Event S59. In SWellEx-96 Experiment Acoustic Data

Event S59, like Event S5, is a source tow along an isobath during the SWellEx-96 Experiment. However, unlike Event S5, Event S59 contains a loud interferer. This event is particularly useful for investigating the effects of a loud interferer on detecting/localizing a quiet target. The source ship (R/V Sproul) began its track between and slightly east of the two HLA's and traveled at a speed of 5 knots (2.5 m/s) roughly northward along the 180 m isobath. During the last 25 minutes of the event, the tow ship bears to port and completes a loop. The interferer of interest began west of the all of the arrays, proceeded southeast and between the two HLA's, and ended east of the arrays. A radar system aboard the R/P FLIP was videotaped, providing ranges and bearings between the interferer and the four arrays. Sources Two sources were simultaneously towed by the R/V Sproul: a "deep" source (J-15) and a "shallow" source (J-13); see component, “S59 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. 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, “S59 source frequencies”. As mentioned in the previous section, the interferer's position relative to the arrays can be determined using radar data and the program "geod." Aside: From the center of the HLA North array, the R/P FLIP is at a range of 1.9 km and at a bearing of 5 degs east of True North. Using the radar data, we can find the range and bearing between the interferer and the R/P FLIP (see component “Range and bearing between interferer and R/P FLIP”). Using the "geod" program, the above information, and the a priori knowledge of FLIP's position, the latitude and longitude of the interferer can then be calculated. Similarly, the range and bearing from the interferer to the HLA North array can be computed (see component “Range and bearing between interferer and HLA North”). Sensors All four arrays (VLA, TLA, HLA North, and HLA South) recorded the full 65-minute event. The start time of Event S59 is J134, 11:45 GMT and it ends at J134, 12:50 GMT. Note: Day J134 corresponds to 5/13/96. Environment On J134, four CTDs were taken on the R/V LaSalsa. Of these, CTD #20 was the closest spatially (32d40.60' N 117d22.20' W) and temporally (13 May, 16:18 GMT) to the S59 Event. This sound speed profile has a weak mixing layer (~5 m) over a strongly downward refracting layer to about 40 m. The remainder of the profile is essentially isovelocity to the seafloor. 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 S59 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”.

事件S59与事件S5类似，均为SWellEx-96实验中沿等深线拖曳声源的实验。但与事件S5不同的是，事件S59包含一个强干扰源。该事件尤其适用于研究强干扰源对弱目标探测与定位的影响。

声源船（R/V Sproul）在两个HLA之间略偏东的位置开始其航行轨迹，以5节（2.5 m/s）的速度沿180米等深线大致向北航行。在该事件的最后25分钟，拖曳船向左舷转向并完成一个环形机动。

目标干扰源始于所有阵列的西侧，向东南方向航行并穿过两个HLA之间的区域，最终停留在阵列东侧。R/P FLIP船上的雷达系统进行了视频记录，提供了干扰源与四个阵列之间的距离和方位信息。

本次实验由R/V Sproul同时拖曳两个声源：一个"深水声源（J-15）"与一个"浅水声源（J-13）"，详见组件"S59声源频率"。深水声源的拖曳深度约为54米，发射了频率介于49 Hz至400 Hz之间、多种声源级的多个单频音，该单频音组被称为T-49-13。T-49-13单频模式由5组各13个单频音组成，每组13个单频音的频率覆盖范围均为49 Hz至400 Hz。第一组13个单频音以最大电平发射，被称为"高单频组"，其发射声级约为158 dB。第二组单频音的发射声级约为132 dB，后续三组（第三、第四、第五组）的发射声级均较前一组低4 dB。

浅水声源的拖曳深度约为9米，发射了频率介于109 Hz至385 Hz之间的9个频率，该单频组被称为C-109-9S。部分初始后处理采用了所谓的"噪声频率"，即选取代表噪声场的特征频率，相关频率列于组件"S59声源频率"中。

如前文所述，可利用雷达数据与"geod"程序确定干扰源相对于阵列的位置。补充说明：以HLA北阵列的中心为原点，R/P FLIP的距离为1.9 km，方位为真北偏东5度。借助雷达数据，可获取干扰源与R/P FLIP之间的距离和方位（详见组件"干扰源与R/P FLIP的距离及方位"）。结合上述信息与FLIP位置的先验知识，通过"geod"程序即可计算得到干扰源的经纬度。同理，也可计算得到干扰源至HLA北阵列的距离与方位（详见组件"干扰源与HLA北阵列的距离及方位"）。

传感器与事件时长
四个阵列（VLA、TLA、HLA北阵列与HLA南阵列）均完整记录了整场持续65分钟的事件。事件S59的开始时间为世界时J134的11:45，结束时间为J134的12:50。注：J134对应1996年5月13日。

环境部分
1996年5月13日，科研船R/V LaSalsa完成了四次CTD（温盐深剖面仪，Conductivity Temperature Depth）测量。其中，CTD #20在空间位置（32°40.60' N，117°22.20' W）与时间（1996年5月13日16:18 GMT）上均最接近事件S59的发生时段。该声速剖面存在一层厚度约5米的弱混合层，其下方为厚度约40米的强负折射层，剖面剩余部分基本为等声速层直至海底。声速数据经过了盐度尖峰剔除处理，并以每0.5米为间隔进行了深度插值。地声参数源自测深与粒度数据库。如需了解波导参数的更多细节，请查看合集条目"环境数据（1996-05-10至1996-05-18）"。

声源至接收器距离部分
已针对事件S59的每一分钟，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-接收器距离以及用于计算此类数据的MATLAB M文件的压缩包，请选择组件"声源-接收器距离数据"。总结该数据的图表见"声源-接收器距离数据绘图"。

GPS数据部分
R/P FLIP（VLA位置）与R/V Sproul（声源位置）的原始GPS数据均已提供。在R/P FLIP船上，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FLIP的GPS信息。在R/V Sproul船上，两套GPS系统记录了声源拖曳船的GPS信息：MicroMariner系统的记录时段为1996年5月10日至1996年5月15日GMT，PCode系统的记录时段为1996年5月11日至1996年5月15日GMT。如需下载包含所有GPS数据的压缩包，请选择组件"GPS数据"。