S-1 Tops Split Error: Operation Exception. Index=size=0

Hello all,
I just recently started using SNAP and trying to follow "TOPS Interferometry Tutorial
" by Braun and Veci (2021). But faced problem with initial step on [Radar] – [Sentinel-1 Tops] – [S1 TOPS Split].

The ID of S1 data that I’m using is “S1A_IW_SLC__1SDV_20180330T230608_20180330T230635_021251_0248CE_9238.SAFE.”
And the area of interest is a small area marked on blue star.

Question 1: As mentioned above, my AOI is located on the tip of right side which is part of IW3 as seen on images below (not included in IW2)

When I process IW1+VV or IW2+VV, the operation works fine and creates “split” data. But when I try IW3+VV, it gives error:

I was not able to find any useful information on what the cause is and how to solve it. Is this becasue if most part of IW3 is outside of the red box? What should I do in this case?

Question 2: I am trying to generate a elevation difference between two S1 data. Do I have to use IW3 since my AOI is located within it? Does it also mean that split of IW1 and IW2 will be uselss to me?

Question 3: Is TOPS split with selction of subswath (IW1, IW2, IW3) essential process? Why can I just skip and pre-process the entire SAR data and just crop (subset) a small area at the end?

Thank you so much for the help and please let me know if any additional information is needed.

I just found out that my original SLC data does not include any IW3. Is this why?

Maybe @jun_lu or @lveci could help you

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I think it has to do with the ecosystem. It seems like the meta data of S1 SLC is corrupted and might be related to:


I asked about it 4 days ago.

In the newly downloaded files snap fails to read the IW3, even though the tiff files are in the folder.
You can also see the boundingbox of the split dialogue does not fit the IW3, usually it would fit at least the corners.

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For a quick fix deleting the ql.jpg from the .zip file and zipping the product back together does the trick. Which is an annoying amount of IO if you process 100s of images.

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This is the S-1 product that I downloaded from ASF Data Search
It has three sub-swaths and I can do the TOPS split without problem. Can you try to download the product again to see if you get the complete product? Thanks

I am having this same problem right now. Won’t process IW3.

Hello Sir/Ma’am, may I ask how I can do this? Can you provide a more detailed instruction as I am also experiencing this problem with my Snap Software? Best regards.


I think the easiest is the following: Once you downloaded a zipped product, you right click it and select extract. A folder with the same name should be created. In that folder there is a file called “manifest.safe” which can you can use to open the product in snap.

If you are using Linux and CLI you can use
zip -r <your_filename.zip> <product_filename>

If that does not help you can Google “how to extract zip archive”

Good luck


Thank you very much!

Thank you for this!