Data Set Overview  :  The Mars Global Surveyor (MGS) Radio Science (RS) Raw Data  Archive (RDA) is a time-ordered collection of raw and partially  processed data collected during the MGS Mission to Mars.  For more information on the investigations proposed see  [TYLERETAL1992] and [TYLERETAL2001].   This data set was collected during the MGS Mars Mapping (MAP)  mission phase -- while the spacecraft was in a near-circular  orbit and systematically collecting data from Mars. Some of  the data supported MGS Navigation activities, but the majority  went directly to science analysis.   Two types of measurements were conducted during MAP; these  are known as closed-loop and open-loop recordings. The closed-  loop system used a phase-lock loop in the receiver to track the  downlink signal, reporting both amplitude and frequency at  rates typically of 1-10 times per second. In the open-loop  system, the signal was simply converted to a baseband frequency  range; the entire passband was sampled and recorded for later  processing. Typical open-loop sampling rates for MGS were  5000 samples per second. Closed-loop data are efficient for  characterizing slowly changing signals; open-loop data  (because of their much higher volume) are collected only  when the signal is very dynamic -- such as during an  occultation.   The data set includes three primary data types. Archival  Tracking Data Files (ATDFs or TDFs) are the most primitive (and  most voluminous) product of the closed-loop system. Orbit Data  Files (ODFs) are edited versions of ATDFs, specifically  targeted to spacecraft navigators and scientists interested in  gravity fields. Original Data Records (ODRs) are the primary  data type from the open-loop system.   Typical users of these data might analyze range and Doppler  measurements in ATDFs or ODFs to derive the spacecraft  trajectory during MAP and, from that, to search for variations  in the gravity field of Mars. Related questions would include  the measurement uncertainties in range and Doppler at different  DSN antennas; these could set constraints on any model of Mars'  gravity field developed later. Users of ODRs could use the  frequency and amplitude variations in the MGS signal to infer  the temperature and pressure as a function of altitude in the  atmosphere of Mars. Other uses could include identification  and characterization of anomalous signals within the recorded  passband, derivation of the drift of the UltraStable Oscillator  (USO), and calculation of Allan Deviation for various radio  science equipment configurations.    Parameters  :  The ATDF is the primary output from the MGS closed-loop system.  ATDFs have 150 fields, though not all had been assigned during  the MGS era. Each ATDF in the data set is accompanied by a  full PDS label which defines both the content and the format  of the file at the bit level. ATDF data fields include:  Range  High- or low-rate Doppler  High or low-rate downlink phase  Differential Range vs Integrated Doppler (DRVID)  Allan deviation  Smoothed noise  Uplink phase  Other information included in ATDF data records is date and  time; spacecraft ID; ground station and its configuration;  status flags and values reported by various ground systems;  calibration values, noise estimates, and tolerances (station  delay, transmitter power, etc.); and signal strength.   The ODF is an edited version of the ATDF; it is a smaller file,  issued more frequently than the ATDF. It contains the most  important information (range and Doppler) needed by spacecraft  navigators and investigators interested in determining  gravitational fields of bodies such as Mars. Each ODF is  accompanied by a full PDS label which describes both the  content and format of the associated file. ODF data fields  include:  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)   Open loop data records (ODRs) contain 8- or 12-bit samples of  receiver output. Each block of (typically) 1000 data samples  is accompanied by a 166 byte header. Each ODR is accompanied  by a full PDS label which describes both the content and format  of the file at the bit level. Header information includes:  Date and time of the first data sample  Sample rate and channel assignments  Receiver local oscillator (POCA) frequency  Attenuator settings  RMS voltages at several stages in the receiving chain    Processing  :  ATDFs are screened for 'bad' data points, which are removed  before the file is released by the Jet Propulsion Laboratory  (JPL) Radio Metric Data Conditioning Team (RMDCT).   ODFs are abstracted from subsets of ATDF data.   The open-loop data delivered to Stanford were usually in the  ODS (Original Data Stream) format. ODS packets were converted  to the older ODR (Original Data Record) format for consistency  in subsequent processing and archive. Headers applied by the  Ground Data System (GDS) during packet handling have not been  retained; they contained no additional information about the  data acquisition. In some cases, where the GDS corrupted the  ODS during delivery, lost it entirely, or were unable to  deliver it electronically because of volume constraints, data  have been recovered from tape in ODR format. The resultant  data (whether from ODS conversion or tape) accurately  represent the output of the DSCC Spectrum Processing (DSP)  Subsystem at the DSN station. A full PDS label accompanies  each ODR file and gives a bit level description of the content  and format.   A 32-byte label at the beginning of each ODR tape (when tape  was used) is not included in the data file. The 32-byte label  gives the version of the data taking software; this information  has been copied to the PDS label that accompanies the data  file. The software version recorded in the 'NOTE' keyword is  more likely to be accurate than the version recorded with the  'SOFTWARE_VERSION' keyword. Because the 32-byte label is no  longer part of the data stream, users can treat the remaining  file as an integral number of fixed-length records. The  32-byte label was never defined in the ODS.    Data  :  Data are stored on CD-WO volumes approximately chronologically.  This data set contains data from the MGS Mapping phase only.  