Seeker/Sensor Technology Assessment for ECAP

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Seeker/Sensor Technology Assessment for ECAP

• Presented by Tim Carroll

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Seeker/Sensor Technology AssessmsntHuntsville,
Alabama January 16, 2004

• Tim Carroll
• AMCOM
• tjcarroll_at_knology.net

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Seeker/Sensor Technology Assessment

• Outline
• Definitions
• Background Information
• Seeker Types
• Radar Seekers
• Electro-Optical Seekers
• Laser Seekers

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Definition of a Seeker

• Definition - The seeker is the eye of a missile.
  Its job is to acquire and track the target until
  the missile impacts the target. The seeker
  provides bore-sight error signals (position of
  the target relative to the center axis of the
  missile) to the guidance algorithms. This energy
  is usually electromagnetic (EM) but can be other
  forms of energy as well (i.e., acoustic).
• Seeker Block Diagram

Target
To Guidance Computer
Electrical Processor
Gimbal Platform
Receiver/Detector
Transmitter
Aperture (Antenna or Optics)
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Seeker Field-of-View and Field-of-Regard

• Field-of-View The angular area in space at
  which the seeker can observe at any given time
  (the FoV for radar seekers if referred to as
  Beam Width).
• Field-of-Regard The total angular area that a
  seeker can view by slewing the seeker aperture up
  and down and left to right on gimbals. Some
  missile seekers have no slewing mechanism and are
  called strap-down seekers (then the FoV and FoR
  are the equal).

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Seeker/Sensor Discipline Interaction
Operational Engagement Requirements Engagement
Time Lines Coverage Area
Aerodynamics Nose Shape
Guidance Scheme Seeker Type (Active or Passive)
System Simulation FoV Detection Range
Size Constraints Diameter Length
Seeker/Sensor Design
Mechanical Design and Layout Size Weight
Target Type Wavelength Power Requirements
Cost Constraints Strap-Down vs.
Gimballed Multi-Mode
Electrical System Power Requirements Voltage Curre
nt
Logistics Considerations Packaging and Handling
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Electromagnetic Waves

• An electromagnetic disturbance that is composed
  of time-varying electric and magnetic fields and
  can transport energy through space, even if no
  matter is present in that space, is called an
  electromagnetic wave (abbreviated EM).
• EM waves propagate at the speed of light.
• The electric and magnetic waves in an EM wave are
  oriented at 90 degrees to each other and to the
  direction of propagation.
• EM waves travel in straight lines.
• Objects in temperature above absolute zero emit
  EM waves in the Infrared (IR) spectrum.

Direction of Propagation
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EM Wavelengths and Frequencies

• EM frequencies and wavelengths are related by the
  following expression

where l wavelength, c speed of light (3x108
meters/sec), and f frequency of oscillation.
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EM Atmospheric Attenuation
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Classification of Seekers/SensorsSpectral Band

• Seekers are catagorized by which spectral band of
  EM radiation they operate within
• Microwave
• MMW
• E-O (Visual and IR)
• Laser (CO2 10.6mm, YAG 1.06mm, GaAs 0.9mm)

Band Frequency Wavelength
L 1,000 2,000 MHz. 30 15 cm
S 2,000 4,000 MHz. 15 7.5 cm
C 4,000 8,000 MHz. 7.5 3.75 cm
X 8,000 12,500 MHz. 3.75 2.4 cm
Ku 12.5 18 GHz. 2.4 1.67 cm
K 18 26.5 GHz. 1.67 1.13 cm
Ka 26.5 40 GHz. 1.13 0.75 cm
MMW gt 30 GHz. lt 1.0 cm
Visible 0.38 0.76 mm
Middle IR 3 8 mm
Long IR 8 14 mm
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Classification of Seekers/SensorsActive/Passive/S
emi-Active

