49 



Specifications for the RS-7 systems are as follows: 



System Accuracy (RMS error as % of slant range) 



Precision Position Mode: less than 1% of slant range. 

 Acquire Mode: Offsets up to 50% of vertical separations (VS) , 



less than 2% of slant range. Offsets up to 100% of VS , less 



than 3% of slant range. 

 Precision Mode, Differential Operations: less than 0.5% of slant 



range. 

 Acquire Mode, Differential Operations (relative position of two 



subsea beacons): Offsets up to 50% of VS, less than 2% of slant 



range. Offsets up to 100% of VS , less than 3% of slant range. 



RS/902 System - The RS/902 system is used by Taylor Diving and Salvage Company 

 and Ocean Systems, Inc. Shipboard components of the system consist of a 

 hydrophone, signal processor, vertical reference unit and a display console. 

 Sub-surface components consist of an acoustic beacon mounted on the vehicle 

 and a second bottom - or hardware - mounted beacon (optional) for vehicle 

 tracking relative to a sub-surface reference point. 



The beacon is composed of a rechargeable battery-pack, signal-generating 

 electronics and a transducer. The transducer converts the beacon's electronic 

 signals to acoustic pulses, which are then transmitted through the water to 

 the hydrophone. Standard beacon types include floating and hardmounted models; 

 both come with a variety of battery configurations. The hydrophone receives 

 the acoustic signals from the subsea beacon, converts them to equivalent electrical 

 signals, and conditions them for transmission to the signal processor. The 

 hydrophone contains a multisensor array, preamplifiers, and other signal- 

 conditioning electronics. These components are packaged in a watertight 

 housing, allowing the hydrophone to be mounted on the hull of the surface 

 vessel below the waterline. The signal processor calculates the vessel's 

 position for presentation on the CRT display. The processor includes two 

 receivers, a microcomputer, CRT controller, system power supplies, and A/D 

 and D/A interface and timing circuitry. These components are contained in 

 a NEMA-type, drip-proof enclosure. A 17-slot card cage holds the circuit 

 cards. The vertical reference unit (VRU) consists of pitch-and-roll sensors 

 which provide vessel attitude information. The microcomputer uses the vessel's 

 pitch-and-roll angle at the moment the position measurement is taken to adjust 

 the apparent position calculations. The display console contains a single 

 digital CRT for both graphic and alphanumeric data display, together with 

 keyboards for system setup and operation. The basic controls consist of eight 

 variable- function keys along the bottom of the CRT. During system setup 

 and operation, the microcomputer assigns functions to these keys, displaying 

 the appropriate labels on the CRT directly above the keys. As the operator 

 selects a task, the computer changes the key labels on the CRT to reflect 

 the next set of choices that the operator is to make. It also prompts the 

 operator with a brief message concerning the next step - for example , SELECT 

 DATA DISPLAY. 



The RS/902 is an ultrashort-baseline position-reference system. This means' 

 that it requires only one free-running subsea beacon and one shipboard hydro- 

 phone to determine the position of a vessel. The system uses a phase-comparison 

 position- measurement technique. With this method, the beacon transmits a short 