CD volumes were usually defined by the dates of included  spacecraft engineering and DSN monitor data (data types ECH and  MCH, respectively). ECH and MCH files were the most regular,  and often the largest, collected on a daily basis. Files of  other types were sometimes delayed in delivery to Stanford and  may be out of strict chronological order on the CDs. Users  should consult listings in the INDEX/CUMINDEX.TAB file to  ascertain full coverage of each data type. Users working with  data near the beginning and end of the Mapping phase should  check INDEX/CUMINDEX.TAB in the data sets covering the adjacent  phases for files that appear to be missing; in general, files  that bridge a phase boundary were stored with the earlier  data set only. The data sets immediately before and after are  MGS-M-RSS-1-MOI-V1.0 and MGS-M-RSS-1-EXT-V1.0, respectively.   ATDFs were delivered approximately weekly during MGS MAP.  ATDFs are stored in the TDF directory on archival volumes.  File names are of the form ydddeeeC.TDF where y is the  one-digit year of the first data, ddd is the three-digit  day-of-year of the first data, eee is the three-digit day-  of-year of the last data, and C is a single letter (beginning  with 'A') denoting the sequence in which files with the same  ydddeee were handled. Generally ydddeeeB.TDF is a revised  version of ydddeeeA.TDF. The PDS label has file name  ydddeeeC.LBL. The typical ATDF contains about 39 Mbytes.   ODFs were typically issued daily throughout MGS MAP; during  periods of high spacecraft activity (such as around maneuvers)  ODFs were released more often. Most ODFs released  during MAP are included in the archival data set. Of those  that were missed, most were generated by special request, and  Stanford did not receive a release notice. ODFs are stored in  the ODF directory. File names are of the form ydddeeeC.ODF  where the file name components are the same as for the ATDF  (previous paragraph). In most cases ydddeeeB.ODF was NOT  simply a revised version of ydddeeeA.ODF; there were many  requests for special ODF processing -- to obtain higher time  resolution over short intervals, for example. The PDS label  has file name ydddeeeC.LBL. Typical ODF file sizes are small  multiples of 8064 bytes (e.g., less than 100 kB).   Original Data Records (ODRs) were produced whenever the DSP  was set to 'run' mode. These files are stored in the ODR  directory. In most cases, the entire DSP run was collected  into a single ODR file. But in other cases, it was more  convenient to subdivide the DSP data; queries were issued for  shorter time spans, and separate files were produced. File  names are of the form ydddhhmm.ODR where y is the one-digit  year of the first data, ddd is the day-of-year of the first  data, hh is the hour on which the first sample was taken, and  mm was the minute on which the first sample was taken. In  cases where two files had the same ydddhhmm (for example, two  DSN stations began recording at the same time, or a second query was submitted for data which appeared suspicious after the  first query was processed), the less significant digit in mm  of the second file was converted to a letter ('0' became 'A',  '1' became 'B', ..., '9' became 'J'). In cases where three  files had the same ydddhhmm, the less significant mm digit  was converted to 'K', 'L', etc. The PDS label has file name  ydddhhmm.LBL.   At 5000 12-bit samples per second, a 7-minute occultation would  yield a 3.5 MB ODR -- one X-band (RCP) channel; 5 records per  second, each with 1000 12-bit samples and a 166-byte header.   Three one-hour surface scattering experiments were conducted on  14 May 2000. These data were collected in two channels (RCP and LCP) with 50000 8-bit samples per second in each channel. The  data volume from each of these observations was about 375 MB.    Ancillary Data  :  An extensive set of ancillary files is needed for proper  analysis and interpretation of the radio data (file types  TDF, ODF, and ODR). These are organized in parallel  directories and stored approximately chronologically. When  a file type is not represented on a CD-WO volume, the  corresponding directory has been omitted. With the exception  of files stored in the CALIB directory, ancillary files  appear on only one CD-WO volume. Users should refer to  the INDEX/CUMINDEX.TAB listing to locate ancillary files.   Files in the CALIB Directory  ----------------------------  Files in the CALIB directory are those likely to have wide  applicability in working with the raw data. They help  unpack and allow use of the raw data, rather than being  'instrument' calibration data per se. They include  decommutation maps, clock conversion files, files of  planetary constants, leapsecond files, and files needed for  display of data on the MGS Science Operations Planning  Computer (SOPC). Each file is accompanied by a PDS minimal  label.   Clock Conversion files were produced by the JPL/PDS  Navigation Ancillary Information Facility (NAIF) for use  with NAIF-developed and MGS-provided software. These are  ASCII files of variable length records. Each record is  delimited by an ASCII carriage-return  (ASCII 13)  line-feed pair  (ASCII 10), which may need to be  converted to either  or  before the file is used  on the local machine. File names have the form TSCnnnnn.SCK  where nnnnn is a sequence number beginning with 00001  and the file with the highest number is the most recent.  The value of nnnnn is set by NAIF.   Planetary Constants files were produced by the JPL/PDS  Navigation Ancillary Information Facility (NAIF) for use  with NAIF-developed and MGS-provided software. These are  ASCII files of variable length records. Each record is  delimited by an ASCII carriage-return  (ASCII 13)  line-feed pair  (ASCII 10), which may need to be  converted to either  or  before the file is used  on the local machine. File names have the form PCKydddC.TPC  where y is the one-digit year of the file creation date,  ddd is the day-of-year of the file creation date, and C  is a character denoting sequence when more than one file  with the same yddd is handled. C starts from 'A'  and progresses to 'B', 'C', etc. with increasing numbers  of similar coverage files.   Leapsecond files were produced by the JPL/PDS  Navigation Ancillary Information Facility (NAIF) for use  with NAIF-developed and MGS-provided software. These are  ASCII files of variable length records. Each record is  delimited by an ASCII carriage-return  (ASCII 13)  line-feed pair  (ASCII 10), which may need to be  converted to either  or  before the file is used  on the local machine. File names have the form LSKydddC.TLS  where y is the one-digit year of the file creation date,  ddd is the day-of-year of the file creation date, and C  is a character denoting sequence when more than one file  with the same yddd is handled. C starts from 'A'  and progresses to 'B', 'C', etc. with increasing numbers  of similar coverage files.   