Data Set Overview : The Gravity Recovery and Interior Laboratory (GRAIL) Radio Science (RSS) Raw Data Archive is a time-ordered collection of raw and partially processed data collected during the GRAIL mission to the Moon.  The DATA_SET_ID 'GRAIL-L-RSS-2-EDR-V1.0' includes the following components: Instrument host (i.e., 'GRAIL') Target (i.e., 'L' for Lunar) Instrument (i.e., 'RSS' for Radio Science Subsystem) CODMAC Data processing level number (i.e., '2') Description (i.e., 'EDR' for Experiment Data Record) Version number (i.e., 'V1.0')  This data set was collected beginning in September 2011.  Two types of measurements were obtained; these are known as closed-loop and open-loop recordings. The closed-loop system uses a phase-lock loop in the receiver to track the downlink signal, reporting both amplitude and frequency 1-10 times per second. In the open-loop system, the signal is simply converted to a baseband frequency range; the entire passband is sampled and recorded at 1000 or more samples per second for later processing.  Closed-loop data are efficient for characterizing slowly changing signals and are the input to operational navigation and orbit-determination processes. Open-loop data (because of their much higher rate and volume) are usually collected when the signal is expected to be very dynamic.  The data set includes two primary data types. Orbit Data Files (ODFs) are a product of the closed-loop system, and they are specifically targeted to spacecraft navigators and scientists interested in gravity fields. Also included are Tracking and Navigation Service Data Files (TNFs), the most primitive (and most voluminous) product of the closed-loop system. Orbit Data Files (ODFs) are compressed versions of TNFs. In the GRAIL context TNFs are not considered to be a primary data type. Radio Science Receiver records (RSRs) are the primary data type from the open-loop system.  Typical users of these data might analyze range and Doppler measurements in ODFs to reconstruct the spacecraft trajectory. Relevant questions would include the measurement uncertainties in range and Doppler at different DSN antennas; these could set constraints on any model of the Moon's gravity field developed later, for example.   Parameters : The ODF is a compressed version of the TNF. It contains the most important information (range, Doppler and frequency ramps) needed by spacecraft navigators and investigators interested in determining gravity fields. 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)  The Radio Science Receiver (RSR) files are the primary output from the Cassini open-loop system and they contain 16-bit samples of receiver output. Each RSR file is accompanied by a full PDS label which describes both the content and format of the file at the bit level [JPLD-16765].   Processing : ODFs are constructed by the RMDCT; they are constructed so that each file contains the data for approximately one day each. ODFs are abstracted from subsets of TNF data.  A full PDS label accompanies each ODF file and gives a bit level description of the content and format.  The open-loop Radio Science Receiver (RSR) files are screened for gaps. No gaps were found in the RSR files for this archive. Each RSR file corresponds to one tracking pass at the DSN.   Data : ODFs in this archive are primarily 1-sec Doppler S-band data. RSRs in this archive are X-Band data.  The typical ODF contains about 3 Mbytes. The typical RSR contains from about 30 Mbytes to about 165 Mbytes depending on Doppler mode and station (i.e., track duration).  TNFs, from which ODFs originate, are included in this archive for completeness.   Secondary Data : Secondary data are needed for proper analysis and interpretation of the radio data (ODF and RSR). Sky frequency has been computed from open-loop data (RSR) by the GRAIL Radio Science Systems Group in file type XFR. The TDM contains the same information as the XFR except in Tracking Data Message Standard format. The Open Loop File (OLF) contains the sky frequency information derived from RSR data, but in the format of the ODF.  The 'biased TDM' product (BTM) is in exactly the same format as the TDM. It is generated by subtracting off a one-way Doppler frequency bias at X-band from the TDM file containing the raw one-way Doppler measurement provided by the radio science team. The one-way Doppler frequency bias was estimated every orbit (approximately 2 hours) as part of the gravity field determination process and the estimates are reported in the USO1A data product (in the LGRS CDR data set). The one-way Doppler bias is computed by linearly interpolating the one-way Doppler bias time series in the USO1A product to the time tag of the one-way Doppler measurement. The computed one-way Doppler bias is then subtracted from the original raw TDM value and the result is stored in the 'biased TDM' product. The 'biased TDM' product is intended to remove non-linear drifts in the one-way Doppler bias induced by solar activity during the GRAIL mission.  