TECHNOLOGICAL FIELD

An example of the present disclosure relates generally to a bathythermograph buoy and associated method of operation and, more particularly, to a bathythermograph buoy that measures temperature and/or other parameter(s) within an ocean or another body of water and that wirelessly reports information regarding the temperature and/or other parameter(s).

BACKGROUND

It is instructive to know the temperature of a body of water at different depths within the body of water for a variety of different purposes. For example, the temperature within a body of water impacts the speed of sound transmitted through the body of water. As such, measurement of the temperature of the body of water at different depths permits the speed of sound to be more accurately estimated at different depths and, as a result, permits ray trace and propagation models to produce more accurate results regarding the source of sound within the body of water. Additionally, measurement of the temperature of the body of water at different depths may be instructive for environmental monitoring or other applications.

Bathythermograph buoys, also known as bathythermograph sonobuoys, have been developed to measure water temperatures up to a predefined depth, such as 1000, 2000 or 2625 feet. One type of bathythermograph buoy includes an upper unit that remains at the surface of a body of water and a lower unit that descends into the body of water following deployment. For example, the bathythermograph buoy may be launched, such as being dropped from an aircraft or deployed from a surface vessel, with the lower unit then descending into the body of water while the upper unit remains floating upon the surface of the body of water. The upper and lower units of this type of bathythermograph buoy are connected by a cable. As the lower unit descends, the cable is spooled out until the cable reaches its maximum length, such as 2625 feet, at which point the lower unit can descend no further while remaining connected to the upper unit.

The lower unit of this bathythermograph buoy includes a temperature sensor for measuring the temperature of the body of water at different depths. The cable connecting the upper and lower units serves as a wireline link such that temperature readings captured by the temperature sensor of the lower unit may be transmitted from the lower unit to the upper unit via the cable. The upper unit may, in turn, transmit information regarding the temperature readings captured by the lower unit, such as to a receiver onboard an aircraft or surface vessel, such as the aircraft or surface vessel that launched the bathythermograph buoy.

As an example of the transmission of information regarding temperature readings, a sonobuoy that conforms to a designation such as AN/SSQ-36B bathythermograph sonobuoy linearly maps the temperature readings across a range of 28° F. to 95° F. to a tone frequency, which is transmitted by a transmitter carried by the upper unit. For example, the tone frequency f may be related to the temperature reading T as f=800+20T with the tone frequency f being in Hertz (Hz) and the temperature T being in degrees Fahrenheit. With respect to the AN/SSQ-36B bathythermograph sonobuoy, the depth associated with the temperature readings is calculated as a linear function of time with an assumed descent rate, such as an assumed descent rate of five feet per second. In this regard, the temperature sensor of the lower unit may be configured to capture temperature readings at a predefined rate, such as one temperature reading every one second. As such, the initial temperature reading may be determined to be at the surface of the body of water with each subsequent temperature reading being five feet deeper than the preceding temperature reading (as a result of an assumed descent rate of five feet per second). Based upon the temperature of the body of water as measured at different depths by the bathythermograph sonobuoy, the speed of sound at different depths within the body of water may be estimated so as to permit, for example, ray trace and propagation models to more accurately estimate the location of the source of the sound.

While the connection of the upper and lower units by a cable permits the temperature reading to be transmitted from the lower unit to the upper unit via the wireline connection, the cable limits the depth to which the bathythermograph buoy can obtain temperature readings. While depths of 2625 feet may be sufficient for some applications, it may be desirable in other applications to measure the temperature within a body of water at deeper depths than those allowed by bathythermograph buoys having upper and lower units connected by a cable. Further, the connection of the upper and lower units by a cable may cause the bathythermograph buoy to have a larger volume than is desired in at least some instances as the bathythermograph buoy must include a housing sufficient in size to store the length of cable that will be unspooled as the lower unit descends through the body of water.

Moreover, the estimation of the depth based upon a predefined rate of descent, such as five feet per second, is typically based upon an estimate of the unspooling rate of the cable. However, the use of a predefined descent rate ignores mass changes associated with the lower unit as the cable unspools and, as a result, may not accurately reflect the depth at which a temperature reading is obtained, particularly once a significant length of the cable has been unspooled. Further, the estimation of depth based upon a predefined descent rate may ignore other effects that may lead to depth estimation errors, such as kiting and/or canting of the bathythermograph buoy. Such effects may lead to depth estimation errors on the order of 10% to 20% in some instances. A depth estimation error may, in turn, disadvantageously result in determinations that are premised upon the depth, such as the speed of sound at different depths, being correspondingly inaccurate.

