per day check using an A4 XBT test box provides a quick 

 indication of incipient launcher leakage before it becomes 

 severe enough to affect system accuracy." 



The preceding should be standard operating procedure for all users of Sippican's XBT 

 systems. If this is not possible, independent surface measurements should be made 

 simultaneously with each XBT profile. These measurements may be used to check whether 

 an XBT system is properly functioning. 



• Enter the identification number of the XBT probe carton on the XBT log. 



• When it is recognized that a system has malfunctioned while making 

 measurements, keep the configuration of that system intact. The Sippican Corp 

 should be contacted promptly after the vessel returns to port, so that the cause of the 

 system malfunction can be investigated. 



• Modify the XBT system to include a depth sensor that would measure a single 

 depth independent of the drop time and provide an indication of this depth on the analog 

 record. This measurement could be used to correct for depth bias. 



• Develop a method or technique for identifying visually acceptable but gradient- 

 biasing XBT profiles before they are used in any application and before they are archived. 



• Investigate possible reasons why an XBT system can malfunction and still record 

 visually acceptable but erroneous profiles. Once the reason, or reasons, are identified, 

 modify the XBT system to ehminate the causes. 



