Data Set Overview : IAU-adopted magnitude parameters (absolute V magnitude and slope parameter) for all numbered asteroids.  The absolute magnitude is variously given to 0.01, 0.1, or 1.0 mag precision, depending on the accuracy and consistency of the data used to arrive at the value.  Those slope parameters that were determined by fitting the IAU-adopted phase function (see Bowell et al. 1989 [BOWELLETAL1989]) to data are given an origin code letter of 'f' (for 'fitted'); all others are given a code letter of 'a' (for 'assumed'). The default value is 0.15 in all cases. Note that because most absolute magnitudes are based on apparent magnitudes measured at non-zero phase angles, the value of the absolute magnitude does depend on the assumed value for the slope parameter. A change in the assumed value of the slope parameter (based on a taxonomic classification, for example) should not be made independently of the absolute magnitude.  'MPC' in the reference field stands for 'Minor Planet Circular', published on behalf of Commission 20 of the International Astronomical Union by the Minor Planet Center, Smithsonian Astrophysical Observatory, Cambridge, MA 02138.  This version of the dataset contains magnitude parameters for all asteroids numbered as of the 1999 February 2 batch of Minor Planet Circulars and includes 9999 entries. The absolute magnitude database underwent a major revision during the past year, with updated values being published on Minor Planet Circulars 28104 through 28116. Known errors were corrected at that time, and magnitude parameters that had been taken from the literature for previous versions of the PDS database became formally adopted. Nevertheless, a pointer to the original reference for those magnitude parameters has been retained in the note field. Although the updated list as published in the Minor Planet Circulars includes values for all asteroids numbered as of that time, many were not changed from the previously published list. For purposes of this database, unchanged magnitude parameters retain their original reference, which should make it easier for the user to determine which have been updated.  References: Bowell, E., B. Hapke, D. Domingue, K. Lumme,		J. Peltoniemi and A.W. Harris, Application of photometric		models to asteroids, In Asteroids II (R. P. Binzel, T.		Gehrels, and M.S. Matthews, Eds.), pp. 524-556, Univ. of		Arizona Press, Tucson, 1989 [BOWELLETAL1989] 		Spencer, J.R., L.A. Akimov, C. Angeli, P. Angelini, M.A.		Barucci, P. Birch, C. Blanco, M. Buie, A. Caruso, V.G.		Chiornij, F. Colas, P. Dentchev, M.C. De Sanctis, E.		Dotto, M. Fulchignoni, S. Green, A. Harris, T. Hudecek,		A.V. Kalashnikov, V.V. Kobelev, V.P. Kozhevnikov, Y.		Krugly, D. Lazzaro, J. Lecacheux, J. MacConnell, T.		Michalowski, R.A. Mohamed, B. Mueller, T. Nakamura, C.		Neese, W. Osborn, P. Pravec, D. Riccioli, V. Shevchenko,		D. Tholen, F. Velichko, C. Venditti, R. Venditti, W.		Wisniewski, J. Young, and B. Zellner, The lightcurve of		4179 Toutatis: Evidence for complex rotation. Icarus 117,		71-89, 1995 [SPENCERETAL1995].   Modification History : The astermag data set was first introduced into PDS at the April 1993 asteroid data sets review. It has subsequently been updated at the March 1995, March 1996, and April 1999 asteroid data sets reviews. The updates consist of adding additional data which have become available since the previous update.   Parameters : The data file contains one entry for each numbered asteroid, and each entry includes fields for the following parameters. Asteroid catalog number, absolute V magnitude, slope parameter, a code for the origin of the slope parameter, the reference for the data, and a note flag.   Data : The data are presented in a single ASCII data table, 'astermag.tab'.

Review : This data set underwent formal external review on April 9, 1999.   Data Coverage and Quality : This version of the dataset contains magnitude parameters for all asteroids numbered as of the 1999 February 2 batch of Minor Planet Circulars and includes 9999 entries.