharper

than those made by Spitzer

SOFIA is as

sensitive as ISO

42 R. D. Gehrz42

Results from the First Round of

SOFIA Flights



First Science Results with FORCAST

The FORCAST Team

The DSI Telescope Assembly and

Mission Operations Team

in action during the

First Light Flight

Eight papers have been

published in ApJ Letters, 749,

L17 (April 20 2012)

44 R. D. Gehrz

First Light on May 26, 2010 UT: We demonstrated

diffraction limited imaging capability at 30 microns

Red = 37.1 m, Green = 24.2 m, Blue = 5.4 m


45 R. D. Gehrz

SOFIA Image Quality During Early Science


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May 5, 2011: First Basic Science Flight

46ASTRO 2001, December 5, 2019


Inside the Observatory on the First Basic Science Flight

49 R. D. Gehrz

SOFIA FORCAST Images of the Orion Nebula

Red = 37.1 m, Green = 24.2 m

Wyoming Infrared Image from

Herzog et al., 1980, Sky and Telescope, 59, 18

Red = 20 m

Green = 12 m

Blue = 5 m


• De Buizer etal ApJ Letters 2012 Vol 749 L23

• Shuping etal ApJ Letters 2012 Vol 749 L22

• Adams etal ApJ Letters 2012 Vol 749 L24 (OMC2)

50 R. D. Gehrz

Lbol = 1.3x104 Lsun

Lbol = 2.1x104 Lsun

• IRc4 luminosity is too high to be

caused by external heating

• BN+IRc4 account for ~50% of

the ~105 L⊙ of the BN/KL

region

Like BN, IRc4 is a Self-

Luminous Source

De Buizer et al. (2012)ASTRO 2001, December 5, 2019

51 R. D. Gehrz

First Science Results with GREAT on SOFIA


Twenty two papers on GREAT science have been published in

a special edition of A & A Letters (2012, Volume 542)

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Early Science with GREAT (White CII, Green CO)


• GREAT maps M17 SW

molecular cloud

• CII traces the photo-

dissociation region

created on the surface of

the dark cloud by the

ionizing radiation from

the hot young stars

• CO traces the warm cores

where star formation may

be occuring

53 R. D. Gehrz

• Red-shifted ammonia (NH3) absorption due to infall detected

against the optically thick dust continuum

• Optically thin C17O at 1.27 cm (23.7 GHz) gives the systemic velocity

Vsys

G34.26+0.15 VLA 3.6cm

Probing Protostellar In-Fall with Terahertz Ammonia

Absorption in an Ultra Compact HII Region

F. Wyrowski,et al. 2012, A&A 542, L15

67th International Symposium on Molecular Spectroscopy , Columbus, OH, June 21, 2012

UCHIIR G34.3

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SOFIA and Classical Nova Explosions

What can SOFIA tell us about

Classical Nova Explosions?

• Gas phase abundances

• Stardust formation and

mineralogy, and abundances

• Contributions to ISM clouds

• Kinematics of the Ejection

55 R. D. Gehrz


SOFIA FORCAST Grism Spectrum of V339 Del

• Pure Hydrogen emission spectrum

• Metallic forbidden lines are quenched at the high shell density of ~ 1011 cm-3

411260main_SOFIA_FirstDoorOpenFlight_480_DV.mov

56 R. D. Gehrz

SOFIA FORCAST Grism Spectra of the Dust Forming CN V5668 Sgr

Hu (86)

Hu (76)

Hu (96)

HI (87)

HI (108)

HI (87)

HI (119)


T = 1188 K

T = 718 K

2016 July 15

57 R. D. Gehrz


Occultation Astronomy with SOFIA

Earth

Toward

Occulted Star

Motion of Occulting Object

Shadow of

Occulting Object

Object

• Occultation studies probe sizes,

atmospheres, satellites, and

rings of small bodies in the

outer Solar system.

• SOFIA can fly anywhere on

Earth to position itself in the

occultation shadow. Hundreds

of events are available per year

compared to a handful for fixed

ground and space-base

observatories.

How will SOFIA help determine the properties of small Solar System bodies?

58 R. D. Gehrz


The Importance of Observing the Central Chord

Consider a Total Lunar Eclipse as an Example• The shadow is not dark because of refraction of light by the Earth’s atmosphere

• The light refracted into the shadow is primarily red because Rayleigh scattering

removes the blue light, a clue that reveals the composition of Earth’s atmosphere

• The brightness of the light in the shadow reveals information about haze and

cloud cover in the lower atmosphere

59 R. D. Gehrz

HIPO/FDC Observation of Stellar Occultation by Pluto

Scientific goals

• Measure temperature profile

of Pluto’s atmosphere

• Test atmospheric freeze-out

models

• Target central flash – global

atmospheric shape, possible

extinction

Programmatic Goal

• Demonstrate successful in-

flight prediction update and

flight plan change to enable

observation on the central

chord


Ted Dunham et.al. (HIPO), Lowell Observatory, Jürgen

Wolf (SOFIA DSI) & Mike Person et al., MIT

60 R. D. Gehrz

Pluto Occultation Results

• Central brightening seen in

HIPO blue and red channels

and Fast Diagnostic Camera

(FDC) visual channel

• Post-event data indicates

impact parameter <100 km!

