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Data Set ID:
NSIDC-0159

CLPX-Airborne: Polarimetric Ku-Band Scatterometer (POLSCAT) Data, Version 1

This data set contains Ku-band polarimetric scatterometer (POLSCAT) data collected as part of the Cold Land Processes Field Experiment (CLPX) to enable the development of a retrieval algorithm for snow water equivalent (SWE).

Geographic Coverage

Parameter(s):
  • Radar > Radar Backscatter
Spatial Coverage:
  • N: 40.00833, S: 39.76694, E: -105.71694, W: -106.025

  • N: 40.56667, S: 40.34167, E: -106.54167, W: -106.81694

  • N: 40.78361, S: 40.575, E: -106.14167, W: -106.41694

Spatial Resolution: Not Specified
Temporal Coverage:
  • 21 February 2002
  • 23 February 2002
  • 25 March 2002
  • 25 March 2003
  • 28 March 2003
  • 30 March 2003
Temporal Resolution: Not specified
Data Format(s):
  • ASCII Text
Platform(s) AIRCRAFT
Sensor(s): RADAR
Version: V1
Data Contributor(s): Simon Yueh
Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Yueh, S. 2003. CLPX-Airborne: Polarimetric Ku-Band Scatterometer (POLSCAT) Data, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: http://dx.doi.org/10.5067/UHA2RPUMRDJ4. [Date Accessed].

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Detailed Data Description

Format

The raw data from POLSCAT/CLPX flights have been processed to produce the normalized radar cross section (σ0) of the terrain. Data from each flight line are saved in a fixed-width ASCII text file containing 24 columns, of which only the first 12 are relevant to CLPX: 

Column 1: POLSCAT instrument time in sec (UT time) from the beginning of the day
Column 2: Aircraft GPS time in sec (UT) from the beginning of the day
Column 3: Latitude of the antenna footprint in degrees
Column 4: Longitude of the antenna footprint in degrees
Column 5: Azimuth angle of the vector from the antenna to the antenna footprint (0 degrees at north)
Column 6: Polarization roll angle in degrees
Column 7: Range from the antenna footprint to aircraft in meters
Column 8: Incidence angle in degrees
Column 9: σVV in dB, the σ0 for vertically polarized transmit and vertically polarized receive
Column 10: σHH in dB, the σ0 for horizontally polarized transmit and horizontally polarized receive
Column 11: σHV in dB, the σ0 for vertically polarized transmit and horizontally polarized receive
Column 12: σVH in dB, the σ0 for horizontally polarized transmit and vertically polarized receive

Note that σHV is supposed to be identical to σVH. The measurements agree with this expectation very well; the difference between measured σHV and σVH is within 0.2 dB most of the time, which is within the sensitivity of the POLSCAT system operating on the DC-8 aircraft.

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File and Directory Structure
2002/
  polscat-0219/
    02191615.red, etc.
  polscat-0221/
  polscat-0223/
  polscat-0325/
2003/
  polscat-0325/
    03251230.red, etc.
  polscat-0328/
  polscat-0330/
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File Naming Convention

Each data file has eight numbers in its filename, incorporating the date and time of data collection (mmddhhmm). The first four numbers of the filename represent the month 'mm' and day of month 'dd' and the last four indicate the start time (UT) of each flight line (hhmm). For example, the filename of a flight line commencing at 16:15 on 19 February is 02191615. Files are in directories by year (2002 and 2003).

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File Sizes

Files range in size from 1 to 114 KB.

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Spatial Coverage

Flights were flown over the Fraser, North Park, and Rabbit Ears MSAs of the CLPX. Flight lines are matched to data files in the Flight Summaries section of this document.

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Temporal Coverage

Three flights were flown on 19, 21, and 23 February 2002 during IOP1. Another flight was flown on 25 March 2002, when the DC-8 made a transit from Wisconsin to California (which coincided with IOP2). In 2003, three flights were flown on 25, 28 and 30 March during IOP 4.

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Parameter or Variable

The parameter presented in this data set is backscatter return from a Ku-band polarimetric scatterometer, measured in decibels (dB). This is not a direct measurement of SWE.

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Software and Tools

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Data Acquisition and Processing

POLSCAT is a Ku-band polarimetric scatterometer operating at 13.95 GHz. The transmitting polarization of POLSCAT is alternated between vertical (V) and horizontal (H) from pulse to pulse. Two receivers detect the V- and H-polarized radar echoes simultaneously. Each receiver down-converts the frequency of the backscatter signals and provides in-phase (I) and quadrature-phase (Q) components for data acquisition.

