In this paper, we present a series of results from stereo-imagery of cirrus clouds in the troposphere. These clouds are either of natural origin or are created by aircraft exhausts. They are presently considered to be a major cause for the climate change. Two observation campaigns were conducted in France in 2013 and 2014. The observing sites were located in Marnay (47°17′31.5″N, 5°44′58.8″E; altitude 275m) and in Mont Poupet (46°58′31.5″N, 5°52′22.7″E; altitude 600m). The distance between both sites was 36km. We used numeric CMOS photographic cameras. The image processing sequence included a contrast enhancement and a perspective inversion to obtain a satellite-type view. Finally, the triangulation procedure was used in an area that is a common part of both fields of view.

In this paper, we report the development of low flux short wavelength infrared radio-imaging systems to study the radiance due to nightglow emission. This radiation is mainly due to the desexcitation of hydroxyl molecules in the upper atmosphere. It is present in the visible range and reaches its maximum value (at ground level) in the short wavelength infrared band between 1.4 and 1.8μm. The nightglow may be an interesting additional light source for night vision systems in moonless or cloudy sky conditions. In this paper, we describe the experimental setup and present first results of the measurement campaigns that we performed at the Observatoire de Haute-Provence in France and at the European Southern Observatory site of La Silla in Chile.

A new and original stereo imaging method is introduced to measure the altitude of the OH nightglow layer and provide a 3D perspective map of the altitude of the layer centroid. Near-IR photographs of the OH layer are taken at two sites separated by a 645 km distance. Each photograph is processed in order to provide a satellite view of the layer. When superposed, the two views present a common diamond-shaped area. Pairs of matched points that correspond to a physical emissive point in the common area are identified in calculating a normalized cross-correlation coefficient (NCC). This method is suitable for obtaining 3D representations in the case of low-contrast objects. An observational campaign was conducted in July 2006 in Peru. The images were taken simultaneously at Cerro Cosmos (12°09′08.2″ S, 75°33′49.3″ W, altitude 4630 m) close to Huancayo and Cerro Verde Tellolo (16°33′17.6″ S, 71°39′59.4″ W, altitude 2272 m) close to Arequipa. 3D maps of the layer surface were retrieved and compared with pseudo-relief intensity maps of the same region. The mean altitude of the emission barycenter is located at 86.3 km on July 26. Comparable relief wavy features appear in the 3D and intensity maps. It is shown that the vertical amplitude of the wave system varies as exp (Δz/2H) within the altitude range Δz = 83.5–88.0 km, H being the scale height. The oscillatory kinetic energy at the altitude of the OH layer is comprised between 3 × 10−4 and 5.4 × 10−4 J/m3, which is 2–3 times smaller than the values derived from partial radio wave at 52°N latitude.

The emission of the upper atmosphere introduces an additional variable component into observations of astronomical objects in the NIR 700–3,000 nm range. The subtraction of this component is not easy because it varies during the night by as much as 100% and it is not homogeneous over the sky. A program aimed at measuring and understanding the main characteristics of the atmospheric NIR emission was undertaken. A 512 × 512 CCD camera equipped with a RG780/2 mm filter is used to obtain images of the sky in a 36° × 36° field of view. The intensities of a given star and of the nearby region devoid of star in a 439 arcmin 2 area are monitored during periods of time of several hours. The sky intensity measured in the 754–900 nm bandpass, reduced to zenith and zero airmass is comprised between mag20 and mag18.5 per arcsecond 2 . A diminution by a factor of two during the night is frequently observed. Intensity fluctuations having an amplitude of 15% and periods of 5–40 min are present in the images with a structure of regularly spaced stripes. The fluctuations of the NIR sky background intensity are due to (1) the chemical evolution of the upper atmosphere composition during the night and (2) dynamical processes such as tides with periods of 3–6 h or gravity waves with periods of several tens of minutes. We suggest that a monitoring of the sky background intensity could be set up when quantitative observations of astronomical objects require exposure times longer than ~10 min. The publication is illustrated with several video films accessible on the web site http://www.obs-besancon.fr/nirsky/ . Enter username: nirsky and password: skynir.

