Data Set Information
DATA_SET_NAME MARS ANALOG SOIL BUG OBSERVATIONS V1.0
DATA_SET_ID BUGLAB-E-BUG-4-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Information : OVERVIEW: -------- The Bloomsburg University Goniometer (BUG) was used to make bidirectional reflectance distribution function (BRDF) measurements of 5 Mars soil analogs (AREF_235, AREF_236, AREF_237, AREF_238, and JSC_Mars1). The measurements were made at Mars Exploration Rover (MER) Panoramic Camera (Pancam) wavelengths (450-990 nm) using the Pancam flight spare filters. More information on the center wavelength and passband for each filter can be found in Table 4 and Fig. 6 of BELLETAL2003 (see CATALOG/REF.CAT). The wavelengths used in the file names are rounded and may not precisely agree with those in Table 4 of BELLETAL2003. Additionally, the flight spares may not have the precise characteristics of those flown on the rovers. The following table shows the correspondance between the file-name wavelength and that listed in Table 4 of BELLETAL2003. File name suffix Filter Name Table 4 wavelength (nm) _450 L7/R1 432/436 _480 L6 482 _530 L5 535 _600 L4 601 _670 L3 673 _750 L2/R2 753/754 _800 R3 803 _860 R4 864 _900 R5 904 _930 R6 934 _990 R7 1009 The archive consists of 60 tabular data files, each with an accompanying detached PDS label. Within the DATA directory, the data are organized within 5 folders, corresponding to the 5 soil samples analyzed. Within each of the 5 folders are tabular data files containing the BRDF results for each of the MER Pancam wavelengths. Columns are incidence angle, emission angle, azimuth angle, phase angle (all in degrees, i and e are measured from nadir), and corrected radiance factor. Also contained in each of the 5 folders is a file containing the reflectance spectrum for the particular soil sample. Additional data for each sample can be found in the EXTRAS directory, including an image of each sample in its dish and a close-up image with a 1-cm field-of-view. Also in this directory is a graph showing a comparison of measurements made of a powder from the BUG and the long arm goniometer at the Jet Propulsion Laboratory [HAPKEETAL2007 in CATALOG/REF.CAT]. Please see EXTRINFO.TXT for more information about the files in the EXTRAS directory. SAMPLE INFORMATION: ------------------ Dr. Richard V. Morris (NASA Johnson Space Center) provided the AREF (Athena Reference) samples. Dr. Edward Guinness (Washington University in St. Louis) provided the JSC-Mars-1 sample [ALLENETAL1997 in CATALOG/REF.CAT]. According to Dr. Morris, the AREF samples are also known with another designation system (Hawaii, Mauna Kea, HWMK): AREF_235 is HWMK101 (< 1mm size fraction) AREF_236 is HWMK904 (< 1mm size fraction) AREF_237 is HWMK940 (< 1mm size fraction) AREF_238 is HWMK600 (< 1mm size fraction) More information on these samples can be found in MORRISETAL2000 and MORRISETAL2001 (see CATALOG/REF.CAT). There are two other samples that are proxies for AREF_235: HMWK919 and HMWK606, both of which were collected at the same site as HWMK101 but in different years. According to Dr. Morris, variability in these spectra is often encountered because the spectra are very dependent upon particle diameter, and different particle size fractions are often presented on a given surface poured at different times. DATA SET ACQUISITION: -------------------- To make the measurements, the detector reports a voltage based on the intensity of the light detected in a given wavelength. For reference, we first measure the voltage from a sample of Spectralon(R) viewed at incidence angle, i : 0, emission angle, e : 5 degrees. All sample voltages are divided by this reference to give a raw measure of reflectance. Subsequently, this reflectance is multiplied by cos(i)/cos(e) for each measurement to give radiance factor. We multiply by cos(i) because, as the incidence angle increases, the sample is illuminated by an increasing ellipsoid spot of light. The detector 'sees' the entire spot, so there is no fall-off in incident intensity as incidence angle increases. Multiplying by cos(i) accounts for this. Dividing by cos(e) accounts for the decreasing apparent area of the sample as seen by the detector. Because of the architecture of the goniometer, there are low-level secondary reflections from the sample off of the arm or platform that are also observed by the detector. These reflections have an azimuthal dependence because various parts of the sample platform or arms are within the detector field-of-view as the stage rotates to different azimuths. All surfaces have been flocked with black felt to minimize this, but we apply a correction factor before reporting the radiance factor. The correction factor is determined by holding emission angle at e : 0, fixing i at 15, 30, 45, and 60 deg in steps, and rotating in azimuth for each incidence angle. Because e : 0, there should be no change in the reflected light as the stage rotates in azimuth. Deviations from the minimum reflection observed represent additions due to scattered light. A low order polynomial is fit to the change in reflectance as azimuth varies, and this polynomial is used to correct all sample measurements at a given incidence angle. The corrections typically increase as incidence angle increases but are usually on order of 5% or less. A full set of measurements (cycle) at a given wavelength takes approximately one hour. We use a stabilized power supply with active optical feedback to maintain the intensity within 1% during the measurement cycle. We check the fidelity of our data by duplicating twenty-seven measurements at the same or mirror positions throughout each cycle and comparing results. We find our root-mean-square repeatability to typically be within 2%. Please see the GEOMETRY directory for information regarding the observation geometry for the data in the archive.
DATA_SET_RELEASE_DATE 2006-03-16T00:00:00.000Z
START_TIME 2006-01-01T12:00:00.000Z
STOP_TIME N/A (ongoing)
MISSION_NAME
MISSION_START_DATE
MISSION_STOP_DATE
TARGET_NAME EARTH
TARGET_TYPE PLANET
INSTRUMENT_HOST_ID BUGLAB
INSTRUMENT_NAME BLOOMSBURG UNIVERSITY GONIOMETER
INSTRUMENT_ID BUG
INSTRUMENT_TYPE RELFECTANCE SPECTROMETER
NODE_NAME Geosciences
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE This data set underwent external peer review from July 2 through September 28, 2007.
CITATION_DESCRIPTION Shepard, M.K., and J. Ward, Mars Soil Analog BUG Observations, BUGLAB-E-BUG-4-V1.0, NASA Planetary Data System, 2006.
ABSTRACT_TEXT The Bloomsburg University Goniometer (BUG) was used to make bidirectional reflectance distribution function (BRDF) measurements of Mars soil analogs at Mars Exploration Rover (MER) Panoramic Camera (Pancam) wavelengths.
PRODUCER_FULL_NAME MICHAEL K. SHEPARD
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