Large Binocular Telescope Interferometer LBTI/NOMIC data analysis B. Mennesson, D. Defrère, P. Hinz, B. Hoffmann, O. Absil, B. Danchi, R. Millan-Gabet, and A. Skemer Instrument Status Review Tucson AZ Sep

Large Binocular Telescope Interferometer Group activities Detector and background characterization Noise mitigation strategies Optimization of chopping/nodding frequency Definition of data acquisition sequence Computation of key instrument performance indicators Adaptation of statistical reduction technique

Large Binocular Telescope Interferometer Group activities Detector and background characterization Noise mitigation strategies Optimization of chopping/nodding frequency Definition of data acquisition sequence Computation of key instrument performance indicators Adaptation of statistical reduction technique ✓

Large Binocular Telescope Interferometer Group activities Detector and background characterization Noise mitigation strategies Optimization of chopping/nodding frequency Definition of data acquisition sequence Computation of key instrument performance indicators Adaptation of statistical reduction technique ✓ ✓

Large Binocular Telescope Interferometer Group activities Detector and background characterization Noise mitigation strategies Optimization of chopping/nodding frequency Definition of data acquisition sequence Computation of key instrument performance indicators Adaptation of statistical reduction technique ✓ ✓ ✓

Large Binocular Telescope Interferometer Group activities Detector and background characterization Noise mitigation strategies Optimization of chopping/nodding frequency Definition of data acquisition sequence Computation of key instrument performance indicators Adaptation of statistical reduction technique ✓ ✓ ✓ ✓

Large Binocular Telescope Interferometer Group activities Detector and background characterization Noise mitigation strategies Optimization of chopping/nodding frequency Definition of data acquisition sequence Computation of key instrument performance indicators Adaptation of statistical reduction technique ✓ ✓ ✓ ✓ ✓

Large Binocular Telescope Interferometer Group activities Detector and background characterization Noise mitigation strategies Optimization of chopping/nodding frequency Definition of data acquisition sequence Computation of key instrument performance indicators Adaptation of statistical reduction technique ✓ ✓ ✓ ✓ ✓ ✗

Large Binocular Telescope Interferometer Detector and background Complex spatiotemporal fluctuations Flux-dependent detector behavior Temporal and spatial noise correlation Must be corrected for accurate null measurements Background Detector

Large Binocular Telescope Interferometer Noise mitigation strategies ConcentricVertical offsetHorizontal offset OBVIOUS DRIFT Time series of residual background (DARK frames, June 27 th 2013 – 55ms) Investigated various strategies:

Large Binocular Telescope Interferometer Noise mitigation strategies Detector frame Photometric aperture Background regions (optimized for r=0.64 /D) Corrected Raw DIT=21ms DARKS

Large Binocular Telescope Interferometer Noise mitigation strategies Detector frame Photometric aperture Background regions (optimized for r=0.64 /D) Corrected Raw chopping/nodding DIT=55ms BACKGROUND

Large Binocular Telescope Interferometer Noise mitigation strategies WITHOUT NODDING SUBTRACTION 40-min of sky data nodding every ~1min30 (June 27 th 2013) Offset reduced to ~8 ADU/PSF (+ Gaussian noise) WITH NODDING SUBTRACTION DIT=55ms

Large Binocular Telescope Interferometer Noise mitigation strategies WITHOUT NODDING SUBTRACTION 40-min of sky data nodding every ~1min30 (June 27 th 2013) Offset reduced to ~8 ADU/PSF (+ Gaussian noise) WITH NODDING SUBTRACTION DIT=55ms

Large Binocular Telescope Interferometer Noise mitigation strategies Vega on June 27 th (40 min of integration) Measured Vega’s flux ~ 2.2*10 5 ADU/PSF in 55ms (optimum aperture) Background noise is ~0.2% in 55ms (i.e., 0.07 Jy) Background bias is ~0.004% (i.e., Jy) = bias = noise DIT=55ms

Large Binocular Telescope Interferometer Background Minimum integration time necessary to achieve 3-zodi sensitivity (assuming 1 zodi = ). Comparing shot noise on constant background (ideal non realistic case) with current measured background uncertainty (after spatio/temporal correction of fluctuations) Vega ~ 0.6 sec  Leo ~ 10 sec Altair ~ 1 sec

Large Binocular Telescope Interferometer Chopping/nodding frequency Nodding frequency: Remove quasi-static offsets between photometric aperture and background regions Can be slow (a few minutes or more) Chopping frequency: Relaxed thanks to simultaneous background subtraction technique Will be constrained by photometric calibration (more data needed) Likely to be slow Still needed in conjunction of nodding for accurate background removal

Large Binocular Telescope Interferometer Data acquisition sequence 1 PHOTOMETRIC FRAME - Chop positions: (1,2) - Nod positions: (0,0) L R 2 INTERFEROMETRIC FRAME - Chop positions: (2,2) - Nod positions: (0,0) R+L REF 3 PHOTOMETRIC FRAME - Chop positions: (2,1) - Nod positions: (0,0) R L 4 INTERFEROMETRIC FRAME - Chop positions: (1,1) - Nod positions: (0,0) R+L REF 5 PHOTOMETRIC FRAME - Chop positions: (1,2) - Nod positions: (1,1) L R 6 INTERFEROMETRIC FRAME - Chop positions: (2,2) - Nod positions: (1,1) R+L REF 7 PHOTOMETRIC FRAME - Chop positions: (2,1) - Nod positions: (1,1) R L 8 INTERFEROMETRIC FRAME - Chop positions: (1,1) - Nod positions: (1,1) R+L REF NOD 0 NOD 1

Large Binocular Telescope Interferometer Statistical reduction technique. Adaptation from NIR Palomar Fiber Nuller not straightforward: 1D to 2D data Higher background at 10microns No single-mode fibers used -> higher phase orders than piston Computation of chopping frequency (photometric calibration) Determination of OPD reset frequency - How long does the NIR OPD target remain valid in the MIR ? - Transverse atm dispersion - Other chromatic effects? Ongoing and future analysis

Large Binocular Telescope Interferometer Backup slides

Large Binocular Telescope Interferometer Mitigation of detector drift BEFOR E AFTER