• The atmosphere of Pluto is

still there contrary to

predictions that it will frozen

out as Pluto heads for

aphelion

• Central brightening suggests

the presence of a low-altitude

haze layer FDC

HIPO



The Haze Layer above Pluto from New Horizons

https://www.nasa.gov/sites/default/files/thumbnails/image/nh-pluto-hazy-skies_0.jpg

62 R. D. Gehrz


SOFIA and Comets during Perihelion Passage

What can SOFIA tell us about

The origin of the Solar System for

studies of comets at perihelion

passage?

• Comet dust mineralogy and

physical properties

• Comparisons with IDPs

• Comparisons with meteorites

• Comparisons with Stardust

• Only SOFIA can get these

observationsNASA/UM C. M. Lisse et al., Science 313, 635 (2006)

63 R. D. Gehrz


EXES and Comets: Gas Phase Constituents

• Production rates of water and other volatiles

• Water (H20) H2 ortho/para (parallel – anti-

parallel) hydrogen spin isomer ratio gives

the water formation temperature; a similar

analysis can done on the spin isomers of

methane (CH4)

• Only SOFIA can make these observations

near perihelion

C. E. Woodward et al.

2007, ApJ, 671, 1065

B. P. Bonev et al.

2007, ApJ, 661,

L97

C/2003 K4

Spitzer

Theory

64 R. D. Gehrz


Observation of Exoplanets with the Stratospheric

Observatory for Infrared Astronomy (SOFIA)

R. D. Gehrza, D. Angerhausenb, E. E. Becklinc, M. A. Greenhoused, S. Hornere,

A. Krabbeb, M. R. Swainf, and E. T. Youngc

aDepartment of Astronomy, University of Minnesota, bDeutsches SOFIA Institut (DSI), University of Stuttgart,

cUniversities Space Research Association, dNASA Goddard Space Flight Center, eLockheed Martin, fJPL/Caltech

http://www.sofia.usra.edu

65 R. D. Gehrz


Astro-chemistry of Proto-Planetary Disks with SOFIA

• High spectral resolution can determine where species reside in the disk;

small radii produce double-peaked, wider lines.

• Observing many sources at different ages in this way will trace the disk

chemical and mineral evolution

mineral grains

ices

66 R. D. Gehrz


• Transits provide good estimates for the mass, size and density of the planet

• Transits can reveal the presence of, satellites, and/or planetary rings

• Spectroscopic observations can reveal the presence and composition of an

atmosphere

SOFIA and Extra-solar Planet Transits• There are more than 2030 extra-solar planets in 1288 systems (502 are multiple planet

systems). The masses of 559 have been measured by Doppler velocities.

• SOFIA flies above the scintillating component of the atmosphere where it can detect

transits of planets across bright stars at high signal to noise

HD 209458b transit:

a) artist’s concept and

b) HST STIS data

a)

b)

67 R. D. Gehrz


Detection of Biogenic Molecules in Extrasolar Planetary

Atmospheres by the transit Method

M. R. Swain et al.

2009, ApJ, 690, L114

HD 189733b

68 R. D. Gehrz


FORCAST Imaging and Grism Observations

of Comet C/2012 K1 (PANSTARRS)

C. E. Woodward et al. 2015 (to be submitted)

69 R. D. Gehrz


EXES: The chemistry of disks with radius and Age

• High spatial and spectral

resolution can determine

where different species

reside in the disk

• small radii produce

double-peaked, wider lines.

• Observing

many disks

at different

ages will trace

disk chemical

evolution

70 R. D. Gehrz


Thermal Emission from PAH Rich Objects

• A key question is whether

portions of the aromatic

population of PAHs are

converted to species of

biological significance

• Far-IR spectroscopy can

constrain the size and

shape of PAH molecules

and clusters.

• The lowest lying

vibrational modes

(“drumhead” modes) will

be observed by SOFIA’s

spectrometers

NGC2024

Kandori, R., et al. 2007, PASJ, 59, 487

Vibrational modes of PAHs in a planetary

nebula and the ISM (A. Tielens 2008)

71 R. D. Gehrz



Summary

• The Program is making progress!

Four years of Science flights have produced

interesting results and >60 publications

Pluto occultation observations showcase

SOFIA’s potential

Performance expectations are being met

Cycle 5 observations will begin in 6 months

• SOFIA will be one of the primary observational

facilities for far-IR and submillimeter

astronomy for until 2035

Our Web site: http://www.sofia.usra.edu//

http://www.sofia.usra.edu/

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