diff --git a/app.py b/app.py
index 6aa37cf..cec9f8c 100644
--- a/app.py
+++ b/app.py
@@ -52,7 +52,7 @@ def doppler():
     satellite = ephem.readtle(sat, sat_line_1, sat_line_2)
     print(str(pass_time) + " " + str(local2utc(pass_time)))
     shift_array = []
-    while pass_time < departure_time:
+    while pass_time < departure_time + timedelta(seconds=2):
         AZ, EI, SHITF_UP, SHIFT_DOWN, DIS = head.CAL_DATA(
             satellite, sat_line_1, sat_line_2, float(lng), float(lat),
             float(alt), local2utc(pass_time),