Update error codes for HK table interpolation

interpol_param.pro

 function interpol_param, table, par_name, date, empty_params = empty_params
 	if not keyword_set(empty_params) then empty_params = !null
 	s = where(table.par_name eq par_name, n)
-	if n eq 0 then return, 0.0
+	if n eq 0 then begin
+		journal, 'Error 01: parameter not found in house-keeping table.'
+		journal
+		exit, status = 1
+	endif
+	if n eq 1 then begin
+		journal, 'Error 02: insufficient number of parameter values in house-keeping table.'
+		journal
+		exit, status = 2
+	endif
 	par_time = table.gen_time[s]
 	par_val = table.eng_val[s]
 	par_date = dblarr(n)
@@ -15,10 +24,13 @@ function interpol_param, table, par_name, date, empty_params = empty_params
 	par_date = par_date[s]
 	jul_date = date_conv(date, 'JULIAN')
 	if jul_date ge min(par_date) and jul_date le max(par_date) then value = interpol(float(par_val), par_date, jul_date) else begin
-		; value = 0.0
-		journal, 'Error 01: parameter not found in house-keeping dump table.'
+		journal, 'Error 02: insufficient number of parameter values in house-keeping table.'
 		journal
 		exit, status = 1
 	endelse
-	if finite(value) then return, value else return, 0.0
+	if finite(value) then return, value else begin
+	  	journal, 'Error 03: interpolation of HK parameter ' + par_name.trim() + ' failed.'
+		journal
+		exit, status = 3
+	endif
 end