Channel Conversion Language files come in three types --  source, dependency, and binary. File names are of the  forms CCLydddS.SRC, CCLydddD.BIN, and CCLydddB.BIN,  respectively, where y is the one-digit year of the file  creation date and ddd is the day-of-year of the file  creation date. Source files are ASCII files of variable  length records. Each record is delimited by an ASCII  carriage-return  (ASCII 13) line-feed pair  (ASCII  10), which may need to be converted to either  or   before the file is used on the local machine. Dependency and  binary files are identical to those used on the SOPC. Source  and binary files are typically 500 kB; dependency files are  typically 15 kB. Channel Conversion Language files are used  in converting raw binary data in telemetry streams to  meaningful numbers.   Channel Parameter Table files come in two types -- source and  binary. File names are of the forms CPTydddS.SRC and  CCLydddB.BIN, respectively, where y is the one-digit year  of the file creation date and ddd is the day-of-year of the  file creation date. Source files are ASCII files of variable  length records. Each record is delimited by an ASCII  carriage-return  (ASCII 13) line-feed pair  (ASCII  10), which may need to be converted to either  or   before the file is used on the local machine. Binary files  are identical to those used on the SOPC. Source and binary  files are typically less than 1 MB. Channel Parameter Table  files are used in converting raw binary data in telemetry  streams to meaningful numbers.   Template Description Language files come in two types --  source and binary. File names are of the forms TDLydddS.SRC  and TDLydddB.BIN, respectively, where y is the one-digit  year of the file creation date and ddd is the day-of-year  of the file creation date. Source files are ASCII files of  variable length records. Each record is delimited by an  ASCII carriage-return  (ASCII 13) line-feed pair   (ASCII 10), which may need to be converted to either   or  before the file is used on the local machine. Binary  files are identical to those used on the SOPC. Source and  binary files are typically less than 1 MB. Template  Description Language files are used during display of data on  the SOPC.   Decommutation Map files come in two types -- source and  binary. File names are of the forms DCSxxxxx.SRC and  DCOxxxxx.BIN, respectively, where xxxxx is a mnemonic for  the map. Source files are ASCII files of variable length  records. Each record is delimited by an ASCII carriage-  return  (ASCII 13) line-feed pair  (ASCII 10), which  may need to be converted to either  or  before the  file is used on the local machine. Binary files are identical to those used on the SOPC. Source and binary files are  typically less than 200 kB. Decommutation Map files are used  in converting raw binary packet data to channelized formats.  On the SOPC, they are used with the MGS-provided program  mapx.   Antenna Reconstruction Files are typically used in conjunction with Antenna Gimbal Kernel (AGK) files to determine the  pointing of an antenna or the position of its phase center  with respect to the spacecraft center of mass. There are  three types of Antenna Reconstruction Files: the Antenna SPK  (ASP) File, the Hinge CK (HCK) File, and the Text Frame Kernel (TFK) File. An ASP file contains the locations of low-gain  antennas and boom lengths for the high-gain antenna (HGA).  The HCK file contains hinge angles for the (deployed) HGA.  The TFK file contains information on coordinate frame  definitions for translating between the spacecraft frame and  the frame of the high-gain antenna. File names are of the  forms HGAnnnnn.ASP, HINGEnnn.HCK, and HGAnnnnn.TFK, where the  'n' string gives a sequence number. ASP and HCK files are  ASCII files in NAIF transfer format; TFK files are ASCII  files. In all cases, each record is delimited by the ASCII  carriage-return  (ASCII 13) line-feed  (ASCII 10)  pair. On some systems it may be necessary to convert the   pair to either  or  before using the file on  the local machine. Each Antenna Reconstruction File is  accompanied by a PDS minimal label with the same file name  except for an extension of .LBL.   NB: CCL, CPT, TDL, and decommutation files were used with  MGS-provided software to extract and display engineering data  from telemetry streams originating on the spacecraft or at  ground stations of the DSN -- ECH and MCH data, respectively,  as described below. The most interesting engineering data  were saved as ASCII ECT and MCT files (see below). In early  2007 a JPL-mandated software and hardware system upgrade left  Stanford without the ability to use this software, absent a  major investment in upgrading the routines. Since the MGS  spacecraft had gone silent three months earlier, the decision  was not to make the upgrades. Stanford thus can no longer  process the ECH and MCH data types. It is likely that future  users of these data will find processing the raw engineering  telemetry data to be challenging.   Antenna Gimbal Kernel Files (AGK Directory)  -------------------------------------------  Antenna Gimbal Kernel files were produced by NAIF. Each AGK  file contains information on the state of the HGA azimuth  and elevation gimbals as a function of time. These are ASCII  files in NAIF transfer format. Each record is delimited by  an ASCII carriage-return  (ASCII 13) line-feed (LF> (ASCII 10) pair, which may need to be converted to either  or   before the file is used on the local machine. File  names have the form ydddeeeZ.AGK where 'y' is the least  significant digit of the year in which data in the file begin, 'ddd' is the day-of-year when data begin, 'eee' is the  day-of-year when data end, and 'Z' is a single upper case  letter indicating order of files when there is more than one  with the same 'ydddeee' in the data set. Z is 'A' for the  first file, 'B' for the second, etc. Each AGK file is  accompanied by a PDS minimal label with file name  ydddeeeZ.LBL. Typical file sizes are 1 MByte.   