Gemini near-infrared imager (NIRI)

Hodapp, Klaus W.; Hora, J. L.; Graves, Edward E.; Irwin, Everett M.; Yamada, Haruka; Douglass, Jeffrey W.; Young, Tony T.; Robertson, Louis

doi:10.1117/12.395450

Cited by 24 publications

(17 citation statements)

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“…The ADI technique was first used at the Gemini North telescope using the Altair adaptive optic system (Herriot et al 1998) and the near-infrared camera NIRI (Hodapp et al 2000) in queue mode. Observations and detailed results obtained for three stars of our nearby young star survey, Vega, HD 18803, and HD 97334B are presented.…”

Section: Observationsmentioning

confidence: 99%

Angular Differential Imaging: A Powerful High‐Contrast Imaging Technique

Marois

Lafrenière

Doyon

et al. 2006

ApJ

1,049

1,228

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Angular differential imaging is a high-contrast imaging technique that reduces quasistatic speckle noise and facilitates the detection of nearby companions. A sequence of images is acquired with an altitude/azimuth telescope while the instrument field derotator is switched off. This keeps the instrument and telescope optics aligned and allows the field of view to rotate with respect to the instrument. For each image, a reference point-spread function (PSF ) is constructed from other appropriately selected images of the same sequence and subtracted to remove quasistatic PSF structure. All residual images are then rotated to align the field and are combined. Observed performances are reported for Gemini North data. It is shown that quasistatic PSF noise can be reduced by a factor $5 for each image subtraction. The combination of all residuals then provides an additional gain of the order of the square root of the total number of acquired images. A total speckle noise attenuation of 20-50 is obtained for a 1 hr long observing sequence compared to a single 30 s exposure. A PSF noise attenuation of 100 was achieved for a 2 hr long sequence of images of Vega, reaching a 5 contrast of 20 mag for separations greater than 8 00 . For a 30 minute long sequence, ADI achieves signal-to-noise ratios 30 times better than a classical observation technique. The ADI technique can be used with currently available instruments to search for $1M Jup exoplanets with orbits of radii between 50 and 300 AU around nearby young stars. The possibility of combining the technique with other high-contrast imaging methods is briefly discussed.

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Section: Observationsmentioning

confidence: 99%

Angular Differential Imaging: A Powerful High‐Contrast Imaging Technique

Marois

Lafrenière

Doyon

et al. 2006

ApJ

1,049

1,228

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“…Over the course of the NIRI project, many individual aspects of its design have been reported in a series of SPIE conference proceedings by Hodapp et al (1998Hodapp et al ( , 2000Hodapp et al ( , 2003, Young et al (1998), Bell et al (1998), Douglass et al (1998), Thornton et al (1998), and Hora et al (1995). This paper summarizes the most important design features and discusses some specific issues that proved to be particularly interesting or posed challenges.…”

Section: Introductionmentioning

confidence: 99%

The Gemini Near‐Infrared Imager (NIRI)

Hodapp¹,

Jensen²,

Irwin³

et al. 2003

PUBL ASTRON SOC PAC

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285

234

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ABSTRACT. This paper presents the basic design of the Gemini Near-Infrared Imager (NIRI) and discusses its capabilities. NIRI offers three different pixel scales to match different operating modes of the Gemini telescope and allows polarimetric and spectroscopic observations. It is equipped with an infrared on-instrument wave-front sensor (OIWFS) to allow tip-tilt and focus correction even in highly obscured regions. The science detector array is an Aladdin II InSb pixel device sensitive from 1.0 to 5.5 mm. 1024 # 1024

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“…The algorithm is first tested using data obtained at the Gemini telescope with the Altair adaptive optics system (Saddlemyer et al 1998) and the NIRI near-infrared camera ( Hodapp et al 2000). These data are part of the Gemini Deep Planet Survey ( Lafrenière et al 2007a), which uses the angular differential imaging (ADI) technique ( Marois et al 2006;Lafrenière et al 2007b) to detect faint companions.…”

Section: Application To Observational Datamentioning

confidence: 99%

Confidence Level and Sensitivity Limits in High‐Contrast Imaging

Marois

Lafrenière

Macintosh

et al. 2008

ApJ

115

124

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In long adaptive optics corrected exposures, exoplanet detections are currently limited by speckle noise originating from the telescope and instrument optics, and it is expected that such noise will also limit future high-contrast imaging instruments for both ground-and space-based telescopes. Previous theoretical analyses have shown that the time intensity variations of a single speckle follow a modified Rician. It is first demonstrated here that for a circular pupil, this temporal intensity distribution also represents the speckle spatial intensity distribution at a fixed separation from the point-spread function center; this fact is demonstrated using numerical simulations for coronagraphic and noncoronagraphic data. The real statistical distribution of the noise needs to be taken into account explicitly when selecting a detection threshold appropriate for some desired confidence level (CL). In this paper, a technique is described to obtain the pixel intensity distribution of an image and its corresponding CL as a function of the detection threshold. Using numerical simulations, it is shown that in the presence of speckle noise, a detection threshold up to 3 times higher is required to obtain a CL equivalent to that at 5 for Gaussian noise. The technique is then tested on data acquired by simultaneous spectral differential imaging with TRIDENT and by angular differential imaging with NIRI. It is found that the angular differential imaging technique produces quasi-Gaussian residuals, a remarkable result compared to classical adaptive optic imaging. Finally, a power law is derived to predict the 1 À 3 ; 10 À7 CL detection threshold when averaging a partially correlated non-Gaussian noise.

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Gemini near-infrared imager (NIRI)

Cited by 24 publications

References 0 publications

Angular Differential Imaging: A Powerful High‐Contrast Imaging Technique

Angular Differential Imaging: A Powerful High‐Contrast Imaging Technique

The Gemini Near‐Infrared Imager (NIRI)

Confidence Level and Sensitivity Limits in High‐Contrast Imaging

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