Solar flares catalog
The BDRG device (Lomonosov satellite) was built for the early detection of GRBs in the 10–3000 keV energy range and for the generation of triggers for those events. It can to detect solar flare also. The BDRG consists of three identical detector units connected to the electronic unit. The BDRG instrument detector units (blocks) are mounted on the spacecraft payload platform in such a way that their axes are oriented 90° to each other. Each detector has a cosine angular dependence for a sensitive area not occluded by satellite construction elements within ∼60° of its axis. The monitorʼs central axis, relative to which the detector axes are inclined, is directed toward to the local zenith. Thus, the total field of view (FOV) for all three detectors is about 2π sr; and one quarter of this field, i.e., π/2 sr, has the value of a solid angle, within which limits the GRB error can be estimated with sufficiently high accuracy through the comparison of all three detector outputs.
Each BDRG detector unit consists of a thin layer of (0.3 cm) Na I(Tl) crystals optically coupled to a considerably thicker layer (1.7 cm) of Cs I(Tl) crystals situated underneath. The diameter of these scintillators is 13 cm, and both layers are read by a single photomultiplier tube. Thus, the overall detector area is about 130 cm2. The thickness of the Na I(Tl) layer is optimized for the soft part of energy range, and the working ranges of the units are 0.01–0.5 MeV for the Na I(Tl) layer and 0.05–3 MeV for Cs I(Tl). As such, the Na I(Tl) layer serves as the main detector for hard X-ray timing, while the Cs I(Tl) operates as an active shield against background gamma-rays. Additionally, the Cs I(Tl) crystals can also detect gamma-rays with energies up to a few MeV. The difference in decay times for the Na I(Tl) (∼0.25 ms) and Cs I(Tl) (∼2.0 ms) crystals permits the separation of light flashes in the scintillators through special electronic circuits that differentiate pulse shapes.
The BDRG instrument operates in two main observational modes: the monitor or continuous mode, and the event mode. In the monitor mode, all instrument outputs are recorded and stored continuously with time resolutions adjustable by commands from Earth. On the other hand, the burst mode is activated by onboard instrument triggers to record detailed information of each photon during the pre-burst, burst, and after-burst intervals.
The information provided by the BDRG units consists of a number of different categories for the data frames generated continuously (continuous mode) as well as irregularly by various triggers (burst mode). The continuous data stream includes three types of frames corresponding to the instruments’ monitoring, spectrum, and event. Monitoring frames provide count rates in 8 energy channels for the Na I(Tl) and Cs I(Tl) scintillator crystals for each of the BDRG detector units, while spectrum frames contain 724 channel spectra for Na I(Tl) and Cs I(Tl), separately. Event frames give the primary values for energy release within the Na I(Tl) and Cs I(Tl) crystals, combined with time data for a fixed number of detected gamma quanta. Likewise, information about the main parameters for all GRB triggers is stored and transferred in the form of “trigger logs.” There are three trigger types categorized as “fast,” “slow,” and “super-slow,” with characteristic times of 10 ms, 1 s, and 20 s, respectively. Corresponding to each trigger type, three data frame sequences for the monitoring, spectrum, and event are generated continuously in a manner similar to the continuous mode discussed above. A portion of data collected before the trigger is always included for all trigger types.