The first imaging photometer of the PAIPS system was installed at the Verkhnetulomsky observatory (VTL, 68.63 N, 31.78 E) in September 2021 and made observations throughout the winter season until May 2022.

The imaging photometer is a lens telescope consisting of:

• an optical system in the form of a lens with a diameter of 5 cm (transparent in the near UV range: 300–400 nm);
• photodetector—a matrix of 4 multi-anode photomultiplier tubes (MAPMTs) (16×1616×16 pixels, covered with BG3 filters transparent in the range of 300–400 nm);
• analog-to-digital conversion board based on specialized SPACIROC-3 microcircuits [1].

MAPMTs operate in a single photoelectron mode, which ensures the high sensitivity of the equipment. The structure of the photometer and the logic of its operation are similar to the Mini-EUSO telescope [2]. There are three operating modes working in parallel with different time resolutions: 2.5 μs, 320 μs and 41 ms. These modes allow phenomena of different duration and nature to be recorded. Since 2022 the detector operates in continuous monitoring mode with 1 ms temporal resolution.

Additionally, a spectrometer is installed in the photometer housing, which is a set of 16 single-channel PMTs with an analog electronics board. In front of each PMT there is a light filter that determines the wavelength range. The spectrometer operates in a direct current mode based on electronics similar to those implemented earlier in the TUS orbital experiment aboard the Lomonosov satellite [3]. The spectrometer is aimed to measure the characteristic lines of aurora emission to obtain additional information, which can be used for aurora altitude estimations. Wide wavelength band filters UFS-1 (300–400 nm) and KS-11 (600–800 nm) are used, as well as narrow filters with the 337 nm, 390 nm and 430 nm central wavelengths and 10 nm at FWHM.

The photometer and spectrometer have a common digital data processing unit that provides event selection, recording to the internal DDR memory, control of operating modes and detector parameters, as well as an interface with a computer (the server for data storage).

The photometer and spectrometer have the same FOV. The spectrometer allows the measurement of the total radiation spectrum over the entire FOV, and the photometer—the localization of the emission source and its geometric shape.

 

 

Left: The 3D model of the detector PAIP-V. The left part of the device is a 16-channel spectrometer, and the right part is an imaging photometer. Right: Photo of the detector.

 

PAIP-L (Imaging photometer in Lovozero)