Friday, July 20, 2007

WebExclusive: EPIRBs and the s/v Sean Seamour II - Part II

This is the second in a series of reports on the "reported" malfunction of the ACR 406 Rapidfix EPIRB that was used by the s/v Sean Seamour II when the sailboat ran in trouble during Subtropical Storm Andrea.

I say "reported" malfunction becuase as of this writing, no scientific or technical review has been completed. But we do know that something did in fact go wrong with the EPIRB.

In my last post we reviewed a statement from the Master of the s/v Sean Seamour II of what the crew experienced with one of two EPIRBs.

We reviewed what a EPIRB is and how it operates. Today we will visit how it communicates with satellites and how the satellites communicate with rescue personnel. It is important to understand what the system is and how it operates before we jump into the problem encountered by the crew of the s/v Sean Seanour II. No matter what the problem with the Sean Seamour II's EPIRB was. The system is a very valuable asset to the maritime and rescue community. Here are some statistics on just what this system has done.

To date according to COSPAS-SARSAT the system as of: June 29, 2007, the system is responsible for the rescue of 190 persons in the United States.

The breakdown is as follows:
Rescues at sea: 147 people rescued in 43 incidents. Aviation rescues: 14 people rescued in 11 incidents. PLB rescues: 29 people rescued in 14 incidents . Worldwide – Over 20,300 People Rescued (since 1982). United States – 5,586 People Rescued (since 1982). As you can see the system is extremely valuable.

So lets let NOAA Satellite Information Services explain the "search and rescue satellites".

Low-Earth Orbiting Search And Rescue (LEOSAR) Satellites

The keystone to the Cospas-Sarsat System are the low-earth orbiting (LEO) satellites from which the system takes its name. These satellites provide the ability to detect and locate 406 MHz alerts worldwide and 121.5 MHz alerts for about sixty percent of the world.

SARSAT is an instrument package flown aboard the NOAA series of environmental satellites operated by NOAA's National Environmental Satellite, Data and Information Service (NESDIS). These satellites orbit at an altitude of 528 miles and complete an orbit every 100 minutes. Their orbits are inclined 99 degrees from the equator. Typically, each satellite monitors the earth for various weather and climate data. Yet, each satellite also carries a Search and Rescue Repeater (SARR) which receives and retransmits 121.5 MHz, 243 MHz, and 406 MHz signals anytime the satellite is in view of a ground station. Also carried is a Search and Rescue Processor (SARP) which receives 406 MHz transmissions, provides measurements of the frequency and time, then retransmits this data in real-time and stores it aboard for later transmission. The satellite also stores each 406 MHz signal it receives and continuously downloads this data for up to 48 hours ensuring ground stations around the world receive it. That is, if the satellite was not in view of a ground station when it received a beacon signal, the next ground station that sees that satellite views will receive the data. This provides global coverage for 406 MHz distress signals. The SARR is provided by the Canadian Department of National Defence and the SARP is provided by the French Center National D'Etudes Spatiales (CNES).

The COSPAS instrument is carried aboard the NADEZHDA navigation satellite orbiting the Earth every 105 minutes at an altitude of 620 miles and an orbital inclination of 83 degrees. The COSPAS instrument was built by the former Soviet Union and continues to be operated by the Russian Federation. The only major difference between COSPAS and SARSAT is that the Russian satellites do not receive 243 MHz distress signals.

Geostationary Orbiting Search And Rescue (GEOSAR) Satellites

View from GOES-8As you can see from this image taken today from GOES-East, geostationary satellites are capable of continually viewing large areas of the Earth. These geostationary (GEO) satellites are also able to provide immediate alerting and identification of 406 MHz beacons. The GEO satellites are not able to use Doppler location processing since they have no relative motion between them and the emergency beacons. Therefore, they are not able to determine a location for a beacon. They can, however, provide immediate alerts. This is a valuable tool for SAR personnel since it allows them to begin their initial verification of the alert using the National 406 MHz Beacon Registration Database. Often this detective work yields a general location of the vessel or aircraft in distress and SAR assets can be readied or dispatched to that general area. Ideally, a SARSAT or COSPAS (LEO) satellite will fly over the beacon within the next hour and calculate a Doppler location which will be given to the SAR personnel who may already be enroute.

There is also one significant advantage with the GEOSAR constellation and that is the ability to use a GPS receiver with a 406 MHz beacon. Here’s how it works: specially made emergency beacons determine their location using a GPS receiver that is either integrated into the beacon (called a location protocol beacon) or fed by an external GPS receiver. This accurate location information (generally around a football field in size for positional accuracy) is then encoded into the 406 MHz signal that is transmitted by the beacon. The USMCC then receives that signal with the location and notifies the RCC accordingly. This information can often be derived in a matter of minutes! Since every second counts in reaching the scene of a distress this means that there is an increased chance of survival.

Without a doubt, the early warning capability of the GEOSAR constellation provides a valuable tool to increase the effectiveness of the Cospas-Sarsat system and, ultimately, save more lives ; First, a GPS-equipped beacon only works when the receiver has a clear view of the sky in order to permit the receiver to self-locate. Often times, conditions do not permit this which may either distort the positional accuracy or negate it altogether. Because of this, the Cospas-Sarsat System relies upon the Doppler locating effect as the primary means for locating a beacon. This process is able to overcome the limitations of a GPS unit and still generate a fairly accurate location…within a mile for positional accuracy. Secondly, the GEOSAR component only works if the beacon is registered with NOAA. Without registration, the RCCs are unable to react as quickly…and ultimately this may delay a SAR response should you be in an emergency. If you have a 406 MHz beacon and have not registered it, please do so by clicking here to access the National 406 MHz Registration Database.

For further information visit NOAAs Low-Earth Orbiting Search And Rescue (LEOSAR) Satellites page.

As you can see ther system has come a very long way since 1982 and it has experienced it share of problems. I am sure it will continue to have its problems while NOAA and
COSPAS-SARSAT continue its advances. It is my hope that these clitches are limited and without loss of life.

In Part III, we will go back to the future and visit with the pre-trip check of the s/v Sean Seamour II. One maritime note of interest. Thank to Dennis L. Bryant of
Holland & Knight LLP. UK – report on loss of lives due to large waves

The UK Marine Accident Investigation Branch (MAIB) released the joint report of the investigation undertaken by it and the Singapore Maritime and Port Authority (MPA) concerning the loss of two lives and one seriously injured crewmember on a tanker at Scapa Flow in the Orkney Islands on 11 November 2006. The tanker was outbound and four crewmembers were at the bow stowing loose mooring lines. Two large waves shipped over the bow. Three of the crewmembers were swept aft by the waves and incurred serious injuries. Two of the crewmembers died of their injuries. Investigation revealed that the two waves were not abnormal in the prevailing weather conditions. The master should have delayed sailing until the ship was secured for sea. The owners have amended their safety management system to include these recommendations. Report No. 16/2007 (7/18/07).

Have a great weekend!


Previous Posts;

EPIRBs and the s/v Sean Seamour II
NHC Report on Subtropical Storm Andrea
Cheating Death On The High Seas
The s/v Sean Seamour II & The Hatteras Trench
High Sea's Update On Sean Seamour II
The Story of the Sailing Vessel Sean Seamour II