This study investigates the characteristics of space-borne Lightning Mapping Imager (LMI) lightning products and their relationships with cloud properties using ground-based total lightning observations from the Beijing Broadband Lightning Network (BLNET) and cloud information from S-band Doppler radar data. LMI showed generally consistent lightning spatial distributions with those of BLNET, and yielded a considerable lightning detection capability over regions with complex terrain. The ratios between the LMI events, groups and flashes were approximately 9:3:1, and the number of LMI-detected flashes was roughly one order of magnitude smaller than the number of BLNET-detected flashes. However, in different convective episodes, the LMI detection capability was likely to be affected by cloud properties, especially in strongly electrified convective episodes associated with frequent lightning discharging and thick cloud depth. As a result, LMI tended to detect lightning flashes located in weaker and shallower cloud portions associated with fewer cloud shielding effects. With reference to the BLNET total lightning data as the ground truth of observation (both intra-cloud lightning and cloud-to-ground lightning flashes), the LMI event-based detection efficiency (DE) was estimated to reach 28% under rational spatiotemporal matching criteria (1.5 s and 65 km) over Beijing. In terms of LMI flash-based DE, it was much reduced compared with event-based DE. The LMI flash-based ranged between 1.5% and 3.5% with 1.5 s and 35–65 km matching scales. For 330 ms and 35 km, the spatiotemporal matching criteria used to evaluate Geostationary Lightning Mapper (GLM), the LMI flash-based DE was smaller (<1%).

In the solar system satellite systems of Jupiter, Saturn and Uranus are typical ones. The distribution of the semi-major axis of satellite orbits in each system may be expressed by an empirical formula corresponding to the Titius-Bode law. We found that it can be written as a, = B' . B", where B' and B are constants. Values of B' and B depend on formation conditions of each system.Satellites should be formed in the gas-satellitesimal disk around a planet and by aggregation of satellitesimals. The Ras is the major component in the disk and its damping effect must play an important role in the process ofaggregation ofsatellitesimals. It may be proved that radial small perturbation in the disk can cause the gravitational instability and the formation of gaseous rings with increased density, where satellitesimals can easy aggregat into satellites. Distance law of satellite systemsThere are three typical satellite systems in the solar system, those of Jupiter, Saturn, and Uranus. In each system there are more than 15 satellites. The distribution of their orbital semi-major axis may be expressed by an empirical formula like the Titius-Bode law or that or Blag-Richardson or other (NIETO 1972, PRENTICE et al. 1979, NOWOTNY 1979, DOBO 1981. However, it is difficult to understand the evolutionary implications of n = -co, 0 and negative values. We found a more rational experimental formula of the distance law, in which n is a positive integer; it can be written as (Hu et al. 1984) (1)Some satellites have been discovered in recent years and their orbital semi-major axes do not accord with the same formula. If satellites in each system are divided into groups then similar laws are valid in each group (Fig. 1). Values of B' and B, observed a",,* and calculated aca, for each group and the relative derivation, d = (a,,, -aca,)/aohs, are listed in Tables I , 2