There are a variety of sensing hardware
located onboard Limelight. A brief
description of each sub-system is described below. Unmarked sensors are
deployed in Phase-1 of Limelight. Those marked Phase-2 are under research and will
brought into production during subsequent development.
Photocell optical detectors maintain a constant real-time
measure on a wide portion of the electromagnetic spectrum. Primarily,
visible, infrared, and ultraviolet, the optical sensors are located in the upper
sensor portion of Limelight. Abnormalities and spectral patterns consistent
with threatening events, actions, or known pre-threat conditions are noted and
relayed to the central threat processing hardware for analysis.
Measuring a wide range of acoustic disturbances, the small,
high-gain microphones are mounted within the upper sensing area. The
acoustical system is capable of detecting audio fluctuations, reverberations,
and sharp spikes as well as background noises beyond the range of the human ear.
Monitoring and filtering sound signals, the sensing sub-system alerts the
central threat processing hardware of sounds with characteristic profiles
matching threatening vehicles, machines, ordinance, or sounds associated with
Fluctuations in the ambient temperature near
registered with the central threat indicator. Abnormal heating or cooling
curves over time that are inconsistent with natural and safe local events and
activities are flagged high priority and delivered to the central threat
Acceleration / Vibration
Subtle vibrations, sharp blows, and abnormal motions are
identified by a highly sensitive 3-axis MEMS based accelerometer. Capable
of measuring motions as extreme as ten times the force of gravity and as minor
as 1/1000 gravity. Motion is simultaneously measured along three
directions, allowing for richer interpretation of events near
improved threat indication accuracy.
Positioning and Localization
A vital element of determining local threat conditions is
knowing the local position. Embedded global positioning hardware (GPS) and
an antenna are used to record Limelight's current
position. That data drives the proper selection of filters and weights to
use on most of the other sensors. That is, the geography and local habitat
of Limelight strongly dictates the
relevance of various thread indicators. Each macro-location on the planet
dictates that the system use the proper weightings and rules.
This location, recorded over time, is also used to generate
profiles of transport and usage for both Limelight and its local user.
Recall that the identity of the local user is known from the previously captured
fingerprint acquisition hardware.
There is a known direct relationship between the current
threat and the locally measured emission of electrons, alpha particles, gamma
rays, and beta rays. Limelight provides this
important quantity to the threat system. Three distinct types of radiation
are measured internally by Limelight:
Alpha Particles: Helium nuclei, generally emitted from heavy elements
such as uranium and thorium.
Beta Rays: Electrons moving at extremely high (often relativistic)
speeds. They are more penetrating than alpha particles.
Gamma Rays: Electromagnetic waves, similar to light, but at a much higher
energy. Much more penetrating than alpha or beta radiations. High energy gamma
rays can pass through several inches of metal. Note that X-Rays and Gamma Rays
are really the same thing, the term X-Ray is used when the radiation is produced
by electrons striking a material, such as in an X-Ray tube.
Counts of particles over time that exceed normal background
radiation levels are relayed immediately to the central threat processor.
Radio Frequency Scanner
Often early indicators of threat arise from monitoring
various potions of the RF spectrum. For example, simple usage
detection hardware is capable of sensing traffic on known local government,
military, and emergency frequencies. It also monitors air traffic control
frequencies. Traffic patterns inconsistent with normal usage are flagged for
immediate inspection by the system. Similarly, noting transmissions and
signal strengths from orbiting satellites furnishes important threat indicators.
Particular attention is paid to frequencies that broadcast
data for covert operatives in hostile regions of the world. These stations
transmit single use key encrypted streams of numbers providing orders to field
reconnaissance units. You can listen to an actual capture of two such
Number Station 1
Number Station 2 (MP3)
Pressure / Barometric / Humidity (Phase-2)
Continuous pressure changes
within the local environment.
Angle of tilt of
Measurement of small airborne
particles as well as hostile gasses.
and Direction / Compass
Noting local magnetic field
changes and calculating compass directions.
Open flame near the system is detected.