Polarimetric L-band Multibeam Radiometer (PLMR)

Polarimetric L-band Multibeam Radiometer (PLMR)

The Polarimetric L-band Multibeam Radiometer (PLMR) measures both V and H polarisations using a single receiver with polarisation switch at incidence angles ±7°, ±21.5° and ±38.5° in either across-track (pushbroom) or along-track configuration. In the normal pushbroom configuration the 3dB beamwidth is 17° along-track and 14° across-track resulting in an overall 90° across track field of view. The instrument has a frequency of 1.413GHz and band width of 24MHz, with specified NEDT and an accuracy better than 1K for an integration time of 0.5s, and 1K repeatability over 4 hours.

The PLMR calibration accuracy was calculated using ground (sky and blackbody) calibration performed during the SMAPEx experiments. The accuracy of PLMR in the typical brightness temperature range observed over water and land (150–300K) was estimated to be better than 1K at H polarisation and 2.5K at V polarisation (Reference: Panciera, R., "Effect of Land Surface Heterogeneity on Satellite Near- Surface Soil Moisture Observations", PhD Thesis, 2009, The University of Melbourne)

Sensor	Polarimetric L-band Multibeam Radiometer
Center frequency (GHz)	1.413 (L-band; 21cm)
Band width (MHz)	24
Polarisation	H & V (polarimetric mode optional)
Integration time (s)	0.5
Incidence angle (°)	±7, ±21.5, ±38.5
Beam width	3dB beamwidth is 17° along track and 14° across track resulting in an overall 90° across track field of view.
Radiometric resolution (K)	<1
Weight (kg)	46
Dimension (cm)	91.5 × 91.5 × 17.25

PLMR observations

During SMAPEx-1 brightness temperature data were collected at 1km resolution during 3 regional flights and at 100m resolution during 2 target flights on the areas YA and YB, while 1km, multi-angular observations were collected during these 3 regional flights. H-polarized and V-polarized brightness temperature observations for the regional and target flights are shown as example below. PLMR data have been calibrated for each flight using pre and post flight sky and black body calibration data. All brightness temperature data ( in .dat format) can be downloaded via the Download Centre.

Regional observations

 

 

 

 

 

 

 

 

H-polarized Tb data on 06/07

V-polarized Tb data 06/07

 

 

 

 

 

 

 

 

 

 

H-polarized Tb data on 08/07

V-polarized Tb data 08/07

 

 

 

 

 

 

 

 

 

 

H-polarized Tb data on 10/07

V-polarized Tb data 10/07

 

Target observations

 

 

 

 

 

 

 

 

H-polarized Tb data on target area YB, 07/07

V-polarized Tb data on target area YB, 07/07

 

 

 

 

 

 

 

 

 

 

H-polarized Tb data on target area YA, 09/07

V-polarized Tb data on target area YA, 09/07