写一个cesium 卫星覆盖范围

以下是一个基本的 Cesium 卫星覆盖范围的示例代码：

var viewer = new Cesium.Viewer('cesiumContainer');

var position = Cesium.Cartesian3.fromDegrees(-75.59777, 40.03883);
var satelliteHeight = 600; // 卫星高度
var sensorAngle = 30; // 传感器视场角度
var granularity = 0.1; // 颗粒度

// 创建卫星图层
var satellite = viewer.entities.add({
    position : position,
    billboard : {
        image : 'path/to/satellite.png',
        scale : 0.5
    }
});

// 创建卫星传感器
var sensor = new Cesium.RectangularSensorGraphics();
sensor.xHalfAngle = Cesium.Math.toRadians(sensorAngle);
sensor.yHalfAngle = Cesium.Math.toRadians(sensorAngle);
sensor.radius = satelliteHeight;
sensor.showIntersection = false;
sensor.lineCount = 2;
sensor.material = new Cesium.ColorMaterialProperty(Cesium.Color.BLUE.withAlpha(0.5));
satellite.sensor = sensor;

// 创建卫星覆盖范围
var coverage = new Cesium.CustomPatternSensorVolumeGraphics();
coverage.radius = satelliteHeight;
coverage.sensorVolumePortionToDisplay = 0.5;
coverage.lineCount = 2;
coverage.pattern = [true, true, false, false];
coverage.fill = new Cesium.Color(0.0, 1.0, 0.0, 0.3);
satellite.coverage = coverage;

// 计算卫星覆盖范围
var startTime = Cesium.JulianDate.fromDate(new Date());
var stopTime = Cesium.JulianDate.addSeconds(startTime, 3600, new Cesium.JulianDate());
var timeStep = Cesium.JulianDate.addSeconds(startTime, granularity, new Cesium.JulianDate());

var positions = [];
for(var i = 0; i < 360; i += granularity) {
    var heading = Cesium.Math.toRadians(i);
    var cartesian = Cesium.Cartesian3.fromRadians(position.longitude, position.latitude, satelliteHeight);
    var direction = Cesium.Matrix3.multiplyByVector(Cesium.Transforms.headingPitchRollToFixedFrame(cartesian, new Cesium.HeadingPitchRoll(heading, 0, 0)), new Cesium.Cartesian3(0, 1, 0), new Cesium.Cartesian3());
    var intersection = Cesium.IntersectionTests.rayEllipsoid(position, direction, Cesium.Ellipsoid.WGS84);
    if(intersection !== undefined) {
        var intersectionCartographic = Cesium.Ellipsoid.WGS84.cartesianToCartographic(intersection);
        positions.push(intersectionCartographic);
    }
}

// 更新卫星传感器和覆盖范围
viewer.clock.onTick.addEventListener(function() {
    var currentTime = viewer.clock.currentTime;
    var position = Cesium.Property.getValueOrUndefined(satellite.position, currentTime);
    var sensor = satellite.sensor;
    var coverage = satellite.coverage;

    if(position !== undefined && sensor !== undefined && coverage !== undefined) {
        sensor.radius = satelliteHeight;
        sensor.position = position;

        coverage.radius = satelliteHeight;
        coverage.pattern = [true, true, false, false];
        if(positions.length > 0) {
            coverage.positions = positions;
            coverage.show = true;
        } else {
            coverage.show = false;
        }
    }
});

需要注意的是，这只是一个简单的示例代码，实际应用中还需要根据具体需求进行修改和优化。