From wlee@stout.atd.ucar.edu  Thu Sep 28 13:14:07 1995
From: wlee@stout.atd.ucar.edu (Wen Chau Lee)


Subject: VORTEX ELDORA message #4


                         VORTEX ELDORA MESSAGE #4

	This message concerns the long waited VORTEX ELDORA navigation
corrections.  The correction factors will be given in three groups which
correspond to two system parameter changes during the experiment.  The
correction factors in each period, in theory, should be the same.  However,
some individual variability still exists. The technique to obtain these
corrections can be found in Testud et al. (1995) August issue of the 
Journal of Atmospheric and Oceanic Technology.  A Fortran program to 
calculate these corrections is available from RSF upon request.

	The following parameters (drift, pitch, ground speed, aircraft
altitude) should be the same for the fore and aft radars while the rests
(range delay, rotation angle, and tilt angle) can be different for the
fore and aft radars.  All other parameters that mentioned in the paper 
but not included here are very small and can be ignored.
	
	The drift and ground speed are still the most uncertain parameters.
All days except 5/12/95 were computed using data from the calibration leg
at the beginning of the flight.  These days possess a relative small drift
corrections. On 5/12/95, the calculation was done on the return leg due to
unusable velocities at the beginning of the flight.  The drift angle correction
is large.  This is not surprising because the accuracy of the INS drift
degrades with time, especially with each turn.  During VORTEX, the flight
pattern normally contained numerous turns in both the clear air mode and
convective mode.  Therefore, the drift corrections listed here are only
served as a reference.  If your data is near the end of a mission, the
drift correction can be quite different. All other parameters should be
stable for the entire flight. 

	The following table contains my best estimates of the correction
factors for each day. I am still working on a few days (4/19/95, 5/22/95
and 5/31/95) and will announce those in a few days.   

	Enjoy ELDORA data.

Wen-Chau Lee

                           NAVIGATION CORRECTIONS FOR VORTEX ELDORA FLIGHTS

                                  PERIOD I (4/17/95 - 5/2/95)
    DATE  RANGEF  RANGEA     ALT  GRDSPD   PITCH   DRIFT    ROTF    ROTA   TILTF   TILTA
  950417   107     104     -0.04   0.0     -1.60   -0.21    1.14   -0.88   -0.20    0.30
  950430   140     150     -0.04   0.0     -1.5    -0.21    1.0    -1.1    -0.2     0.3
                                  PERIOD II (5/6/95 - 5/12/95)
    DATE  RANGEF  RANGEA     ALT  GRDSPD   PITCH   DRIFT    ROTF    ROTA   TILTF   TILTA 
  950506   100     100     -0.04   0.40    -1.50   -0.1     2.40   -1.20   -0.20    0.30
  950507   170     160     -0.03  -0.8     -1.40   -0.1     2.70   -1.0    -0.2     0.3
  950512   130     125     -0.04   0.0     -1.40   -1.4     2.70   -0.90   -0.20    0.3
                                  PERIOD III (5/16/95 - 6/8/95)
    DATE  RANGEF  RANGEA     ALT  GRDSPD   PITCH   DRIFT    ROTF    ROTA   TILTF   TILTA 
  950516   138     101     -0.04   0.14    -1.36    0.05    0.54    1.10   -0.20    0.30
  950517   138     101     -0.04   -0.2    -1.36   -0.4     0.54    1.10   -0.20    0.30
  950527   130     140     -0.04  -1.2     -1.35   -0.3     0.6     1.2    -0.2     0.3
  950602   111     115     -0.04  -0.30    -1.34   -0.12    0.71    1.25   -0.20    0.30
  950603    42      45     -0.02  -0.40    -1.35   -0.23    0.66    1.19   -0.20    0.30
  950608   140     119     -0.03  -0.50    -1.30   -0.26    0.78    1.32   -0.20    0.30