Sentinel-1 missing data gaps between two images GEE [duplicate]

Question

I am trying to export a Sentinel-1 mosaic with the code below. I keep getting this missing data gap between the two images. Even when I export the images separately, and mosaic them myself in ArcGIS, I still have this problem.

https://code.earthengine.google.com/91fea33548352ade6dd961ed3d34d883

var start_date = ee.Date('2019-08-01');
var finish_date = ee.Date('2019-08-15');
var orbit = 'ASENDING';

// Get the VV collection.
var collectionS1 = ee.ImageCollection('COPERNICUS/S1_GRD')
    .filter(ee.Filter.listContains('transmitterReceiverPolarisation', 'VH'))
    .filter(ee.Filter.eq('instrumentMode', 'IW'))
    //.filter(ee.Filter.eq('orbitProperties_pass', orbit))
    .filterDate(start_date, finish_date)
    .filterBounds(polygons);

 // Get the VV collection.
var collectionVH = collectionS1.select('VH');

var VH = ee.Image(collectionVH.median());

Map.centerObject(polygons, 7);
Map.addLayer(VH, {min: -25, max: 5}, 'VH', true);

//Import Tool
var batch = require('users/fitoprincipe/geetools:batch');

// Change Folder Name

var folder = 'GEE_EXPORT';


// Download Collections
batch.Download.ImageCollection.toDrive(collectionVH, folder,  
        {name: 'VH_'+orbit+'_'+'{id}',
               scale: 10,
              region: polygons,     
                fileFormat: 'GeoTIFF',
                  maxPixels: 1e13,
              type: 'float'});

Answer 1

Guido Lemoine gave a clear answer on your developer forum thread:

Yes, this is due to the terrain correction step. Original GRD scenes are contiguous, and broken up at the 25 second slices (for IW), see the image timestamps. The last line of slice N is exactly adjacent to the first of N+1.

Terrain correction is a bit tight on sampling at scene boundaries, which often causes a 1 pixel gap.

This would be solvable if you would first do slice assembly in s1tbx and then TC the assembled orbit strips. This takes loads of memory, however, esp. since s1tbx is not very efficient in memory management. SAR is just a series of time samples in range arranged in azimuth, the "scene" concept is actually somewhat old fashioned, inherited from "GIS" concepts.

But given that 80% of the GEE crowd seems to be still concerned with downloading "scenes", it's probably not a good idea to create mega-size assembled orbit strips.

https://groups.google.com/d/msg/google-earth-engine-developers/9qdJ9IUFdWE/vmof4jB4AAAJ