Tools for Looking for the Downed AirAsia flight 8501

Navy Times reports here:

USS Fort Worth (LCS3) hosting Navy divers and involved in recovery ops

The search has been hampered at times by bad weather, but divers with Mobile Diving and Salvage Unit 1 have launched their Tow Fish sonar system from an 11-meter rigid hull inflatable boat.

"That is a fairly sophisticated piece of technology that allows us to map the ocean floor, at least to be able to find wreckage and debris," said Rear Adm. John Kirby, the Pentagon spokesman.

"What," you might ask, is a "Tow Fish Sonar?"

First, let's look at what "side scan sonar" is. According to NOAA:

Side scan sonar is a specialized system for detecting objects on the seafloor. Most side scan systems cannot provide depth information.

Like other sonars, a side scan transmits sound energy and analyzes the return signal (echo) that has bounced off the seafloor or other objects. Side scan sonar typically consists of three basic components: towfish, transmission cable, and topside processing unit.

In a side scan, the transmitted energy is formed into the shape of a fan that sweeps the seafloor from directly under the towfish to either side, typically to a distance of 100 meters. The strength of the return echo is continuously recorded, creating a "picture" of the ocean bottom. For example, objects that protrude from the bottom create a light area (strong return) and shadows from these objects are dark areas (little or no return) as in the image at left above, or vice versa, depending on operator preference.

As noted above, the container that holds the active components of the side scan sonar being used is referred to as a "towfish" since it deployed by letting it sink to a predetermined depth and then towing it ("swimming" or "flying" it) along a path than allows the sonar to send its signals and return them to a receiver from which its electronic data is processed and converted into images of what the device was towed over.

For example, see the information at Tritech about its "SeaKing Towfish Sidescan Sonar":

SeaKing towfish from Tritech

The SeaKing towfish side scan sonar system is an extremely compact and low cost high definition side scan sonar system. The SeaKing towfish is designed for a wide range of seabed survey and inspection duties.

The fish combines the very latest Tritech DST (Digital Sonar Technology) electronics with industry leading transducer design and digital CHIRP signal processing techniques to dramatically improve range resolution and generate sonar images of unprecedented clarity.

The sonar 'fish' is designed to be easily deployed by hand with excellent stability under all towing conditions. Fitted with durable polycarbonate stabiliser fins, in the event of ground contact the fins will break away and are retained for recovery by a shock cord line.
****
As part of Tritech’s SeaKing range of sonars, sensors it is possible to run the SeaKing towfish with other SeaKing sensors over one communication link. All products in the SeaKing family (or third-party products within the ARCNET communications link), can be run simultaneously, using the same processor and display; such as Tritech’s Surface Control Unit (SCU) or a customer supplied PC or laptop. In addition to the display of side scan sonar data, the system will take position input from DGPS. This information is recorded with the side scan sonar data to allow a 'fix' of a target. The customer's own bit map chart may be displayed on the same screen as the sonar data.

All data produced by the subsea towfish is processed within the fish and transmitted to the surface in digital format. All data may be stored on the built-in hard disk drive, in the surface control unit. The post processing export facility will convert the logged data to XTF and CSV formats for third party software packages.

Processing the data is the job of software, such as SonarWiz from Chesapeake Technologies:

You work hard to get the data – make sure you see all that it has to show. SonarWiz sidescan and sub-bottom sonar mapping software helps with sonar mission planning, data acquisition and post processing to ensure you use your time on the water effectively and capture all of the data you need before heading back to port.
***
The new High Resolution capability for SonarWiz doubles the resolution of the earlier version, for sidescan waterfall, mosaic, and digitizer views of the data. Surveyors in all types of industries can use High Resolution mode to resolve smaller features and see finer detail to improve productivity, security, and safety.

An example of the combination of side scan sonar and SonarWiz borrowed from the Chesapeake site:

Useful tools.

Enhanced Submarine Invisibilty?

Perhaps a game changer in the world of submarine warfare? Reported here:

Led by mechanical science and engineering professor Nicholas Fang, Illinois researchers have demonstrated an acoustic cloak, a technology that renders underwater objects invisible to sonar and other ultrasound waves.

“We are not talking about science fiction. We are talking about controlling sound waves by bending and twisting them in a designer space,” said Fang, who also is affiliated with the Beckman Institute for Advanced Science and Technology.

While materials that can wrap sound around an object rather than reflecting or absorbing it have been theoretically possible for a few years, realisation of the concept has been a challenge. In a paper accepted for publication in the journal Physical Review Letters, Fang’s team describe their working prototype, capable of hiding an object from a broad range of sound waves.

Probably not the best news for your friendly neighborhood sonar tech. They had a hard job anyway.

Super stealth stuff.

