National Aeronautics and Space Administration

Wallops Flight Facility

NPOL Specifications

Design Criteria

The radar design was guided by the following desires

  • S-band to minimize attenuation problems
  • Easy to transport and set up
  • Dual linear polarization
  • Maximum use of off the shelf proven components
  • Well matched H and V beam patterns
  • Low side lobes

Physical Characteristics

  1. The NPOL radar is transportable via tractor-trailer truck, container ship, or cargo aircraft. The NPOL radar consists of three seatainer, 8′ X 20′(2.44mm X 2.44mm X 6.1m)
  2. Each seatainer weighs between 14,000 and 20,000 pounds (6350kg and 9075kg) when fully loaded for shipping.
  3. A fourth seatainer, 8′ X 8′ X 20′( 2.44m X 2.44m X 1.6m) contains a diesel generator rated at 39 KVA and a 500-gallon fuel tank. The weight is approximately 18,000 pounds (8170 kg).
  4. The antenna is mounted on top of a tubular steel pedestal that is 12 feet (3.6m) in length. The antenna/pedestal assembly weighs
    approximately 3200 pounds (1450 kg). Any structure, such as a tower,
    that is to be used to support their antenna/pedestal assembly must be of sufficient strength to withstand the static weight plus the dynamic forces created by the movement of the antenna.
  5. The antenna may be mounted on top of the three seatainers, if
    desired. When mounted on the seatainers, the antenna/pedestal assembly is attached to the top of an addition 10-foot (3m) length of tubular steel to give the antenna a height of approximately 30 feet (9.1 meters)above the ground.

Antenna Assembly


  • Reflector Type: Flat Passive Array (Malibu Research FLAPS antenna)
  • Reflector Size: 18′ by 18′ (5.5m by 5.5m)
  • Feed Type: Dual Polarized
  • Operating Modes

    1. Simulaneous Dual Transmit and Receive (STAR mode)
    2. Alternating H/V Transmit : Dual Channel Receive (ALT mode)
    3. Single Channel Transmit : Dual Channel Receive (H only mode)

  • Antenna Gain: 38.5 dB to 39.9 dB, typical (frequency dependent)
  • Beam Width:

    1.4 degrees, horizontal polarization
    1.3 Degrees, vertical polarization

  • Side Lobes

    1st Side Lobe Level (2740 MHz)

    -25.2 dB at +- 2.8 degrees off axis Vert.
    -23 dB at +- 2.6 degrees off axis, Vert

    1st Side Lobe Level (2800 MHz)

    -26.6 dB at +- 2.8 degrees off axis, Vert.
    -25.2 dB at +- 2.75 degrees off axis, Vert

  • Pedestal Type: Elevation over Azimuth
  • Azimuth/ Elevation Modes: Manual or computer controlled
  • Types of scan patterns: Surveillance, volume, sector, RHI, RTI, Manual
  • Azimuth Angular Limits: None

Operational Limits


Azimuth Angular Velocity : 18 degrees/second, maximum
Azimuth Acceleration : More than 18 degs/sec/sec
Elevation Angular Limits : -3 to +95 degrees (mechanical stops)
Elevation Angular Velocity : -10 to 100 degrees/Sec/max
15 degrees/second, maximum
Elevation Acceleration : More than 18 degs/sec/sec
Single speed synchro resolution : 0.1 degree (azimuth and elevation)

Transmitter Modulator

  • Operating Frequency: 2700-2900MHz
  • Modulator Type: Solid State
  • Peak Pulse Power Output: H & V polarization transmitted – 425 KW peak H channel and 425 KW peak V channel,simultaneously.
    Alternative H & V polarizations – 850 KW peak
    Single polarization (H or V) – 850 KW peak
  • Pulse Width: 0.8 or 2.0 microseconds
  • Duty Cycle: 0.0012 maximum
  • Pulse Recurrence Frequency (PRF): 250 to 1200 pps, duty cycle limited


    • Radar Constant (.8 us pulse width): 78 dB (typical)
    • dBZo (Reflectivity at 1km @ 0.8 us pulse width): -28 dBZ (typical)
    • Radar Constant (2.0 us pulse width): 74 dB (typical)
    • dBZo (1km. 2 us pulse width): -32 dBZ (typical)


  • Independent Dual Receivers
  • Independent, seperate receivers for Horizontally and Vertically signals
  • Operating Frequencies : 2700 MHz to 2900MHz
  • Mixer: Image Reject
  • IF Frequencies: 30 MHz and 24 MHz (Dual Channels)
  • Digital Receiver: RVP7 /IFD Digitizer (SIGMET, Inc.)
  • Noise Floor at Waveguide: 109 dBm approximately (See Note)

NOTE: The Noise Floor at the Waveguide Directional Couplers does not account for waveguide losses from directional couplers to the feedhorn, nor for external noise (e.g., sky noise).

NPOL and TOGA radar support teams

Transportability is a key element in both NPOL and TOGA operations, but it requires the support of a dedicated team to setup and conduct the science missions. Both radars were operated continuously, 24-hours/day, during the NAMMA campaign with the support from:
Lester Atkinson (NASA/GSFC CSC), lead radar engineer at NPOL, Nathan Gears (NASA/GSFC CSC), radar engineer at TOGA, Micheal Watson (NASA/GSFC CSC), lead radar technician TOGA and NPOL and Paul Bashor (NASA/GSFC CSC), radar and rain gauge technician. Tim Parks (NASA/GSFC LJT), TOGA radar technician. Chuck Bradford, and Gregg Frostrom (NOAA) lead the setup team for both radars. Bob Bowie (CSU), radar technician for TOGA. Paul Le Hardy (UND), radar technician for NPOL. Andy Newman (UND), NPOL radar scientist. Amber Reynolds, (TAMU) NPOL radar scientist. Chris Foltz (UND), NPOL science support. Adam Theisen (UND), NPOL science support.