The POLSCAT antenna, mounted on a 62-degree port in the DC-8, pointed approximately in the center of the JPL Airborne Synthetic Aperture Radar (AIRSAR) swath. The front-end radio frequency box, where the calibration loop is located, was temperature-controlled to 35°±0.1°C to achieve 0.1 dB calibration stability. 

Raw data from POLSCAT flights have been processed to produce the normalized radar cross section of the terrain. The range from the target to the antenna was calculated using the aircraft altitude, aircraft GPS altitude, and a digital elevation map.

In-flight calibration was performed using a calibration loop consisting of one waveguide attenuator and two directional waveguide couplers in the radar front-end, which leaks a small transmit signal into the receivers. Tests conducted in the laboratory, and aircraft flight data, suggest that the calibration loop measurements are very stable, with a drift of less than 0.1 dB over several hours. The key parameters of POLSCAT are described in the following table.

POLSCAT Key Parameters

* Actual incidence angle depends on the aircraft attitude

Parameter Characteristics
Frequency 13.95 GHz
Polarization VV, HH, HV, VH
Nominal Incidence Angle* 40°
Antenna Beamwidth
Antenna Peak Gain 28 dB
Antenna Sidelobe <-30 dB
Polarization Isolation >35 dB
Footprint size 1 km x 0.7 km at 8 km altitude
Radar Transmit Peak Power 6 W at OMT flange
Radar Transmit PRF 2857 Hz
Radar Transmit Pulse Length 27 µs
Noise Equivalent σ0 -35 dB at 8 km altitude
Receiver A/D Converter 12 bits
Flight Summaries

The following tables summarize data from all the flight lines over the CLPX intensive study areas (ISAs). 

Column 1 indicates the day of data acquisition
Column 2 is the filename for the data from each flight line
Column 3 is the name of flight line
Column 4 is the nominal above-ground flight altitude
Column 5 is the ISA.

