As part of the FIFE experiment, natural terrestrial gamma radiation data over a network of 24 flight lines were collected. The data acquisition procedure was designed to accumulate and store spectral radiation data along a flight line from which estimates of soil moisture could be computed. Ground-based soil moisture measurements were used to make a one-time calibration of the natural terrestrial radioisotope signal over the flight line network. A time-series of airborne soil moisture measurements (to a depth of 20 cm) was compared to an extensive, independent data set of ground-based soil moisture measurements. Estimates for flight line segments were found to have an average RMS error of approximately 2.5 % soil moisture (Peck et al., 1990).
Gamma Ray Data: Peck (FIFE).
(Peck Airborne Gamma Ray Soil Moisture).
The Peck Airborne Gamma Ray Soil Moisture Data Set contains airborne soil moisture measurements. A time-series of airborne soil moisture measurements (to a depth of 20 cm) was compared to an extensive, independent data set of ground-based soil moisture measurements.
The objectives of this research were: 1) to obtain improved estimates of the soil moisture conditions for the FIFE experimental area during the period of Intensive Field Campaigns, and 2) to provide the information for validating and calibrating other remote sensing methods for measuring soil moisture.
Percent soil moisture.
As part of the FIFE experiment, natural terrestrial gamma radiation data over a network of 24 flight lines were collected in June and July 1987, and in August 1989. Ground-based soil moisture measurements were used to make a one-time calibration of the natural terrestrial radioisotope signal over the flight line network. A time-series of airborne soil moisture measurements (to a depth of 20 cm) was compared to an extensive, independent data set of ground-based soil moisture measurements. Airborne soil moisture measurements were made over the flight line network with an average bias of 1.7 percent, an average absolute error of 2.30 percent soil moisture, and a root mean square error of 3.02 percent soil moisture when compared to independent, ground-based soil moisture measurements for 97 airborne soil moisture observations (Carroll and Peck 1988). Estimates for flight line segments were found to have an average RMS error of approximately 2.5 % soil moisture (Peck et al., 1990).
PECK_GAMMA_RAY_DATA.
Dr. Eugene L. Peck
Hydex Corporation
Dr. Tom Carroll
National Weather Service, NOAA
Alternative Approach to Ground Truth Soil Moisture.
Contact 1:
Dr. Eugene L. Peck
Hydex Corporation
Vienna, VA
(703) 281-6284 55450
FAX (703)281-6284
Contact 2:
Dr. Tom Carroll
NRSHP, Office of Hydrology
NWS, NOAA
Minneapolis, MN
(612) 725-3039
FAX (612) 725-3338
The assistance of the staff of the Kansas State University in the analysis of the ground samples in support of the Peck Airborne Gamma Ray Soil Moisture data is acknowledged. The field assistance rendered by Carrie Miller, in collecting ground soil moisture samples during FIFE 1989 was sincerely appreciated. The cooperation of Dr. Jim Wang, NASA, in providing transect gravimetric soil moisture measurements and supplying digital information on estimates of soil moisture by microwave (PBMR) has been greatly appreciated and contributed to the usefulness of the airborne gamma soil moisture estimates.
Airborne soil moisture measurement is based on the difference between natural terrestrial gamma radiation flux measured for comparatively wet and dry soils. The presence of moisture in the soil causes an effective increase in the soil density resulting in an increased attenuation of the gamma flux for relatively wet soil and a correspondingly lower flux at the ground surface. The gamma flux from the ground is a function primarily of the water mass and radioisotopes concentration (which remains constant over time) near the surface. Only the mass of the moisture, not the phase, affects the attenuation. The gamma flux originates from the potassium, uranium and thorium radioisotopes in the soil. In a typical soil, 91 percent of the gamma radiation is emitted from the top 10 cm of the soil, 96 percent from the top 20 cm and 99 percent from the top 30 cm. Other sources of radiation, which contribute to the measured gamma flux, include the daughter products of radon gas in the atmosphere, high energy cosmic particles (i.e., greater than 3.0 MeV), and trace sources of radioactivity within the aircraft and the detection system itself (Carroll and Allen 1988).
The airborne detector package consists of five downward-looking 10.2 x 10.2 x 40.6 cm NaI(Tl) scintillation detectors; two 10.2 x 10.2 x 20.3 cm, upward-looking detectors (used to isolate the effects of the random gas contribution); a pulse height analyzer (PHA); a Hewlett-Packard 9825 minicomputer used to reduce and record the output data onto magnetic tape; temperature, pressure, and radar altitude sensors; and a remote control unit used by the system operator or navigator to control and monitor the data collection (Carroll and Allen 1988).