Whales v. Navy Sonar: "...[I]t's not just you turn sonar on and instantly all the whales head for the beach..."

Background
For several years now, there has been an on-going controversy between certain environmental organizations, particularly the Natural Resources Defense Council (NRDC) and the United States Navy over the use of sonar in certain environments. In the last couple of years, the NDRC has brought lawsuits against the Navy which have resulted in lower level federal courts enjoining the Navy from using sonar under certain specified circumstances and at certain levels, felt by the courts and by NRDC to pose a threat to various whales and marine mammals. The Navy has adopted many preemptive measures to mitigate potential damage to whales and other marine mammals but asserts that adopting the full range of protective measures proposed by the NRDC would, for all practical purpose, effectively end its ability to conduct training necessary for it to prepare sailors to detect and combat quiet submarines in littoral waters.

A collection of various orders and an opinion from the Ninth Circuit can be found here. The underlying substance of the case is well set in a 2007 order lifting a complete prohibition against the use of sonar during training in the Southern California Fleet Operating Area:

The Navy and environmental advocacy organizations have battled for years about whether Navy training using sonar is too harmful to the environment, particularly whales. The Navy uses something called medium frequency active sonar, which basically bounces a loud noise off the hulls of extremely quiet submarines to detect their presence. The loud noise may be quite harmful to whales and other marine mammals. In a previous round of this litigation, the district court had approved a settlement that allowed Navy sonar training to
proceed, but required mitigation “measures.” The measures consisted of such
precautions as requiring some sailors to be on deck looking for whales, and
reducing the decibel level when whales were present, weather prevented seeing
whether any whales were around, or “surface ducting” would let the noise carry
more.(footnotes omitted)

The matter has gone back and forth to court, with the federal government attempting to invoke various other avenues to limit interference in Navy training. The current order appealed from does not put a complete halt to sonar training, neither does it give the Navy free rein in its training exercises. The basis for injunction granted by district court was set out by the Ninth Circuit as follows:

In granting NRDC’s motion for a preliminary injunction, the district court found that NRDC had demonstrated probable success on the merits of its claim that the Navy violated the National Environmental Policy Act (“NEPA”), 42 U.S.C. § 4321 et seq., by failing to prepare an Environmental Impact Statement (“EIS”). The district court also found that NRDC had demonstrated probable success on the merits of its claim that the Navy violated the Coastal Zone Management Act (“CZMA”), 16 U.S.C. § 1451 et seq., by submitting a consistency determination to the California Coastal Commission (“CCC”) that did not take into account the planned use of MFA sonar and by failing to adopt the mitigation measures the CCC determined were necessary for the SOCAL exercises to be consistent with the
California Coastal Management Program (“CCMP”).

On January 15, 2008, the Council on Environmental Quality (“CEQ”)purported to approve “alternative arrangements,” pursuant to 40 C.F.R. § 1506.11,
that would permit the Navy to continue its exercise without first completing an
EIS. On the same day, President George W. Bush, pursuant to 16 U.S.C. §
1456(c)(1)(B), exempted from the requirements of the CZMA the Navy’s use of
MFA sonar in the SOCAL exercises.

On February 4, 2008, the district court upheld its injunction on the basis of
plaintiffs’ NEPA claim, concluding CEQ’s action was invalid and therefore not
entitled to deference. The district court also expressed concerns about the
constitutionality of the President’s CZMA exemption on the ground that it
appeared to amount to an executive revision of a judicial decision and thus violated
the principle, recognized in Hayburn’s Case, 2 U.S. (2 Dall.) 408 (1792), that
Congress cannot vest review of the decisions of Article III courts in officials of the officials of the Executive Branch. However, the court declined to decide the constitutionality of the CZMA exemption because it concluded the preliminary injunction was firmly supported on NEPA grounds.3 The district court also found that plaintiffs had demonstrated a possibility of irreparable harm and that the balance of hardships tipped in plaintiffs’ favor. Natural Res. Def. Council v. Winter, --- F.Supp 2d ----, 2008 WL 314192 (C.D. Cal. Feb. 4, 2008) (“Feb. 4, 2008 Dist. Ct. Order”).

The Ninth Circuit, in the order appealed by the Navy, affirmed the lower court and that affirmation is what is on now on appeal to the Supreme Court.

The Navy's need for certain types of training was well presented to the Ninth Circuit: (from pages 11-13 of the 2/29/08 opinion)

According to the Navy, the ability to execute anti-submarine warfare (“ASW”) is critical to a Commander’s certification of a strike group.

Improving ASW is the Pacific Fleet’s top “war-fighting” priority because of the
proliferation of extremely quiet diesel electric submarines throughout the world.

