Pop-up satellite archival tag
Encyclopedia
Pop-up satellite archival tags (PSATs) are used to track movements of (usually large, migratory) marine
animals. A PSAT is an archival tag (or data logger
) that is equipped with a means to transmit the data via satellite. Though the data are physically stored on the PSAT, its major advantage is that it does not have to be physically retrieved like an archival tag for the data
to be available. They have been used to track movements of ocean sunfish
, marlin
, blue shark
s, bluefin tuna, swordfish
and sea turtles. Location, depth, and temperature data are used to answer questions about migratory patterns, seasonal feeding movements, daily habits, and survival after catch and release, for examples.
A PSAT is generally constructed of several components: a data-logging section, a release section, a float, and an antenna
. The release sections includes a energetically popped off release section or a pin that is actively corroded on a preset date or after a specified period of time. Some disadvantages of using PSAT are their depth limitations (2000m), their costs ($1500-4000), and their vulnerability to loss by environmental issues (biofouling) or ingestion by a predator. For the PSAT that functions by measuring ambient light, they have a functional depth limitation of about 1000 meters. Additionally these tags cost between $3500-4000 per unit is the main reason many studies employ a dozen or fewer PSATs. However, newer tag technologies employed in the SeaTag product line (SeaTag-MOD, etc) use Earth's magnetic field to replacement light measurements for latitude estimations. Therefore, depth is no longer a cause for location uncertainty. Additionally these newer tags cost about half that of existing tagging technologies, on the order of $1500-2200 per PSAT.
PSATS range in length from about 125-175 mm and weigh 65-75 grams in air. A tag must be small compared to the size of the animal so that it does not interfere with normal behavior. Smaller versions of about half that length and weight have been recently introduced and are more suitable for use on smaller species or younger animals. Furthermore, the SeaTag-GEO/PSAT is the lightest PSAT manufactured at under 30g including it's float, release section, and antenna.
PSATS record such information as temperature, magnetics, accerlation, light level, and pressure at set intervals of a few seconds to several hours. Data are often collected for several weeks, and memory capacity may allow data to be taken for up to a year with older tags. Newer tags that use microSD as memory storage allow data to be collected and stored for centuries. PSATS record data in non-volatile memory
so that data are retained even if battery or solar power runs out.
When the PSAT releases from the animal on which it was attached, it floats to the surface, and begins to transmit data to one of the manufacturer’s satellite
s at a frequency of about 400 MHz. Therefore, the PSAT does not have to be physically recovered for the data to be obtained. Depending on the number and coverage of the satellites, it can take 7 to 10 days or longer for the data to be completely transmitted.
Major disadvantages of the PSAT are that it is subject to loss by malfunction of any key component, environmental effects such as biofouling, ingestion by a predator, its depth limitation and cost. Most PSATS have internal software designed to detect damaging or sub-optimal conditions that will trigger an early release and transmission of data. For example, PSATs can withstand pressures to depths of 2000 to 2500 meters depending on the model. If data indicate no change in pressure (depth) for a period of time, this could indicate an early release due to malfunction or death of the animal to which it was attached. Such internal checks can alert researchers to unexpected or undesirable events. Ingestion by a predator is more difficult to detect; loss of ambient light might trigger release, but the device may not be free to float to the surface as designed.
Previously the cost of $3500-$4000 per PSAT was the main impediment to researchers using more than a dozen units during a project. With small sample sizes, the loss of a single tag can significantly affect the results. Also, there is greater risk that the animals tagged could display unusual behavior or only one of several types of behavior. Thus an observer could come to an incorrect or incomplete generalization about the entire species. However, with recent technologies and manufacturing companies, the PSAT costs have significantly dropped to nearly $1500 per PSAT.
and longitude
. These tags also record temperature and depth. The temperature can also be coupled with the light level readings to improve accuracy in depth and location through different software packages available to researchers. The tags are attached to the animal in various ways including adhesives, and are released to "pop up" and begin transmitting data via the galvanic release. Manufacturers of this type include Wildlife Computers, Microwave Telemetry, and soon-to-be Lotek Wireless.