Angular Momentum Desaturation Files (AMD Directory)  ---------------------------------------------------  Angular Momentum Desaturation files were produced by the MGS  Spacecraft Team (SCT). Each AMD file documents a set of AMD  events on the spacecraft. These are ASCII files of variable  length records. Each record is delimited by an ASCII  carriage-return  (ASCII 13) line-feed pair  (ASCII  10), which may need to be converted to either  or   before the file is used on the local machine. File names  have the form ydddeeeC.AMD where y is the one-digit year  of the first data in the file, 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.  Each AMD file is accompanied by a PDS minimal label with file  name ydddeeeC.LBL. Typical file sizes are less than 1500  bytes.   Browse Files (BRO Directory)  ----------------------------  Browse files are composite PostScript files summarizing  quick-look processing of ODR data. Each file has a name of  the form ydddhhmm.PSn where ydddhhmm is identical to  the character string in the source ODR file and n is the  receiver channel represented in the data. Each BRO file is  accompanied by a detached PDS label with name ydddhhmm.LBL.  Only one channel n is expected from each ODR. Each  PostScript file is sized to fit on a single 8-1/2x11 inch  page. Each landscape format page includes four panels  showing a histogram of raw data (12-bit) samples (upper  left), one-minute average power spectra derived from the  raw samples (upper right), one-second averages of raw sample  power versus time (lower left), and an extract of the first  few lines of the source ODR PDS label (lower right). BRO  files may be helpful in quickly scanning data to determine  which files are suitable for closer study.   Channelized Engineering Data Files (ECH Directory)  ---------------------------------------------------  Channelized Engineering Data files were produced by the MGS  query server, operating on telemetry packets stored in the  MGS Central Data Base (CDB). These are binary files, usually  representing the collection of raw spacecraft engineering  data received from a 24 hour period; they are not readily  interpretable by end users. File names have the form  ydddeeeC.ECH where y is the one-digit year  of the first data in the file, 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.  Each ECH file is accompanied by a PDS minimal label with file  name ydddeeeC.LBL. File sizes can be as large as 200 MB.  In general, an ECH file can be derived from the corresponding  EPK file using MGS-provided software and a decommutation map.   Also in some ECH directories are ASCII tables of extracted  channel values--channelized state vectors, or CSV files.  These are values for a limited number of potentially  useful ECH channels that have been saved in tabular form.  CSV files in the ECH directory have names of the form  CSVydddC.ECH where y, ddd, and C are the same as for  the corresponding ECH file. Each CSV file is accompanied  by a detached PDS label with name CSVydddC.LBL which  completely describes the format and content of the CSV file.   NB: See note at the end of the section 'Files in the CALIB  Directory' (above) regarding processing of ECH files.   Engineering Channelized Data Summary Files (ECS Directory)  ---------------------------------------------------  Engineering Channelized Summary Data Files were created at  Stanford during ingestion of spacecraft engineering data.  Each file contains a summary line for each channel processed  from the previous day's telemetry. The ECS file thus gives  a snapshot (mean and standard deviation) of each channel  on each day. ECS files are PDS TABLE objects; each is  fully described as to format and content by a detached PDS  label. File names are of the form ydddeeeC.ECS where  y is the one-digit year of the first data, ddd is the  three-digit day-of-year of the first data, eee is the  three-digit day-of-year of the last data, and C is a  character denoting sequence when more than one file with  the same ydddeee is handled. File sizes vary depending  on the number of channels processed; typical growth is  4000 bytes per day.   Engineering Channel Table Files (ECT Directory)  ---------------------------------------------------  Engineering Channel Table Data Files are created at Stanford  during ingestion of spacecraft engineering data. Each ECT  file is an ASCII table of time-ordered values from a single  spacecraft engineering channel, and each file is fully  described by a detached PDS label. File names are of the  form XXXydddC.ECT where XXX is a unique identifier for  the engineering channel, y is the one-digit year of the  first data, ddd is the three-digit day-of-year of the first  data, and C is a character denoting sequence when more  than one file with the same yddd is handled. File sizes  vary depending on the rate at which a channel was sampled;  they are typically under 100 kB. The detached label has  file name XXXydddC.LBL.   Experimenters Notebook Files (ENB Directory)  --------------------------------------------  Experimenters Notebook files are e-mail messages and other  notes collected during and shortly after data acquisition.  They document expectations of various measurements and  anomalies discovered in subsequent analysis. File names  have the form ENByyddd.TXT, where yy is the two-digit  year and ddd is the three-digit day-of-year. In general  the messages in file ENByyddd.TXT refer to activities on  that date regardless of when the message was sent. These  are ASCII files with variable length records. Each record  is delimited by an ASCII carriage-return line-feed pair.   Earth Orientation Parameter Files (EOP Directory)  ---------------------------------------------------  Earth Orientation Parameter files were produced by the Time  and Earth Motion Precision Observation (TEMPO) Group at JPL.  They documented and predicted Earth rotation (rate and axis).  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 of the first data in the file, 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 were typically  released on Tuesdays and Fridays. There are both 'long'  and 'short' versions. The long file covered past motion  since about 1962 and a prediction for about three months into  the future; these files have typical sizes of 860 kB. The  short file covered 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.   