Introduction to the 120-Color Lunar NIR Spectrophotometry Data December 5, 2000 Contents 1. Quick Access to the Data 2. Description of the Data Set 3. Archive Contents 4. File Formats 5. Whom to Contact for Information 6. Cognizant Persons 1. Quick Access to the Data To begin browsing the data immediately, open the file index/index.htm in a Web browser. 2. Description of the Data Set This data set consists of reflectance spectra of small lunar areas (3-10 km in diameter) measured in 120 spectral channels from 0.62 to 2.6 micrometers using the McCord two-component circular-variable-filter (CVF) near-infrared photometer. Approximately 400 spectra are included that were acquired in the late 1970s and 1980s. Observational approach is described in McCord et al., 1981 (MCCORDETAL1981), Pieters, 1986 (PIETERS1986), and Pieters and Pratt, 2000 (PIETERSANDPRATT2000). (See CATALOG/REF.CAT for complete references.) A small aperture allows light from the selected lunar area to pass through the CVF and onto a single InSb detector. Each spectral channel is obtained sequentially as the CVF is rotated. Data were acquired using the 2.2 m telescope on Mauna Kea, Hawaii. Since absolute albedo information is not obtained, all spectra have been scaled to unity near 1.02 micrometers, a wavelength relatively free of atmospheric absorptions. The precise wavelengths of spectral channels varies somewhat from run to run because wavelength calibration shifts the effective band center from night to night. The first half of the CVF produces data at a spectral resolution of ~100 Angstroms while resolution of the second half is ~200 Angstroms. Data points where the two sections of the CVF were joined are unreliable. The overlap area typically involves about 5 data points near 1.34 micrometers. All data were acquired as relative reflectance spectra and were calibrated to scaled reflectance data using a directional-hemispheric (diffuse) spectrum of Apollo 16 soil acquired by J. B. Adams. At the time these telescopic spectra were acquired, bi-directional reflectance data for lunar soils were not available for calibration. Acquisition of the 120 data points takes a few minutes; thus, a 120-point spectrum can be affected by the accuracy of guiding on the Moon as well as changing sky conditions and instrument stability. In most cases, several independent runs of data taken in sequence were averaged. Error bars are the standard deviation of this average and only refer to the repeatability of the measurement under these conditions. Data values of zero or error bar values of 99.99 or negative numbers are used to designate data for a channel that is likely to be in error (typically at the beginning, end, or join of the CVF). Spectral calibration and correction factors for bi-directional data are discussed in more detail under Spectral Calibration, in the file DOCUMENT/CALIB.TXT (hypertext version CALIB.HTM). See Pieters, 1993 (PIETERS1993), for a review of data interpretations. In addition to file identification, the following information is provided for each spectrum: name of the area designated by the astronomer, date of data acquisition, lunar coordinates of the area observed derived from images and finding charts, general classification (see below), and an overall data quality assessment made by astronomers after data reduction. Lunar coordinates are in decimal degrees with positive being north and east from 0 latitude, 0 longitude on the central nearside. Negative values are south and west from 0, 0. Coordinates for areas observed use the reference images of Whitaker (WHITAKERETAL1963). For areas named after Apollo and Luna landing sites the coordinates given are for the region actually observed, which are not necessarily directly over the landing site. General classification of the areas observed includes the following: CF (Crater Feature) Ejecta Floor Halo Ray Wall CP (Central Peaks) CR (Crater) Dark halo Highland Mare Rim H (Highlands) H-RS (Highland "Red Spot") M (Mare) MM (Mantling Material) MT (Mountain) Massif The spatial resolution of these telescopic data depends on the aperture used and the telescope configuration. Most data are for areas 5-10 km in diameter. For small lunar features the measured spectrum also contains radiation from surrounding soil. An example of this relation is shown by the figure in the file document/clemspec.gif where the telescopic spectrum for a small crater in Mare Serenitatis (MSA: located at 19.5 degrees north, 24.5 degrees east) is compared with multispectral data from Clementine. All the Clementine spectra are centered on the crater, but are sampled at 1, 3, 5, 7, 9, 11,13, 15, 17, and 19 kilometers (square). The aperture used for this telescopic data was estimated to cover about a 5 km region, a value consistent with the Clementine data. The documentation files in the CATALOG directory contain more information about the data set (DATASET.CAT), the photometer (INST.CAT), and the telescope (INSTHOST.CAT), along with a list of personnel associated with the data set (PERSON.CAT) and references to other documentation (REF.CAT). 