Event S5. In SWellEx-96 Experiment Acoustic Data

Event S5 is a source tow along an isobath during the SWellEx-96 Experiment. During this event, there were no loud interferers present. The source ship (R/V Sproul) started its track south of all of the arrays and proceeded northward at a speed of 5 knots (2.5 m/s). Most of the source tow track occurred in water between 180 and 220 meters deep, with the second half of the tow along the 180 m isobath.

Sources
Two sources were simultaneously towed by the R/V Sproul: a "deep" source (J-15) and a "shallow" source (J-13), see component, “S5 source frequencies”. The deep source was towed at a depth of about 54 m. It transmitted numerous tonals of various source levels between 49 Hz and 400 Hz. This tonal set is known as T-49-13. The T-49-13 tonal pattern consists of 5 sets of 13 tones. Each set of 13 tones spans the frequencies between 49Hz and 400Hz. The first set of 13 tones is projected at maximum level and is referred to as the "High Tonal Set." These tones are projected with transmitted levels of approximately 158 dB. The second set of tones are projected with levels of approximately 132 dB. The subsequent sets (3rd, 4th, and 5th) are each projected 4 dB down from the previous set. Aside: At the beginning, midway point, and end of the track, the deep source stopped projecting CW tones and started projected FM chirps. The shallow source was towed at a depth of about 9m. It transmitted 9 frequencies between 109 Hz and 385 Hz, known as the C-109-9S tonal set. Some initial post-processing utilized so-called "noise frequencies." Those frequencies chosen to be representative of the noise field are listed in the component, “S5 source frequencies”.

Sensors
The vertical array (VLA) and tilted array (TLA) both recorded the full 75 minute event, while the two horizontal arrays (HLA North and South) recorded only the last 50 minutes. For the VLA and TLA, the start time of Event S5 is J131, 23:15 GMT. The HLA data begins at J131, 23:40 GMT. Note: Day J131 corresponds to 5/10/96.

Environment
A sound speed profile was generated from a local CTD cast, file "i9606.prn" located in the “CTD data” component of the collection item, “Environment data (1996-05-10 to 1996-05-18).” The downcast from Station 6 was obtained on 10 May 1996 from 21:05 to 21:21 PST, located at 117d22.11’W, between 32d39.12’N to 32d38.73’N. Alternatively, the CTD cast from Station 5, file "i9605.prn," would be an even more appropriate choice due to its temporal and spatial proximity to the source tow event. The sound speed data was salinity-despiked and depth-interpolated to every half meter. The geoacoustic parameters were derived from a database of soundings and grainsizes. For more details on waveguide parameters, view the collection item, “Environment data (1996-05-10 to 1996-05-18).”

Source-to-Receiver Range
Ranges from the towed source to the various receiving arrays have been calculated for each minute of the S5 Event and are available here. To download a tarball containing source position, source-to-receiver ranges, and a MATLAB M-file for calculating such, select the component, "Source-to-receiver range data". A figure summarizing that data is shown in “Plot of source-to-receiver range data”.

GPS
The raw GPS data is also available for both the R/P FLIP (VLA location) and the R/V Sproul (source location). Onboard the R/P FLIP, a differential GPS system recorded GPS information for FLIP from 5/8/96, 16:52 GMT to 5/19/96, 15:00 GMT. Onboard the R/V Sproul, two GPS systems recorded GPS information for the source tow ship: a MicroMariner system recorded from 5/10/96 to 5/15/96 GMT, and a PCode system recorded from 5/11/96 to 5/15/96. To download a tarball containing all of the GPS data, select the component, "GPS data".

S5事件是SWellEx-96实验中沿等深线（isobath）拖曳声源的一次实验过程。本次实验期间无强干扰源存在。声源船（R/V Sproul）从所有水听器阵列以南的位置开始航行，以5节（2.5 m/s）的速度向北行进。其拖曳声源的航迹大部分处于水深180至220米的海域，后半段航迹沿180米等深线布设。

声源：R/V Sproul同时拖曳了两台声源：分别为"深水源"（J-15）与"浅水源"（J-13），详见组件"S5声源频率"。深水源的拖曳深度约为54米，发射了频率覆盖49 Hz至400 Hz、声源级各异的多组单频信号，该单频信号组被命名为T-49-13。T-49-13单频信号组包含5组、每组13个单频信号，每组信号的频率跨度均为49 Hz至400 Hz。第一组13个单频信号以最大功率发射，被称为"高单频组"，其发射声源级约为158 dB；第二组信号的发射声源级约为132 dB；后续三组（第三、第四、第五组）的发射声源级相较于前一组依次降低4 dB。补充说明：在航迹的起始、中途及终点位置，深水源会停止发射连续波（Continuous Wave, CW）单频信号，转而发射调频（Frequency Modulation, FM）线性扫频信号。浅水源的拖曳深度约为9米，发射了频率覆盖109 Hz至385 Hz的9个单频信号，该信号组被称为C-109-9S单频组。部分早期后处理工作使用了所谓的"噪声频率"，即能表征噪声场特征的选定频率，相关频率列表详见组件"S5声源频率"。

传感器：垂直阵列（Vertical Line Array, VLA）与倾斜阵列（Tilted Line Array, TLA）均完整记录了此次时长75分钟的事件，而两台水平阵列（北水平阵列HLA North与南水平阵列HLA South）仅记录了最后50分钟的数据。对于VLA与TLA而言，S5事件的起始时间为格林尼治标准时间J131日23:15；HLA的数据起始时间为格林尼治标准时间J131日23:40。注：J131日对应1996年5月10日。

环境：声速剖面由当地温盐深仪（Conductivity-Temperature-Depth, CTD）投放数据生成，对应文件为"i9606.prn"，该文件收录于集合项"环境数据（1996-05-10至1996-05-18）"的"CTD数据"组件中。6号站位的下行投放数据采集于1996年5月10日太平洋标准时间21:05至21:21，站位坐标为西经117°22.11′、北纬32°39.12′至32°38.73′。另有5号站位的CTD投放数据文件"i9605.prn"，由于其在时空维度上更接近本次声源拖曳实验，因此是更为合适的参考数据。声速数据已进行盐度尖峰剔除处理，并以0.5米为步长进行深度插值。地声参数由测深与粒径数据库推导得到。如需了解波导参数的更多细节，请查看集合项"环境数据（1996-05-10至1996-05-18）"。

声源-接收阵距离：针对S5事件的每分钟时刻，已计算得到拖曳声源至各接收阵列的距离数据，可在此处获取。如需下载包含声源位置、声源-接收阵距离以及用于计算此类数据的MATLAB M文件的tar压缩包，请选择组件"声源-接收阵距离数据"。该数据的汇总图示详见"声源-接收阵距离数据绘图"。

GPS数据：R/P FLIP（垂直阵列部署位置）与R/V Sproul（声源船）的原始GPS数据均已公开。在R/P FLIP平台上，差分GPS系统记录了1996年5月8日16:52 GMT至1996年5月19日15:00 GMT期间的FLIP定位信息。在R/V Sproul船上，两套GPS系统记录了声源船的定位信息：一套MicroMariner系统的记录时段为1996年5月10日至5月15日GMT，另一套PCode系统的记录时段为1996年5月11日至5月15日GMT。如需下载包含全部GPS数据的tar压缩包，请选择组件"GPS数据"。