Systematic errors in nulling interferometers

Lay, Oliver P.

doi:10.1364/ao.43.006100

Cited by 72 publications

(106 citation statements)

References 7 publications

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“…These values will be used thorough this study (see appendix A for further details). Although our computation has been done at 7 μm where instability noise is much higher than at 10 μm, these constraints are not far from the values derived by Lay (2004) for two reasons. First, the telescopes considered here are smaller so that shot noise is relatively more dominant than in the previous analyses (shot noise is proportional to the square root of the stellar flux while the planetary signal and instability noise are directly proportional to the stellar flux).…”

Section: Instability Noisementioning

confidence: 93%

“…At the output of the interferometer, the total detected photon rate (excluding stray light) can be written as (Lay 2004):…”

Section: Methodsmentioning

confidence: 99%

“…Instability noise is defined as the component of the demodulated nulled signal that arises from phase, amplitude and polarisation errors (Lay 2004). The power spectra of these instrumental effects mix with each other so that perturbations at all frequencies, including DC, have an effect.…”

Section: Instability Noisementioning

confidence: 99%

“…There is no phase chopping scheme that can remove the systematic errors without also removing the planetary signal. Three independent studies (Lay 2004;D'Arcio 2005;Chazelas et al 2006) have reviewed the instrumental requirements on the Darwin/TPF mission that reduce the instrumental stellar leakage to a sufficiently low level for Earth-like planet detection. Assuming the presence of 1/f-type noise, these studies showed that the requirements on amplitude and phase control are not driven by the null-floor leakage, but by instability noise.…”

Section: Instability Noisementioning

confidence: 99%

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Nulling interferometry: impact of exozodiacal clouds on the performance of future life-finding space missions

Defrère¹,

Absil²,

Hartog

et al. 2010

A&A

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Context. Earth-sized planets around nearby stars are being detected for the first time by ground-based radial velocity and space-based transit surveys. This milestone is opening the path toward the definition of instruments able to directly detect the light from these planets, with the identification of bio-signatures as one of the main objectives. In that respect, both the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) have identified nulling interferometry as one of the most promising techniques. The ability to study distant planets will however depend on the amount of exozodiacal dust in the habitable zone of the target stars. Aims. We assess the impact of exozodiacal clouds on the performance of an infrared nulling interferometer in the Emma X-array configuration. The first part of the study is dedicated to the effect of the disc brightness on the number of targets that can be surveyed and studied by spectroscopy during the mission lifetime. In the second part, we address the impact of asymmetric structures in the discs such as clumps and offset which can potentially mimic the planetary signal. Methods. We use the DarwinSIM software which was designed and validated to study the performance of space-based nulling interferometers. The software has been adapted to handle images of exozodiacal discs and to compute the corresponding demodulated signal. Results. For the nominal mission architecture with 2-m aperture telescopes, centrally symmetric exozodiacal dust discs about 100 times denser than the solar zodiacal cloud can be tolerated in order to survey at least 150 targets during the mission lifetime. Considering modeled resonant structures created by an Earth-like planet orbiting at 1 AU around a Sun-like star, we show that this tolerable dust density goes down to about 15 times the solar zodiacal density for face-on systems and decreases with the disc inclination. Conclusions. Whereas the disc brightness only affects the integration time, the presence of clumps or offset is more problematic and can hamper the planet detection. Based on the worst-case scenario for debris disc structures, the upper limit on the tolerable exozodiacal dust density is approximately 15 times the density of the solar zodiacal cloud. This gives the typical sensitivity that we will need to reach on exozodiacal discs in order to prepare the scientific programme of future Earth-like planet characterisation missions.

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Section: Instability Noisementioning

confidence: 93%

“…At the output of the interferometer, the total detected photon rate (excluding stray light) can be written as (Lay 2004):…”

Section: Methodsmentioning

confidence: 99%

Section: Instability Noisementioning

confidence: 99%

Section: Instability Noisementioning

confidence: 99%

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Nulling interferometry: impact of exozodiacal clouds on the performance of future life-finding space missions

Defrère¹,

Absil²,

Hartog

et al. 2010

A&A

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“…On the PDT a realistic planet signal can be created by controlling the optical path relationships between four planet source beams, simulating the phase changes caused by rotation of the telescope array around the line of sight to the star. Moreover, as a four-beam combiner, the testbed produces instability noise (Lay 2004); the testbed has systems and control loops analogous to those needed for flight in order to control the instability noise and maintain deep nulls.…”