2002 Flight Summary

Date Filename Flight Line Nominal Altitude (ft) Remark
19 February 2002 02191615 NP270-1 26000 North Park
02191626 NP90-1 26000 North Park
02191637 NP270-2 26000 North Park
02191650 NP360-1 26000 North Park
02191703 NP270-3 26000 North Park
02191715 NP90-2 26000 North Park
02191726 NP270-4 26000 North Park
02191744 NP282-1 26000 North Park
02191800 RE270-1 26000 Rabbit Ears
02191810 RE90-1 26000 Rabbit Ears
02191821 RE270-2 26000 Rabbit Ears
02191834 RE180-1 26000 Rabbit Ears
02191851 RE270-3 26000 Rabbit Ears
02191902 RE90-2 26000 Rabbit Ears
02191913 RE270-4 26000 Rabbit Ears
02191925 RE90-3 26000 Rabbit Ears
02191942 FR270-1 26000 Fraser
02191953 FR90-1 26000 Fraser
02192003 FR270-2 26000 Fraser
02192017 FR360-1 26000 Fraser
02192030 FR270-3 26000 Fraser
02192041 FR90-2 26000 Fraser
02192054 FR270-4 26000 Fraser
02192119 PSR RE-1 5000 Rabbit Ears
02192131 PSR RE-2 5000 Rabbit Ears
02192140 PSR RE-3 5000 Rabbit Ears
02192151 PSR RE-4 5000 Rabbit Ears
02192202 PSR RE-5 5000 Rabbit Ears
02192213 PSR RE-6 5000 Rabbit Ears
02192224 PSR RE-7 5000 Rabbit Ears
21 February 2002 02211648 PSR FR-1 (AA 270-1) 5000 Fraser, Partly cloudy
02211658 PSR FR-2 (AA90-1) 5000 Fraser
02211710 PSR FR-3 (AA270-2) 5000 Fraser
02211720 PSR FR-4 (AA90-2) 5000 Fraser
02211731 PSR FR-5 (AA270-3) 5000 Fraser
02211742 PSR FR-6 (AA90-3) 5000 Fraser
02211754 PSR FR-7 (AA270-4) 5000 Fraser
02211801 Way pt 17-18 5000 Transit
02211811 PSR RE-2-180 (CC270-1) 5000 Rabbit Ears
02211820 PSR RE-6 (CC90-1) 5000 Rabbit Ears
02211833 PSR NP-5 (BB270-1) 5000 North Park
02211844 PSR NP-4 (BB90-1) 5000 North Park
02211933 NP270-1 26000 North Park
02211944 NP90-1 26000 North Park
02211955 NP270-2 26000 North Park
02212010 NP360-1 26000 North Park
02212023 NP270-3 26000 North Park
02212034 NP90-2 26000 North Park
02212045 NP270-4 26000 North Park
02212104 NP282-1 26000 North Park
02212123 RE270-1 26000 Rabbit Ears
02212134 RE90-1 26000 Rabbit Ears
02212145 RE270-2 26000 Rabbit Ears
02212159 RE180-1 26000 Rabbit Ears
02212214 RE270-3 26000 Rabbit Ears
02212225 RE90-2 26000 Rabbit Ears
02212236 RE270-4 26000 Rabbit Ears
02212247 RE90-3 26000 Rabbit Ears
02212305 FR270-1 26000 Fraser
02212316 FR90-1 26000 Fraser
02212327 FR270-2 26000 Fraser
02212341 FR360-1 26000 Fraser
02212356 FR270-3 26000 Fraser
02220007 FR90-2 26000 Fraser
02220021 FR270-4 26000 Fraser
23 February 2002 02231642 PSR FR-55 5000 Fraser
02231652 PSR FR-3-180 5000 Fraser
02231709 PSR RE-2-180 5000 Rabbit Ears
02231718 PSR RE-6 5000 Rabbit Ears
02231731 PSR NP-1 5000 North Park
02231741 PSR NP-2 5000 North Park
02231754 PSR NP-3 5000 North Park
02231806 PSR NP-4 5000 North Park
02231818 PSR NP-5 5000 North Park
02231828 PSR NP-6 5000 North Park
02231840 PSR NP-7 5000 North Park
02231915 NP270-1 26000 North Park
02231926 NP90-1 26000 North Park
02231939 NP270-2 26000 North Park
02231953 NP360-1 26000 North Park
02232005 NP270-3 26000 North Park
02232017 NP90-2 26000 North Park
02232028 NP270-4 26000 North Park
02232048 NP282-1 26000 North Park
02232104 RE270-1 26000 Rabbit Ears
02232118 RE90-1 26000 Rabbit Ears
02232128 RE270-2 26000 Rabbit Ears
02232140 RE180-1 26000 Rabbit Ears
02232155 RE270-3 26000 Rabbit Ears
02232206 RE90-2 26000 Rabbit Ears
02232217 RE270-4 26000 Rabbit Ears
02232229 RE90-3 26000 Rabbit Ears
02232252 FR270-1 26000 Fraser
02232302 FR90-1 26000 Fraser
02232313 FR270-2 26000 Fraser
02232327 FR360-1 26000 Fraser
02232339 FR270-3 26000 Fraser
02232351 FR90-2 26000 Fraser
02240003 FR270-4 26000 Fraser
25 March 2002 03251926 NP270-1 26000 North Park
03251937 NP90-1 26000 North Park
03251956 NP270-2 26000 North Park
03252011 NP360-1 26000 North Park
03252024 NP270-3 26000 North Park
03252035 NP90-2 26000 North Park
03252046 NP270-4 26000 North Park
03252104 NP282-1 26000 North Park
03252120 RE270-1 26000 Rabbit Ears
03252131 RE90-1 26000 Rabbit Ears
03252142 RE270-2 26000 Rabbit Ears
03252155 RE180-1 26000 Rabbit Ears
03252211 RE270-3 26000 Rabbit Ears
03252223 RE90-2 26000 Rabbit Ears
03252234 RE270-4 26000 Rabbit Ears
03252246 RE90-3 26000 Rabbit Ears
03252304 FR270-1 26000 Fraser
03252315 FR90-1 26000 Fraser
03252326 FR270-2 26000 Fraser
03252340 FR360-1 26000 Fraser
03252353 FR270-1 26000 Fraser
03260003 FR90-2 26000 Fraser
03260015 FR270-3 26000 Fraser
03260035 FR270-4 26000 Fraser
03260116 GS01B 26000 Sand Dunes
03260127 GS02B 26000 Sand Dunes
03260240 Criver 26000 Colorado River

