diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 4136a78..ad8a43e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -20,6 +20,8 @@ jobs:
             spec: >-
               rasterio
               gdal
+              libgdal-netcdf
+              libgdal-hdf5
               asf_search
           - label: Minimum
             spec: >-
diff --git a/src/opera_utils/_cslc.py b/src/opera_utils/_cslc.py
index 46cf223..c583fd0 100644
--- a/src/opera_utils/_cslc.py
+++ b/src/opera_utils/_cslc.py
@@ -439,13 +439,13 @@ def make_nodata_mask(
         test_f = f"NETCDF:{opera_file_list[-1]}:{dataset_name}"
         # convert pixels to degrees lat/lon
         gt = _get_raster_gt(test_f)
-        # TODO: more robust way to get the pixel size... this is a hack
-        # maybe just use pyproj to warp lat/lon to meters and back?
-        dx_meters = gt[1]
-        dx_degrees = dx_meters / 111000
-        buffer_degrees = buffer_pixels * dx_degrees
-    except RuntimeError:
-        raise ValueError(f"Unable to open {test_f}")
+    except RuntimeError as e:
+        raise ValueError(f"Unable to get geotransform from {test_f}") from e
+    # TODO: more robust way to get the pixel size... this is a hack
+    # maybe just use pyproj to warp lat/lon to meters and back?
+    dx_meters = gt[1]
+    dx_degrees = dx_meters / 111000
+    buffer_degrees = buffer_pixels * dx_degrees
 
     # Get the union of all the polygons and convert to a temp geojson
     union_poly = get_union_polygon(opera_file_list, buffer_degrees=buffer_degrees)
diff --git a/src/opera_utils/download.py b/src/opera_utils/download.py
index 66d0358..1e3f85b 100644
--- a/src/opera_utils/download.py
+++ b/src/opera_utils/download.py
@@ -241,7 +241,7 @@ def _download_for_burst_ids(
         raise ValueError(msg)
     logger.info(msg)
     session = _get_auth_session()
-    urls = _get_urls(results)
+    urls = get_urls(results)
     asf.download_urls(
         urls=urls, path=str(output_dir), session=session, processes=max_jobs
     )
@@ -293,23 +293,30 @@ def filter_results_by_date_and_version(results: ASFSearchResults) -> ASFSearchRe
     return ASFSearchResults(filtered_results)
 
 
-def _get_urls(
+def get_urls(
     results: asf.ASFSearchResults,
     type_: Literal["https", "s3"] = "https",
+    file_ext: str = ".h5",
 ) -> list[str]:
+    """Parse the `ASFSearchResults` object for HTTPS or S3 urls."""
     if type_ == "https":
         return [r.properties["url"] for r in results]
     elif type_ == "s3":
-        # TODO: go through .umm, find s3 url
-        raise NotImplementedError()
+        out: list[str] = []
+        for r in results:
+            if "s3Urls" not in r.properties:
+                raise ValueError(f"No S3 URL for {r}")
+
+            for url in r.properties["s3Urls"]:
+                if url.endswith(file_ext):
+                    out.append(url)
+                    break
+            else:
+                raise ValueError(f"Failed to find HDF5 S3 url for {r}")
+        return out
+
     else:
         raise ValueError(f"type_ must be 'https' or 's3'. Got {type_}")
-    # r.umm
-    # 'RelatedUrls': [...
-    #     {'URL': 's3://asf-cumulus-prod-opera-products/OPERA_L2_CSLC
-    #    'Type': 'GET DATA VIA DIRECT ACCESS',
-    #    'Description': 'This link provides direct download access vi
-    #    'Format': 'HDF5'},
 
 
 def _get_auth_session() -> asf.ASFSession:
diff --git a/tests/requirements.txt b/tests/requirements.txt
index 152a5d5..134923e 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -2,7 +2,7 @@ asf_search
 pre-commit
 pytest
 pytest-cov
-pytest-randomly # control random seed
+pytest-randomly
 pytest-recording
-pytest-xdist # parallel tests: https://pytest-xdist.readthedocs.io/en/latest/
+pytest-xdist
 ruff