diff --git a/antarest/study/storage/rawstudy/model/filesystem/root/input/thermal/prepro/area/thermal/thermal.py b/antarest/study/storage/rawstudy/model/filesystem/root/input/thermal/prepro/area/thermal/thermal.py
index bab6d2145a..f2ae671336 100644
--- a/antarest/study/storage/rawstudy/model/filesystem/root/input/thermal/prepro/area/thermal/thermal.py
+++ b/antarest/study/storage/rawstudy/model/filesystem/root/input/thermal/prepro/area/thermal/thermal.py
@@ -1,12 +1,22 @@
 from antarest.study.storage.rawstudy.model.filesystem.folder_node import FolderNode
 from antarest.study.storage.rawstudy.model.filesystem.inode import TREE
 from antarest.study.storage.rawstudy.model.filesystem.matrix.input_series_matrix import InputSeriesMatrix
+from antarest.study.storage.rawstudy.model.filesystem.matrix.matrix import MatrixFrequency
 
 
 class InputThermalPreproAreaThermal(FolderNode):
+    """
+    Folder containing thermal cluster data: `input/thermal/prepro/{area_id}/{cluster_id}`.
+
+    This folder contains the following files:
+
+    - `data.txt` (matrix): TS Generator matrix (daily)
+    - `modulation.txt` (matrix): Modulation matrix (hourly)
+    """
+
     def build(self) -> TREE:
         children: TREE = {
-            "data": InputSeriesMatrix(self.context, self.config.next_file("data.txt")),
+            "data": InputSeriesMatrix(self.context, self.config.next_file("data.txt"), freq=MatrixFrequency.DAILY),
             "modulation": InputSeriesMatrix(self.context, self.config.next_file("modulation.txt")),
         }
         return children
diff --git a/tests/integration/studies_blueprint/test_study_matrix_index.py b/tests/integration/studies_blueprint/test_study_matrix_index.py
new file mode 100644
index 0000000000..69880cb357
--- /dev/null
+++ b/tests/integration/studies_blueprint/test_study_matrix_index.py
@@ -0,0 +1,100 @@
+from starlette.testclient import TestClient
+
+
+class TestStudyMatrixIndex:
+    """
+    The goal of this test is to check that the API allows to retrieve
+    information about the data matrices of a study.
+
+    The values are used byt the frontend to display the time series
+    with the right time column.
+    """
+
+    def test_get_study_matrix_index(
+        self,
+        client: TestClient,
+        user_access_token: str,
+        study_id: str,
+    ) -> None:
+        user_access_token = {"Authorization": f"Bearer {user_access_token}"}
+
+        # Check the matrix index for Thermal clusters
+        # ===========================================
+
+        # Check the Common matrix index
+        res = client.get(
+            f"/v1/studies/{study_id}/matrixindex",
+            headers=user_access_token,
+            params={"path": "input/thermal/prepro/fr/01_solar/modulation"},
+        )
+        assert res.status_code == 200, res.json()
+        actual = res.json()
+        # We expect to have an "hourly" time series with 8760 hours
+        expected = {
+            "first_week_size": 7,
+            "level": "hourly",
+            "start_date": "2001-01-01 00:00:00",
+            "steps": 8760,
+        }
+        assert actual == expected
+
+        # Check the TS Generator matrix index
+        res = client.get(
+            f"/v1/studies/{study_id}/matrixindex",
+            headers=user_access_token,
+            params={"path": "input/thermal/prepro/fr/01_solar/data"},
+        )
+        assert res.status_code == 200, res.json()
+        actual = res.json()
+        # We expect to have a "daily" time series with 365 days
+        expected = {
+            "first_week_size": 7,
+            "level": "daily",
+            "start_date": "2001-01-01 00:00:00",
+            "steps": 365,
+        }
+        assert actual == expected
+
+        # Check the time series
+        res = client.get(
+            f"/v1/studies/{study_id}/matrixindex",
+            headers=user_access_token,
+            params={"path": "input/thermal/series/fr/01_solar/series"},
+        )
+        assert res.status_code == 200, res.json()
+        actual = res.json()
+        # We expect to have an "hourly" time series with 8760 hours
+        expected = {
+            "first_week_size": 7,
+            "level": "hourly",
+            "start_date": "2001-01-01 00:00:00",
+            "steps": 8760,
+        }
+        assert actual == expected
+
+        # Check the default matrix index
+        # ==============================
+
+        res = client.get(f"/v1/studies/{study_id}/matrixindex", headers=user_access_token)
+        assert res.status_code == 200
+        actual = res.json()
+        expected = {
+            "first_week_size": 7,
+            "start_date": "2001-01-01 00:00:00",
+            "steps": 8760,
+            "level": "hourly",
+        }
+        assert actual == expected
+
+        # Check the matrix index of a daily time series stored in the output folder
+        # =========================================================================
+
+        res = client.get(
+            f"/v1/studies/{study_id}/matrixindex",
+            headers=user_access_token,
+            params={"path": "output/20201014-1427eco/economy/mc-all/areas/es/details-daily"},
+        )
+        assert res.status_code == 200
+        actual = res.json()
+        expected = {"first_week_size": 7, "start_date": "2001-01-01 00:00:00", "steps": 7, "level": "daily"}
+        assert actual == expected
diff --git a/tests/integration/test_integration.py b/tests/integration/test_integration.py
index 539db9bd0e..41bceae525 100644
--- a/tests/integration/test_integration.py
+++ b/tests/integration/test_integration.py
@@ -23,7 +23,6 @@
     TableTemplateType,
     TransmissionCapacity,
 )
-from antarest.study.model import MatrixIndex, StudyDownloadLevelDTO
 from antarest.study.storage.rawstudy.model.filesystem.config.binding_constraint import BindingConstraintFrequency
 from antarest.study.storage.rawstudy.model.filesystem.config.renewable import RenewableClusterGroup
 from antarest.study.storage.rawstudy.model.filesystem.config.thermal import LawOption, TimeSeriesGenerationOption
@@ -92,7 +91,6 @@ def test_main(client: TestClient, admin_access_token: str, study_id: str) -> Non
     )
     assert len(res.json()) == 1
     study_id = next(iter(res.json()))
-    comments = "<text>Hello</text>"
 
