function RefreshPage(Period) {
    setTimeout("location.reload(true);", Period);
}

var wms = new OpenLayers.Layer.WMS("NASA Global Mosaic",
    "http://wms.jpl.nasa.gov/wms.cgi",
    {
        layers: "modis,global_mosaic",
        transparent: true,
        myData: Math.random()
    }, {
        opacity: 0.5,
        singleTile: true
    });

myWMSLayer.redraw(true);

redraw: function(force) {
    if (force) {
        return this.mergeNewParams({"_olSalt": Math.random()});
    } else {
        return OpenLayers.Layer.prototype.redraw.apply(this, []);
    }
},