Engineering Packet Data Files (EPK Directory)  ---------------------------------------------------  Engineering Packet Data files were produced by the MGS  query server, operating on telemetry packets stored in the  MGS Central Data Base (CDB). These are binary files, usually  representing the collection of raw spacecraft engineering  data received from a 24 hour period; they are not readily  interpretable by end users. File names have the form  ydddeeeC.EPK where y is the one-digit year  of the first data in the file, 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.  Each EPK file is accompanied by a PDS minimal label with file  name ydddeeeC.LBL. File sizes can be as large as 100 MB.  No EPK files were collected during the MAP phase; all  spacecraft engineering data are in the ECH format.   NB: No EPK files were collected during the MAP phase.   Filtered Body Rate Files (FBR Directory)  ---------------------------------------------------  Filtered Body Rate Files were created at Stanford from  body rate data in the spacecraft engineering telemetry  stream. They give spacecraft attitude as a function of  time. FBR files are PDS TABLE objects; each is  fully described as to format and content by a detached PDS  label. File names are of the form ydddeeeC.FBR where  y is the one-digit year of the first data, ddd is the  three-digit day-of-year of the first data, eee is the  three-digit day-of-year of the last data, and C is a  character denoting sequence when more than one file with  the same ydddeee is handled. File sizes vary depending  on the time interval covered.   FBR files were created during MGS Cruise to support the  search for gravitational waves (GWE); no FBR files were  created during the MAP Phase.   GEODYN Trajectory Files (GDN Directory)  ---------------------------------------------------  GEODYN SPK files were quick look orbit reconstructions  produced by the MOLA Precise Orbit Determination Team. They  were used for preliminary analysis of MOLA data and some radio occultations. These files give spacecraft and planetary  ephemerides and are identical in format to SPK files (see  below) by the MGS NAV Team. Files with ORIGINAL_PRODUCT_ID  including 'qlnn' were based on the following gravity models:  ql15 mgm0989a  ql16 mgm0989c  ql17 gmm2b (with no one-way Doppler daya)  ql18 gmm2b (with one-way Doppler data if available) These are ASCII files of variable length records in a special  NAIF 'transfer' format. Each record is delimited by a  carriage-return (ASCII 13) line-feed  (ASCII 10) pair,  which may need to be removed before the file is used on the  local machine. After delimiter conversion (if needed) the  file would ordinarily be passed through the NAIF utility  SPACIT or TOBIN to convert it to the local binary format.  File names have the form ydddeeeC.GDN where y is the  one-digit year of the first data in the file, 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. Each GDN file is accompanied by a  PDS minimal label with file name ydddeeeC.LBL. Typical file  sizes are less than 5 MB.   GEODYN Trajectory Files (GDF Directory)  ---------------------------------------------------  GDF files are the same as GDN files (above) except that they  are considered 'final' versions of the orbits. File names  end with the .GDF suffix. No GDF files were created during  the MAP phase; all GEODYN reconstructions appear in the GDN  directory.   NB: No GDF files were created during the MAP phase.   Daily Health Report Files (HEA Directory)  ---------------------------------------------------  Daily Health Report Files were created at Stanford; they  summarize spacecraft engineering data of interest for Radio  Science, list recently acquired radio data, summarize any  analysis performed on recent radio data, summarize anomalies  in recent radio science operations, and list files that have  been obtained from the MGS CDB or other sources. Daily  Health Report Files are PDS TEXT objects; each has an  attached PDS label. File names are of the form HEAydddC.TXT  where y is the one-digit year of the report, ddd is the  three-digit day-of-year of the report, and C is a  character denoting sequence when more than one file with  the same ydddeee is generated. The first report on a day  would be HEAydddA.TXT; subsequent revisions or updates  would be HEAydddB.TXT, HEAydddC.TXT, etc.   Some Health Reports are accompanied by plots, saved as  PostScript files. File names for these plot files  have names of the form HEAydddC.PSn where y and ddd  are as defined above and n is the figure number.  The PostScript files are accompanied by a detached  PDS label with name HEAydddC.LBL.   Both Health Reports themselves and accompanying PostScript  files have variable length records delimited by carriage-  return (ASCII 13) line-feed (ASCII 10) pairs.   Ionosphere Calibration Files (ION Directory)  ---------------------------------------------------  Ionosphere Calibration files were produced by the Tracking  System Analytic Calibration (TSAC) Group at JPL. They  documented and predicted Earth ionospheric conditions.  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, 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. ION files were usually released at one week  intervals to cover a single month; ydddeeeA.ION would be  the file released during the first week, ydddeeeB.ION would  be the file released during 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 50 kB.   Light Time Files (LIT Directory)  ---------------------------------------------------  Light Time files were produced by the MGS Navigation Team  (NAV). They gave radio propagation time from the spacecraft  to Earth vs time. These are ASCII files of fixed  length records. Each record is delimited by an ASCII  carriage-return  (ASCII 13) line-feed pair  (ASCII  10), which may need to be converted to either  or   before the file is used on the local machine. File names  have the form ydddeeeC.LIT where y is the one-digit year  of the first data in the file, 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.  Each LIT file is accompanied by a PDS minimal label with file  name ydddeeeC.LBL. Typical file sizes are less than 1 MB.   Channelized DSN Monitor Data Files (MCH Directory)  ---------------------------------------------------  Channelized DSN Monitor Data files were produced by the MGS  query server, operating on DSN Monitor packets stored in the  MGS Central Data Base (CDB). These are binary files, usually  representing the collection of DSN Monitor data received from  a 24 hour period; they are not readily interpretable by end  users. File names have the form ydddeeeC.MCH where y is  the one-digit year of the first data in the file, 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. Each MCH file is accompanied by a PDS minimal label  with file name ydddeeeC.LBL. File sizes can be as large as  30 MB. In general, an MCH file can be derived from the  corresponding MPK file using MGS-provided software and a  decommutation map. Monitor data are collected according to  MST (Monitor Sample Time) measured in UTC.   