Airborne.
A twin-engine Aero Commander aircraft.
The mission objectives were as follows:
Soil moisture.
Flight lines established for the FIFE investigation are, on average, 6.2 km long and 305 m wide. The airborne technique requires a one-time flight line calibration in which background gamma radiation data and ground-based soil moisture data are collected simultaneously and used to calibrate each flight line. Reliable, real-time, mean areal soil moisture measurements can be made for the upper 20 cm of soil over the average 1.9 square km flight line once both the background and current, uncollided terrestrial gamma count rates and background soil moisture data are available. Once a flight line is calibrated, airborne soil moisture measurements can be made with no future ground-based soil moisture data support required.
The aircraft flies at an altitude of 150 m and measures natural terrestrial gamma radiation over a path 305 m wide. Consequently, radiation data collected over each flight line are mean areal measurements over approximately 1.9 km^2.
National Weather Service NOAA
Minneapolis, Minnesota.
Calibration is accomplished by collecting radiation data at different altitudes and using the changing airmass as an attenuation medium. A reliable calibration can be generated in one area and used in another with a different radioisotope concentration.
The radioisotope concentration in the soil does not significantly change with time; consequently, there is no need for additional background data collection once a radiation spectrum has been collected for a particular flight line.
The airborne technique requires a one-time flight line calibration in which background gamma radiation data and ground-based soil moisture data are collected simultaneously and used to calibrate each flight line. Once a flight line is calibrated, airborne soil moisture measurements can be made with no future ground-based soil moisture support required.
During the calibration procedure, stripping equations are derived for isolating other extraneous sources of radiation.
Twenty-four (24) flight lines were flown a number of times during the FIFE experiment. Ambient radiation data are collected by the detection system and immediately reduced using algorithms developed to describe the presence of atmospheric radon, high-energy cosmic radiation, Compton scattering effects within the radiation spectra, and extraneous background radiation contributed by the aircraft and detection system. Pressure, temperature, and radar altitude data are also recorded and used to calculate the attenuation of terrestrial radiation due to the air mass between the source and sensor (approx. 17 g cm^-2 at an altitude of 150 m).
Not available.
Locations Of Flights Lines
Twenty-four flight lines were flown during the FIFE experiment (nineteen in 1987 and five additional ones in 1989). A general overview of the FIFE gamma-ray surveys showing a map of the 24 flight lines has been published (Peck et al., 1992). Each flight line is divided into a specific number (varying from 3 to 22) of equally spaced sections. The first section begins at the start of the flight line. A flight line may be a straight line or a series of straight line segments.
The FIFE study area with areal extent of 15 km by 15 km, is located south of the Tuttle Reservoir and Kansas River, about 10 km from Manhattan, Kansas, USA. The northwest corner of the area has UTM coordinates of 4,334,000 Northing and 705,000 Easting in UTM Zone 14.
Twenty-four flight lines were flown during the FIFE experiment (nineteen in 1987 and five additional ones in 1989). Each flight line is divided into a specific number (varying from 3 to 22) of equally spaced sections. Section One begins at the start of the flight line. The SITEGRID_ID gives the location of the start of each flight line. A flight line may be a straight line or a series of straight line segments. The exact location for the start of each flight is as listed below.
See the Other Relevant Information Section for more information on the location of the entire flight lines.
