EO Browser shows two different resluts for S1 when we try it the day after imagery?

Hi,

I check my corner reflector time to time in EO browser and it is very useful. However, I have experienced two different results when I visualize the S1 IW mode products in two different days, one in the imagery day and one the days after. For example, there was a Satellite pass over my location yesterday and I visualized it in VV linear gamma and found bright pixels associated with my corner reflector. When I search and look at it again today, the number and location of the brighter pixels (corresponding to my CR location) are different. I cannot get the same results the day after. This is an example which showed two different results. I have got the screenshots but unfortunately cannot attach it here.

s3://sentinel-s1-l1c/GRD/2021/3/9/IW/DV/S1A_IW_GRDH_1SDV_20210309T051457_20210309T051522_036917_0457BA_7227/

What can be the problem?

Thanks

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I would guess that you are noticing differences between “NRT” (near real time) products and reprocessed products, that are published a few hours later.

Thanks. Maybe, but not a few hours after. The whole day of imagery EO shows the same and then the day after I get different results. When should we expect reprocessed products (how many hours after NRT)? And what are the main differences between NRT and reprocessed products?

I suggest you check

sentinel.esa.int

Sentinel-1 - Data Distribution Schedule - Missions - Sentinel Online - Sentinel

These products are made available within 1 hour of observation over NRT areas with a subscription and, in every case, within 24 hours of observation.

Thanks, this is the availability, but just wondering why the results are different. It doesn’t say something about reprocessed data for the day after, maybe I miss it.

Hi,

this is guessing because I am not sure how your corner reflector is set up but could this be related to ascending/descending orbits? This is easy to test in EO Browser, search only one of the orbit directions and compare data from different dates.

Thanks. The CR is well oriented for S1 descending orbits and I only check the descending images and compare them.

Hi, I think I found the problem. Actually, it seems there is a problem for the search function and visualization.

When I search for S1, IW, only Desc. in EO Browser, it lists all the results which shows the descending images taken in the morning, but in fact for visualization it shows the ascending images. But when I use timespan and narrow the time to the morning which is the time for Descending images, then it shows the right descending image and consequently my corner reflector (see the attached screenshot). To me it is strange, when we select only descending, it should show only those ones, not both orbits.

And that’s why, when I am searching in the first hours after the satellite passage, I can see a good signal for my CR, but when I check it the day after, it has both ascending and descending images and shows only ascending, even if I have select the descending in the search step.

I think maybe this issue needs to be fixed.

Thanks