diff --git a/src/algorithms/telemetry_decoder/gnuradio_blocks/galileo_telemetry_decoder_gs.cc b/src/algorithms/telemetry_decoder/gnuradio_blocks/galileo_telemetry_decoder_gs.cc
index 80a94aab0..991fb6895 100644
--- a/src/algorithms/telemetry_decoder/gnuradio_blocks/galileo_telemetry_decoder_gs.cc
+++ b/src/algorithms/telemetry_decoder/gnuradio_blocks/galileo_telemetry_decoder_gs.cc
@@ -465,6 +465,8 @@ void galileo_telemetry_decoder_gs::decode_INAV_word(float *page_part_symbols, in
                 }
             this->message_port_pub(pmt::mp("telemetry"), pmt::make_any(tmp_obj));
             d_first_eph_sent = true;  // do not send reduced CED anymore, since we have the full ephemeris set
+
+            d_flag_osnma_ephemeris = true;
         }
     else
         {
@@ -514,6 +516,8 @@ void galileo_telemetry_decoder_gs::decode_INAV_word(float *page_part_symbols, in
                               << d_satellite << " with CN0=" << std::setprecision(2) << cn0 << std::setprecision(default_precision)
                               << " dB-Hz" << TEXT_RESET << std::endl;
                 }
+
+            d_flag_osnma_iono_and_time = true;
         }
 
     if (d_inav_nav.have_new_utc_model() == true)
@@ -549,6 +553,8 @@ void galileo_telemetry_decoder_gs::decode_INAV_word(float *page_part_symbols, in
 
             d_delta_t = tmp_obj->A_0G + tmp_obj->A_1G * (static_cast<double>(d_TOW_at_current_symbol_ms) / 1000.0 - tmp_obj->t_0G + 604800 * (std::fmod(static_cast<float>(d_inav_nav.get_Galileo_week() - tmp_obj->WN_0G), 64.0)));
             DLOG(INFO) << "delta_t=" << d_delta_t << "[s]";
+
+            d_flag_osnma_utc_model = true;
         }
 
     if (d_inav_nav.have_new_almanac() == true)
@@ -584,7 +590,9 @@ void galileo_telemetry_decoder_gs::decode_INAV_word(float *page_part_symbols, in
             DLOG(INFO) << "d_nav.WN_0=" << d_inav_nav.get_Galileo_week();
         }
 
-    if (d_band == '1' && d_inav_nav.have_new_nma() == true)
+    // get osnma message if the needed nav data is available
+    auto adkd_4_12_nav_data_available = d_flag_osnma_iono_and_time && d_flag_osnma_ephemeris;
+    if (d_band == '1' && d_inav_nav.have_new_nma() == true && adkd_4_12_nav_data_available == true && d_flag_osnma_utc_model == true)
         {
             const std::shared_ptr<OSNMA_msg> tmp_obj = std::make_shared<OSNMA_msg>(d_inav_nav.get_osnma_msg());
             this->message_port_pub(pmt::mp("OSNMA_from_TLM"), pmt::make_any(tmp_obj));
diff --git a/src/algorithms/telemetry_decoder/gnuradio_blocks/galileo_telemetry_decoder_gs.h b/src/algorithms/telemetry_decoder/gnuradio_blocks/galileo_telemetry_decoder_gs.h
index a6391a2e0..bad8c8fc5 100644
--- a/src/algorithms/telemetry_decoder/gnuradio_blocks/galileo_telemetry_decoder_gs.h
+++ b/src/algorithms/telemetry_decoder/gnuradio_blocks/galileo_telemetry_decoder_gs.h
@@ -155,6 +155,9 @@ private:
     bool d_there_are_e1_channels;
     bool d_there_are_e6_channels;
     bool d_use_ced;
+    bool d_flag_osnma_ephemeris; // flag to indicate if the ephemeris is complete for OSNMA processing
+    bool d_flag_osnma_utc_model; // flag to indicate if the GST conversion parameters are complete for OSNMA processing
+    bool d_flag_osnma_iono_and_time; // flag to indicate if the iono correction and time is complete for OSNMA processing
 };
 
 
diff --git a/src/core/system_parameters/galileo_inav_message.cc b/src/core/system_parameters/galileo_inav_message.cc
index 565009dc7..7a500d788 100644
--- a/src/core/system_parameters/galileo_inav_message.cc
+++ b/src/core/system_parameters/galileo_inav_message.cc
@@ -1387,15 +1387,17 @@ OSNMA_msg Galileo_Inav_Message::get_osnma_msg()
     nma_position_filled = std::array<int8_t, 15>{};
     // Fill TOW and WN
     nma_msg.WN_sf0 = WN_0;
-    int32_t TOW_sf0 = TOW_5 - 24;
+    int32_t TOW_sf0 = TOW_5 - 24; // TODO - why not TOW_0?
     if (TOW_sf0 < 0)
         {
             TOW_sf0 += 604800;
         }
     nma_msg.TOW_sf0 = static_cast<uint32_t>(TOW_sf0);
-    // TODO - draft for retrieving NavData for use during Tag verification.
-    nma_msg.t0e_1 = static_cast<uint32_t>(t0e_1);
-    nma_msg.IOD_nav = static_cast<uint32_t>(IOD_nav_1);
+//    nma_msg.TOW_sf0 = static_cast<uint32_t>(TOW_0);
+    // get ephemeris, clock and iono correction datn and GST-UTC and GST-GPS converstion parameters (may be incomplete)
+    nma_msg.EphemerisData = get_ephemeris();
+    nma_msg.IonoData = get_iono();
+    nma_msg.UtcModelData = get_utc_model();
     return nma_msg;
 }
 
diff --git a/src/core/system_parameters/galileo_inav_message.h b/src/core/system_parameters/galileo_inav_message.h
index d6139c7e0..13db80706 100644
--- a/src/core/system_parameters/galileo_inav_message.h
+++ b/src/core/system_parameters/galileo_inav_message.h
@@ -39,7 +39,9 @@ class ReedSolomon;  // Forward declaration of the ReedSolomon class
  * \{ */
 /** \addtogroup System_Parameters
  * \{ */
-
+/*!
+ * \brief This class fills the OSNMA_msg structure with the data received from the telemetry blocks.
+ */
 class OSNMA_msg
 {
 public:
@@ -47,13 +49,15 @@ public:
     std::array<uint32_t, 15> mack{};
     std::array<uint8_t, 15> hkroot{};
     uint32_t PRN{};
-    uint32_t WN_sf0{};
+    uint32_t WN_sf0{}; // TODO - this is present in UtcModelData already
     uint32_t TOW_sf0{};
-    // TODO - NavData to be retrieved correctly
     std::vector<uint8_t> EphemerisClockAndStatusData {};
     std::vector<uint8_t> TimingData {};
-    uint32_t t0e_1{};
-    uint32_t IOD_nav{};
+    Galileo_Ephemeris EphemerisData {};
+    Galileo_Iono IonoData {};
+    Galileo_Utc_Model UtcModelData {};
+
+
 };
 
 /*!