Misplaced Pages

#762237

59-531: SeaWiFS was the only scientific instrument on GeoEye 's OrbView-2 (AKA SeaStar) satellite , and was a follow-on experiment to the Coastal Zone Color Scanner on Nimbus 7 . Launched August 1, 1997 on an Orbital Sciences Pegasus small air-launched rocket , SeaWiFS began scientific operations on September 18, 1997 and stopped collecting data on December 11, 2010, far exceeding its designed operating period of 5 years. The sensor resolution

118-495: A n t i l o g ( 0.366 − 3.067 R + 1.93 R 2 + 0.64 R 3 − 1.53 R 4 ) {\displaystyle Chl=antilog(0.366-3.067{\mathsf {R}}+1.93{\mathsf {R}}^{2}+0.64{\mathsf {R}}^{3}-1.53{\mathsf {R}}^{4})} This formula, along with others, was derived empirically using observed chlorophyll concentrations. To facilitate these comparisons, NASA maintains

177-471: A "fourth big scientific revolution" after World War II is the development of scientific instrumentation, not only in chemistry but across the sciences. In chemistry, the introduction of new instrumentation in the 1940s was "nothing less than a scientific and technological revolution" in which classical wet-and-dry methods of structural organic chemistry were discarded, and new areas of research opened up. As early as 1954, W. A. Wildhack discussed both

236-505: A central control focus, this arrangement was inflexible as each control loop had its own controller hardware, and continual operator movement within the control room was required to view different parts of the process. With coming of electronic processors and graphic displays it became possible to replace these discrete controllers with computer-based algorithms, hosted on a network of input/output racks with their own control processors. These could be distributed around plant, and communicate with

295-501: A collection of equipment might be used to automate the testing of drinking water for pollutants. Instrumentation engineering is the engineering specialization focused on the principle and operation of measuring instruments that are used in design and configuration of automated systems in areas such as electrical and pneumatic domains, and the control of quantities being measured. They typically work for industries with automated processes, such as chemical or manufacturing plants, with

354-449: A desired output variable, and provide either remote monitoring or automated control capabilities. Each instrument company introduced their own standard instrumentation signal, causing confusion until the 4–20 mA range was used as the standard electronic instrument signal for transmitters and valves. This signal was eventually standardized as ANSI/ISA S50, "Compatibility of Analog Signals for Electronic Industrial Process Instruments", in

413-536: A destination. Automotive instrumentation must be cheap and reliable over long periods in harsh environments. There may be independent airbag systems that contain sensors, logic and actuators. Anti-skid braking systems use sensors to control the brakes, while cruise control affects throttle position. A wide variety of services can be provided via communication links on the OnStar system. Autonomous cars (with exotic instrumentation) have been shown. Early aircraft had

472-575: A few sensors. "Steam gauges" converted air pressures into needle deflections that could be interpreted as altitude and airspeed. A magnetic compass provided a sense of direction. The displays to the pilot were as critical as the measurements. A modern aircraft has a far more sophisticated suite of sensors and displays, which are embedded into avionics systems. The aircraft may contain inertial navigation systems , global positioning systems , weather radar , autopilots, and aircraft stabilization systems. Redundant sensors are used for reliability. A subset of

531-584: A modeled product. NASA offers free software designed specifically to work with SeaWiFS data through the ocean color website. This software, entitled SeaDAS (SeaWiFS Data Analysis System), is built for visualization and processing of satellite data and can work with Level 1, 2, and 3 data. Though it was originally designed for SeaWiFS data, its capabilities have since been expanded to work with many other satellite data sources. Other software or programming languages can also be used to read in and work with SeaWiFS data, such as Matlab , IDL , or Python . Estimating

590-451: A pressurized bellows displaces a pen. Integrating sensors, displays, recorders, and controls was uncommon until the industrial revolution, limited by both need and practicality. Early systems used direct process connections to local control panels for control and indication, which from the early 1930s saw the introduction of pneumatic transmitters and automatic 3-term (PID) controllers . The ranges of pneumatic transmitters were defined by

649-448: A specific region of the globe, whereas the standard SeaWiFS data products are designed for global accuracy with necessary tradeoffs for specific regions. Scientists who are more interested in relating the standard SeaWiFS outputs to other processes will commonly use Level 3 data, particularly if they do not have the capacity, training, or interest in working with Level 1 or 2 data. Level 4 data may be used for similar research if interested in