BRIEF SUMMARY

A bathythermograph buoy and an associated method of operation are provided to measure temperature and/or optionally other parameter(s), such as pressure, within an ocean or another body of water. In an example, the bathythermograph buoy is configured to ascend after having measured one or more parameters, such as temperature, during its descent through the body of water and to then transmit representations of the one or more parameters that have been measured following its ascent. Thus, the depth to which the bathythermograph buoy descends and measures one or more parameters is not limited by a cable such that the one or more parameters, such as temperature, may be measured at deeper depths. By no longer relying upon a cable for communication, the bathythermograph buoy may be more compact as the housing of the bathythermograph buoy need not store the cable spool. Further, by no longer being tethered by a cable, the rate of descent of the bathythermograph buoy may be more consistent and, as a result, the resulting temperature profile with depth may be more accurate by avoiding changes that may otherwise occur in the rate of descent as the cable unspools and the mass that is descending is correspondingly reduced.

In an example of the present disclosure, a bathythermograph buoy is provided that includes a housing and one or more sensors carried by the housing and configured to repeatedly measure one or more respective parameters as the bathythermograph buoy descends. The bathythermograph buoy also includes a memory carried by the housing and configured to store representations of the one or more respective parameters measured by the one or more sensors. The bathythermograph buoy further includes a buoyancy modification device configured to increase buoyancy of the bathythermograph buoy to permit the bathythermograph buoy to ascend.

The bathythermograph buoy of an example also includes a transmitter configured to transmit at least some of the representations of the one or more respective parameters measured by the one or more sensors and stored by the memory. The bathythermograph buoy of this example may further include a surface flotation device configured to be or remain inflated during operation of the transmitter. The bathythermograph buoy may also include a receiver configured to receive instructions regarding at least some of the operations of the bathythermograph buoy.

The housing of an example includes first and second portions. In this example, the first portion may include ballast and the second portion may carry the memory, and the buoyancy modification device may be configured to release the first portion of the housing to permit the second portion of the housing to ascend without the first portion of the housing. In this example, the one or more sensors may be carried by the first portion of the housing. Alternatively, the one or more sensors may be carried by the second portion of the housing and may also be configured to measure one or more respective parameters as the bathythermograph buoy ascends. The buoyancy modification device of another example includes a flotation device configured to be inflated following descent to at least a predefined depth.

In another example of the present disclosure, a bathythermograph buoy is provided that includes a receiver configured to receive instructions regarding at least some of operations of the bathythermograph buoy. The bathythermograph buoy also includes a housing and one or more sensors carried by the housing and configured to repeatedly measure one or more respective parameters as the bathythermograph buoy descends. The bathythermograph buoy also includes a buoyancy modification device configured to increase buoyancy of the bathythermograph buoy to permit the bathythermograph buoy to ascend. The bathythermograph buoy further includes a transmitter configured to transmit representations of at least some of the one or more respective parameters measured by the one or more sensors following the increase in buoyancy provided by the buoyancy modification device.

The transmitter of an example is configured to transmit representations of at least some of the one or more respective parameters measured by the one or more sensors once the bathythermograph buoy reaches a surface. In an example, the bathythermograph buoy also includes a surface flotation device configured to be or remain inflated during operation of the transmitter.

The housing of an example includes first and second portions. In one example, the first portion includes ballast and the second portion carries the memory. In this example, the buoyancy modification device is configured to release the first portion of the housing to permit the second portion of the housing to ascend without the first portion of the housing. In one example, the one or more sensors are carried by the first portion of the housing, while in another example, the one or more sensors are carried by the second portion of the housing and are also configured to measure one or more respective parameters as the bathythermograph buoy ascends. In an example, the buoyancy modification device includes a flotation device configured to be inflated following descent to at least a predefined depth.

In a further example of the present disclosure, a method is provided for operating a bathythermograph buoy. The method includes launching the bathythermograph buoy such that the bathythermograph buoy descends through a body of water and then measuring one or more parameters with one or more sensors of the bathythermograph buoy as the bathythermograph buoy descends. The method also includes increasing the buoyancy of the bathythermograph buoy following descent of the bathythermograph buoy to at least a predefined depth. Following the increase in the buoyancy of the bathythermograph buoy, the method further includes transmitting representations of the one or more parameters measured by the one or more sensors.

The method of an example also includes storing representations of the one or more parameters measured by the one or more sensors prior to ascent of the bathythermograph buoy and transmission of the representations of the one or more parameters. In an example, the method also includes inflating a surface flotation device or causing the surface flotation device to remain inflated while transmitting the representations of the one or more respective parameters measured by the one or more sensors. In an example in which the bathythermograph buoy includes a housing comprising first and second portions and the first portion comprises ballast, the method increases the buoyancy of the bathythermograph buoy by releasing the first portion of the housing to permit the second portion of the housing to ascend without the first portion of the housing. In an example in which the one or more sensors are carried by the second portion of the housing, the method further includes measuring one or more parameters with the one or more sensors as the second portion of the housing of the bathythermograph buoy ascends.

