Satellite anomaly detection based on reconstruction discrepancy theory utilizing a new dual-branch reconstruction model

To enhance the accuracy of deep learning methods based on reconstruction discrepancy in satellite anomaly detection tasks,this study proposes a dual-branch reconstruction model(DBRM)and designs a comprehensive satellite anomaly detection framework around this model.Firstly,we introduce the temporal-channel mixer(TC-Mixer)module,which mainly comprises a self-attention layer for capturing long-range temporal dependencies in telemetry data,and two types of feed-forward networks(FFN)for extract-ing complex patterns in the temporal and channel dimension of telemetry data.This design endows the TC-Mixer module with robust capabilities for extracting complicated dependencies in telemetry data.Secondly,with the TC-Mixer module as the main component,we designed the DBRM.This model utilizes a shared latent representation layer,allowing the regeneration branch and forecasting branch of the DBRM to share most of the feature extraction network architecture.This approach significantly en-hances the model’s regression accuracy while reducing computational complexity.Thirdly,using the DBRM as the core network model,we devised a comprehensive satellite anomaly detection framework.This includes an anomaly criterion that considers the reconstruction discrepancy of both the regeneration and forecasting branches,the peak-over-threshold(POT)method for anomaly thresholding,and the MIC-based feature engineering method,etc.Finally,we conducted comparative experiments with several SOTA anomaly detection algorithms on two public and one private satellite anomaly detection datasets.The experimental results validate the effectiveness and superiority of our proposed method.

Hierarchical Disturbance Propagation Mechanism and Improved Contract Net Protocol for Satellite TT&C Resource Dynamic Scheduling

The practical engineering of satellite tracking telemetry and command(TT&C)is often disturbed by unpredictable external factors,including the temporary rise in a significant quantity of satellite TT&C tasks,temporary failures and failures of some TT&C resources,and so on.To improve the adaptability and robustness of satellite TT&C systems when faced with uncertain dynamic disturbances,a hierarchical disturbance propagation mechanism and an improved contract network dynamic scheduling method for satellite TT&C resources were designed to address the dynamic scheduling problem of satellite TT&C resources.Firstly,the characteristics of the dynamic scheduling problem of satellite TT&C resources are analyzed,and a mathematical model is established with the weighted optimization objectives of maximizing the revenue from task completion and minimizing the degree of plan disturbance.Then,a bottom-up distributed dynamic collaborative scheduling framework for satellite TT&C resources is proposed,which includes a task layer,a resource layer,a central internal collaboration layer,and a central external collaboration layer.Dynamic disturbances are propagated layer by layer from the task layer to the central external collaboration layer in a bottom-up manner,using efficient heuristic strategies in the task layer and the resource layer,respectively.We use improved contract network algorithms in the center internal collaboration layer and the center external collaboration layer,the original scheduling plan is quickly adjusted to minimize the impact of disturbances while effectively completing dynamic task requirements.Finally,a large number of simulation experiments were carried out and compared with various comparative algorithms.The results show that the proposed algorithm can effectively improve the solution effect of satellite TT&C resource dynamic scheduling problems,and has good application prospects.

Human activities and elevational constraints restrict ranging patterns of snub-nosed monkeys in a mountainous refuge

Both natural conditions and anthropogenic factors affect the survivability,distribution,and population density of wildlife.To understand the extent and how these factors drive species distributions,a detailed description of animal movement patterns in natural habitats is needed.In this study,we used satellite telemetry to monitor elevational ranges favored by endangered golden snub-nosed monkeys(Rhinopithecus roxellana),in the Qinling Mountains,central China.We investigated the abundance and distribution of food resources through sampling vegetation quadrats at different elevations and sampled anthropogenic activities using field surveys.Our results indicated that although there was no significant variation in food resources between low-(<1500 m)and middle-elevations(1500–2200 m),monkeys were found most often in areas above 1500 m,where there was less anthropogenic development(e.g.houses and roads);however,monkeys rarely ranged above 2200 m and had limited food availability at this altitude.There was limited human disturbance at this elevation.We suggest that both human activity and ecological constraints(i.e.food resources)have considerable effects on elevational use of R.roxellana in the Qinling Mountains.This study highlights the critical roles these factors can play in shaping the vertical distribution of high-altitude primates.This research provides useful insights for habitat-based conservation plans in which human disturbance management and habitat restoration should be prioritized.