Also in some MCH directories are ASCII tables of extracted  channel values--channelized state vectors, or CSV files.  These are values for a limited number of potentially  useful MCH channels that have been saved in tabular form.  CSV files in the MCH directory have names of the form  CSVydddC.MCH where y, ddd, and C are the same as for  the corresponding MCH file. Each CSV file is accompanied  by a detached PDS label with name CSVydddC.LBL which  completely describes the format and content of the CSV file.   NB: See note at the end of the section 'Files in the CALIB  Directory' (above) regarding processing of MCH files.   Monitor Channel Tables (MCT Directory)  --------------------------------------   Monitor Channel Tables were derived from MCH CSV files at  Stanford. Each table lists a single Monitor channel versus  time in an ASCII PDS TABLE format. File names have the form  XXXydddC.MCT where XXX is a three-character mnemonic for  the channel, y is the one-digit year, ddd is the three-  digit day-of-year, and C is a single character (starting  with 'A') denoting the version. Each MCT file is  accompanied by a PDS label with file name XXXyddC.LBL which  completely describes both the content and the format of the  table. Examples of MCT files include:   XXX Description  --- ---------------------------------------------  AGC AGC level from M-0349 (Ant A, Rcv A)  DSS DSS antenna ID from M-0300  ELA Elevation angle from M-0304 (Ant A)  TSY System temperature from M-0725 (Ant A, Rcv A)  TSZ System temperature from M-0725 (Ant A, Rcv B)   Maneuver Implementation/Reconstruction Files (MIF Directory)  ---------------------------------------------------  Maneuver Implementation/Reconstruction files were produced by  the MGS Spacecraft Team (SCT); they documented spacecraft  maneuver events. 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.MIF where y  is the one-digit year of the first data in the file, 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. Each MIF file is accompanied by a PDS minimal label  with file name ydddeeeC.LBL. Typical file sizes are 2327  bytes.   Maneuver Performance Data Files (MPD Directory)  ---------------------------------------------------  Maneuver Performance Data files were produced by the MGS  Spacecraft Team (SCT). They contain estimates of spacecraft  mass and center of mass; moments of inertia; thruster  locations, directions, and magnitudes; and propellant flow  rate. 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.MPD where  y is the one-digit year of the first data in the file,  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. Each MPD file is accompanied by a  PDS minimal label with file name ydddeeeC.LBL. Typical  file sizes are 4 kB.   Maneuver Profile Files (MPF Directory)  ---------------------------------------------------  Maneuver Profile Files were produced by the MGS Navigation  Team (NAV). They are generic descriptions of orbit  adjustments used by MGS during aerobraking. These are ASCII  files of variable length records. Each record is delimited  by a carriage-return  (ASCII 13) line-feed   (ASCII 10) pair. File names have the form XnnnDDCC.MPF  where X is a character, nnn is a 3-digit number, DD  indicates the adjustment direction ('UP' or 'DN'), and  CC indicates the sequence if there is more than one file  with the same XnnnDD. CC starts from 'AA'. Each MPF  is accompanied by a PDS minimal label with file name  XnnnDDCC.LBL. Typical file sizes are less than 700 bytes.   DSN Monitor Packet Data Files (MPK Directory)  ---------------------------------------------------  DSN Monitor Packet Data files were produced by the MGS  query server, operating on DSN Monitor packets stored in the  MGS Central Data Base (CDB). Monitor data are records of  DSN status and radio measurements. These are binary files,  data received from a 24 hour period; they are not readily  interpretable by end users. File names have the form  ydddeeeC.MPK where y is the one-digit year  of the first data in the file, 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.  Each MPK file is accompanied by a PDS minimal label with file  name ydddeeeC.LBL. File sizes can be as large as 30 MB.   No MPK data were collected during the MAP phase; all DSN  Monitor data are in the MCH directories.   Orbit Propagation and Time Generation Files (OPT Directory)  ---------------------------------------------------  Orbit Propagation and Time Generation files were produced by  the MGS Navigation Team (NAV). They contain estimates of  event timing (e.g., equator crossings) that depend on  precise knowledge of the spacecraft orbit. 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.OPT where y is the one-digit year  of the first data in the file, 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.  Each OPT file is accompanied by a PDS minimal label with file  name ydddeeeC.LBL. Typical file sizes are less than 100 kB.  Typical OPT files during MAP included one day of orbit  reconstructions followed by several days of orbit  predictions.   Solar Array Kernel Files (SAK Directory)  ---------------------------------------------------  Solar Array Kernel files were produced by the MGS Spacecraft  Team (SCT). They give the attitude of each solar array  panel as a function of time. These are ASCII files of  variable length records in a special NAIF 'transfer' format.  Each record is delimited by a carriage-return (ASCII 13)  line-feed  (ASCII 10) pair, which may need to be  removed before the file is used on the local machine.  After delimiter conversion (if needed) the file would  ordinarily be passed through the NAIF utility SPACIT or  TOBIN to convert it to the local binary format. File names  have the form ydddeeeC.TCK where y is the one-digit year  of the first data in the file, 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.  Each TCK file is accompanied by a PDS minimal label with  file name ydddeeeC.LBL. Typical file sizes are less than  5 MB.   