Near-infrared thermal emissivity from ground-based atmospheric dust measurements at ORM★

Lombardi, G.; Zitelli, V.; Ortolani, S.; Melnick, J.; Ghedina, A.; Garcia, A.; Molinari, E.; Gatica, C.

doi:10.1111/j.1365-2966.2011.19152.x

Cited by 4 publications

(6 citation statements)

References 21 publications

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“…Making use of satellite measurements, the dust density over the Canary Islands has been found to be approximately constant at altitudes between 2500 and 5000 meters above sea level, dropping close to zero above 5000 m (Smirnov et al 1998;Hsu et al 1999;Alpert et al 2004;Lombardi et al 2008). Following this evidence, at the ORM the column densities can be approximated to the volume densities multiplied by 2500 m (Lombardi et al 2011).…”

Section: Effects Of the Aerosolsmentioning

confidence: 92%

“…The same happened for the night of the 7th of July 2017, when we experienced a negligible increase of dust concentration, with an average of 3.74 𝜇g/m 3 for particles smaller than 25 𝜇m, and 0.84 𝜇g/m 3 for particles larger than 25 𝜇m. The measured values can be used to calculate the total optical depth 𝜏 𝜆 as the sum of the contribution of the optical depth of each particle size (Lombardi et al 2011):…”

Section: Effects Of the Aerosolsmentioning

confidence: 99%

“…the Saharan dust called Calima) cannot be evaluated in this Paper. It is widely demonstrated that the Calima may have non-negligible effects on astrophysical observation at the ORM, for example by slightly increasing both the atmospheric extinction in visible wavelengths (Lombardi et al 2008) and the thermal emissivity in the near-infrared (Lombardi et al 2011). It has of course also an impact on the transmission and scattering of the LGS laser beam.…”

Section: Effects Of the Aerosolsmentioning

confidence: 99%

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Laser Guide Star uplink beam: scattering and Raman emission measurements with the 10.4m Gran Telescopio CANARIAS

Lombardi¹,

Calia²,

Centrone³

et al. 2022

Preprint

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Laser Guide Star Adaptive Optics (LGS-AO) is becoming routine in several astronomical observatories. The use of powerful lasers generates sensible Raman emissions on the uplink laser beam path, plus secondary Rayleigh scattering from atmospheric molecules and Mie scattering from aerosols. This paper reports the results of a campaign done with the 10.4m Gran Telescopio CANARIAS (GTC); this campaign was undertaken to assess the spectral and photometric contamination coming from a 589 nm laser uplink beam scattering and Raman emission induced on the GTC spectro-imager OSIRIS by laser launched ∼1 km off-axis. The photometric contamination is due to primary and secondary scattering of the uplink photons, as well by the Raman inelastic scattering. We have propagated the laser beam creating a mesospheric LGS, then pointed and focused the GTC telescope toward the uplink laser beam, at different heights and up to the LGS, taking into account the observing geometry. In our observations, the Raman emissions for O 2 and N 2 vibrational lines are visible at 20 km, weakening with altitude and becoming undetectable above 30 km. The scattering of the focused uplink beam is detectable at less than ±0.2 arcmin from the center of the beam, while for the focused LGS the scattering is narrower, being detectable at less than ±0.1 arcmin around the plume. Recommendations for Laser Traffic Control Systems (LTCS) are given accordingly.

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Section: Effects Of the Aerosolsmentioning

confidence: 92%

Section: Effects Of the Aerosolsmentioning

confidence: 99%

Section: Effects Of the Aerosolsmentioning

confidence: 99%

See 1 more Smart Citation

Laser Guide Star uplink beam: scattering and Raman emission measurements with the 10.4m Gran Telescopio CANARIAS

Lombardi¹,

Calia²,

Centrone³

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…MNRAS 517, 201-212 ( 2022) Hsu et al 1999 ;Alpert et al 2004 ;Lombardi et al 2008 ). Following this evidence, at the ORM the column densities can be approximated to the volume densities multiplied by 2500 m (Lombardi et al 2011 ).…”

Section: Effects Of the Aerosolsmentioning

confidence: 98%

“…The same happened for the night of the 7th of July 2017, when we experienced a negligible increase of dust concentration, with an average of 3.74 μg m −3 for particles smaller than 25 μm, and 0.84 μg m −3 for particles larger than 25 μm. The measured values can be used to calculate the total optical depth τ λ as the sum of the contribution of the optical depth of each particle size (Lombardi et al 2011 ):…”

Section: Effects Of the Aerosolsmentioning

confidence: 99%

Laser Guide Star uplink beam: scattering and Raman emission measurements with the 10.4m Gran Telescopio CANARIAS

Lombardi

Calia

Centrone

et al. 2022

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Laser Guide Star Adaptive Optics (LGS-AO) is becoming routine in several astronomical observatories. The use of powerful lasers generates sensible Raman emissions on the uplink laser beam path, plus secondary Rayleigh scattering from atmospheric molecules and Mie scattering from aerosols. This paper reports the results of a campaign done with the 10.4m Gran Telescopio CANARIAS (GTC); this campaign was undertaken to assess the spectral and photometric contamination coming from a 589 nm laser uplink beam scattering and Raman emission induced on the GTC spectro-imager OSIRIS by laser launched ∼1 km off-axis. The photometric contamination is due to primary and secondary scattering of the uplink photons, as well by the Raman inelastic scattering. We have propagated the laser beam creating a mesospheric LGS, then pointed and focused the GTC telescope toward the uplink laser beam, at different heights and up to the LGS, taking into account the observing geometry. In our observations, the Raman emissions for O2 and N2 vibrational lines are visible at 20 km, weakening with altitude and becoming undetectable above 30 km. The scattering of the focused uplink beam is detectable at less than ±0.2 arcmin from the center of the beam, while for the focused LGS the scattering is narrower, being detectable at less than ±0.1 arcmin around the plume. Recommendations for Laser Traffic Control Systems (LTCS) are given accordingly.

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Off-disk straylight measurements for the Swedish 1-m Solar Telescope

Löfdahl

2016

A&A

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Context. Accurate photometry with ground-based solar telescopes requires characterization of straylight. Scattering in Earth's atmosphere and in the telescope optics are potentially significant sources of straylight, for which the point spread function (PSF) has wings that reach very far. This kind of straylight produces an aureola, extending several solar radii off the solar disk. Aims. We want to measure such straylight using the ordinary science instrumentation. Methods. We scanned the intensity on and far off the solar disk by use of the science cameras in several different wavelength bands on a day with low-dust conditions. We characterized the far wing straylight by fitting a model to the recorded intensities involving a multicomponent straylight PSF and the limb darkening of the disk. Results. The measured scattered light adds an approximately constant fraction of the local granulation intensity to science images at any position on the disk. The fraction varied over the day but never exceeded a few percent. The PSFs have weak tails that extend to several solar radii, but most of the scattered light originates within ∼1 . Conclusions. Far-wing scattered light contributes only a small amount of straylight in SST data. Other sources of straylight are primarily responsible for the reduced contrast in SST images.

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Near-infrared thermal emissivity from ground-based atmospheric dust measurements at ORM★

Cited by 4 publications

References 21 publications

Laser Guide Star uplink beam: scattering and Raman emission measurements with the 10.4m Gran Telescopio CANARIAS

Laser Guide Star uplink beam: scattering and Raman emission measurements with the 10.4m Gran Telescopio CANARIAS

Laser Guide Star uplink beam: scattering and Raman emission measurements with the 10.4m Gran Telescopio CANARIAS

Off-disk straylight measurements for the Swedish 1-m Solar Telescope

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