After we switched over to assets.agi.com for stk-terrain tiles, all worked very well to correct our 'space with stars' issue. Many thanks for pointing that out.
Now, we're seeing an issue with Bing Maps, which is our default load with STK world Terrain meshes.
If you load our site at startup, http://paperdrone.com, we get that space with stars issues we saw below.
But if we switch over to any other, such as ESRI World Imagery for instance, (using the Maps button upper left) all is fine.
I see the bing maps imagery load fine.
But it does appear you are using our API key. You will need to create your own key in order to continue using the Bing Maps imagery. We output a warning to the console with instructions for how to do this:
This application is using Cesium’s default Bing Maps key. Please create a new key for the application as soon as possible and prior to deployment by visiting https://www.bingmapsportal.com/, and provide your key to Cesium by setting the Cesium.BingMapsApi.defaultKey property before constructing the CesiumWidget or any other object that uses the Bing Maps API.