SITEGRID STN_ID NORTHING EASTING LATITUDE LONGITUDE
-------- ------ -------- ------- -------- ---------
0563-GRP 619 4333085 717545 39 07 18 -96 29 01
1930-GRP 620 4330223 711036 39 05 51 -96 33 35
2036-GRP 603 4329945 712150 39 05 41 -96 32 49
2714-GRP 605 4328561 707714 39 05 00 -96 35 55
2826-GRP 608 4328472 710145 39 04 55 -96 34 14
3014-GRP 611 4327913 707707 39 04 39 -96 35 56
3025-GRP 606 4328098 710035 39 04 43 -96 34 19
3126-GRP 607 4327854 710138 39 04 35 -96 34 15
3520-GRP 604 4327082 708956 39 04 11 -96 35 05
3527-GRP 609 4326998 710401 39 04 07 -96 34 05
3634-GRP 622 4326727 711828 39 03 57 -96 33 06
3639-GRP 602 4326844 712739 39 04 00 -96 32 28
3757-GRP 616 4326546 716499 39 03 47 -96 29 52
3830-GRP 621 4326457 710969 39 03 49 -96 33 42
3856-GRP 618 4326354 716264 39 03 41 -96 30 02
3907-GRP 601 4326241 706308 39 03 46 -96 36 56
3939-GRP 612 4326104 712735 39 03 36 -96 32 29
4041-GRP 617 4326085 713192 39 03 35 -96 32 10
4427-GRP 610 4325146 710403 39 03 07 -96 34 07
5110-GRP 613 4323729 707000 39 02 24 -96 36 30
5534-GRP 623 4322994 711832 39 01 56 -96 33 10
6562-GRP 615 4320926 717448 39 00 44 -96 29 19
6936-GRP 614 4320230 712292 39 00 26 -96 32 54
8749-GRP 624 4316628 714869 38 58 27 -96 31 11
The aircraft flew at an altitude of 150 m and measures natural terrestrial gamma radiation, on average, over a path 6.2 km long and 305 m wide.
Not available.
The data acquisition procedure is designed to accumulate and store spectral radiation data along a flight line from which estimates of soil moisture may be computed.
Not available.
Not available.
Airborne gamma radiation data were collected during two periods, June 2 - 10, 1987 and August 1 - 10, 1989. Airborne measurements were made on the following dates:
August 1, 1989
June 2, 1987 August 2, 1989
June 3, 1987 August 4, 1989
July 6, 1987 August 5, 1989
July 7, 1987 August 6, 1989
July 8, 1987 August 7, 1989
July 9, 1987 August 8, 1989
July 10, 1987 August 9, 1989
August 10, 1989
Not available.
The data acquisition procedure is designed to accumulate and store window data in multiple cycles of 5 seconds or longer.
The SQL definition for this table is found in the PECK_GAM.TDF file located on FIFE CD-ROM Volume 1.
Parameter/Variable Name
Parameter/Variable Description Range Units Source
SITEGRID_ID This is a FIS grid location code. FIS Site grid codes (SSEE-III) give the south (SS) and east (EE) cell number in a 100 x 100 array of 200 m square cells. The last 3 characters (III) are an instrument identifier.
STATION_ID The three-digit FIFE site min = 601, FIS identification number for the site max = 624 where the data were collected.
OBS_DATE The date on which the observation min = 03-JUN-87, HYDEX CORP was made. max = 10-AUG-89
DURATION The length of time it took to min = 10.8, [sec] HYDEX CORP collect the data. max = 460
START_SEGMENT The identification number for the min = 1, HYDEX CORP first transect segment the data is max = 21 averaged over. If this column is null, then the average is over the entire transect.
END_SEGMENT The identification number for the min = 1, HYDEX CORP last transect segment the data is max = 22 averaged over. Several segments may be averaged together if there are not enough data for a single segment average.
NUM_SEGMENT The number of transect segments min = 1, HYDEX CORP averaged together. max = 4
SOIL_MOISTURE The soil moisture as determined min = 8.22, [percent] GAMMA RAY from the gamma ray instrument. max = 47.58, SENSOR missing = -99.9 9 or -99.9
SOIL_MOISTURE_SDEV The standard deviation of the min = .4, HYDEX CORP soil moisture. max = 6.93, missing = -99
FIFE_DATA_CRTFCN_CODE * The FIFE Certification Code for CPI = checked FIS the data, in the following format: by principal CPI (Certified by PI), CPI-??? investigator (CPI - questionable data).
LAST_REVISION_DATE The last revision date for the min = 14-MAY-91, FIS data, in the format (DD-MMM-YY). max = 15-MAY-92
Footnote:
* Decode the FIFE_DATA_CRTFCN_CODE field for the following:
The primary certification codes are:
The certification code modifiers are:
SITEGRID_ID STATION_ID OBS_DATE DURATION START_SEGMENT END_SEGMENT
----------- ---------- --------- --------- ------------- ------------
2036-GRP 603 03-JUN-87 33.500 1 1
3520-GRP 604 03-JUN-87 73.300 1 1
3639-GRP 602 03-JUN-87 44.100 1 1
3907-GRP 601 03-JUN-87 21.300 1 2
NUM_SEGMENT SOIL_MOISTURE SOIL_MOISTURE_SDEV FIFE_DATA_CRTFCN_CODE
----------- ------------- ------------------ ---------------------
1 31.420 4.150 CPI
1 25.690 2.110 CPI
1 35.940 1.510 CPI
2 -99.990 -99.000 CPI
LAST_REVISION_DATE
------------------
08-JUN-93
08-JUN-93
08-JUN-93
08-JUN-93
The Peck Airborne Gamma Ray Soil Moisture Data Set contains a time-series of airborne soil moisture measurements (to a depth of 20 cm) collected in June and July 1987, and in August 1989.