Section: Principle and Objectives Of The Testbedmentioning

confidence: 99%

Demonstration of exoplanet detection using an infrared telescope array

Martin¹,

Booth

2010

A&A

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Context. Technology is being developed for the characterization and detection of small, Earth-size exoplanets by nulling interferometry in the mid-infrared waveband. While high-performance nulling experiments have shown the possibility of using the technique, to achieve these goals, nulling has to be done on multiple beams, with high stability over periods of hours. To address the issues of the perceived complexity and difficulty of the method, a testbed was developed for the Terrestrial Planet Finder Interferometer (TPF-I) project which would demonstrate four beam nulling and faint exoplanet signal extraction at levels traceable to flight requirements. Containing star and planet sources, the testbed would demonstrate the principal functional processes of the TPF-I beam-combiner by generating four input beams of star and planet light, and recovering the planet signature at the output. Aims. Here we report on experiments designed with traceability to a flight system, showing faint exoplanet signal detection in the presence of strong starlight. The experiments were designed to show nulling at the flight level of ≈10 −5 , starlight suppression of 10 −7 or better, and detection of an exoplanet at a contrast of 10 −6 compared to the star. This performance level meets the flight requirements for the parts of the detection process that can be demonstrated using a monochromatic source. To achieve these results, the testbed would have to operate stably for several hours, showing control of disturbances at levels equivalent to the flight requirements. Methods. A test process was designed which would show that the necessary performance could be achieved. To show reproducibility, the tests were run on three separate occasions, separated by several days. The tests were divided into three main parts which would show first, starlight suppression, second, a realistic faint exoplanet signal production, and finally, exoplanet signal detection in the presence of the starlight. Results. A number of data sets were acquired showing the achievement of the required performance. The data reported here show nulling at levels between about 5.5 and 8.5 × 10 −6 , starlight suppression between 8.4 × 10 −9 and 1.4 × 10 −8 , and detection of planet signals with contrast to the star between 3.8 × 10 −7 and 4.4 × 10 −7 . The signal to noise ratios for the detections were between 14.0 and 26.9. These data met all the criteria of the demonstration, showing reproducible stable performance over several hours of operation. Conclusions. These data show the successful execution, at flight-like performance levels, of almost the whole exoplanet detection process using a four beam, nulling beam-combiner.

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Interferometric Space Missions for Exoplanet Science: Legacy of Darwin/TPF

Defrère¹,

Absil²,

Beichman³

2017

Handbook of Exoplanets

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DARWIN/TPF is a project of an infrared space-based interferometer designed to directly detect and characterize terrestrial exoplanets around nearby stars. Unlike spectro-photometric instruments observing planetary transits, an interferometer does not rely on any particular geometric constraints and could characterize exoplanets with any orbital configuration around nearby stars. The idea to use an infrared nulling interferometer to characterize exoplanets dates back to Bracewell (1978), and was extensively studied in the 1990s and 2000s by both ESA and NASA. The project focuses on the mid-infrared regime (5-20 µm), which provides access to key features of exoplanets, such as their size, their temperature, the presence of an atmosphere, their climate structure, as well as the presence of important atmospheric molecules such as H 2 O, CO 2 , O 3 , NH 3 , and CH 4 . This wavelength regime also provides a favorable planet/star contrast to detect the thermal emission of temperate (∼ 300 K) exoplanets (10 7 vs 10 10 in the visible). In this chapter, we first review the scientific rationale of a mid-infrared nulling interferometer and present how it would provide an essential context for interpreting detections of possible biosignatures. Then, we present the main technological challenges identified during the ESA and NASA studies, and how they have progressed over the last 10 years. Finally, we discuss which technologies remain to be developed before flying such an instrument, and possible ways to make DARWIN/TPF a reality in the mid-term future.

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Systematic errors in nulling interferometers

Cited by 72 publications

References 7 publications

Nulling interferometry: impact of exozodiacal clouds on the performance of future life-finding space missions

Nulling interferometry: impact of exozodiacal clouds on the performance of future life-finding space missions

Demonstration of exoplanet detection using an infrared telescope array

Interferometric Space Missions for Exoplanet Science: Legacy of Darwin/TPF

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