In turn, an important part of ASW is the use of active sonar, a technology
which the Navy deems absolutely necessary to detect today’s extremely quiet
submarines. The type of active sonar, the use of which NRDC challenges, is midfrequency active sonar; other categories of active sonar are low-frequency active
sonar and high-frequency active sonar.

Active sonar involves a vessel or other sonar source emitting a loud noise
underwater and then listening for whether the noise comes back to the source,
indicating that the noise may have bounced off the hull of a previously undetected
submarine. According to the Navy, active sonar has two important advantages
over passive sonar, which merely involves listening for noise made by submarines
themselves: active sonar gives both the bearing and the distance of the target
submarine, while passive sonar gives only the bearing; and active sonar allows the
Navy to target submarines that emit sound at levels below those of the surrounding
marine environment. Accordingly, the Navy has concluded that in
certain environments, including shallow coastal waters where ambient noise levels
are high, MFA sonar allows better detection of quiet submarines than passive
sonar.

According to the Navy, personnel using MFA sonar must train with it
regularly, under realistic conditions, and in a variety of situations.
The Navy therefore trains with MFA sonar in the ASW exercises that constitute an
important component of the SOCAL exercises. (notes and references omitted)

The court also sets out the allegations of potential harm to marine mammals in the SOCAL Op Areas. No one who has lived on the California coast will be surprised to learn that the Op Areas are teeming with marine mammals. It seems that of particular interest to both the district court and the appellate court was the effect of MFA sonar on "beaked" whales which seem to be particularly sensitive to MFA sonar:

As the record demonstrates, substantial evidence suggests that beaked
whales are particularly vulnerable to MFA sonar. While it is not settled what
causes this vulnerability, it is clear that use of MFA sonar may lead to the
stranding of beaked whales. A 2004 Navy-sponsored study concluded that “the
evidence of sonar causation is . . . completely convincing and that therefore there is a serious issue of how best to avoid/minimize future beaching events.” Likewise,
the Standing Working Group on Environmental Concerns of the International
Whaling Commission’s Scientific Committee concluded in 2004 that “[t]he weight
of accumulated evidence now associates mid-frequency, military sonar with
atypical beaked whale mass strandings,” and found that “[t]his evidence is very
convincing and appears overwhelming.”

Thus battle lines are drawn. The delicate balance between national security and environmental protection is in the hands of the highest court in the land.

Blogger Rountable with Rear Admiral Rice

On June 24, 2008, Rear Admiral Lawrence Rice engaged in a "blogger roundtable" with me, Grim from Blackfive, Colin Clark of DOD Buzz, and by submitted questions, Steeljaw Scribe. The audio of the roundtable is
available by clicking here. A transcript is available here.

Grim started off with an interesting question that I think was meant to invoke issues of "lawfare" - whether the environmental movement worldwide was using lawsuits to restrain U.S. (and allied) military operations. Admiral Rice, probably wisely, declined the opportunity to speculate on the motivations of such organizations.

My questions were (however rambling they might have been) about the differences in the approach the Navy was taking to mitigate environmental impact and still conduct necessary training with the approach the NRDC is pursuing. The response was that they are not compatible.

The Navy attempting to find work arounds and is also funding substantial research into marine mammals. (For example here). RADM Rice stated that some research was being done to determine, essentially, whether the sonar may be sending a "wrong message" to the beaked whales, causing them to panic in some way.

He noted that not every use of sonar causes whales to throw themselves onto the beach- that research has found that only in certain circumstances-

"So it's not just you turn sonar on and instantly all the whales head for the beach, there have to be very specific circumstances present."

I like the quote, because it does take away the simple "Sonar = Evil" argument I have seen in some less enlightened environmental comments.

Another matter that may not have occurred to some whale lovers is that the Navy is actually leading the way in getting scientists access to the heretofore scarcely known beaked whales, which seem to spend very little time near the surface but Navy hydrophones are helping to locate them for researchers:

The problem is because of their diving habits, we don't see them very often. And when we do our exercises -- excuse me -- when we do our research on beaked whales we have to find them with hydrophones, then send of boat out to where the hydrophone is and wait for them to surface. They dive down, as I'm sure you may have seen literature, they dive down in excess of 1,000 meters, more than a kilometer deep and they're down there for 45 minutes holding their breath. It's absolutely amazing. And then they come up to the surface for a quick breath of air and then they're back down again. So we don't see them very much; not very much is known about them so initially we thought there weren't very many of them. But when we started looking at our hydrophones on the different ranges, we found out that they are everywhere...

And that research may be the key to finding a long-term solution to "whales versus U.S. Navy." As the admiral said, we await the decision of the Supreme Court to sort out a short-term balance of national security and environmental concerns.

Now, I wonder if NRDC has an answer to ultra-quiet submarines in the littorals?

More on beaked whales here and here.