model{

  ## Likelihood ##
      for( i in 1 : Nbobs ) {
    
      M[i] ~ dnorm(theta, prec.obs[i])
      
      prec.obs[i] <- 1/(s[i]*s[i])
      
      }
      
  ## Prior distribution of the date of interest ##  
      theta ~ dunif(ta,tb)
      
}
