Data Set Overview : The Near Earth Asteroid Rendevous (NEAR) Mathilde Radio Science (RS) Data Set is a time-ordered collection of raw and partially processed data collected during the NEAR flyby of minor planet 253 Mathilde. For more information and the results of the investigation conducted, see 'Estimating the Mass of Asteroid 253 Mathilde from Tracking Data During the NEAR Flyby', D.K. Yeomans, J.P. Barriot, D.W. Dunham, R.W. Farquhar, J.D.Giorgini, C.E. Helfrich, A.S. Konopliv, J.V. McAdams, J.K. Miller, W.M. Owen Jr., D.J. Scheeres, S.P. Synnott and B.G. Williams, Science, 19 December 1997, Volume 278, pp. 2106-2109.  Only data collected in the month prior to the June 27, 1997 flyby through the July 3 trajectory correction maneuver was used for the mass determination. The radio data also supported NEAR Navigation.  The data set includes:  Directory Description --------- ----------- ODF Orbit Data Files containing closed-loop (two-way) Doppler and sequential range measurements. EOP Earth-Orientation Parameter file ION Ionosphere calibration file TRO Troposphere calibration file TXT Text files describing physical model inputs and estimated solution parameters  Typical users of these data might analyze range and Doppler measurements in the ODF to derive the NEAR trajectory during the flyby.   Parameters : The ODF contains the most important information (range and Doppler) needed by spacecraft navigators and those interested in determining gravitational parameters of Mathilde. Each ODF is accompanied by a full PDS label which describes both the content and format of the associated file. ODF data types can include those listed below. Only those marked below with an asterisk are present in this data set ODF.  Narrowband spacecraft VLBI, Doppler mode (cycles) Narrowband spacecraft VLBI, phase mode (cycles) Narrowband quasar VLBI, Doppler mode (cycles) Narrowband quasar VLBI, phase mode (cycles) Wideband spacecraft VLBI (nanoseconds) Wideband quasar VLBI (nanoseconds) * One-way Doppler (Hertz) * Two-way Doppler (Hertz) * Three-way Doppler (Hertz) One-way total count phase (cycles) Two-way total count phase (cycles) Three-way total count phase (cycles) PRA planetary operational discrete spectrum range (range units) * SRA planetary operational discrete spectrum range (range units) RE[GSTDN] range (nanoseconds) Azimuth angle (degrees) Elevation angle (degrees) Hour angle (degrees) Declination angle (degrees) X angle (where +X is east) (degrees) Y angle (where +X is east) (degrees) X angle (where +X is south) (degrees) Y angle (where +X is south) (degrees)   Processing : ODF's are screened for 'bad' data points, which are removed prior to analysis by the navigation and radio science teams.  Data : ODFs were issued approximately daily prior to the NEAR Mathilde flyby, more often during the immediate approach to Mathilde. The individual ODFs were merged into the single file of this dataset.  This ODF is stored in the ODF directory under the file name 7152O184.ODF, where '7' is the one-digit year (1990's implicit), '152' is the 3-digit day of year for data start, and '184' is the 3-digit day of year for data stop.  The results of this investigation, the solved-for Mathilde GM in units of km^3/s^2, appear as parameter GM9 in PARAMSUM.TXT in the TXT directory.   Ancillary Data : Ancillary files are needed for proper analysis and interpretation of the radio data (file type ODF). These are organized in parallel directories and stored approximately chronologically.   Earth Orientation Parameter Files (EOP Directory) --------------------------------------------------- Earth Orientation Parameter files are produced by the Time and Earth Motion Precision Observation (TEMPO) Group at JPL. These are ASCII files of variable length records. Each record is delimited by an ASCII line-feed  (ASCII 10). File names have the form ydddzeee.EOP where y is the one-digit year (1990s implicit) of the first data in the file (i.e. 199y), ddd is the day-of-year of the first data in the file, z is the one-digit year of the last data, and eee is the day-of-year of the last data in the file. EOP files are typically released on Tuesdays and Fridays. The files cover the most recent nine months of past motion and a prediction for three months into the future; these files are typically 30 KB. Each EOP file is accompanied by a PDS minimal label with file name ydddzeee.LBL.   