SECTION 10

#1732782414763

708-799: A system of oceanographic and atmospheric data called SeaBASS (SeaWiFS Bio-optical Archive and Storage System). This data archive is used to develop new algorithms and validate satellite data products by matching chlorophyll concentrations measured directly with those estimated remotely from a satellite. These data can also be used to assess atmospheric correction (discussed below) that also can greatly influence chlorophyll concentration calculations. Numerous chlorophyll algorithms were tested to see which ones best matched chlorophyll globally. Various algorithms perform differently in different environments. Many algorithms estimate chlorophyll concentrations more accurately in deep clear water than in shallow water. In shallow waters reflectance from other pigments, detritus, and

767-430: A thousand years. Therefore, the degree of primary production from the ocean could play a large role in slowing climate change. Or, if primary production slows, climate change could be accelerated. Some have proposed fertilizing the ocean with iron in order to promote phytoplankton blooms and remove carbon dioxide from the atmosphere. Whether these experiments are undertaken or not, estimating chlorophyll concentrations in

826-504: A uniform space/time grid. Level 3 data contain derived geophysical variables binned or mapped to a uniform grid. Lastly, Level 4 data contain modeled or derived variables such as ocean primary productivity . Scientists who aim to create calculations of chlorophyll or other parameters that differ from those provided on the OceanColor website would likely use Level 1 or 2 data. This might be done, for example, to calculate parameters for

885-488: Is 1.1 km (LAC, "Local Area Coverage") and 4.5 km (GAC, "Global Area Coverage"). The sensor recorded information in the following optical bands: The instrument was specifically designed to monitor ocean characteristics such as chlorophyll-a concentration and water clarity. It was able to tilt up to 20 degrees to avoid sunlight from the sea surface. This feature is important at equatorial latitudes where glint from sunlight often obscures water colour. SeaWiFS had used

944-451: Is a device that produces an output signal, often in the form of a 4–20  mA electrical current signal, although many other options using voltage , frequency , pressure , or ethernet are possible. The transistor was commercialized by the mid-1950s. Instruments attached to a control system provided signals used to operate solenoids , valves , regulators , circuit breakers , relays and other devices. Such devices could control

1003-648: Is a measure of photosynthesis on land. SeaWiFS data are freely accessible from a variety of websites, most of which are government run. The primary location for SeaWiFS data is NASA's OceanColor website [1] , which maintains the time series of the entire SeaWiFS mission. The website allows users to browse individual SeaWiFS images based on time and area selections. The website also allows for browsing of different temporal and spatial scales with spatial scales ranging from 4 km to 9 km for mapped data. Data are provided at numerous temporal scales including daily, multiple days (e.g., 3, 8), monthly, and seasonal images, all

1062-598: Is also a field of study about the art and science about making measurement instruments, involving the related areas of metrology , automation , and control theory . The term has its origins in the art and science of scientific instrument-making . Instrumentation can refer to devices as simple as direct-reading thermometers , or as complex as multi- sensor components of industrial control systems . Instruments can be found in laboratories , refineries , factories and vehicles , as well as in everyday household use (e.g., smoke detectors and thermostats ). Instrumentation

1121-449: Is based on sensed antenna direction and sensed time delay. The other information is embedded in the transponder transmission. Among the possible uses of the term is a collection of laboratory test equipment controlled by a computer through an IEEE-488 bus (also known as GPIB for General Purpose Instrument Bus or HPIB for Hewlitt Packard Instrument Bus). Laboratory equipment is available to measure many electrical and chemical quantities. Such

1180-706: Is called atmospheric correction. A description of the light, or radiance, observed by the satellite's sensor can be more formally expressed by the following radiative transfer equation: L T ( λ ) = L r ( λ ) + L a ( λ ) + L r a ( λ ) + T L g ( λ ) + t ( L f ( λ ) + L W ( λ ) ) {\displaystyle L_{T}(\lambda )=L_{r}(\lambda )+L_{a}(\lambda )+L_{ra}(\lambda )+TL_{g}(\lambda )+t(L_{f}(\lambda )+L_{W}(\lambda ))} Where L T (λ)

1239-407: Is often knowledgeable of techniques to minimize temperature gradients that cause air turbulence within the telescope. Instrumentation technologists, technicians and mechanics specialize in troubleshooting, repairing and maintaining instruments and instrumentation systems. Ralph Müller (1940) stated, "That the history of physical science is largely the history of instruments and their intelligent use

SECTION 20

#1732782414763

1298-442: Is reflected from the atmosphere and from aerosols within the atmosphere. In order to estimate chlorophyll concentrations this non-water-leaving radiance must be accounted for. Some light reflected from the ocean, such as from whitecaps and sun glint, must also be removed from chlorophyll calculations since they are representative ocean waves or the angle of the sun instead of the subsurface ocean. The process of removing these components

