diff --git a/pyrfu/pyrf/cart2sph_ts.py b/pyrfu/pyrf/cart2sph_ts.py
index e429816..d0cdcc6 100644
--- a/pyrfu/pyrf/cart2sph_ts.py
+++ b/pyrfu/pyrf/cart2sph_ts.py
@@ -3,6 +3,7 @@
 
 # 3rd party imports
 import numpy as np
+import xarray as xr
 
 # Local imports
 from .ts_vec_xyz import ts_vec_xyz
@@ -37,8 +38,14 @@ def cart2sph_ts(inp, direction_flag: int = 1):
 
     """
 
-    if inp.attrs["TENSOR_ORDER"] != 1 or inp.data.ndim != 2:
-        raise TypeError("Input must be vector field")
+    # Check input type
+    assert isinstance(inp, xr.DataArray), "inp must be a xarray.DataArray"
+
+    # Check that inp is a vector time series
+    assert inp.data.ndim == 2 and inp.shape[1] == 3, "inp must be a vector time series"
+
+    # Check direction +/-1
+    assert direction_flag in [-1, 1], "direction_flag must be +/-1"
 
     if direction_flag == -1:
         r_data = inp.data[:, 0]
@@ -52,7 +59,7 @@ def cart2sph_ts(inp, direction_flag: int = 1):
         x_data = r_data * cos_the * cos_phi
         y_data = r_data * cos_the * sin_phi
 
-        out_data = np.hstack([x_data, y_data, z_data])
+        out_data = np.transpose(np.vstack([x_data, y_data, z_data]))
 
     else:
         xy2 = inp.data[:, 0] ** 2 + inp.data[:, 1] ** 2
diff --git a/pyrfu/tests/test_pyrf.py b/pyrfu/tests/test_pyrf.py
index 2d35fd3..f5f85b3 100644
--- a/pyrfu/tests/test_pyrf.py
+++ b/pyrfu/tests/test_pyrf.py
@@ -465,6 +465,24 @@ def test_cart2sph_output(self):
         )
 
 
+class Cart2SphTsTestCase(unittest.TestCase):
+    def test_cart2sph_ts_input(self):
+        with self.assertRaises(AssertionError):
+            pyrf.cart2sph_ts(0.0)
+            pyrf.cart2sph_ts(generate_data(100, "vector"))
+            pyrf.cart2sph_ts(generate_ts(64.0, 100, "scalar"))
+            pyrf.cart2sph_ts(generate_ts(64.0, 100, "vector"), 2)
+
+    def test_cart2sph_ts_output(self):
+        result = pyrf.cart2sph_ts(generate_ts(64.0, 100, "vector"), 1)
+        self.assertIsInstance(result, xr.DataArray)
+        self.assertListEqual(list(result.shape), [100, 3])
+
+        result = pyrf.cart2sph_ts(generate_ts(64.0, 100, "vector"), -1)
+        self.assertIsInstance(result, xr.DataArray)
+        self.assertListEqual(list(result.shape), [100, 3])
+
+
 class CdfEpoch2Datetime64TestCase(unittest.TestCase):
     def test_cdfepoch2datetime64_input_type(self):
         ref_time = 599572869184000000