diff --git a/src/mission_constants.hh b/src/mission_constants.hh
index 248411a..f537023 100644
--- a/src/mission_constants.hh
+++ b/src/mission_constants.hh
@@ -5,8 +5,18 @@
 
 
 //*****************************************************************************
-//                                MISSION MODES
+//                          PHYSICS CONVERSION FACTORS
+//*****************************************************************************
+const float DEG_2_RAD = 0.017453292519943295;  // (rad/deg) conversion factor from degrees to radians
+const float RAD_2_DEG = 57.29577951308232;  // (deg/rad) conversion factor from radians to degrees
+const float G_2_MS2 = 9.80665;  // (m/s^2/gee) conversion factor from gee to m/s^2
+
+const float MEGA = 1.0e9;  // (--) SI Mega prefix
+
+//*****************************************************************************
+//                                  MISSION
 //*****************************************************************************
+// Missing modes (controls what happens in the loop)
 enum Mode {
     STARTUP_STABLE = 0,
     NAVIGATION = 1,
@@ -14,6 +24,26 @@ enum Mode {
     SHUTDOWN_STABLE = 3
 };
 
+// timing
+const int COUNTDOWN_WAIT = 10;  // (TODO: units) TODO: what is this?
+const int CALIBRATE_TIME = 0;  // (TODO: units) TODO: what is this?
+
+// TODO: determine what all these are for
+const float fireTBuffer = 0.01*MEGA;  // (TODO: units) TODO: what is this?
+const float fireBuffer = 3276.0/2.0/16.0;  // (m/s^2) ~0.25 TODO: what is this
+const float fireGoal = 0.0;  // -g TODO: what is this?
+
+const float landTBuffer = 0.5*MEGA;  // (TODO: units) TODO: what is this? 
+const float landBuffer = 3276.0/2.0/8.0; // (TODO: units) TODO: what is this?
+const float landGoal = 0.0;  // (TODO: units) TODO: what is this?
+
+// TODO: what are these?
+long fireTime;
+long liftoffTime;
+long landTime;
+bool buffStatus;
+float buffCountDown;
+
 //*****************************************************************************
 //                              HARDWARE-SPECIFIC
 //*****************************************************************************
@@ -29,16 +59,15 @@ const float LSB_LINEAR = 2048.0;  // (milli-gee/LSB) note documentation gives in
  */
 const float LSB_ANGULAR = 131.0;  // (deg/s/LSB) note documentation gives incorrectly inverted units
 
-// TODO: define these quaternions based on IMU installation in rocket
-const float qr_imu_to_body[4] = {1.0, 0.0, 0.0, 0.0};  // (--) right, scalar-first, Hamiltonian quaternion transforming IMU frame to body frame
-const float qr_body_to_imu[4] = {1.0, 0.0, 0.0, 0.0};  // (--) right, scalar-first, Hamiltonian quaternion transforming body frame to IMU frame
+/* These bias calibration values account for sensor bias
+ * in linear acceleration measurements.
+ */
 
 
-//*****************************************************************************
-//                          PHYSICS CONVERSION FACTORS
-//*****************************************************************************
-const float DEG_2_RAD = 0.017453292519943295;  // (rad/deg) conversion factor from degrees to radians
-const float RAD_2_DEG = 57.29577951308232;  // (deg/rad) conversion factor from radians to degrees
-const float G_2_MS2 = 9.80665;  // (m/s^2/gee) conversion factor from gee to m/s^2
+
+// TODO: define these quaternions based on IMU installation in rocket
+const float QR_IMU_TO_BODY[4] = {1.0, 0.0, 0.0, 0.0};  // (--) right, scalar-first, Hamiltonian quaternion transforming IMU frame to body frame
+const float QR_BODY_TO_IMU[4] = {1.0, 0.0, 0.0, 0.0};  // (--) right, scalar-first, Hamiltonian quaternion transforming body frame to IMU frame
+
 
 #endif  // __MISSION_CONSTANTS_HH__
\ No newline at end of file