/**
  * Check if observation time is valid, by comparing it with the transmission time.
  *
  * @return
  */
 public boolean isObservationTime() {
   if (observationTime == null) {
     return false;
   }
   if (transmissionTime != null) {
     return !observationTime.isEqual(transmissionTime);
   } else {
     return true;
   }
 }
 /**
  * Check if analyse time is valid, by comparing it with the transmission time.
  *
  * @return
  */
 public boolean isAnalyseTime() {
   if (analyseTime == null) {
     return false;
   }
   if (transmissionTime != null) {
     return !analyseTime.isEqual(transmissionTime);
   } else {
     return true;
   }
 }