Stepped Frequency Microwave Radiometer (SFMR)

The Stepped Frequency Microwave Radiometer (SFMR) is the primary instrument used by the National Hurricane Center to determine hurricane intensity. SFMR is an airborne radiometer designed to measure surface brightness temperature in 6 frequency bands spanning 4.6 to 7.2 GHz. Calibrated values of brightness temperature generated by SFMR are reported in real time to a windspeed retrieval algorithm, developed in cooperation with NOAA’s Hurricane Research Division. This algorithm generates a real time measure of surface level wind speed and rain rate in hurricanes and tropical storms.

Each of the Air Force Reserves’ C-130 Hurricane Hunter aircraft is equipped with an SFMR,  as are NOAA’s P-3 and Gulfstream 2 hurricane research aircraft.

 

 

 

SFMR Features

• Wide band (4.6 – 7.2 GHz) receiver

• High efficiency, wide band corrugated horn antenna

• System control and data reporting via RS-422

• Microprocessor-based thermal control maintains receiver at a constant temperature

• Outputs radiometric brightness temperature at six frequencies

• Single board computer with a flat panel screen display

• Real-time wind retrieval algorithm

• One second ocean surface wind speed and rain rate updates

• Internal cold calibration developed by ProSensing provides significantly improved measurement accuracy

SFMR Radiometer Specifications
Radiometer Type: Hach
Tuning bandwidth: 4.6 -7.2 GHz
Number of channels: Up to 8
Receiver Channel Bandwidth: 100 MHz (at RF)
Antenna Type: Corrugated horn
Antenna Beamwidth (3 dB): 20-28 deg (over the tuning bandwidth)
Polarization: Linear
Cross-polarization isolation: 25 dB
Front End Loss: 0.25 dB
System Noise Temperature: 490 K (Noise figure = 4.3 dB)
Measurement precision: 0.4 K (0.5s averaging per channel)
Electronics Power Requirements: 28VDC, 2A
Thermal Control Power Requirements: 28VDC, 4A (max)
Power: 168 W
Operating Temperature: -10°C to +25°C
Survival Temperature: -51°C to +43°C per MIL-STD-810F
Humidity: 0 to 100%
Size (L x W x H): 29″ x 11″ x 15″
Weight: 55 lbs.
SFMR Processor Specifications
Computer: PC/104
CPU: ATLAS 133 MHz
System Memory: 62 MB
Compact Flash Memory: 512 MB
Display: LCD (size 2″ by 1.5″)
Interface Inputs: Military style circular multi pin connector (1) (interface with the SFMR radiometer)
BNC (4) (radar blanking)
RS-232 (1) (AUX data)
Interface Outputs: RS-232 (1)(SFMR data)
LAN (1) (ethernet)
Power Supply: 110 V AC
Electronics Power Requirements: 18W (163 mA @ 110V)
Operating Temperature: 0°C to 60°C (32°F to 104°F)
Humidity: 0% to 90%, non-condensing
Size (L x W x H): 13″ x 19″ x 3.5″
Weight: 15 lbs

SFMR installed on Air Force Reserve C-130J Hurricane Hunter

SFMR features pressure sealed RF Unit and hydrophobic radome