Prepare for 2025 solar activity

The DP equipment class 2 vessel is fitted with six position references systems, three DGNSS, two HPR and one laser based. At the time of the DP Incident the vessel was employed in subsea operations with two ROVs and a deck crane and operating with only two DGNSS position references systems selected into the DP control.

Late one evening the DPO noted instability of the DGNSS differential signal and shortly after DGNSS 1 and 2 both dropped out of DP control. When the systems were accepted back into DP control the vessel had made a 30m uncontrolled movement.

This was not however an isolated event and over the next four-month period whilst the vessel was engaged on that specific project the DPOs regularly experienced unstable DGNSS differential signals between the hours of 18:30hrs and 22:45hrs. On occasions the vessel was left in a dead reckoning mode for several minutes, therefore after consideration and a risk assessment being undertaken the vessel had to suspend all critical operations during these hours.

Both DGNSS receivers were of the same type and model. The OEM was contacted, and the support team clarified that the issues they were experiencing were caused by excessive ionospheric disturbances in the area – scintillation.

Initial recommendation to switch one DGNSS receiver to another correction service provided a short-lived response until ionospheric activities increased further and then both satellite correction services were both affected again.

The next step was for the vessel to upgrade the receivers to the most up to date model, which has been designed to track not only GPS and GLONASS, but also Galileo and BeiDou constellations, and is also capable of receiving signals on L2, L3 and L5 frequencies, thus the impact of ionospheric jamming could be reduced.

Four months after the receiver upgrades the vessel witnessed two simultaneous GNSS losses, due to satellite dropout. On this occasion the vessel-maintained position on the remaining position reference system GNSS 3, which was a different manufacturer. The vessel sought advice from the OEM and subsea operations were suspended until stable GNSS positions could be maintained.

Following the most recent DP incident, the OEM of GNSS 1 & 2 were contacted and solar interference was again confirmed as the problem for the dropouts and that many other vessels operating in the same area were also experiencing technical problems.

Having already upgraded the hardware of the two receivers the OEM support advised the update of firmware and Quantum software in both GNSS receivers. Following the updates, final checks and tuning were completed along with DP checklists and the vessel was able to resume the subsea operations.