diff --git a/lisainstrument/instrument.py b/lisainstrument/instrument.py
index f177d9c6db4d41000a773ca580543cb9631ab527..3161772d86380753e733034e601383a39376ef92 100644
--- a/lisainstrument/instrument.py
+++ b/lisainstrument/instrument.py
@@ -204,7 +204,7 @@ class Instrument:
         self.telemetry_downsampling = int(telemetry_downsampling)
         self.telemetry_dt = self.dt * self.telemetry_downsampling
         self.telemetry_fs = 1 / self.telemetry_dt
-        self.telemetry_size = self.size // self.telemetry_downsampling
+        self.telemetry_size = int(np.ceil(self.size / self.telemetry_downsampling))
         self.telemetry_t = \
             self.telemetry_t0 + np.arange(self.telemetry_size, dtype=np.float64) * self.telemetry_dt