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. 2003. CLPX-Airborne: Polarimetric Ku-Band Scatterometer (POLSCAT) Data. Boulder, CO: National Snow and Ice Data Center. Digital Media.
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 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 5° 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
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
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