Large Binocular Telescope Interferometer LBTI/NOMIC data analysis B. Mennesson, D. Defrère, P....

Large Binocular Telescope Interferometer

LBTI/NOMIC data analysisB. Mennesson, D. Defrère, P. Hinz, B. Hoffmann, O.

Absil, B. Danchi, R. Millan-Gabet, and A. Skemer

Instrument Status ReviewTucson AZ Sep 4 2013

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

Concentric Vertical offset Horizontal offset

OBVIOUS DRIFT

Time series of residual background (DARK frames, June 27th 2013 – 55ms)

• Investigated various strategies:

Large Binocular Telescope Interferometer

Noise mitigation strategiesDetector frame

Photometric apertureBackground regions

(optimized for r=0.64l/D)

Corrected

Raw

DIT=21ms

DARKS

Large Binocular Telescope Interferometer

Noise mitigation strategiesDetector frame

Photometric apertureBackground regions

(optimized for r=0.64l/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 27th 2013)

• Offset reduced to ~8 ADU/PSF (+ Gaussian noise)

WITH NODDING SUBTRACTION

DIT=55msDIT=55ms

Large Binocular Telescope Interferometer

Noise mitigation strategies

WITHOUT NODDING SUBTRACTION

• 40-min of sky data nodding every ~1min30 (June 27th 2013)

• Offset reduced to ~8 ADU/PSF (+ Gaussian noise)

WITH NODDING SUBTRACTION

DIT=55msDIT=55ms

Large Binocular Telescope Interferometer

Noise mitigation strategies

Vega on June 27th (40 min of integration)

• Measured Vega’s flux ~ 2.2*105 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., 0.001 Jy)

= bias= noise

DIT=55ms

Large Binocular Telescope Interferometer

Background

Minimum integration time necessary to achieve 3-zodi sensitivity (assuming 1 zodi = 5.10-5).

Comparing shot noise on constant background (ideal non realistic case) withcurrent measured background uncertainty (after spatio/temporal correction of

fluctuations)

Vega ~ 0.6 sec

b 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

NO

D 0

NO

D 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