     res = client.get(
         f"/v1/studies/{study_id}/outputs",
@@ -172,37 +170,6 @@ def test_main(client: TestClient, admin_access_token: str, study_id: str) -> Non
     )
     assert res.status_code == 200
 
-    # study matrix index
-    res = client.get(
-        f"/v1/studies/{study_id}/matrixindex",
-        headers={"Authorization": f'Bearer {george_credentials["access_token"]}'},
-    )
-    assert res.status_code == 200
-    assert (
-        res.json()
-        == MatrixIndex(
-            first_week_size=7,
-            start_date="2001-01-01 00:00:00",
-            steps=8760,
-            level=StudyDownloadLevelDTO.HOURLY,
-        ).dict()
-    )
-
-    res = client.get(
-        f"/v1/studies/{study_id}/matrixindex?path=output/20201014-1427eco/economy/mc-all/areas/es/details-daily",
-        headers={"Authorization": f'Bearer {george_credentials["access_token"]}'},
-    )
-    assert res.status_code == 200
-    assert (
-        res.json()
-        == MatrixIndex(
-            first_week_size=7,
-            start_date="2001-01-01 00:00:00",
-            steps=7,
-            level=StudyDownloadLevelDTO.DAILY,
-        ).dict()
-    )
-
     res = client.delete(
         f"/v1/studies/{study_id}/outputs/20201014-1427eco",
         headers={"Authorization": f'Bearer {george_credentials["access_token"]}'},