It's not often that the passing of an underwater TV camera product into history causes a little stir within the industry that spawned it. That is exactly what is happening with the demise of the venerable SIT low-light underwater camera. The SIT, or Silicon Intensifier Target to give it its full name, has been the mainstay of long-range underwater viewing and navigation within the Offshore ROV industry for almost thirty years.
The incredible success of the SIT low-light camera for underwater ROV navigation began in the early 80’s with the beginning of the boom in ROV operations within the fledgling Offshore Oilfield industry in the North Sea. As demand for larger, deeper, more powerful and more capable work-class ROV systems grew, so did the demand for the SIT camera as a primary ROV navigation tool. Almost every serious work-class ROV in the industry since then has used a SIT as its main navigation camera. For almost 30 years, the SIT camera has been providing excellent performance in this role, and even today with all of the recent advances in solid-state CCD sensor technology the SIT camera continues to provide a performance level in water that is difficult to match with newer camera sensors.
Uniquely suited to the underwater environment
SIT technical note
|The SIT sensor has a light sensitivity
characteristic that peaks in the blue/green region of the visible light
spectrum (a wavelength of around 450 nanometres for those more scientifically
minded). This coincides almost exactly with the peak light transmission
characteristic for sea-water. Being designed primarily for military use,
the SIT sensor was exceptionally rugged (especially considering it was based
on a glass vacuum tube design). The “noise” characteristics of the image
intensification system within the SIT is very unobtrusive, and provides
a better image definition than the more modern solid-state image-intensifier
technologies that replaced it for military use. |
Impressive as it seems that the SIT camera technology has not only survived, but continued to provide competitive performance for almost 30 years in the ROV industry, it is even more surprising to think that the SIT technology was originally developed way back in the 60’s, during the era of the Vietnam War. It was conceived as an improved “image intensifier” technology to provide front-line army troops with a tactical advantage during night operations. Although it wasn’t designed specifically for underwater operations, the SIT sensor had a few performance characteristics that meant it was uniquely well suited to the underwater environment.
The SIT sensor has a light sensitivity characteristic that peaks in the blue/green region of the visible light spectrum (a wavelength of around 450 nanometres for those more scientifically minded). This coincides almost exactly with the peak light transmission characteristic for sea-water. Being designed primarily for military use, the SIT sensor was exceptionally rugged (especially considering it was based on a glass vacuum tube design). The “noise” characteristics of the image intensification system within the SIT is very unobtrusive, and provides a better image definition than the more modern solid-state image-intensifier technologies that replaced it for military use.
Osprey Electronics Ltd (now Kongsberg Maritime Ltd – Camera Group) was at the forefront of developing reliable SIT camera technology for the Offshore ROV industry, and became the dominant supplier to Offshore, Military and Scientific users around the world. In total, Osprey/Kongsberg has delivered more than 2,600 of the OE132x series underwater SIT camera product into the industry. Many of them still in daily use in every ocean around the world, they continue to provide an outstanding level of underwater performance.
|The SIT Camera has now been replaced
in the Kongsberg Maritime product line by the OE15-102 and OE15-103 Enhanced
CCD camera products. These state-of-the-art solid state cameras utilise
Cooled-CCD sensor technology combined with high-gain low-noise amplification
to provide equivalent low-light performance to the SIT in underwater operations.
They also provide the considerable operational advantage that they are virtually
immune to the image burn-in problems that can affect all image-intensifier
cameras in bright daylight conditions. Kongsberg Maritime will continue
to provide long-term repair and maintenance support for their SIT camera
products and can also provide guidance to all SIT camera users on how to
maximise the life of their SIT camera product.
So it was with some sadness that just recently the last production OE1324 SIT camera rolled off the Kongsberg Maritime production line, and it was lovingly packed and shipped to the final customer. And it was somehow very fitting that this customer should be Oceaneering International – a company that has pioneered underwater ROV operations since the early days of the Offshore Oil exploration boom. To mark the end of the SIT camera product era, Kongsberg has presented Oceaneering International with a commemorative SIT product replica. The unique blue anodised Titanium Alloy pressure housing bears a simple inscription: “Legendary Performance – Navigating the Deep”. And for a whole generation of Offshore ROV pilots, maybe there is a small pang of regret at the slow passing of the SIT camera into history.