Space Flight Operation Schedule Files (SFO Directory)  ---------------------------------------------------  Space Flight Operations Schedule Files were produced by the  MGS Mission Control Team, usually in parallel with  a corresponding Sequence of Events (SOE) file. They  graphically present parts of the SOE. These are  ASCII files of variable length records in a special format  that allows use with the MGS-provided sfosedt program.  Each record is delimited by a carriage-return (ASCII 13)  line-feed  (ASCII 10) pair, which may need to be removed  before the file is used on the local machine. File names  have the form ydddeeeC.SFO where y is the one-digit year  of the first data in the file, 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. Each SFO  file is accompanied by a PDS minimal label with file name  ydddeeeC.LBL. Typical file sizes are less than 100 kB.   No SFO files were produced after 1998-08-20.   Sequence of Events Files (SOE Directory)  ---------------------------------------------------  Sequence of Events Files were produced by the MGS Mission  Control Team. These are ASCII files of variable length  records. Until 1998-08-20 SOE files were produced in a  special format that allowed use with the MGS-provided soeedt  program. After 1998-08-20, files were produced in a straight  ASCII format that required no special software; these may be  identified by the '.tsoe' suffix in the ORIGINAL_PRODUCT_ID.  Each record is delimited by a carriage-return (ASCII 13)  line-feed  (ASCII 10) pair, which may need to be removed  before the file is used on the local machine. File names  have the form ydddeeeC.SOE where y is the one-digit year  of the first data in the file, 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.  Each SOE file is accompanied by a PDS minimal label with  file name ydddeeeC.LBL. Typical file sizes are less than  1 MB.   Spacecraft/Planetary Ephemeris (SPK) Files (SPK Directory)  ---------------------------------------------------  Spacecraft/Planetary Ephemeris Files (also known as SP  kernels or SPK files) were produced by the MGS Navigation Team (NAV). These files give spacecraft and planetary ephemerides. These are ASCII files of variable length records in  a special NAIF 'transfer' format. Each record is delimited  by a carriage-return (ASCII 13) line-feed  (ASCII 10)  pair, which may need to be removed before the file is used on  the local machine. After delimiter conversion (if needed)  the file would ordinarily be passed through the NAIF utility  SPACIT or TOBIN to convert it to the local binary format.  File names have the form ydddeeeC.SPK where y is the  one-digit year of the first data in the file, 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. Each SPK file is accompanied by a  PDS minimal label with file name ydddeeeC.LBL. Typical file  sizes are less than 5 MB. Typical SPK files during MAP  included one day of orbit reconstructions followed by several  days of orbit predictions.   Spacecraft Attitude (CK) Files (TCK Directory)  ---------------------------------------------------  Spacecraft Attitude Files (also known as C kernels or CK  files) were produced by the MGS Spacecraft Team (SCT).  These are ASCII files of variable length records in  a special NAIF 'transfer' format. Each record is delimited  by a carriage-return (ASCII 13) line-feed  (ASCII 10)  pair, which may need to be removed before the file is used on  the local machine. After delimiter conversion (if needed)  the file would ordinarily be passed through the NAIF utility  SPACIT or TOBIN to convert it to the local binary format.  File names have the form ydddeeeC.TCK where y is the  one-digit year of the first data in the  file, 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. Each TCK file is accompanied by a  PDS minimal label with file name ydddeeeC.LBL. Typical file  sizes are less than 5 MB.   Troposphere Calibration Files (TRO Directory)  ---------------------------------------------------  Troposphere Calibration files were produced by the  Tracking System Analytic Calibration (TSAC) Group at JPL.  They documented and predicted Earth tropospheric conditions.  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, 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 were typically released at the beginning of  a month and covered 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.   UltraStable Oscillator Files (USO Directory)  --------------------------------------------  UltraStable Oscillator (USO) files are calibration data  derived from open-loop radio measurements. Files are PDS  table objects with detached labels. Examples include USO  Allan Deviation (type A files) and the piecewise-continuous  linear model of USO frequency (type M files). File names  are of the form USOtyddd.TAB, where t is the file type  ('A' or 'M'), y is the one-digit year in which the file was  created, and ddd is the three-digit day-of-year in which  the file was created. Each USO file is accompanied by a  detached PDS label with name USOtyddd.LBL which completely  describes the content and format of the file.   DSN Weather Files (WEA Directory)  ---------------------------------------------------  DSN Weather files were produced by the Tracking System  Analytic Calibration (TSAC) Group at JPL. Files give weather  calibration information for DSN complexes. These are ASCII  files of variable length records. Each record is delimited  by an ASCII line-feed  (ASCII 10). File names have  the form ydddeeeD.WEA where y is the one-digit year of  the first data in the file, 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 D is a single digit denoting the  DSN complex at which the data were acquired ('1' for  Goldstone, '4' for Canberra, or '6' for Madrid). WEA files  were typically released weekly and contain all weather data  for the complex since 1 January. Each WEA file is  accompanied by a PDS minimal label with file name  ydddeeeC.LBL. The files grow at the rate of approximately  90 kB per month.    Coordinate System  :  SPK ephemeris files and TCK files were produced for the  J2000 inertial reference frame until the second orbit after  Mars Orbit Insertion, when the TCK files were referenced to  the Mars Mean Equator frame. SAK files presumably follow the  same format as TCK files. NAIF reader routines may be  used to convert these to other coordinate systems.   Other data types are not dependent on definition of a  coordinate system.    Software  :  Software for parsing, reducing, and analyzing data such as  these has been developed at Stanford University and elsewhere.  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.    Media/Format  :  The archival data set is written on CD-WO media and conforms  to ISO 9660 standards.

