Set a priori clock model.            SET_ACM    05/10/98
                       ~~~~~~~~~~~~~~~~~~~~~~~~~

     A priori clock model should be applied to theoretical in the case when
contribution of clocks exceeds 0.0001 sec. SET_ACM provides user interface
for displaying values of a priori clock model, adding new parameters of 
a priori clock model for specified station, deletion parameters of a priori
clock model for those stations where it has been applied.

     Command synopsis:

(A)  Add parameters of a priori clock model for a station where it has not 
     been already applied.

(D)  Delete a priori clock model for a station where it has been already 
     applied.

(H)  Look at on-line help file.

(O)  Quit SET_ACM without saving changes in a priori clock model.

(S)  Quit SET_ACM after saving changes in a priori clock model.

(R)  Refresh screen.

     How to use SET_ACM

1. To add a priori clock model the for certain station we hit A. SET_ACM asks
   us the letter-code of the station. Type letter code. Typing <Enter> causes
   abort of the operation. Then we should enter the value of clock offset
   NB: in seconds!! This value will be added to theoretical delay. Thus, if
   we noticed on listing of our preliminary solution that clocks of NY ALESUND
   had adjustments 179823473.222 ns we should enter this value in seconds
   (or something near to it) with the same sign. For example: 0.17982
   Typing <Enter> causes abort of the operation. Then SET_ACM asks us to enter 
   a priori clock rate. NB: in sec/sec!! If we don't need it we should enter 
   0, since typing <Enter> with empty input causes abort of the operation. 

2. If we need delete a priori clock model for a certain site we enter D
   and then SET_ACM asks as letter-code of the station. SET_ACM asks us
   a confirmation of the operation before deletion. To confirm it we should 
   type Y

3. If we need change a priori clock model for a certain station we should 
   firstly delete model and then add it again.

4. To apply a priori clock model to theoretical delays and rates we should
   hit S. Hitting O causes leaving SET_ACM without saving update of a priori
   clock model. Applied values of a priori clock model are printed at the
   header of spool file. These values are stored in database when we make
   its update. They are read by SDBH when the database or superfile is read.


   RESTRICTIONS:

1) We are able to apply a priori clock model for only 4 stations in one 
   session.

2) Clock offset should not exceed by modulo 100.0 seconds.

3) Clock rate should not exceed by modulo 1.d-3 sec/sec.