Abstract
The SPHERE project studies primary cosmic rays by detection of the Cherenkov light of extensive air showers reflected from the snow covered surface of the earth. Measurements with the aerial-based detector SPHERE-2 were performed in 2011–2013. The detector was lifted by a balloon to altitudes of up to 900 m above the snow covered surface of Lake Baikal, Russia. The results of the experiment are summarized now in a series of papers that opens with this article. An overview of the SPHERE-2 detector telemetry monitoring systems is presented along with the analysis of the measurements conditions including atmosphere profile. The analysis of the detector state and environment atmosphere conditions monitoring provided various cross-checks of detector calibration, positioning, and performance.
Highlights
The SPHERE-2 experiment was designed for primary cosmic ray studies in the10–1000 PeV energy range
Primary cosmic ray particles induce secondary particle cascades named extensive air showers (EAS) and secondary radiations such as Cherenkov light, fluorescent light, radio emission, etc. in the atmosphere that can be registered by different methods by ground-based detectors
Our preliminary studies indicate that the mass-sensitive parameter based on the Cherenkov light lateral distribution function steepness is extremely sensitive to the atmosphere model
Summary
The satellite-based projects like TUS [17,18], EUSO [19,20], or POEMMA [21] utilize both compact detectors and large observation area These experiments are aimed at ultrahigh energy region since they are positioned far from the shower. The method of detection of the reflected Cherenkov light allows, on the one hand, to register EAS on a relatively large area and later reconstruct the lateral distribution function of Cherenkov photons, and, on the other hand, to utilize a small size compact detector with all the advantages of such a setup. The main drawback of this design, is that the detector is significantly limited in its weight and, size This means that the detector’s sensitive element should preferably operate in photon counting mode. These data, collected during and in some cases before and after EAS measurements, was used in the subsequent analysis for detector state and environment conditions monitoring, allowing various cross-checks of detector calibration, positioning, and performance
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