1357-480: Is total radiance at the top of the atmosphere, L r (λ) is Rayleigh scattering by air molecules, L a (λ) is scattering by aerosols in the absence of air, L ra (λ) is interactions between air molecules and aerosols, TL g (λ) is reflections from glint, t(L f (λ) is reflections from foam, and L W (λ)) is reflections from the subsurface of the water, or the water-leaving radiance. Others may divide radiance into some slightly different components, though in each case

1416-502: Is used to measure many parameters (physical values), including: The history of instrumentation can be divided into several phases. Elements of industrial instrumentation have long histories. Scales for comparing weights and simple pointers to indicate position are ancient technologies. Some of the earliest measurements were of time. One of the oldest water clocks was found in the tomb of the ancient Egyptian pharaoh Amenhotep I , buried around 1500 BCE. Improvements were incorporated in

1475-470: Is well known. The broad generalizations and theories which have arisen from time to time have stood or fallen on the basis of accurate measurement, and in several instances new instruments have had to be devised for the purpose. There is little evidence to show that the mind of modern man is superior to that of the ancients. His tools are incomparably better." Davis Baird has argued that the major change associated with Floris Cohen ' s identification of

1534-488: The Marine Optical Buoy for vicarious calibration. The SeaWiFS Mission is an industry/government partnership, with NASA 's Ocean Biology Processing Group at Goddard Space Flight Center having responsibility for the data collection, processing, calibration, validation, archive and distribution. The current SeaWiFS Project manager is Gene Carl Feldman . Chlorophyll concentrations are derived from images of

1593-417: The 1970s. The transformation of instrumentation from mechanical pneumatic transmitters, controllers, and valves to electronic instruments reduced maintenance costs as electronic instruments were more dependable than mechanical instruments. This also increased efficiency and production due to their increase in accuracy. Pneumatics enjoyed some advantages, being favored in corrosive and explosive atmospheres. In

1652-425: The amount of global or regional chlorophyll, and therefore phytoplankton, has large implications for climate change and fisheries production. Phytoplankton play a huge role in the uptake of the world's carbon dioxide, a primary contributor to climate change . A percentage of these phytoplankton sink to ocean floor, effectively taking carbon dioxide out of the atmosphere and sequestering it in the deep ocean for at least

1711-600: The biomedical instrumentation of laboratory rats has very different concerns than the expert in rocket instrumentation. Common concerns of both are the selection of appropriate sensors based on size, weight, cost, reliability, accuracy, longevity, environmental robustness, and frequency response. Some sensors are literally fired in artillery shells. Others sense thermonuclear explosions until destroyed. Invariably sensor data must be recorded, transmitted or displayed. Recording rates and capacities vary enormously. Transmission can be trivial or can be clandestine, encrypted and low power in

1770-491: The clocks. By 270 BCE they had the rudiments of an automatic control system device. In 1663 Christopher Wren presented the Royal Society with a design for a "weather clock". A drawing shows meteorological sensors moving pens over paper driven by clockwork. Such devices did not become standard in meteorology for two centuries. The concept has remained virtually unchanged as evidenced by pneumatic chart recorders, where

1829-479: The control racks to be networked and thereby located locally to plant to reduce cabling runs, and provided high level overviews of plant status and production levels. In some cases, the sensor is a very minor element of the mechanism. Digital cameras and wristwatches might technically meet the loose definition of instrumentation because they record and/or display sensed information. Under most circumstances neither would be called instrumentation, but when used to measure

SeaWiFS - Misplaced Pages Continue

1888-733: The data repository began in the 1990s around the time of the launch of the SeaWiFS satellite sensor, and the same data archive has been used ever since. Oceanography projects funded by the NASA Earth Science program are required to upload data collected on research campaigns to the SeaBASS data repository to increase the volume of open-access data available to the public. As of 2021 the data archive contained information from thousands of field campaigns uploaded by over 100 principal investigators. This database -related article

1947-422: The diffuse attenuation coefficient, particulate organic carbon (POC) concentration, particulate inorganic carbon (PIC) concentration, colored dissolved organic matter (CDOM) index, photosynthetically active radiation (PAR), and normalized fluorescence line height (NFLH). In addition, despite being designed to measure ocean chlorophyll, SeaWiFS also estimates Normalized Difference Vegetation Index (NDVI), which

2006-435: The early years of process control , process indicators and control elements such as valves were monitored by an operator, that walked around the unit adjusting the valves to obtain the desired temperatures, pressures, and flows. As technology evolved pneumatic controllers were invented and mounted in the field that monitored the process and controlled the valves. This reduced the amount of time process operators needed to monitor