The hydroxyl nightglow layer is an excellent tracer of the dynamical processes occurring within the mesosphere. A new stereo-imaging method is applied that not only measures the altitude of the airglow layer but also provides a three-dimensional map of the OH-layer centroid heights. A campaign was conducted in July 2006 in Peru to obtain NIR images of the OH nightglow layer which were simultaneously taken for two sites separated by 645km: Cerro Cosmos (12°09′08.2″S, 75°33′49.3″W, altitude 4630m) and Cerro Verde Tellolo (16°33′17.6″S, 71°39′59.4″W, altitude 2330m). Data represented by pairs of images obtained during the nights of July 26–27 and 28–29 are analyzed to yield satellite-type views of the wave field. These are obtained by application of an inversion algorithm. In calculating the normalized cross-correlation parameter for the intensity, three-dimensional maps of the OH nightglow layer surface are retrieved. The mean altitude of the emission profile barycenter is found to be at 87.1km on July 26 and 89.5km on July 28. In these two cases the horizontal wavelengths determined are 21.1 and 24.6km with periods of 18 and 34min, respectively. A panoramic view of the OH nightglow emission obtained on July 29 at 8h51–9h26 UT is presented, in which the overall direction of the waves is found to be N–NW to S–SE, azimuth 150°–330° (counted from South). The wave kinetic energy density at the OH nightglow layer altitude is 3.9×10−4W/kg, which is comparable to the values derived from partial reflection radiowave data.

Context. Polycyclic aromatic hydrocarbons (PAHs) have been detected in many interstellar medium (ISM) sources. They are considered among the most abundant organic compounds in these environments.Aims. We aim at identifying the carriers of the near UV fluorescence bands that appear in the spectra of 1P/Halley's inner coma. Methods. Near UV spectra of 1P/Halley were recorded on March 9, 1986 by the three-channel spectrometer onboard the Vega2 spacecraft at projected distances of between 421 and 932 km. We compare these data to laboratory spectra obtained under laser-induced fluorescence conditions in a jet-cooled molecular beam.Results. The cometary spectral features are found to be consistent with the laboratory fluorescence spectrum of anthracene. Four main peaks coincide at 363, 367.5, 373 and 382.5 nm. We then report the identification of anthracene, a three-ring PAH in the inner coma of 1P/Halley at projected distances of less than thousand km. We derive an abundance relative to water of 5 x 10(-5) to 1 x 10(-4) for this molecule. This new detection adds to the previously reported UV identifications of phenanthrene and pyrene in the innermost coma of 1/P Halley.Conclusions. Recently, three small PAHs, namely naphtalene, phenanthrene and pyrene, were identified in dust grains collected by the Stardust probe in the environment of Comet 81P/Wild2. These findings, together with the present identification of anthracene in 1P/Halley's near UV spectra, confirm that similarities exist between the composition of comets and that of the ISM.

The mesospheric emissive layer is an efficient tracer of the dynamical processes propagating in the atmosphere at that level. CCD images in the near infrared taken from the ground at slant angles often reveal the existence of wavy fields. A series of such images has been transformed, using matrix operations, producing a downward satellite‐type view that covers a circular area of radius ∼1000 km at the altitude of the layer. The Fourier characteristics of the wave system are measured using a Morlet‐type wavelet generator function with horizontal wavelengths of mostly ∼20–40 km and 100–150 km and temporal periods of ∼15–30 min. An oxygen‐hydrogen model is used to evaluate the response of the emissive layer to a progressive density wave. The altitude of the layer is modulated with an amplitude of ∼0.8–1.8 km when a density wave propagates vertically. The layer thickness is slightly modulated and is equal to ∼7 km. Stereoscopic pairs of photographs taken simultaneously on 8–9 September 2000 at the Château‐Renard and Pic du Midi observatories are used to obtain surface maps of the emission layer barycenter altitude. A stereocorrelation method suitable for low contrast objects without discrete contours is employed. Preliminary results for areas ∼50 × 50 km2 are presented. The surface maps of the layer barycenter altitude depict the existence of waves. They show the same wavy structure and compare favorably with the maps showing the emission intensity.

Emission spectra of comet P/Halley in the 275–710nm wavelength range were obtained using a spectrometer mounted on the Vega 2 spacecraft, which encountered the comet on March 9, 1986. The spectra, after the removal of the dust-scattered solar continuum, show the presence of a broad-band emissive feature between 340 and 390nm with three peaks at 371, 376 and 382nm. Near the nucleus, the intensity increase illustrates that the molecules responsible for the emission are most likely of the parent type. Our cometary spectra were compared with UV laboratory spectra of polycyclic aromatic hydrocarbons having 4 benzenoid rings. A laser-induced fluorescence experiment conducted in the laboratory recorded the dispersed emission spectrum of pyrene under jet-cooled conditions. Moreels et al. (Astron. Astrophys. 284 (1994) 643) demonstrated that phenanthrene was a possible candidate for the four bands at 347, 356, 364 and 374nm.The comparison between the cometary and laboratory spectra suggests the possible presence of another PAH, probably pyrene, in Halley's comet. This new suggestion illustrates the link between cometary and interstellar matter. These observations are coherent with the detection of the cometary IR band at 3.28μm assigned to an X–CH organic compound.