Statistics of the sodium layer parameters at low geographic latitude and its impact on adaptive-optics sodium laser guide star characteristics

Moussaoui, N.; Clemesha, B. R.; Holzlöhner, Ronald; Simonich, D. M.; Calia, Domenico Bonaccini; Batista, P. P.

doi:10.1051/0004-6361/200913281

Cited by 35 publications

(32 citation statements)

References 24 publications

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“…11). The correction also leads to the rise of the Na lines to altitude values of ≈80 km, a value in agreement with the literature (Plane 2003;Moussaoui et al 2010). Nevertheless, the width of the terrestrial Na I peaks are observed to be ≈0.4 Å.…”

Section: Results From Eq (1) (Method1)supporting

confidence: 90%

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The Earth as an extrasolar transiting planet

Arnold

Ehrenreich

Vidal‐Madjar

et al. 2014

A&A

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Context. The atmospheric composition of transiting exoplanets can be characterized during transit by spectroscopy. Detections of several chemical species have previously been reported in the atmosphere of gaseous giant exoplanets. For the transit of an Earth twin, models predict that biogenic oxygen (O 2 ) and ozone (O 3 ) atmospheric gases should be detectable, as well as water vapour (H 2 O), a molecule linked to habitability as we know it on Earth. Aims. The aim is to measure the Earth radius versus wavelength λ -or the atmosphere thickness h(λ) -at the highest spectral resolution available to fully characterize the signature of Earth seen as a transiting exoplanet. Methods. We present observations of the Moon eclipse of December 21, 2010. Seen from the Moon, the Earth eclipses the Sun and opens access to the Earth atmosphere transmission spectrum. We used two different ESO spectrographs (HARPS and UVES) to take penumbra and umbra high-resolution spectra from ≈3100 to 10 400 Å. A change of the quantity of water vapour above the telescope compromised the quality of the UVES data. We corrected for this effect in the data processing. We analyzed the data by three different methods. The first method is based on the analysis of pairs of penumbra spectra. The second makes use of a single penumbra spectrum, and the third of all penumbra and umbra spectra. Results. Profiles h(λ) are obtained with the three methods for both instruments. The first method gives the best result, in agreement with a model. The second method seems to be more sensitive to the Doppler shift of solar spectral lines with respect to the telluric lines. The third method makes use of umbra spectra, which bias the result by increasing the overall negative slope of h(λ). It can be corrected for this a posteriori from results with the first method. The three methods clearly show the spectral signature of the Rayleigh scattering in the Earth atmosphere and the bands of H 2 O, O 2 , and O 3 . Sodium is detected. Assuming no atmospheric perturbations, we show that the E-ELT is theoretically able to detect the O 2 A-band in 8 h of integration for an Earth twin at 10 pc. Conclusions. Biogenic O 2 , O 3 , and water vapour are detected in Earth observed as a transiting planet, and, in principle, would be within reach of the E-ELT for an Earth twin at 10 pc.

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Section: Results From Eq (1) (Method1)supporting

confidence: 90%

“…It is indeed known that meteor showers can temporarily increase the amount of sodium in the atmosphere by a factor up of 10 (Plane 2003;Moussaoui et al 2010). This corroborates the detection of the sodium layer by Vidal-Madjar et al (2010) in August 2008.…”

Section: Results From Eq (1) (Method1)mentioning

confidence: 99%

The Earth as an extrasolar transiting planet

Arnold

Ehrenreich

Vidal‐Madjar

et al. 2014

A&A

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“…NaI is known to be present in the Earth atmosphere within a layer at about 92 km, presenting an average thickness of about 11 km (Moussaoui et al 2010). If it was completely opaque in the two NaI lines, we should have found the same level in both lines at lower altitudes than the 92 km, depending on the ratio between the atmospheric line width (∼0.03 Å) and the instrument spectral resolution (∼0.09 Å).…”

Section: Sodium Detectionmentioning

confidence: 86%

The Earth as an extrasolar transiting planet

Vidal‐Madjar

Arnold

Ehrenreich

et al. 2010

A&A

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Context. An important goal within the quest for detecting an Earth-like extrasolar planet, will be to identify atmospheric gaseous bio-signatures. Aims. Observations of the light transmitted through the Earth's atmosphere, as for an extrasolar planet, will be the first important step for future comparisons. We have completed observations of the Earth during a lunar eclipse, a unique situation similar to that of a transiting planet. We aim at showing what species could be detected in its atmosphere at optical wavelengths, where a lot of photons are available in the masked stellar light. Methods. We present observations of the 2008 August 16 Moon eclipse performed with the SOPHIE spectrograph at the Observatoire de Haute-Provence (France). Locating the spectrograph's fibers in the penumbra of the eclipse, the Moon irradiance is then a mix of direct, unabsorbed Sun light and solar light that has passed through the Earth's atmosphere. This mixture essentially reproduces what is recorded during the transit of an extrasolar planet. Results. We report here the clear detection of several Earth atmospheric compounds in the transmission spectra, such as ozone, molecular oxygen, and neutral sodium as well as molecular nitrogen and oxygen through the Rayleigh signature. Moreover, we present a method that allows us to derive the thickness of the atmosphere versus the wavelength for penumbra eclipse observations. We quantitatively evaluate the altitude at which the atmosphere becomes transparent for important species like molecular oxygen and ozone, two species thought to be tightly linked to the presence of life. Conclusions. The molecular detections presented here are an encouraging first attempt, necessary to better prepare for the future of extremely-large telescopes and transiting Earth-like planets. Instruments like SOPHIE will be mandatory when characterizing the atmospheres of transiting Earth-like planets from the ground and searching for bio-marker signatures.

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“…For an ELT, with elongation varying more significantly across the WFS, the total performance gain may be smaller, though still significant. We also note that the LGS elongation was varying during the night and from night to night, following the sodium layer thickness variations (Moussaoui et al 2010). …”

Section: On-sky Results Summarymentioning

confidence: 78%

On-sky demonstration of matched filters for wavefront measurements using ELT-scale elongated laser guide stars

Basden

Bardou

Calia

et al. 2017

Mon. Not. R. Astron. Soc.

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The performance of adaptive optics systems is partially dependant on the algorithms used within the real-time control system to compute wavefront slope measurements. We demonstrate use of a matched filter algorithm for the processing of elongated laser guide star (LGS) Shack-Hartmann images, using the CANARY adaptive optics instrument on the 4.2 m William Herschel Telescope and the European Southern Observatory Wendelstein LGS Unit placed 40m away. This algorithm has been selected for use with the forthcoming Thirty Meter Telescope, but until now had not been demonstrated on-sky. From the results of a first observing run, we show that the use of matched filtering improves our adaptive optics system performance, with increases in on-sky H-band Strehl measured up to about a factor of 1.1 with respect to a conventional centre of gravity approach. We describe the algorithm used, and the methods that we implemented to enable on-sky demonstration.

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Statistics of the sodium layer parameters at low geographic latitude and its impact on adaptive-optics sodium laser guide star characteristics

Cited by 35 publications

References 24 publications

The Earth as an extrasolar transiting planet

The Earth as an extrasolar transiting planet

The Earth as an extrasolar transiting planet

On-sky demonstration of matched filters for wavefront measurements using ELT-scale elongated laser guide stars

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