2065-409: The elapsed time of a race and to document the winner at the finish line, both would be called instrumentation. A very simple example of an instrumentation system is a mechanical thermostat , used to control a household furnace and thus to control room temperature. A typical unit senses temperature with a bi-metallic strip . It displays temperature by a needle on the free end of the strip. It activates

2124-589: The examples of DDT monitoring and the use of UV spectrophotometry and gas chromatography to monitor water pollutants . SeaBASS (data archive) The SeaWiFS Bio-optical Archive and Storage System (SeaBASS) is a data archive of in situ oceanographic data used to support satellite remote sensing research of ocean color . SeaBASS is used for developing algorithms for satellite-derived variables (such as chlorophyll-a concentration ) and for validating or “ground-truthing” satellite-derived data products. The acronym begins with “S” for SeaWiFS, because

2183-406: The furnace by a mercury switch . As the switch is rotated by the strip, the mercury makes physical (and thus electrical) contact between electrodes. Another example of an instrumentation system is a home security system . Such a system consists of sensors (motion detection, switches to detect door openings), simple algorithms to detect intrusion, local control (arm/disarm) and remote monitoring of

2242-408: The goal of improving system productivity , reliability, safety, optimization and stability. To control the parameters in a process or in a particular system, devices such as microprocessors, microcontrollers or PLCs are used, but their ultimate aim is to control the parameters of a system. Instrumentation engineering is loosely defined because the required tasks are very domain dependent. An expert in

2301-446: The graphic display in the control room or rooms. The distributed control concept was born. The introduction of DCSs and SCADA allowed easy interconnection and re-configuration of plant controls such as cascaded loops and interlocks, and easy interfacing with other production computer systems. It enabled sophisticated alarm handling, introduced automatic event logging, removed the need for physical records such as chart recorders, allowed

2360-496: The information may be transferred to a crash recorder to aid mishap investigations. Modern pilot displays now include computer displays including head-up displays . Air traffic control radar is a distributed instrumentation system. The ground part sends an electromagnetic pulse and receives an echo (at least). Aircraft carry transponders that transmit codes on reception of the pulse. The system displays an aircraft map location, an identifier and optionally altitude. The map location

2419-439: The maximum of several wavelengths (443, 490, or 510 nm) by the reflectance at 550 nm. This roughly equates to a ratio of blue light to green light for two of the numerator wavelengths, and a ratio of two different green wavelengths for the other possible combination. The reflectance (R) returned by this formula is then plugged into a cubic polynomial that relates the band ratio to chlorophyll. C h l =

SeaWiFS - Misplaced Pages Continue

2478-439: The need to control valves and actuators in the field. Typically, a signal ranged from 3 to 15 psi (20 to 100kPa or 0.2 to 1.0 kg/cm2) as a standard, was standardized with 6 to 30 psi occasionally being used for larger valves. Transistor electronics enabled wiring to replace pipes, initially with a range of 20 to 100mA at up to 90V for loop powered devices, reducing to 4 to 20mA at 12 to 24V in more modern systems. A transmitter

2537-431: The number of trophic links in the food chain, and how efficient each link is. Estimates of the number of trophic links and trophic efficiencies from phytoplankton to commercial fisheries have been widely debated, though they have been little substantiated. More recent research suggests that positive relationships between chlorophyll a and fisheries production can be modeled and can be very highly correlated when examined on

2596-544: The ocean bottom may cause inaccuracies. The stated goals of the SeaWiFS chlorophyll estimates are "… to produce water leaving radiances with an uncertainty of 5% in clear-water regions and chlorophyll a concentrations within ±35% over the range of 0.05–50 mg m-3.". When accuracy is assessed on a global scale, and all observations are grouped together, then this goal is clearly met. Many satellite estimates range from one-third to three times of those directly recorded at sea, though

2655-510: The ocean's color. Generally speaking, the greener the water, the more phytoplankton are present in the water, and the higher the chlorophyll concentrations. Chlorophyll a absorbs more blue and red light than green, with the resulting reflected light changing from blue to green as the amount of chlorophyll in the water increases. Using this knowledge, scientists were able to use ratios of different reflected colors to estimate chlorophyll concentrations. Many formulas estimate chlorophyll by comparing

2714-418: The overall relationship is still quite good. Differences arise when examined by region, though overall the values are still very useful. One pixel may not be particularly accurate, though when averages are taken over larger areas, the values average out and provide a useful and accurate view of the larger patterns. The benefits of chlorophyll data from satellites far outweigh any flaws in their accuracy simply by

