Visibility Sensors Implementation Plan.

Abstract

The Federal Aviation Administration (FAA) has used visibility sensors at major airports for many years, but the requirement within the maritime industry came in 1980, when the MV Summit Venture hit the Sunshine Skyway Bridge over Florida’s Tampa Bay. The disaster, in part due to lack of adequate visibility, was the impetus for the present day Physical Oceanographic Real-time System (PORTS®) system, and prompted much interest in and research on visibility sensors. The addition of visibility sensors to the PORTS® suite of instruments offers users another valuable tool to increase efficiency and to help avoid disasters that could cause loss of life and extensive property damage. The Center for Operational Oceanographic Products and Services (CO-OPS) became involved in testing visibility sensors in 1999, after signing a Memorandum of Understanding (MOU) with the National Weather Service (NWS) to test Belfort Model 6100 visibility sensors at the Sterling Research and Development Center in Sterling, VA. Several other visibility sensors were tested from 1999 through 2003. Since 1999, the Ocean Systems Test and Evaluation Program (OSTEP), has evaluated eight different sensors at five separate locations. These eight sensors represent four different kinds of technologies, and the evaluations have been conducted in cooperation with five Federal agencies. None of the sensors tested seemed to meet all 15 standards set forth by the NWS in the Federal Meteorological Handbook (FMH) #1; however, an FAA requirement for a new visibility sensor provided an excellent interagency opportunity to partner in the test and evaluation of the latest technology. Based on a six-month FAA test conducted at the John A. Volpe National Transportation Systems Center at the Otis Weather Test Facility at Cape Cod, MA, the FAA selected the Vaisala FS11, which uses forward scatter technology, as its sensor of choice. OSTEP found that results from several other tests suggest that the Vaisala FS11 is also the best sensor for marine applications. Additionally, OSTEP is participating with the U. S. Coast Guard (USCG) in a joint test of six sensors in a long-term field test that began in March 2008 at U.S. Army Corps of Engineers (USACE) Field Research Facility (FRF) in Duck, NC. OSTEP is evaluating two Vaisala FS11 sensors to determine the optimal maintenance schedule, including how often the sensor lens must be cleaned, as well as to determine how the FS11 sensor readings compare with those of the other sensors. In addition to the sensors at the FRF, OSTEP is also testing a Vaisala FS11 located in the courtyard at the CO-OPS Chesapeake facility. This fully functional sensor has performed well, has done a good job of monitoring itself, and has been interfaced successfully to a Sutron Xpert data collection platform (DCP). The sensor is now generating data, and, although the data are not ingested into the CO-OPS system, they are being transmitted on the GOES test channel. The steps toward full implementation of an operational visibility sensor system include data system integration, site reconnaissance and selection of a specific PORTS® location, development of deployment standards, site preparation, development of a proper maintenance schedule, and performance of preliminary installation and startup. Additionally, as the visibility product is fully developed, users must be educated and a Web interface must be built to enable ease of use. User education is critically important to achieve the desired results. Because visibility data often represent a small geographic area, users and product developers should consider placing multiple sensors within an operational visibility system so that users can observe the appropriate range of existing conditions. Continuing efforts are needed to address issues such as power requirements for the FS11 and long-term field tests. Visibility sensors consume significant power due to hood and lens heaters, and presently require access to 110-Volt service to deliver accurate and reliable information. Sensors that are currently in the field at the USACE FRF and at the Chesapeake facility offer an ideal way to conduct long-term tests that provide more information about power requirements, corrosion, and maintenance issues. Collaboration with other agencies is in the forefront of this visibility effort and has the potential to improve the technology. For example, the FAA has continued testing the FS11 and has worked with Vaisala to make modifications that improve its function within the aviation application. These changes have led Vaisala to offer the FS11 as a unique FAA sensor with its own part number; however the modifications do not make a significant difference for maritime use. Even so, the FAA keeps CO-OPS apprised of the status of modifications through distribution of a PowerPoint presentation, and the opportunity for partnership with the FAA and other agencies remains. Interagency cooperation may play a role in finding a solution to challenging issues, such as the visibility sensor’s large power requirements.