Satellite technology tracks cargo across the globe
Release #111208-1 posted on Dec 8, 2011
By Lori Barnhill, U.S. Transportation Command
111202-D-YC450-001 Radios and integrated chips are are some of the components inside at Satellite-Enabled Tracking and Intrusion Device. Photo by Christine Pesout, USTRANSCOM/PA
A Satellite-Enabled Tracking and Intrusion Detection tag’s plain, brick-like exterior belies the fascinating — and mission-critical — capabilities that lie within the device and the complex communication processes it completes. SETIDs (pronounced “set I-D”) provide troops on the ground the ability to track their cargo and gain general insight on cargo safety.
U.S. Transportation Command and its components began using SETID tags last year. Although SETID tags are currently expensive, they are vital in austere locations without existing infrastructure.
“Reliability is the key,” said Army Col. Steve Fraunfelter, chief of USTRANSCOM’s In-Transit Visibility Integration Division. “And in geographical areas where we cannot place active radio-frequency identification tags [which require nearby readers], SETIDs provide key bits of cargo tracking data including near real-time location, intrusion, light, humidity, and temperature for sensitive and high value cargo travelling through ‘high threat’areas.”
Inside a SETID is a battery compartment and circuit board. In addition, there are round-edged square chips, or antennas that send and receive information to and from satellites, a cellular phone system or other radio frequency sources (e.g., mesh networks).
On the reverse of the circuit board are several shiny radios, no bigger than a thumbnail. Each radio listens to (receives) or sends (broadcasts) using different technologies, or waveforms. SETID programming can automatically select the least-cost communication route available. Some SETID tag manufacturers have added radios that communicate with active radio frequency identification tags and/or form ad-hoc networks among its brand of tags.
All SETID tags have a Global Positioning System device. The GPS is another radio, one that “asks” for its position in relation to precisely positioned satellites and then calculates its earthly location using mathematics programmed into one of the antennas.
Transmissions to and from SETIDs involve satellites. The satellites include a piece of equipment called a transponder (short for “transmitter-responder”) which automatically receives a signal, amplifies it and then retransmits it on a different frequency. Translating the frequency of an incoming signal to a different frequency for the outgoing signal avoids interference between the two signals. Man-made satellites “talk” to a large number of ground, or Earth, stations.
Ground stations use one of two types of communications, usually based on SETID manufacturer’s license with a satellite carrier (or satellite constellation). One is called “bent pipe” which is a pass back and forth of data between a ground station and a SETID tag via a satellite, with any signal boosting (amplification) or translation (frequency shifting) done on Earth. The second is called “regenerative” and uses satellites as intermediaries between ground stations. Equipment on board the satellite boosts and translates the signal between ground stations.
The satellite constellation usually has many ground stations or hubs. These hubs have several displays that track satellites and can re-task (move, via limited propulsion subsystems) satellites for gentle corrections or in the event of major solar events.
A ground station listens (receives) and sends (broadcasts) information from a tag. SETID providers package the data and send it to the Department of Defense’s Global Exchange. DOD in-transit visibility systems subscribe to the GEX to obtain this data and use it according to their respective missions. If the DOD needs to adjust speed at which a tag provides data (e.g., change the report rate from once every six hours to once every 15 minutes) the tag provider is notified and the ground station broadcasts the change to the tags.
To review: given an unauthorized opening of a SETID-tagged container somewhere en route, the following is a typical sequence of events.
–SETID tag detects intrusion and sends alert message to an Earth station by an appropriate channel
–Earth station sends alert data (including GPS information) to service provider
–Service provider packages data and sends it to the DOD GEX \
–DOD ITV system receives the data as dictated by its software program
Total time: usually less than 15 minutes. Response to the alert message depends on many factors; one of which is the physical location of the SETID (and therefore, cargo). It takes less than 10 minutes to turn off a SETID if requested by the DOD.
A split-second after Barry Schulhofer aimed the stubby, weapon and called out “Taser, taser, taser,” Army Sgt. Brant Hall realized that volunteering to be shot with the Human Electro-Muscular Incapacitation device may not have been his wisest decision.