Wind effects on the migration routes of trans-Saharan soaring raptors： geographical, seasonal, and interspecific variation

Wind is among the most important environmental factors shaping birds＇ migration patterns. Birds must deal with the displacement caused by crosswinds and their behavior can vary according to different factors such as flight mode, migratory season, experience, and distance to goal areas. Here we analyze the relationship between wind and migratory movements of three raptor species which migrate by soaring-gliding flight： Egyptian vulture Neophron percnopterus, booted eagle Aquila pennata, and short-toed snake eagle Circaetus gallicus. We analyzed daily migratory segments （i.e., the path joining consecutive roosting locations） using data recorded by GPS satellite telemetry. Daily movements of Egyptian vultures and booted eagles were significantly affected by tailwinds during both autumn and spring migrations. In contrast, daily movements of short-toed eagles were only significantly affected by tailwinds during autumn migration. The effect of crosswinds was signifi- cant in all cases. Interestingly, Egyptian vultures and booted eagles showed latitudinal differences in their behavior： both species compensated more frequently at the onset of autumn migration and, at the end of the season when reaching their wintering areas, the proportion of drift segments was higher. In contrast, there was a higher drift at the onset of spring migration and a higher compensation at the end. Our results highlight the effect of wind patterns on the migratory routes of soaring raptors, with different outcomes in relation to species, season, and latitude, ultimately shaping the loop migration patterns that current tracking techniques are showing to be widespread in many long distance migrants.

Regional and age-dependent differences in the effect of wind on the mi^ratorv routes of Eleonora＇s falcon

During migration, birds can show different responses to wind in relation to distance to the goal, experience, ecologi- cal barriers and visibility of landmarks. We analysed the effect of wind （tailwinds and crosswinds） on daily movement rates （for- ward and perpendicular） of Eleonora＇s falcons using ARGOS satellite telemetry, during their trans-continental autumn migration to Madagascar, in relation to the different crossed regions and individuals＇ age class. Our results showed that the effect of wind on daily movement rates was not uniform, being stronger in the farthest region from the migration goal, the Sahara desert, with adults being more affected than juveniles in this region. In the Sahel, the results were more conflicting, perhaps because daily movements were more shaped by the distribution of food resources. In Equatorial Africa, daily movement rates were mainly af- fected by crosswinds. Still, it remains unclear which orientation mechanism allows Eleonora＇s falcons to reach such a narrow wintering area compensating also for wind displacement

Movements and diving behavior of internesting green turtles along Pacific Costa Rica

Using satellite transmitters,we determined the internesting movements,spatial ecology and diving behavior of East Pacific green turtles(Chelonia mydas)nesting on Nombre de Jesús and Zapotillal beaches along the Pacific coast of northwestern Costa Rica.Kernel density analysis indicated that turtles spent most of their time in a particularly small area in the vicinity of the nesting beaches(50%utilization distribution was an area of 3 km^(2)).Minimum daily distance traveled during a 12 day internesting period was 4.6±3.5 km.Dives were short and primarily occupied the upper 10 m of the water column.Turtles spent most of their time resting at the surface and conducting U-dives(ranging from 60 to 81%of the total tracking time involved in those activities).Turtles showed a strong diel pattern,U-dives mainly took place during the day and turtles spent a large amount of time resting at the surface at night.The lack of long-distance movements demonstrated that this area was heavily utilized by turtles during the nesting season and,therefore,was a crucial location for conservation of this highly endangered green turtle population.The unique behavior of these turtles in resting at the surface at night might make them particularly vulnerable to fishing activities near the nesting beaches.