Ionosphere Calibration Files (ION Directory) --------------------------------------------------- Ionosphere Calibration files are produced by the Tracking System Analytic Calibration (TSAC) Group at JPL. These are ASCII files of variable length records. Each record is delimited by an ASCII line-feed  (ASCII 10). File names have the form ydddeeeC.ION where y is the one-digit year of the first data in the file (1990s are implicit, i.e. 199y), ddd is the day-of-year of the first data in the file, eee is the day-of-year of the last data in the file, and C is a character denoting sequence when more than one file with the same ydddeee is handled. C starts from 'A' and progresses to 'B', 'C', etc. with increasing numbers of similar coverage files. Frequently, ION files are released at one week intervals to cover a single month; ydddeeeA.ION would be the file released the first week, ydddeeeB.ION would be the file released the second week, etc. Each ION file is accompanied by a PDS minimal label with file name ydddeeeC.LBL. Typical file sizes are less than 50KB.   Troposphere Calibration Files (TRO Directory) --------------------------------------------------- Troposphere Calibration files are produced by the Tracking System Analytic Calibration (TSAC) Group at JPL. These are ASCII files of variable length records. Each record is delimited by an ASCII line-feed  (ASCII 10). File names have the form ydddeeeC.TRO where y is the one-digit year of the first data in the file (1990s are implicit, i.e. 199y), ddd is the day-of-year of the first data in the file, eee is the day-of-year of the last data in the file, and C is a character denoting sequence when more than one file with the same ydddeee is handled. C starts from 'A' and progresses to 'B', 'C', etc. with increasing numbers of similar coverage files. TRO files are typically released at the beginning of a month and cover the previous month. Each TRO file is accompanied by a PDS minimal label with file name ydddeeeC.LBL. Typical file sizes are less than 50 KB.  Text Files (TXT Directory) -------------------------- Two file types are included in the TXT directory. The first type is NMLMODL.TXT and is accompanied by a minimal PDS label NMLMODL.LBL. It is the nominal set of namelist parameters used to define physical characteristics of the spacecraft's motion and tracking observables used by the JPL orbit determination software suite. The second file is PARAMSUM.TXT, accompanied by minimal PDS label PARAMSUM.LBL, which is a summary of the estimated (solved-for) parameter set. GM9 is the solved-for Mathilde GM in units of km^3/s^2.   Coordinate System : Analysis was conducted in the frame of the DE-403 solar system model, aligned with the 1993 ICRF/J2000 reference frame.   Software : Software for parsing, reducing, and analyzing data such as these has been developed at several institutions. Because such software must usually operate at the bit-level and is written for a narrow range of platforms, it is not suitable for general distribution. No software is included with this archival data set.

Overview : Data in this archival data set have been processed as part of health monitoring activities of the NEAR Radio Science Team. In general, this is a good data set.   Review : This archival data set was reviewed by the NEAR Radio Science Team prior to submission to the Planetary Data System (PDS).  Prior to creation of the final version of the archival data set, key elements of the archive were distributed for preliminary review. These included electronic versions of example PDS labels, CATALOG files, and Software Interface Specifications. These materials were distributed to PDS personnel, the experiment investigator, and others, as appropriate.   Data Coverage and Quality : Significant events for Radio Science during Mathilde Flyby are as follows:  START STOP YY/DDD TDB Time YY/DDD TDB Time Comments ------ -------- ------ -------- ---------------- 97/176 13:00:00 97/181 19:00:00 Earth-point, except for encounter 97/178 12:56:57 Mathilde close-approach 97/184 10:31:03 TCM-7 maneuver burn  Limitations : The limitations in this data set derive from tracking geometry and measurement data type. There is no known defective data.