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FIGURE 3: Finite State Automaton For DCP Message Analysis 
such as the message standards which are used to transfer both 
orbit prediction and status of the Ground Station receivers from 
the Satellite Control Center. The automaton designed for that 
purpose is independent of the automaton presented in FIGURE 
3. In that case, because the logical channel is the same for both 
messages, only one automaton was designed to analyze both 
messages formats. 
Whenever a new format message has to be treated by the 
SCMCD and the original site of the message does not match a 
logical channel already in use, the implementation of such 
aggregation requires only the problem modeling to a new finite 
state automaton, without any modification in the format 
analysis previously implemented. ^ Otherwise, some 
modifications have to be done in the decision table previously 
implemented in order to enable the existing automaton to 
distinguish the additional formats being received by the same 
logical channel. 
136 
5. CONCLUSIONS 
With this technique, the software SCMCD is already prepared 
to support the automatic acquisition of other kinds of DCP 
message formats. It is only necessary to work on the software 
analysis in order to model the message format problem using a 
finite state automaton. That work is followed by the mapping of 
the automaton in the decision table and further by the 
aggregation of such data structure to the software. 
Message features such as fix length and end of message field 
are very helpful for the message format analysis. These kind of 
messages might be modeled in a very simple finite state 
automaton. For instance, the finite state automaton designed to 
analyze the format of both the orbit prediction and status of the 
Ground Station receivers messages has only 3 states, 5 events 
and 6 actions. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B1. Vienna 1996 
  
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