• Active seekers transmit energy and the receive
  the reflected energy. Examples are Microwave
  Radars, Millimeter Wave Radars, and Laser Radars
  (LADAR).
• Passive seekers look for natural occurring EM
  radiation (Infrared) or reflected EM radiation
  (Visual).
• Semi-Active Seekers operate in one of two modes
• Other asset illuminates target while missile
  seeker operates in a passive mode to detect
  reflect EM radiation.
• Missile is guided to target by other asset and
  then the missile seeker becomes active near the
  target. This is also called Terminal Active

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Classification of Seekers/SensorsStabilization
Mechanization

• Stabilized Seeker Head
• Seeker Head is isolated from the missile body
  motion through gimbals, servo motors, and rate
  sensors. A clear stabilized image/signal is
  presented to the seeker detectors.
• Increase cost,complexity, size and weight
• Strap-Down Seeker
• Seeker is rigidly attached to the missile body
  and observes the same motion as the missile
• Cheaper, lower quality image/signal, smaller
  Field of Regard
• Limited engagement geometries

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Microwave Radar Seekers/Sensors

• Advantages
• All Weather
• Range and Range Rate Information
• Long Operating Ranges
• Low degradation due to battlefield obsurants
• Doppler detection for moving targets
• Low drag nose shapes

• Disadvantages
• Large Components
• Large Aperature
• Active Mode
• Large Angular Resolution
• High Cost

• State of the Art
• Phased Array Radars
• Doppler Beam Sharpening
• Synthetic Aperture Radar
• Radiometric
• Multisensor/Sensor Fusion

Microwave Radars are best suited for large
missiles or ground based systems
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Millimeter Wave Seekers/Sensors

• Advantages
• All Weather with some degradation
• Range and Range Rate Information
• Small Components
• Small Angular Resolution
• Doppler detection for moving targets
• Low drag nose shapes

• Disadvantages
• Active Mode
• High Cost
• Relatively Short Operating Ranges

• State of the Art
• Small Components
• Doppler Beam Sharpening
• Strapdown Configurations
• Radiometric
• Multisensor/Sensor Fusion

MMW Wave Radars are suited well for small
missiles and short detection ranges
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IR Seekers/Sensors

• Advantages
• Small Components
• Small Aperture
• Very Small Angular Resolution
• Passive Mode
• Small Miss Distances
• Aim-point Bias Capability

• Disadvantages
• Weather Degradation - Moderate
• Battlefield Obscurant Degradation - Moderate
• No Range or Range Rate Information
• High Cost
• High Drag Nose Shapes Required

• State of the Art
• Focal Plane Array
• Uncooled IR Sensors
• Strapdown Configurations
• Multisensor/Sensor Fusion

IR Seekers are suited well for small missiles and
short detection ranges that require precise hit
locations
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Visual Seekers/Sensors

• Advantages
• Small Components
• Small Aperture
• Very Small Angular Resolution
• Passive Mode
• Small Miss Distances
• Aim-point Bias Capability

• Disadvantages
• Weather Degradation - High
• Battlefield Obscurant Degradation - High
• No Range or Range Rate Information
• High Cost
• High Drag Nose Shapes Required
• Cannot Operate at Night

• State of the Art
• Strapdown Configurations
• Multisensor/Sensor Fusion

Visual Seekers are not in use much anymore due to
the lack of night vision and lack of capability
in obscured environments
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Laser Seekers/Sensors

• Advantages
• Small Components
• Small Aperture
• Range and Range Rate Information
• Small Miss Distances
• Aim-point Bias Capability

• Disadvantages
• Weather Degradation - High
• Battlefield Obscurant Degradation - High
• Dependency on Designator (Semi-Active)
• High Cost
• No Fire-and-Forget Capability
• Small Search Areas

• State of the Art
• LADAR
• Side-Looking Beamriders
• Multisensor/Sensor Fusion

Laser Seekers are used in semi-active missiles
where designating assets are available
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Sample Calculations
Snapshot from MS Excel utility used
in Seeker/Sensor Design.