Radiometer Data Format

Airborne microwave brightness temperature observations were made at three frequencies (10.65, 18.7, and 36.5 GHz; a.k.a., X, Ku and Ka bands, respectively), at horizontal polarization with a nominal 45-degree look angle. There were repeated acquisitions over the three science target lines, named North, South, and Cross. 

Data file is in CSV (comma separated values) format. Each file contains:

  • Date & Time (UTC),
  • Footprint center Longitude (deg),
  •  Footprint center Latitude (deg),
  •  Footprint center elevation (m),
  •  TB X (K),
  •  TB Ku (K),
  •  TB Ka (K),
  • Aircraft Longitude (deg),
  • Aircraft Latitude (deg),
  • Aircraft Altitude (m),
  • Aircraft Yaw (deg),
  • Aircraft Pitch (deg),
  • Aircraft Roll (deg),
  • Positioner Roll (deg) 

File Naming Convention

For this product, there is one file per pass over a given science line, named for example 

GRMCT1_31603_20009_TB_200212_XKuKa225H_v03.csv 

GRM: Grand Mesa, CO 

C: Science target line name (either N, S, or C, signifying North, South, or Cross) 

Each filename consists of the following components, separated by underscores “_”: 

– Site Name: Six character abbreviation for the desired target site (files may contain other sites, e.g., when science lines cross each other). 

– Heading and Repeat Count: Three digits aircraft heading (clockwise from 0 degrees due North) followed by an auto-increment alphanumeric repeat counter, showing the repeat passes collected on the same flight (i.e., the counter is reset after each flight). 

– Flight Number: Five digits in which the first two digits are the last two digits of the year of the SWESARR flight, and the next three digits are the flight number by SWESARR counted sequentially from the first flight of the calendar year. 

– Date (YYMMDD): Six digits, two for year, month, and day (UTC). 

– FrequenciesLook angle, Polarization: List of radiometric frequency bands collected by SWESARR (characters), followed by the look angle (three digits), followed by the polarization (one character). Pointing angle is defined as 90 degrees for starboard side, 180 degrees for nadir and 270 for port side. Acquisitions were done with a 45 degree incidence angle port of nadir, resulting in 225 degrees. 

– Version: Two digits indicating the processing version number. 

– Extension: Three character file extension indicating the data type. 

Spatial Resolution 

The field of view depends on the frequency of observations and the aircraft altitude. At a nominal elevation of 1,500 ft the spatial resolutions are (across x along track): 

  • X band 496 m x 352 m  
  • Ku band 282 m x 200 m 
  • Ka band 144 m x 102 m 

SWESARR is a nonscanning instrument, collecting observations in pushbroom alignment at an incidence angle of 45 degrees.