to acquire light (for longitude). The advantage is two-fold. First the solar cell acts as a charging mechanism for a capacitor
. Therefore the tag itself is not battery powered, and can store and transmit more data (in theory centuries of data when coupled with the tag's internal microSD card). The tag's stored solar power system utilizes new capacitor technologies allowing it to power its internal components for up to two weeks of total darkness; the tag recharges when it is at two times water visibility depth. Location estimates using this tag are more accurate than those using only light, especially in areas where it is difficult to determine length of day (North and South Poles) and during equinoxes. Additionally, this tag uses an energetic release rather than a galvanic release; this different release design allows a greater breaking strength to reduce the risk of accidental release. Finally, the per tag costs are half that of the other companies using light level technologies allowing for significantly increased sample sizes.
Specifications of a PSAT product offered by Desert Star Systems
Description and specifications of a PSAT offered by Microwave Telemetry, Inc.
Description and specifications of a smaller size PSAT offered by Microwave Telemetry, Inc.
Specifications of a PSAT product offered by Wildlife Computers
Description of a smaller "miniPAT" offered by Wildlife Computers
Specifications and description of PSAT made by Lotek.
Marine (ocean)
Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...
animals. A PSAT is an archival tag (or data logger
Data logger
A data logger is an electronic device that records data over time or in relation to location either with a built in instrument or sensor or via external instruments and sensors. Increasingly, but not entirely, they are based on a digital processor...
) that is equipped with a means to transmit the data via satellite. Though the data are physically stored on the PSAT, its major advantage is that it does not have to be physically retrieved like an archival tag for the data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
to be available. They have been used to track movements of ocean sunfish
Ocean sunfish
The ocean sunfish, Mola mola, or common mola, is the heaviest known bony fish in the world. It has an average adult weight of . The species is native to tropical and temperate waters around the globe. It resembles a fish head with a tail, and its main body is flattened laterally...
, marlin
Marlin
Marlin, family Istiophoridae, are fish with an elongated body, a spear-like snout or bill, and a long rigid dorsal fin, which extends forward to form a crest. Its common name is thought to derive from its resemblance to a sailor's marlinspike...
, blue shark
Blue shark
The blue shark is a species of requiem shark, family Carcharhinidae, that inhabits deep waters in the world's temperate and tropical oceans. Preferring cooler waters, blue sharks migrate long distances, for example from New England to South America. Although generally lethargic, they can move very...
s, bluefin tuna, swordfish
Swordfish
Swordfish , also known as broadbill in some countries, are large, highly migratory, predatory fish characterized by a long, flat bill. They are a popular sport fish of the billfish category, though elusive. Swordfish are elongated, round-bodied, and lose all teeth and scales by adulthood...
and sea turtles. Location, depth, and temperature data are used to answer questions about migratory patterns, seasonal feeding movements, daily habits, and survival after catch and release, for examples.
A PSAT is generally constructed of several components: a data-logging section, a release section, a float, and an antenna
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
. The release sections includes a energetically popped off release section or a pin that is actively corroded on a preset date or after a specified period of time. Some disadvantages of using PSAT are their depth limitations (2000m), their costs ($1500-4000), and their vulnerability to loss by environmental issues (biofouling) or ingestion by a predator. For the PSAT that functions by measuring ambient light, they have a functional depth limitation of about 1000 meters. Additionally these tags cost between $3500-4000 per unit is the main reason many studies employ a dozen or fewer PSATs. However, newer tag technologies employed in the SeaTag product line (SeaTag-MOD, etc) use Earth's magnetic field to replacement light measurements for latitude estimations. Therefore, depth is no longer a cause for location uncertainty. Additionally these newer tags cost about half that of existing tagging technologies, on the order of $1500-2200 per PSAT.