A general description of data granularity as it applies to the IMS appears in the EOSDIS Glossary.
The CD-ROM file format consists of numerical and character fields of varying length separated by commas. The character fields are enclosed with a single apostrophe. There are no spaces between the fields. Each file begins with five header records. Header records contain the following information:
Each field represents one of the attributes listed in the chart in the Data Characteristics Section and described in detail in the TDF file. These fields are in the same order as in the chart.
Ambient radiation data collected by the detection system are reduced using algorithms to describe the presence of atmospheric radon, high energy cosmic radiation, Compton scattering effects within the radiation spectra, and extraneous background radiation. Pressure, temperature, and radar altitude data are also recorded continuously and used to calculate the attenuation of terrestrial radiation due to the airmass between the source and the sensor. Uncollided terrestrial radiation count rates, normalized to time and airmass, are used as the background and current gamma radiation data sets.
Tapes of the airborne data are processed at the National Weather Service, Office of Hydrology, Minneapolis, MN with soil moisture estimates for flight lines determined.
The processed data from the National Weather Service were used to compute mean soil moisture values for the flight line sections.
Some soil moisture estimates for flight line sections were found during comparison studies to be unreliable and have been indicated in the table. The apparent reason for the unreliable estimates was that ground soil moisture samples were insufficient or not representative of the section during the calibration of the flight line.
Three independent soil moisture values are calculated by measuring the attenuation of the gamma flux as a consequence of increased (or decreased) soil density due to the presence of soil moisture. Soil moisture values are calculated using data from the potassium window (1.36 to 1.56 MeV), the thorium window (2.41 to 2.81 MeV) and the total energy spectrum (0.41 to 3.0 MeV). These independent soil moisture values are weighted (weighing values are dependent upon the airborne collection time for the flight line or section of a flight line) to obtain the values in the tables of airborne soil moisture.
Evaluation of the flight line soil moisture estimates have indicated that some of the section values are not reliable and these values have been noted. The FIFE_DATA_CRTFCN_CODE column for those data has been set to CPI-HIGH for soil moisture measurements that are higher than normal and to CPI-LOW for measurements that are lower than normal.
Soil moisture.
Not available.
Errors associated with the airborne percentage of soil moisture calculation stem from two principal sources: (1) the uncertainty of the background soil moisture data [M(0)], and (2) the uncertainty of the pure uncollided gamma count rates (i.e., background and current radiation data).
Because only a finite number of ground-based soil samples are available over a flight line, a degree of uncertainty is incorporated into the population mean soil moisture estimate [M(0)].
A time-series of airborne soil moisture measurements (to a depth of 20 cm) is reported and compared to an extensive, independent data set of ground-based soil moisture measurements.
The accumulated ground soil moisture data base allows an estimate of the population soil moisture variance to be calculated with reasonable confidence. Using the estimate of the population variance, it is possible to calculate the number of ground soil samples required per flight line to estimate the population mean soil moisture for the flight line with a confidence interval of 95%.
Airborne soil moisture measurements were made over the flight line network with an average bias of 0.48 percent soil moisture, a percent bias of 1.7 percent. This translates to an average absolute error of 2.30 percent soil moisture, and a root mean square error of 3.02 percent soil moisture when compared to independent, ground-based soil moisture measurements for 97 airborne soil moisture observations (Carroll et al. 1988). Soil moisture values for sections of flight lines had an RMS error of approximately 2.5 % (Peck et al. 1990).
The airborne gamma radiation soil moisture values have been compared with the CORE soil moisture measurements (Carroll et al. 1988), with the Pushbroom Microwave Radiometer (PBMR) measurements (Peck and Carroll 1991), and with estimates from water balance model for the Kings Creek basin (Peck and Carroll 1992).
The data verification performed by the ORNL DAAC deals with the quality of the data format, media, and readability. The ORNL DAAC does not make an assessment of the quality of the data itself except during the course of performing other QA procedures as described below.
