Observations of sunlit N2+ aurora at high altitudes during the RENU2 flight

We present measurements of sunlit aurora during the launch of the Rocket Experiment for Neutral Upwelling 2 (RENU2) on the 13 December 2015, 07:34 UTC. The in situ auroral conditions coincide with those of sunlit aurora and were characterised by the 391.4 and 427.8 nm N2 + emissions. A correlation between several auroral wavelengths, as measured by a meridian-scanning photometer, was used to detect sunlit aurora and indirectly neutral upwelling. These results, based on ground data, agree well with the RENU2 measurements recorded during its pass through the sunlit polar cusp. Using in situ data from RENU2 and the solar photon flux, it was estimated that the sunlit aurora was a major part (≈ 40 %) of the observed 427.8 nm emissio

The red-sky enigma over Svalbard in December 2002

On 6 December 2002, during winter darkness, an extraordinary event occurred in the sky, as viewed from Longyearbyen (78° N, 15° E), Svalbard, Norway. At 07:30 UT the southeast sky was surprisingly lit up in a deep red colour. The light increased in intensity and spread out across the sky, and at 10:00 UT the illumination was observed to reach the zenith. The event died out at about 12:30 UT. Spectral measurements from the Auroral Station in Adventdalen confirm that the light was scattered sunlight. Even though the Sun was between 11.8 and 14.6deg below the horizon during the event, the measured intensities of scattered light on the southern horizon from the scanning photometers coincided with the rise and setting of the Sun. Calculations of actual heights, including refraction and atmospheric screening, indicate that the event most likely was scattered solar light from a target below the horizon. This is also confirmed by the OSIRIS instrument on board the Odin satellite. The deduced height profile indicates that the scattering target is located 18–23km up in the stratosphere at a latitude close to 73–75° N, southeast of Longyearbyen. The temperatures in this region were found to be low enough for Polar Stratospheric Clouds (PSC) to be formed. The target was also identified as PSC by the LIDAR systems at the Koldewey Station in Ny-Ålesund (79° N, 12° E). The event was most likely caused by solar illuminated type II Polar Stratospheric Clouds that scattered light towards Svalbard. Two types of scenarios are presented to explain how light is scattered.publishedVersio

HYPSO-1 CubeSat: First Images and In-Orbit Characterization

The HYPSO-1 satellite, a 6U CubeSat carrying a hyperspectral imager, was launched on 13 January 2022, with the Goal of imaging ocean color in support of marine research. This article describes the development and current status of the mission and payload operations, including examples of agile planning, captures with low revisit time and time series acquired during a campaign. The in-orbit performance of the hyperspectral instrument is also characterized. The usable spectral range of the instrument is in the range of 430 nm to 800 nm over 120 bands after binning during nominal captures. The spatial resolvability is found empirically to be below 2.2 pixels in terms of Full-Width at Half-Maximum (FWHM) at 565 nm. This measure corresponds to an inherent ground resolvable resolution of 142 m across-track for close to nadir capture. In the across-track direction, there are 1216 pixels available, which gives a swath width of 70 km. However, the 684 center pixels are used for nominal captures. With the nominal pixels used in the across-track direction, the nadir swath-width is 40 km. The spectral resolution in terms of FWHM is estimated to be close to 5 nm at the center wavelength of 600 nm, and the Signal-to-Noise Ratio (SNR) is evaluated to be greater than 300 at 450 nm to 500 nm for Top-of-Atmosphere (ToA) signals. Examples of images from the first months of operations are also shown.publishedVersio

Results from the intercalibration of optical low light calibration sources 2011

Following the 38th Annual European Meeting on Atmospheric Studies by Optical Methods in Siuntio in Finland, an intercalibration workshop for optical low light calibration sources was held in Sodankylä, Finland. The main purpose of this workshop was to provide a comparable scale for absolute measurements of aurora and airglow. All sources brought to the intercalibration workshop were compared to the Fritz Peak reference source using the Lindau Calibration Photometer built by Wilhelm Barke and Hans Lauche in 1984. The results were compared to several earlier intercalibration workshops. It was found that most sources were fairly stable over time, with errors in the range of 5–25%. To further validate the results, two sources were also intercalibrated at UNIS, Longyearbyen, Svalbard. Preliminary analysis indicates agreement with the intercalibration in Sodankylä within about 15–25%.publishedVersio

La mystérieurse lumière rouge dans le ciel de Svalbard

A phenomenon which provoked fear and curiosity, and was acknowledged all around the world, was observed early in December 2002 in the sky over Longyearbyen, Svalbard. The sky took a bright red colour and day broke despite its latitude where night is continuous at this time of the year. This phenomenon can be explained by the combination of particular meteorological conditions in the upper atmosphere, leading to the formation of large ice clouds between continental Norway, Svalbard and the sun.Au début du mois de décembre 2002, s'est produit dans le ciel de Longyearbyen, au Svalbard, un phénomène qui a déclenché à la fois peur et curiosité et dont on a parlé dans le monde entier : le ciel a pris une couleur rouge éclatante et le jour est venu, alors qu'à cette latitude, la nuit est habituellement continue à cette période de l'année. Ce phénomène s'explique par une combinaison de conditions météorologiques particulières dans les couches supérieures de l'atmosphère, qui ont conduit à la formation d'importants nuages de glace entre la Norvège continentale, le Svalbard et le Soleil

Tropopause height at 78°N 16°E: average seasonal variation 2007-2010

We present a seasonal climatology of tropopause altitude for 78° N 16° E derived from observations 2007–2010 by the SOUSY VHF radar on Svalbard. The spring minimum occurs one month later than that of surface air temperature and instead coincides with the maximum in ozone column density. This confirms similar studies based on radiosonde measurements in the arctic and demonstrates downward control by the stratosphere. If one is to exploit the potential of tropopause height as a metric for climate change at high latitude and elsewhere, it is imperative to observe and understand the processes which establish the tropopause – an understanding to which this study contributes

Do it yourself hyperspectral imager for handheld to airborne operations

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Optical airglow patches in relation to EISCAT Svalbard Radar electron density measurements

Drifting polar cap patches are localized regions of enhanced F-region plasma densities with scale sizes of several hundreds of kilometre. The patches are seen to drift antisunward with velocities of several hundreds meters per second, and can have densities up to 10 times the ambient background. We present simultaneous ground based optical and radar data of nightside polar cap patches. Using meridian scanning photometer data, the optical airglow signature of patches are seen to drift into the auroral oval. The field aligned radar shows high electron density, with low electron temperature during the period of interest. This indicates that there is no electron precipitation in the radar field of view, and that the radar electron density signal stems from the drifting polar cap patches. It is seen that there is a very good match between enhancements in the 6300 Å airglow signature and enhancements in the radar electron density measurements