3. Archive Contents This archive contains data files in the DATA directory, documentation in the CATALOG and DOCUMENT directories, and an index to the data files in the INDEX directory, including a tabular summary of data available. The table below shows the organization and content of each of these directories. Root Directory AAREADME.TXT - The file you are reading AAREADME.HTM - HTML version of AAREADME.TXT AAREADME.LBL - PDS label that describes AAREADME.HTM and AAREADME.TXT VOLDESC.CAT - Description of this volume for the PDS Catalog CALIB Directory CALINFO.TXT - Description of files in the CALIB directory JBADHR.TAB - Table containing original Adams directional hemispheric Apollo 16 62231 data used to calibrate the telescopic data JBADHR.LBL - PDS label for JBADHR.TAB JBADHRWC.TAB - Table containing Adams directional hemispheric Apollo 16 62231 wavelength corrected data JBADHRWC.LBL - PDS label for JBADHRWC.TAB RELABBDR.TAB - Table containing bi-directional reflectance data for Apollo 16 62231, used for Clementine calibrations RELABBDR.LBL - PDS label for RELABBDR.TAB CORRBDR.TAB - Table containing correction factors used to correct the 120 channel lunar data to bi-directional reflectance CORRBDR.LBL - PDS label for CORRBDR.TAB CATALOG Directory CATINFO.TXT - Description of files in the CATALOG directory DATASET.CAT - Data set description INST.CAT - Instrument description INSTHOST.CAT - Instrument host (observatory) description PERSON.CAT - Personnel associated with this archive volume REF.CAT - References mentioned in the above catalog files DATA Directory Data subdirectories HnXXXX, where n = one of {8, 9, A, B, C, D, E}. For example, subdirectory H8XXXX contains files with names between H80001 and H89999. The "n" represents the original tape, and the following four-digit integer represents the number of the file on the tape. H8XXXX H9XXXX HAXXXX HBXXXX HCXXXX HDXXXX HEXXXX DOCUMENT Directory DOCINFO.TXT - Description of files in this directory CALIB.TXT - Description of calibration applied to this data set CALIB.HTM - HTML version of CALIB.TXT CALIB.LBL - PDS label that describes CALIB.TXT and CALIB.HTM CALFIG1.GIF - Figure 1 to accompany CALIB.TXT and CALIB.HTM CALFIG2.GIF - Figure 2 to accompany CALIB.TXT and CALIB.HTM CLEMSPEC.GIF - Figure comparing telescopic spectra with Clementine spectra of the same area CLEMSPEC.LBL - PDS label that describes CLEMSPEC.GIF PIETER00.PDF - Description of this data set (LPSC XXXI Abstract #2059) PIETER00.LBL - PDS label that describes PIETER00.PDF PIETER99.PDF - Discussion of spectral calibration of lunar data PIETER99.LBL - PDS label that describes PIETER99.PDF INDEX Directory INDXINFO.TXT - Description of files in this directory INDEX.TAB - Index table of data products in this archive INDEX.HTM - HTML version of INDEX.TAB. Open this file in a Web browser to begin browsing the data. INDEX.LBL - PDS label for INDEX.TAB and INDEX.HTM 4. File Formats The spectral data in this archive are stored as tables in ASCII files with fixed-length records. Each record is terminated with a carriage return and a line feed character, so that the files are readable on various computer platforms. Each table file has an associated PDS label in a separate file with the same name and the extension ".LBL". The PDS label describes the content and format of the table file. All text files in this archive are stream format files, with a carriage return and line feed at the end of each record. 5. Whom to Contact for Information For questions concerning this data set, contact: Dr. Carle M. Pieters Dept. of Geological Sciences Box 1846 Brown University Providence, RI 02912 Electronic mail: Carle_Pieters@brown.edu 6. Cognizant Persons The spectra data files and data set documentation were provided by Carle Pieters and Stephen Pratt of the Keck/NASA Reflectance Experiment Laboratory (RELAB), Brown University. Raymond Arvidson and Susan Slavney of the PDS Geosciences Node, Washington University, provided ancillary documentation and prepared the archive in PDS-compatible format.