2773-597: The presence of jamming. Displays can be trivially simple or can require consultation with human factors experts. Control system design varies from trivial to a separate specialty. Instrumentation engineers are responsible for integrating the sensors with the recorders, transmitters, displays or control systems, and producing the Piping and instrumentation diagram for the process. They may design or specify installation, wiring and signal conditioning. They may be responsible for commissioning, calibration, testing and maintenance of

2832-451: The process indicators. This again reduced the number and amount of time process operators were needed to walk around the units. The most standard pneumatic signal level used during these years was 3–15 psig. Process control of large industrial plants has evolved through many stages. Initially, control would be from panels local to the process plant. However, this required a large manpower resource to attend to these dispersed panels, and there

2891-410: The process. Latter years, the actual controllers were moved to a central room and signals were sent into the control room to monitor the process and outputs signals were sent to the final control element such as a valve to adjust the process as needed. These controllers and indicators were mounted on a wall called a control board. The operators stood in front of this board walking back and forth monitoring

2950-408: The productive and destructive potential inherent in process control. The ability to make precise, verifiable and reproducible measurements of the natural world, at levels that were not previously observable, using scientific instrumentation, has "provided a different texture of the world". This instrumentation revolution fundamentally changes human abilities to monitor and respond, as is illustrated in

3009-568: The proper scale. For example, Ware and Thomson (2005) found an r of 0.87 between resident fish yield (metric tons km-2) and mean annual chlorophyll a concentrations (mg m-3). Others have found the Pacific's Transition Zone Chlorophyll Front (chlorophyll density of 0.2 mg m-3) to be defining feature in loggerhead turtle distribution. Measuring instrument Instrumentation is a collective term for measuring instruments , used for indicating, measuring, and recording physical quantities . It

SECTION 50

#1732782414763

3068-414: The ratio of blue to green light and relating those ratios to known chlorophyll concentrations from the same times and locations as the satellite observations. The color of light is defined by its wavelength, and visible light has wavelengths from 400 to 700 nanometers, progressing from violet (400 nm) to red (700 nm). A typical formula used for SeaWiFS data (termed OC4v4) divides the reflectance of

3127-404: The reflectance parameters must be resolved in order to estimate water-leaving radiance and thus chlorophyll concentrations. Though SeaWiFS was designed primarily to monitor ocean chlorophyll a concentrations from space, it also collected many other parameters that are freely available to the public for research and educational purposes. These parameters aside from chlorophyll a include reflectance,

3186-415: The spatial and temporal coverage possible. Ship-based measurements of chlorophyll cannot come close to the frequency and spatial coverage provided by satellite data. Light reflected from the sub-surface ocean is called water-leaving radiance and is used to estimate chlorophyll concentrations. However, only about 5–10% of light at the top of the atmosphere is from water-leaving radiance. The remainder of light

3245-731: The system so that the police can be summoned. Communication is an inherent part of the design. Kitchen appliances use sensors for control. Modern automobiles have complex instrumentation. In addition to displays of engine rotational speed and vehicle linear speed, there are also displays of battery voltage and current, fluid levels, fluid temperatures, distance traveled, and feedback of various controls (turn signals, parking brake, headlights, transmission position). Cautions may be displayed for special problems (fuel low, check engine, tire pressure low, door ajar, seat belt unfastened). Problems are recorded so they can be reported to diagnostic equipment . Navigation systems can provide voice commands to reach

3304-408: The system. In a research environment it is common for subject matter experts to have substantial instrumentation system expertise. An astronomer knows the structure of the universe and a great deal about telescopes – optics, pointing and cameras (or other sensing elements). That often includes the hard-won knowledge of the operational procedures that provide the best results. For example, an astronomer

3363-460: The way up to composites of the entire mission. Data are also available via ftp and bulk download. Data can be browsed and retrieved in a variety of formats and levels of processing, with four general levels from unprocessed to modeled output. Level 0 is unprocessed data that is not usually provided to users. Level 1 data are reconstructed but either unprocessed or minimally processed. Level 2 data contain derived geophysical variables, though are not on

3422-409: The world's oceans and their role in the ocean's biological pump could play a key role in our ability to foresee and adapt to climate change. Phytoplankton is a key component in the base of the oceanic food chain and oceanographers have hypothesized a link between oceanic chlorophyll and fisheries production for some time. The degree to which phytoplankton relates to marine fish production depends on

3481-469: Was no overall view of the process. The next logical development was the transmission of all plant measurements to a permanently staffed central control room. Effectively this was the centralization of all the localized panels, with the advantages of lower manning levels and easy overview of the process. Often the controllers were behind the control room panels, and all automatic and manual control outputs were transmitted back to plant. However, whilst providing

#762237