Description of the 24-COLOR ASTEROID SURVEY bundle V1.0 ======================================================= Bundle Generation Date: 2020-06-12 Peer Review: 24-Color Review, 1993-04-05 Discipline node: Small Bodies Node Content description based on the data set catalog file description for the PDS3 version, EAR-A-DBP-3-RDR-24COLOR-V2.1 ===================================================================================================================== Note: for PDS3 data sets migrated to PDS4, the following text is taken verbatim from the data set description and confidence level note of the PDS3 data set catalog file. In these cases, some details may not be correct as a description of the PDS4 bundle. This dataset is comprised of asteroid flux data measured in 26 filters using the McCord dual beam photometer. Of the 26 filters used for the full dataset, a maximum of 24 were used for any one measurement. The wavelength range covered is from 0.32 to 1.08 microns. Processing Level Id : 3 Software Flag : N Processing Start Time : 1975 Processing Stop Time : 1984 Parameters ========== Sampling Parameter Name : WAVELENGTH Data Set Parameter Name : FLUX RATIO Minimum Sampling Parameter : 0.330000 Maximum Sampling Parameter : 1.100000 Data Set Parameter Unit : DIMENSIONLESS Noise Level : 2.000000 Sampling Parameter Unit : MICROMETER Data ==== FLUX RATIO is defined as the ratio of two measured photon fluxes from a photometric or spectrometric instrument. For instance, the ratio of the measured spectrum of a target relative to the measured spectrum of a calibration standard will yield a value that is a flux ratio. This parameter is dimensionless. Ancillary Data ============== Atmospheric Conditions ---------------------- An estimate of the quality of the observing conditions for each night of observing is given in the original papers, Chapman (1972) [CHAPMAN1972], Chapman and Gaffey (1979) [CHAPMAN&GAFFEY1979A] [CHAPMAN&GAFFEY1979B] and McFadden et al. (1984) [MCFADDENETAL1984]. Calibration Standard -------------------- The data are calibrated to flux ratio (asteroid/inferred sun) with reference to a set of standard stars. During the observation sessions, the standard stars are observed both to determine extinction corrections in each filter and as color standards. Many of the standard stars used are A- or B- Oke/Hayes standard stars and others of the solar type. Modification History ==================== As part of a general review and upgrade of current asteroid data sets, these data were reviewed and an additional format added. The following changes were made to existing files: o The 24color.lbl file was edited slightly for grammar and to add the internal PDS reference keys corresponding to the cited references. o The asteroid number corresponding to object 1980 AA was added to the 24color.tab file. In addition, a program was written and used to split the 24color.tab file into separate spectrum files for each observation, each with its own label file. These files are named by the number and name of the corresponding asteroid. The first two columns of each spectrum file indicate the specific filter wavelength and FWHM used; these are followed by the reflectance and uncertainty. Only one object, 1685 Toro, had two observations in the main data file. These are in separate files: '1685toro1' contains the data from Chapman & Gaffey (1979b); '1685toro2' contains the data from McFadden, et al. (1984). Asteroid 1865 Cerberus, which had no data recorded in the original file, has no individual spectrum file. No changes were made to the recorded data values. Known issues or problems with the data ====================================== Acquisition of the 24 data points takes time; thus, a 24-point spectrum can be affected by the varying light curve of the asteroid, as well as by the changing sky conditions and instrument stability. In most, but not all, cases, data were co-added from numerous rapid rotations of the filter wheel. Uncertainties in the relative calibration between stars and Alpha Lyrae may contribute an uncertainty of up to 2 percent in the visible and 4 percent in the infrared bands. It is believed that this uncertainty is larger than other systematic errors in the data. PDS3 Source =========== Version 1.0 of this bundle was migrated from version 2.1 of the PDS3 data set EAR-A-DBP-3-RDR-24COLOR-V2.1.