Overview  :  Data in this archival data set have been processed as part of  health monitoring activities of the MGS Radio Science Team.  In general, this is a good data set.    Review  :  This archival data set was reviewed by the MGS Radio Science  Team prior to submission to the Planetary Data System (PDS).  The MGS Science Data Validation Team (SDVT) set standards and  procedures.   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.   ODR files on the CD-WO volumes were checked using Stanford  parsing and reduction software to ensure that they were both  complete and accurate replicas of the data contained in the  original files.    Data Coverage and Quality  :  Significant events for Radio Science during MGS MAP were as  follows (EGR : egress; HGA : high-gain antenna; ING : ingress;  TLM : telemetry):   YY/DDD Start DSP Stop DSP Comments  ------ -------- -------- ----------------  99/069 02:20:00 Begin Fixed HGA Mapping  99/069 18:26:35 18:45:00 First occultation  99/093 10:40:00 10:47:00 First occn w/HGA deployed  99/106 04:37:00 04:46:00 Begin HGA AZ anomaly (LGA data)  99/119 18:09:00 18:19:00 Begin Fixed HGA Mapping  99/126 05:06:00 05:11:49 Resume nominal HGA operations  99/179 HGA rewind begins to impact ING  99/180 HGA rewind begins to impact EGR  99/182 EGR ionosphere only w/TLM on  99/199 Last regular EGR recording  99/285 Resume open-loop data collection  00/038 Begin Beta Supplement operations  with occasional Fixed HGA  00/135 11:46:00 16:41:00 MPL/DS2 surface scatter expmnt  00/174 Last open-loop operations  00/183 Solar Conjunction  00/195 Resume open-loop operations  00/203 Max Earth-Mars distance  01/032 End of Mapping phase   Quality of data was affected by anomalous conditions. Examples  include:   Open-Loop (ODR) Data Anomalies  ------------------------------  a) 'Sawtooth' frequency residuals infrequently (all stations)  Apparently caused by a buffering and merging problem in  data acquisition system; strict synchronization lost and  either data samples or POCA readings (or both) were lost.  b) Amplitude baseline variations more than +/-0.1 dB  (various). Caused by spacecraft activities, ground  antenna pointing errors (or increasing Earth atmospheric  opacity at low elevation angles, weather changes, and  precipitation).  c) Uplink Sweeps - Signals drifting through spectrum, usually  2-3 minutes after egress and strengths as high as -35 dBc  when using DSS 15, 45, or 65; 5-10 dB weaker when using  lower powered ground transmitters (e.g., DSS 34).  Caused by leakage of uplink sweep into downlink chain  aboard the spacecraft. Durations typically 10 s.  Not usually apparently at Earth-Mars distances exceeding  1 AU.  d) HGA gimbal spurs: 5 Hz spurs on either side of the carrier  when gimbal stepper motors were active. Typically -35 to  -45 dBc. Caused usually by elevation gimbal motor, which  ran continuously at 5 Hz during nominal mapping. Not  present before HGA deployment or during Fixed HGA Mapping  after deployment.  e) Incorrect attenuator settings (occasional)  f) Empty data records: no signal and/or no noise (occasional;  causes varied)  g) No occultation: HGA rewind overlapped grazing occultation;  data collected may be useful for characterizing radio  system but probably contain little of interest for  atmospheric science (July through mid-December 1999)  h) During June-July 2000, when Sun-MGS-Earth angle was less  than 10 deg, Allan Deviation increased significantly.  These are not noted in daily logs because they were  ubiquitous.   A one-line summary for each radio occultation attempted is  included in OCCLOGxx.TAB files in the DOCUMENT directory of  various reduced data archival volumes. Included in these  summaries are dates/times, orbit numbers, ground antennas  used, a shorthand data quality estimation and anomaly  indicator, a code for quick-look detection of surface echoes,  and brief comments. Users interested in these files should  consult the MGS-M-RSS-5-SDP-V1.0 data set.   Closed-Loop Data Anomalies (mostly observed in ODF)  ---------------------------------------------------  Thermal sensitivity of the USO was observed during one-way  tracking.   The quality of ranging data decreased at the beginning of  2000, but the reasons (other than generally lower signal  strength as Mars moved farther away) were never determined.  In early February 2000, Beta Supplement operations interrupted many ranging measurements and the number of good points went  down even further. Ranging was discontinued a couple months  later and did not resume until the beginning of the Extended  Mission.   Quality of data deteriorated markedly during the solar  conjunction period centered on early July 2000.   Other Notes  -----------   a) During Fixed HGA Mapping (March 1999 and late April to  early May) no spacecraft engineering data were captured  while the spacecraft was transmitting to Earth. Thus  there are no USO temperature measurements, no spacecraft  attitude data, and no HGA pointing information while  radio science measurements were being conducted.  b) The 2 kHz filter in the open-loop receiver at SPC 60 was  changed after 1999-03-27 and before 1999-04-11; there are  no good SPC 60 data between those dates, so pinning the  swap down more closely is unnecessary.  c) About 15 minutes was required to 'unwind' the HGA during  each orbit. This was normally done while the spacecraft  was hidden from Earth. But in late June 1999, the  occultation time was reduced to less than 15 minutes.  Ingress was lost first, then egress. Starting in early  July only egress occultations were recorded, and those  were limited to times after surface egress and with  telemetry on. In February 2000, egress operations  could not be conducted because the Beta Supplement  spacecraft configuration brought the HGA reflector too  close to the HGA boom. Approximately once per month,  the spacecraft attitude was adjusted so that egress  occultations could be captured over a 24-hour period.  d)Two-way tracking time was also  lost during Beta Supplement because the HGA had to  'unwind' on the front side of the planet.    Limitations  :  The limitations in this data set follow from the quality of  the execution, which is described above under Data Coverage  and Quality.