2003 Flight Summary

Date Filename Flight Line Nominal AG 
Altitude (ft)
Remark
25 March 2003 03251209 NP270-1 26000 North Park; DC-8 ICAT Failed
03251244 NP360-1 26000 North Park
03251258 NP270-3 26000 North Park
03251308 NP90-2 26000 North Park
03251318 NP270-4 26000 North Park
03251337 NP282-1 26000 North Park
03251343 26000 wing wag
03251402 RE270-1  26000 Rabbit Ears
03251412 RE90-1 26000 Rabbit Ears
03251422 RE270-2 26000 Rabbit Ears
03251436 RE180-1 26000 Rabbit Ears
03251504 RE270-3 26000 Rabbit Ears
03251516 RE90-2 26000 Rabbit Ears
03251528 RE270-4 26000 Rabbit Ears
03251538 RE90-3 26000 Rabbit Ears
03251555 FR270-1 26000 Fraser
03251605 FR90-1 26000 Fraser
03251616 FR270-2 26000 Fraser
03251629 FR360-1 26000 Fraser
03251643 FR270-3 26000 Fraser
03251653 FR90-2 26000 Fraser
03251707 FR270-4 26000 Fraser
03251720 FR180-1 option 26000 Fraser
03251731 FR Orbit 26000 Fraser ISA, -30 deg roll
03251753 315-1 26000 Hayman Fire Scar
03251806 26000 Negative 60 deg roll
28 March 2003 03281157 NP270-1 26000 North Park
03281207 NP90-1 26000 North Park; Mouse touched keypad and interrupted polscat acquisition
03281218 NP270-2 26000 North Park
03281233 NP360-1 26000 North Park
03281246 NP270-3 26000 North Park
03281257 NP90-2 26000 North Park
03281307 NP270-4 26000 North Park
03281325 NP282-1 26000 North Park
03281339 NP Orbit E-W 26000 North Park
03281348 NP Orbit N-S 26000 North Park
03281356 NP Option 90-1 26000 North Park
03281402 Windrad cal 26000 wing wag-pitch
03281430 RE90-1 26000 Rabbit Ears
03281439 RE270-2 26000 Rabbit Ears
03281452 RE180-1 26000 Rabbit Ears
03281507 RE270-3 26000 Rabbit Ears
03281517 RE90-2 26000 Rabbit Ears
03281527 RE270-4 26000 Rabbit Ears
03281537 RE90-3 26000 Rabbit Ears
03281604 FR90-1 26000 Fraser
03281614 FR270-2 26000 Fraser
03281627 FR360-1 26000 Fraser
03281645 FR270-3 26000 Fraser
03281656 FR90-2 26000 Fraser
03281709 FR270-4 26000 Fraser
30 March 2003 03301207 NP270-1 26000 North Park; Thin scattered low-level clouds
03301217 NP90-1 26000 North Park
03301227 NP270-2 26000 North Park
03301241 NP360-1 26000 North Park
03301254 NP270-3 26000 North Park
03301304 NP90-2 26000 North Park
03301315 NP270-4 26000 North Park
03301332 NP282-1 26000 North Park
03301340 wing wag Transit
03301352 RE270-1 26000 Rabbit Ears
03301402 RE90-1 26000 Rabbit Ears
03301412 RE270-2 26000 Rabbit Ears
03301426 RE180-1 26000 Rabbit Ears
03301440 RE270-3 26000 Rabbit Ears
03301450 RE90-2 26000 Rabbit Ears
03301500 RE270-4 26000 Rabbit Ears
03301511 RE90-3 26000 Rabbit Ears
03301523 RE Option 70-1 (270) 26000 Rabbit Ears
03301534 RE Option Orbit S-N 26000 Rabbit Ears
03301543 RE Option Orbit W-E 26000 Rabbit Ears
03301606 FR90-1 26000 Fraser
03301617 FR270-2 26000 Fraser
03301631/1633 FR360-1 26000 Fraser
03301643 FR270-3 26000 Fraser
03301654 FR90-2 26000 Fraser
03301705 FR270-4 26000 Fraser
03301718 FR Option Orbit S-N 26000 Fraser
03301726 26000
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References and Related Publications

Contacts and Acknowledgments

Simon H. Yueh
Jet Propulsion Laboratory
M/S 300-233
Pasadena, CA 91109 USA

Acknowledgments: 

This research was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Document Information

Document Creation Date

8 January 2004

No technical references available for this data set.
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