Infrared spatial interferometer (ISI) High Spectral resolution, high angular resolution and new techniques K.S. Abdeli P. Barele M. Bester A. Betz* K. Blanchard A.A. Chandler J. Cobb J. Chu W.C. Danchi C.G. Degiacomi M. Ellison R. Fulton D. Finstad W. Fitelson L.J. Greenhill B. Mukergee B. Pope V. Ravi K. Reichl J. Remy C.S. Ryan B. Saduolet J. Shapiro N. Short J. Storey E.C. Sutton* K Tatebe* S. Tevousian P.G. Tuthill V. Toy R.L. Griffith D.D.S. Hale* S. Hoss J. Hudson M. Johnson* K. Konevsky E.A. Lipman* S. Lockwood B. Lopez W. Mallard T. MacDonald J. McMahon H. Mistry D. Michaud J.D. Monnier* Grad students get a * 1987 @ LBL 2008 @ Mt. Wilson and many more… Townes, W. Fitelson, E. Sutton, W. Danchi, M. Bester Manfred Bester Cristina Ryan B. Walp J. Weiner* R.H. Weitzman E.H. Wishnow
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Infrared spatial interferometer (ISI) High Spectral resolution, high angular resolution and new techniques
C. Townes, W. Fitelson, E. Sutton, W. Danchi, M. Bester
Manfred Bester
Cristina Ryan
B. WalpJ. Weiner*R.H. WeitzmanE.H. Wishnow
Heterodyne detection demonstration at McMath-Pierce tele. Kitt PeakNew techniques, High spectral resolution
10 mm interferometry using heterodyne detection. 5.5 m baseline between auxiliary siderostats Johnson, Betz, Townes 1974Atmosphere shown to be stable enough for interference fringes from Mercury to be detected.
Also high resolution spectroscopy of Venus,Mars, and stellar environs.Right: Very sharp CO2 line in Martian atm.later called “natural lasers on Mars”
Infrared Spatial Interferometer
World’s highest frequency radio telescope interferometer, operates at 27 THz (11 mm).Heterodyne detection using 13C16O2 lasers as local oscillators.Geometric delays removed usingRF delay lines.
Currently located at Mt. Wilson Observatory, a site noted for very stable seeing.
Two telescopes in operation 1988First fringes 1988Third telescope 2003Closure phase measured 2004
Telescopes designed for transportas a standard semi-trailer
Interferometry principle of operation: Definition of “Visibility”
Weiner, 2002
Mathematical description: Visibility is the complex 2D FFT of the 2D source intensity distribution (Van Cittert-Zernike theorem)
Phenomenological description: The envelope of fringes in a Young’sdouble slit experiment gives information on the source size
Michelson Visibility20 mas uniform disk
1st zero ~50.e5 cyc/rad50 mas uniform disk
1st zero ~125.e5 cyc/rad
Interferometer scheme, examples of fringes
Heterodyne detection using CO2 lasers as local oscillators
Current system, spectrometer taps A1,A2,A3
ISI optics, control room
Master oscillator table
Telescope optical table, one of three
Control room 2007
Manfred Bester
Manfred Bester Walt Fitelson
Walt Fitelson
ISI two telescope results: Stellar variations over time
Weiner et al. 2003
Fringe visibility measured over various baseline distances.Spatial frequency in units of 105 cycles/radian1 SFU = 0.5 cyc/arcsecTwo main components to the visibility curve: stellar and dust.
Bester et al. 1996
Variations in angular size of Mira over a stellar luminosity periodBetelgeuse visibility variations
Dec 1990Madfred Bester
The perils of daytime observing?
Long term studies: variations of a Her
Tatebe et al. “Observation of a Burst of High-Velocity Dust from a Herculis,”2007, ApJ, 658, 103. From 92 to 93, about 75 km/sec
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0.5
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1992
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1998
2003
Sean Lockwood/Walt Fitelson
Dave HaleBiswaroop Mukerjee
Three telescope array, ~36 m baselines
Group photo, illuminated by moonlight Three telescope linear array, 4,8,12 m baselines
Infrared spatial interferometer (ISI)Combines High Spectral resolution, high angular
resolution and new techniques
Variations in angular size of Miracompared to luminosity phaseWeiner 2000
Long-term monitoring of the angular size of BetelgeuseRavi 2011
Variations in stellar shape and “hot-spots” of BetelgeuseRavi 2011
Measurements of dust shells surrounding red giant starsand their surprisingly rapid changes with time. Danchi 1994, Bester 1996, Tatebe 2007
Measurements that NH3 and SiH4 form at 20-40 and 80 stellar radii from stars, respectively. Monnier 2003
Measurements of dust shell asymmetries using 3 telescopesand phase closure. Tatebe 2006, Chandler 2007
Peter TuthillJohn MonnierBill DanchiC.H. Townes
High Angular Resolution:Aperture masking interferometry
Non-redundant pattern on Keck primary
Image recorded at 2.2 mmover short exposure
Power spectra from 100 coadded FT of exposures
Many samples in UV plane, process much likeRadio Astronomy data. Here can also use triplets forFourier amplitudes and closure phase
Aperture Masking Interferometry
Using adaptive optics,Quintuplet clusterTuthill et al., Science 2006
Wolf Rayet 104Observed on 3 epochs 1998Nature 398, 487 1999
10 epochs, Tuthill et al., ApJ 2008
0.1 arcsec160 parsec
O Ceti, uniform disk fits to visibilities on-off spectral line
Weiner et al. 2003, SPIE, 4838, 172
T Lep, VLTI, 1.4-1.9 mm, Le Bouquin et al. 2009 A&A L
Previous ISISpectroscopic-interferometryRF analog system
VY CmaNH3 forms at ~40R*
IRC +10206NH3 forms at ~20 R*SiH3 forming at ~80R*
Monnier et al. 2000ApJ, 453, 868
Spectral range covered, OH & H2O lines of interest
Previous ISISpectroscopic-interferometryRF analog system
Monnier et al. 2000ApJ, 453, 868
ISI 13CO2 laser lines
Simulation of aOriOH blackH2O greenBand covered red
FPGA digital spectrometer-correlator
6 Gsamp/sec using interleaved ADCs 128 pt FFTs every 22 ns. Data swapped between boards for cross-correlation and accumulation.45000 spectra, every ms.Collaboration with Mallard, Werthimer, CASPER
3 GHz BW, 64 channelSpectral resolution of 600,000
Spectrum of Venus
DARPA program to image geo-synchronous satellitesInterferometry of geo satellites10 cm resolution @ 36000 km~3 nrad ~ 0.6 mas, V band magnitude = 11Many samples in UV plane to form imagesTelescopes w/ /AOlinked with optical fibersMove baselines in 5 minConduct meas. at Starfire in NM
Program did not go forward,but recent developments have brought upagain heterodyne system with optical frequency combs
Similar to Monnier-Ireland Planet Formation Imager?
SETI Studies
???
Bester notebook sep 1993
Participating in ongoing Panchromatic search, support from Templeton Foundation.
Theoretical and experimental work continued by Betz