The FIFE data were transferred to the ORNL DAAC via CD-ROM. These CD-ROMs are distributed by the ORNL DAAC unmodified as a set or in individual volumes, as requested. In addition, the DAAC has incorporated each of the 98 FIFE tabular datasets from the CD-ROMs into its online data holdings. Incorporation of these data involved the following steps:
Each distinct type of data (i.e. "data set" on the CD-ROM), is accompanied by a documentation file (i.e., .doc file) and a data format/structure definition file (i.e., .tdf file). The data format files on the CD-ROM are Oracle SQL commands (e.g., "create table") that can be used to set up a relational database table structure. This file provides column/variable names, character/numeric type, length, and format, and labels/comments. These SQL commands were converted to SAS code and were used to create SAS data sets and subsequently to input data files directly from the CD-ROM into a SAS dataset. During this process, file names and directory paths were captured and metadata was extracted to the extent possible electronically. No files were found to be corrupted or unreadable during the conversion process.
Additional Quality Assurance procedures were performed as follows:
As errors are discovered in the online tabular data by investigators, users, or DAAC staff, corrections are made in cooperation with the principal investigators. These corrections are then distributed to users. CD-ROM data are corrected when re-mastering occurs for replenishment of CD-ROM stock.
Not available.
Discussed under other headings.
Soil moisture estimates for the flight lines have been found to be reliable. Some of the estimated soil moisture values for segments of flight lines have been found to be unreliable when compared with other soil moisture estimates and measurements. These have been indicated in the FIFE_DATA_CRTFCN_CODE column.
The digitized Soil Moisture Contours that have been prepared and are in the GRABBAG section of FIFE CD-ROM Volume 1 are based on all available information on soil moisture for the FIFE research area and should be of value when mean area values are required. The contours values represent mean soil moisture for areas of 0.5 km^2.
Information on the National Weather Service airborne gamma system is available in the reference publications (Carroll 1987, and Carroll and Allen 1988).
The chart below describes the location information which is available for each of the transect segment end points and ground soil moisture sample locations used in the gamma ray soil moisture study. Column names and descriptions are listed below, along with ranges, units, and source for each column. The data associated with the table can be found in the document directory, along with this document.
Parameter/Variable Name
Parameter/Variable Description Range Units Source
SITEGRID_ID This is a FIS grid location code. FIS Site grid codes (SSEE-III) give the south (SS) and east (EE) cell number in a 100 x 100 array of 200 m square cells. The last 3 characters (III) are an instrument identifier.
STATION_ID The station ID designating the min = 601, HYDEX location of the observations. max = 624 CORPORATION, VIRGINIA
LOCN_ID_NUM The identification number for min = 1, HYDEX the transect segment or ground max = 210 CORPORATION, sample point. Transect segments VIRGINIA have numbers less than 100; ground samples have numbers greater than 100.
START_LAT The latitude of the start point min = 38 58 25, [DEGREES NOAA of the segment. max = 39 7 22 MINUTES AEROCOMMANDER SECONDS]
START_LON The longitude of the start point min = 96 27 30, [DEGREES NOAA of the segment. max = 96 36 56 MINUTES AEROCOMMANDER SECONDS]
END_LAT The latitude of the end point of min = 39 0 17, [DEGREES NOAA the segment. max = 39 7 26 MINUTES AEROCOMMANDER SECONDS]
END_LON The longitude of the end point of min = 96 26 45, [DEGREES NOAA the segment. max = 96 37 18 MINUTES AEROCOMMANDER SECONDS]
COMMENTS Any comments about the data. HYDEX CORPORATION, VIRGINIA
The Peck Airborne Gamma Ray Soil Moisture data help provide information for validating and calibrating other remote sensing methods for measuring soil moisture.
The FIFE field campaigns were held in 1987 and 1989 and there are no plans for new data collection. Field work continues near the FIFE site at the Long-Term Ecological Research (LTER) Network Konza research site (i.e., LTER continues to monitor the site). The FIFE investigators are continuing to analyze and model the data from the field campaigns to produce new data products.
Software to access the data set is available on the all volumes of the FIFE CD-ROM set. For a detailed description of the available software see the Software Description Document.
ORNL DAAC User Services
Oak Ridge National Laboratory
Telephone: (865) 241-3952
FAX: (865) 574-4665
Email: ornldaac@ornl.gov
ORNL Distributed Active Archive Center
Oak Ridge National Laboratory
USA
Telephone: (865) 241-3952
FAX: (865) 574-4665
Email: ornldaac@ornl.gov
Users may place requests by telephone, electronic mail, or FAX. Data is also available via the World Wide Web at http://daac.ornl.gov.
