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

Summary

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). POLSCAT is a Ku-band polarimetric scatterometer operating at 13.95 GHz. Flights were flown on 19, 21, and 23 February 2002 (during IOP1), 25 March 2002 (IOP2), and 25, 28 and 30 March 2003 (IOP 4). 205 flight lines of data were collected over Fraser, North Park and Rabbit Ears MSAs.

The NASA CLPX is a multi-sensor, multi-scale experiment that focuses on extending a local-scale understanding of water fluxes, storage, and transformations to regional and global scales. Within a framework of nested study areas in the central Rocky Mountains of the western United States, ranging from 1-ha to 160,000 km2, intensive ground, airborne, and spaceborne observations were collected. Data collection focused on two seasons: mid-winter, when conditions are generally frozen and dry, and early spring, a transitional period when both frozen and thawed, dry and wet conditions are widespread.

Citing These Data

Yueh, S. H. 2003. CLPX-Airborne: Polarimetric Ku-Band Scatterometer (POLSCAT) Data. [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center.

Overview Table

Category Description
Data format fixed-width ASCII text
Spatial coverage Fraser, North Park and Rabbit Ears MSAs of the CLPX
Temporal coverage and resolution 19, 21, and 23 February 2002; 25 March 2002; and 25, 28 and 30 March 2003
File size Individual flight lines range between 1 and 114 KB; total size of all flight lines is 10.34 MB
Parameter(s) Backscatter return from Ku-band polarimetric scatterometer, measured in decibels (dB).
Procedures for obtaining data Data are available via FTP

Table of Contents

1. Contacts
2. Detailed Data Description
3. Data Access
4. Data Acquisition
5. References and Related Publications
6. Document Information

1. Contacts and Acknowledgements

Investigator(s) Name and Title


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

Technical Contact

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

Acknowledgements

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

2. Detailed Data Description

This data set contains Ku-band polarimetric scatterometer (POLSCAT) data collected as part of the CLPX, to enable the development of a retrieval algorithm for snow water equivalent (SWE). POLSCAT is a Ku-band polarimetric scatterometer operating at 13.95 GHz. 205 flight lines of data were collected over Fraser, North Park and Rabbit Ears MSAs.

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.

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/

	

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).

File Size

Files range in size from 1 to 114 KB.

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.

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.

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.

3. Data Access

Data Access

Data are available via FTP at ftp://sidads.colorado.edu/pub/DATASETS/CLP/data/airborne/nsidc0159_polscat/

Related Data Collections

All CLPX Data Sets
CLPX-Ground: Ground-based L and Ku Band Polarimetric Scatterometry

Quality Assessment:

4. Data Acquisition

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 350.1C 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

ParameterCharacteristics
Frequency 13.95 GHz
PolarizationVV, HH, HV, VH
Nominal Incidence Angle*40°
Antenna Beamwidth
Antenna Peak Gain28 dB
Antenna Sidelobe<-30 dB
Polarization Isolation>35 dB
Footprint size1 km x 0.7 km at 8 km altitude
Radar Transmit Peak Power6 W at OMT flange
Radar Transmit PRF2857 Hz
Radar Transmit Pulse Length27 µs
Noise Equivalent σ0 -35 dB at 8 km altitude
Receiver A/D Converter12 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  

5. References and Related Publications

Yueh, Simon H., William J. Wilson, and Steve Dinardo. 2002. Polarimetric Radar Remote Sensing of Ocean Surface Wind. IEEE Trans. Geosci. Remote Sens., Vol. 40, No. 4, pp. 793-800.

6. Document Information

List of Acronyms

CLPX = NASA Cold Land Processes Field Experiment
IOP = Intensive Observation Period
ISA = Intensive Study Area
LRSA = Large Regional Study Area
LSOS = Local Scale Observation Site
MSA = Meso-cell Study Area

Document Creation Date

8 January 2004

Document Revision Date