## 1 Introduction
Load balancing and energy shortage problem have become research hotspots, because of the massive user in mega NTSN. [PERSON] [13] proposed a pre-balancing shortest path algorithm to alleviate congestion in the heavy load zone. A congestion index is the key of this algorithm. [PERSON] [14] proposed a multi-objective optimization model in the congestion prediction. An ant colony algorithm is applied in it. This routing scheme performs well in balancing the traffic load and throughput. [PERSON] [15] proposed a selective iterative Dijkstra algorithm to reduce the congestion rate. It is a distributed strategy, which diverts the traffic flow of congestion nodes to neighboring nodes. Although the above routing scheme alleviates the congestion caused by high traffic density, the energy sensitive problem is ignored. Due to the symmetric structure of NTSN, each satellite is in the 'right side' for about a half cycle. This feature poses a great challenge to energy supply capability, especially for communication satellites. [PERSON] [16] proposed an energy-aware traffic classification routing algorithm based on traffic characteristics. The key technology is to select different network metrics for route calculation according to service characteristics. However, there is no real energy control strategy and energy model in it. [PERSON] [17] proposed a multi-QoS routing strategy for the software-defined satellite network. However, the energy balance is only introduced as an optimization condition, not an optimization goal. In order to increase satellite efficiency, some scholars have carried out research on the satellite power system. [PERSON] [18] proposed an autonomous fault diagnosis for satellite power system to improve the capability of satellite to perform its on-orbit performance. [PERSON] [19] proposed a simulation of the power subsystem of small satellites by Simulink/Matlab. It includes the models of solar cell array, DC/DC converters, battery charge/discharge controller, power control distribution unit and payload. These studies increase system performance by optimizing the satellite power systems, but do not consider the characteristics of mega satellite constellations. The relationship between symmetrical constellations and energy balance is ignored. An energy model that takes into account both the satellite power system and the constellation energy balance is necessary. Based on the above analysis, an energy model is proposed firstly in this paper. A tubular sliding time window (TSTW) model is proposed, which consists of the satellite power model and constellation solar model. Based on it, an energy sensitive and congestion balance (ESCB) routing scheme is proposed, secondly. A multi-objective optimization algorithm is implemented to find the routing path. Lastly, in order to more realistically verify the specific scheme, a reasonable traffic model is proposed. Two different services are contained in it, namely: access services and bearer services. A lot of simulations by the System Tool Kit (STK) and Network X packets indicate that the ESCB routing scheme achieves excellent communication performance and energy balance ability [20; 21].