Given the crucial role of the earth observation satellites in numerous key applications, accessing the Low Earth Orbit (LEO) satellite Internet as intermediaries via Laser Inter-Satellite Links (LISLs) has emerged as a promising solution to help transmit substantial amounts of observation data to ground stations. For Very Low Earth Orbit (VLEO) observation satellites, optimizing the cross-layer topology between themselves and LEO communication satellites has become paramount. To mitigate existing centralized algorithms' reliance on global data transfer requirement information, a Novel Distributed Interactive Mechanism (NDIM) for cross-layer LISLs establishment is proposed. Here, the VLEO observation satellite decides its own access strategy based on local network information gleaned from three information exchanges with the LEO communication satellite. Within this mechanism, the crosslayer link optimization is performed via the formulation of a many-objective topology optimization model, which considers the transmission requirements of observation satellites, load balancing amongst the communication satellite layer, and the transmission delay of emergency tasks. Based on which, we propose a Distributed Many-objective cross-layer Topology Optimization (DMTO) algorithm. Our algorithm is novel in considering the remaining loads of the intermediary communication satellites, and it allows observation satellites to decide on access plans on demand, given incoming data. Additionally, we used real data (from Typhoon LEKIMA) to establish a multi-task scenario and conducted packet-level simulations based on the Starlink and Dove constellations. The results indicate that, compared to the existing baseline, the DMTO algorithm increased the observation data throughput by 326.95 GB and reduced the average transmission delay of emergency task data by 20.5 seconds.

With the rapid development of large-scale Low Earth Orbit (LEO) satellite internet, Very Low Earth Orbit (VLEO) Earth observation constellations are increasingly using InterSatellite Links (LISLs) for cross-layer access to Internet satellites. It is an effective means to enhance data return throughput. When both observation and communication satellite constellations use lasers for networking, cross-layer access between the VLEO and LEO satellite networks requires reallocating lasers. This reallocation disrupts the original topology and impacts network performance. To maximize the collaborative operational efficiency of the double-layer network, we fundamentally analyze the relationship between topology links, throughput, and delay using graph theory. Innovatively, we discover the superiority of two axioms in addressing the cross-layer topology optimization problem, including the “Minimum Hop Count” and “Minimum Overlap Path”. Based on these axioms, a many-objective cross-layer topology optimization model is established that considers the hop count and the average link utilization frequency of both VLEO and LEO satellite networks. To reduce the reliance on centralized algorithms on global transmission demand, a Local Distributed Interaction Mechanism (LDIM) is proposed for cross-layer LISL establishment. An onboard Novel Distributed Many-Objective Topology Optimization (NDMTO) algorithm is also introduced for VLEO satellites to manage access strategies. Finally, we use real data from Typhoon LEKIMA to create a multi-task scenario and conduct packet-level simulations based on the Starlink and Dove constellations. The results indicate that, compared to existing benchmarks, the NDMTO algorithm improves data throughput by 26.73% and reduces the average transmission delay of emergency task data by 20.7%.

Inter satellite link (ISL) is an effective way for the global navigation satellite system (GNSS) to reduce its dependence on ground infrastructure, which guarantees constellation orbit determination and satellite communication. When the number of onboard Ka-band ISL antennas is less than that of visible satellites, the inter-satellite link assignment of GNSS causes a problem. For the problem of inter-satellite link scheduling, considering that the result of the allocated link has a feedback effect on the subsequent link assignment as a priori knowledge, an adaptive topology optimization algorithm based on signed variance (ABSV) is proposed. In order to meet the requirements of communication and ranging performance, the time slot is divided into a communication time slot and a ranging time slot. Taking the waiting delay time of satellite communication and PDOP as measurement indexes, the proposed strategy is simulated for 10080 min. The results show that the ranging performance of this strategy is better than other recently published methods, which verifies the effectiveness of signed variance for adaptive link planning and is also beneficial to the survivability of constellation.