GOES 17 Image Artifacts – Local Weather?
I’ve just started to tweet videos showing the last three days from different satellites so I was intently watching what they looked like to ensure that everything was working perfectly. But the GOES 17 video looked a bit odd.
I’m not used to seeing artifacts like this, so I immediately went to check that the code I’d written to tweet videos was working as it should, but everything looked fine. So I wondered if Twitter do some processing on uploaded videos to potentially cut down the size or quality of the content to save storage space and bandwidth. To validate this I looked at the raw video before it was uploaded and the artifacts are there too, so I can’t blame Twitter.
Of course this could have been a problem with the video generation from the static images, but sure enough there were artifacts in the images. So I can’t blame ffmpeg which I use to create the videos.
There are two sets of artifacts in the video, although some only last a frame or two so you need to be watching closely to see them.
The first is lens flare which is clearly shown here 6 seconds into the video. I’ve discussed this before on Kiwiweather. This is a perfectly normal artifact to get, especially around spring / autumn (fall for those in the US).
The second is very obvious on the tweet where there are some unusual banding artifacts across the whole part of the visible image. Looking at the raw image this effect is seen on three frames in total. This isn’t something I’ve noticed before, although I don’t look at every single image captured so it is may be possibly not the first time.
Checking in with the Discord chat, Carl Reinemann was able to confirm the root cause as being due to the severe local weather in Suitland in MaryLand (USA) where NOAA operate one of their satellite operations centres which receives the data from GOES 17.
I was initially surprised how this would impact the images from the satellite, but this is down to how the satellite data is processed. Data is first downloaded from the satellite at one of the satellite operations centres, processed using their PDA (Product Distribution and Access) service and it is then transmitted back up to the satellite along with additional data obtained from the original image data (GRB, HRIT, EMWIN, SARSAT, DCS).
So if there is severe weather or any other interference around the satellite operations centre in use, this can impact the data being downloaded and / or uploaded. And it will have been this which will have resulted in the artifacts.
Of course it is also possible to get artifacts when downloading locally too, but since these artifacts were seen with multiple different receivers the problem will have been with the local severe weather.