FIFE data are available from the ORNL DAAC. Please contact the ORNL DAAC User Services Office for the most current information about these data.
The Peck Airborne Gamma Ray Soil Moisture data set is contained on FIFE CD-ROM Volume 1. The CD-ROM file name is as follows:
\DATA\SOILMSTR\PECK_GAM\Yyyyy\ydddgrid.PGR
Where yyyy are the four digits of the century and year (e.g., Y1987 = 1987). Note: capital letters indicate fixed values that appear on the CD-ROM exactly as shown here, lower case indicates characters (values) that change for each path.
The format used for the filenames is: ydddgrid.sfx, where grid is the four-number code for the location within the FIFE site grid, y is the last digit of the year (e.g., 7 = 1987, and 9 = 1989), and ddd is the day of the year (e.g., 061 = sixty-first day of the year). The filename extension (.sfx), identifies the data set content for the file (see Data Characteristics) and is equal to .PGR for this data set.
Carroll, T.R. 1987. Operational remote sensing of snow water equivalent and soil moisture in the United States using natural terrestrial gamma radiation. J. Int. Asso. Hydro. Sci. IAHS Pub. 166:213-223.
Carroll, T.R. 1981. Airborne soil moisture measurements using natural terrestrial gamma radiation. Soil Sci. 132:358-366.
Carroll, T.R., E.L. Peck, and D.M. Lipinski. 1988. Airborne time-series measurements of soil moisture using terrestrial gamma radiation. Proc. Ann. Conf. Am. Soc. Photogram. Remote Sens. St. Louis, Missouri.
Peck, E. L. 1992. Airborne Gamma Radiation Measurements of Soil Moisture During FIFE. Activities and Results. Hydex Final Report, NASA Contract NAS5-30959. April.
Peck, E. L., and T. R. Carroll. 1991. Comparison of Airborne Soil Moisture Measurements by Microwave and Gamma Radiation Techniques. Contract Report. August 9, 1991.
Peck, E.L., and T.R. Carroll. 1992. Comparison of Airborne Gamma Radiation Soil Moisture measurements with Hydrologic Model Outputs. Contract Report. December 1, 1991 (revised January 18, 1992).
Peck, E.L., T.R. Carroll, and D.M. Lipinski. 1990. Airborne gamma radiation soil moisture measurements over short flight lines. Sym. on the First ISLSCP Field Experiment. Anaheim, CA. American Meteorological Soc. Boston Massachusetts. p. 79-84.
Peck, E. L., T. R. Carroll, and D.M. Lipinski. 1992. Airborne Soil Moisture Measurements for First International Satellite Land Surface Climatology Program Field Experiment. Jour. Geophys. Res. 97, No. D17. p. 18,961-18,967. Nov 30.
The Collected Data of the First ISLSCP Field Experiment is archived at the EOS Distributed Active Archive Center (DAAC) at Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee (see the Data Center Identification Section). Documentation about using the archive and/or online access to the data at the ORNL DAAC is not available at this revision.
A general glossary for the DAAC is located at Glossary.
May 6, 1994 (citation revised on October 14, 2002).
Warning: This document has not been checked for technical or editorial accuracy by the FIFE Information Scientist. There may be inconsistencies with other documents, technical or editorial errors that were inadvertently introduced when the document was compiled or references to preliminary data that were not included on the final CD-ROM.
Previous versions of this document have been reviewed by the Principal Investigator, the person who transmitted the data to FIS, a FIS staff member, or a FIFE scientist generally familiar with the data.
February 12, 1996.
ORNL-FIFE_PECK_GAM.
Peck, E. L., and T. Carroll. 1994. Gamma Ray Data: Peck (FIFE). Data set. Available on-line [http://www.daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. Also published in D. E. Strebel, D. R. Landis, K. F. Huemmrich, and B. W. Meeson (eds.), Collected Data of the First ISLSCP Field Experiment, Vol. 1: Surface Observations and Non-Image Data Sets. CD-ROM. National Aeronautics and Space Administration, Goddard Space Flight Center, Greenbelt, Maryland, U.S.A. (available from http://www.daac.ornl.gov).
http://daac.ornl.gov/FIFE/Datasets/Soil_Moisture/Peck_Gamma_Ray_Data.html