General Information
PSATS record such information as temperature, magnetics, accerlation, light level, and pressure at set intervals of a few seconds to several hours. Data are often collected for several weeks, and memory capacity may allow data to be taken for up to a year with older tags. Newer tags that use microSD as memory storage allow data to be collected and stored for centuries. PSATS record data in non-volatile memory
Non-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer...
so that data are retained even if battery or solar power runs out.
When the PSAT releases from the animal on which it was attached, it floats to the surface, and begins to transmit data to one of the manufacturer’s satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
s at a frequency of about 400 MHz. Therefore, the PSAT does not have to be physically recovered for the data to be obtained. Depending on the number and coverage of the satellites, it can take 7 to 10 days or longer for the data to be completely transmitted.
Major disadvantages of the PSAT are that it is subject to loss by malfunction of any key component, environmental effects such as biofouling, ingestion by a predator, its depth limitation and cost. Most PSATS have internal software designed to detect damaging or sub-optimal conditions that will trigger an early release and transmission of data. For example, PSATs can withstand pressures to depths of 2000 to 2500 meters depending on the model. If data indicate no change in pressure (depth) for a period of time, this could indicate an early release due to malfunction or death of the animal to which it was attached. Such internal checks can alert researchers to unexpected or undesirable events. Ingestion by a predator is more difficult to detect; loss of ambient light might trigger release, but the device may not be free to float to the surface as designed.
Previously the cost of $3500-$4000 per PSAT was the main impediment to researchers using more than a dozen units during a project. With small sample sizes, the loss of a single tag can significantly affect the results. Also, there is greater risk that the animals tagged could display unusual behavior or only one of several types of behavior. Thus an observer could come to an incorrect or incomplete generalization about the entire species. However, with recent technologies and manufacturing companies, the PSAT costs have significantly dropped to nearly $1500 per PSAT.
Using light level
The most common type of PSAT is a tag that is battery powered and uses a galvanic release. This type of tags relies on light levels to determine latitudeLatitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
and longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....
. These tags also record temperature and depth. The temperature can also be coupled with the light level readings to improve accuracy in depth and location through different software packages available to researchers. The tags are attached to the animal in various ways including adhesives, and are released to "pop up" and begin transmitting data via the galvanic release. Manufacturers of this type include Wildlife Computers, Microwave Telemetry, and soon-to-be Lotek Wireless.
Using Earth’s magnetic field and light level
The alternative approach to light level measurements is to use the earth’s magnetic fields for latitude. These tags still use noon time estimates based on light measurements for longitude. Desert Star Systems LLC takes this approach with their PSAT tag. The tag acquires magnetic values using an on-board magnetometer (for latitude) and uses a solar cellSolar cell
A solar cell is a solid state electrical device that converts the energy of light directly into electricity by the photovoltaic effect....
to acquire light (for longitude). The advantage is two-fold. First the solar cell acts as a charging mechanism for a capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
. Therefore the tag itself is not battery powered, and can store and transmit more data (in theory centuries of data when coupled with the tag's internal microSD card). The tag's stored solar power system utilizes new capacitor technologies allowing it to power its internal components for up to two weeks of total darkness; the tag recharges when it is at two times water visibility depth. Location estimates using this tag are more accurate than those using only light, especially in areas where it is difficult to determine length of day (North and South Poles) and during equinoxes. Additionally, this tag uses an energetic release rather than a galvanic release; this different release design allows a greater breaking strength to reduce the risk of accidental release. Finally, the per tag costs are half that of the other companies using light level technologies allowing for significantly increased sample sizes.
External links
Comparing Electronic Tags for Migratory Marine Animals – technical paper published by Desert Star SystemsSpecifications of a PSAT product offered by Desert Star Systems
Description and specifications of a PSAT offered by Microwave Telemetry, Inc.
Description and specifications of a smaller size PSAT offered by Microwave Telemetry, Inc.
Specifications of a PSAT product offered by Wildlife Computers
Description of a smaller "miniPAT" offered by Wildlife Computers
Specifications and description of PSAT made by Lotek.