The Biased Open Loop File (BOF) is the same format as the OLF and is converted from the BTM.   Sky Frequency Data (XFR Directory) --------------------------------------------------- Sky frequency (XFR) files are ASCII files with columns as follows: year, day of year, seconds past midnight, sky frequency, internal processing parameter generated in the course of creating the XFR but not relevant to GRAIL, internal processing parameter generated in the course of creating the XFR but not relevant to GRAIL. Times are in UTC-ERT and values were computed from RSR data by the Radio Science Systems Group at JPL.  Tracking Data Message Standard (TDM Directory) --------------------------------------------------- XFR files are converted to TDM format by the Radio Science Systems Group at JPL. TDMs are ASCII files, and their complete format requirements are described in TRACKINDATAMESSAGESTANDARD.TXT in the DOCUMENT directory.  Open Loop File (OLF Directory) --------------------------------------------------- For users who prefer to work with software designed for closed- loop data, TDMs (which originate from open-loop data) are converted to the OLF, which is the same (binary) format as the (closed-loop) ODF.  Biased Tracking Data Message Standard (BTM Directory) --------------------------------------------------- BTM files are generated from TDM files as described above. BTMs are ASCII files, and their complete format requirements are described in TRACKINDATAMESSAGESTANDARD.TXT in the DOCUMENT directory.  Biased Open Loop File (BOF Directory) --------------------------------------------------- For users who prefer to work with software designed for closed- loop data, BTMs (which originate from open-loop data) are converted to the BOF, which is the same (binary) format as the (closed-loop) ODF.   Ancillary Data :  The ANCILLARY directory contains calibration files EOP (earth orientation parameters), ION (ionosphere), TRO (troposphere), and WEA (weather).  Earth Orientation Parameter Files (EOP Directory) --------------------------------------------------- Earth Orientation Parameter files are ASCII files; for GRAIL they were produced by the Kalman Earth Orientation Filter (KEOF) Group at JPL. Typical file size is 24 KB.  Ionosphere Calibration Files (ION Directory) --------------------------------------------------- Ionosphere Calibration files were produced by the Tracking System Analytic Calibration (TSAC) Group at JPL. They provided historical and predicted Earth ionospheric conditions. Typical file size is 23 KB.  Troposphere Calibration Files (TRO Directory) --------------------------------------------------- Troposphere Calibration files were produced by the Tracking System Analytic Calibration (TSAC) Group at JPL. They provided historical and predicted Earth tropospheric conditions. Typical file size is 120 KB.  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). WEA files were typically released weekly and contained all weather data for the complex since 1 January.   Naming Conventions : Orbit Data Files (ODFs) and Tracking and Navigation Files (TNFs) are named, respectively, as follows:  sssttaayyyy_ddd_hhmmwuudV#.odf, sssttaayyyy_ddd_hhmmwuudV#.tnf,  where sss 3-character spacecraft identifier GRA GRAIL-A GRB GRAIL-B GRX both tt Target ID, e.g., LU : Moon aa Activity/Experiment ID, e.g. GF : gravity field yyyy year ddd day of year hhmm hours/minutes w Ground Transmitter Band(s): N none M multiple S S-band X X-band uu Uplinking Station(s) : the DSN station number, or NN none MM multiple d way 1 one-way 2 two-way M multiple V# version number  Radio Science Receiver (RSR) data, Tracking Data Messages (TDM), Sky Frequency Files (XFR), Open Loop Files (OLF), Biased Tracking Data Messages (BTM), and Biased Open Loop Files (BOF) are named, respectively, as follows:  sssttaayyyyddd_hhmmxuudrrpD.rcs, sssttaayyyyddd_hhmmxuudrrpD.tdm, sssttaayyyyddd_hhmmxuudrrpD.xfr, sssttaayyyyddd_hhmmxuudrrpD.olf sssttaayyyyddd_hhmmxuudrrpD.btm, sssttaayyyyddd_hhmmxuudrrpD.bof   where: sss 3-character spacecraft identifier GRA GRAIL-A GRB GRAIL-B tt Target ID, e.g., LU : Moon aa Activity/Experiment ID, e.g. GF : gravity field yyyy year ddd day of year hhmm hours/minutes xuu Uplink Transmitter Band (e.g., S, X) and 2-digit Uplinking Station number, or 'NNN' : 1-way drr Downlink Band (e.g., X) and 2-digit Receiving Station number p Polarization L left hand R right hand M mixed D Open-loop data type D RSR data V VSR data W WVSR data rcs RSR number + channel + subchannel tdm Tracking Data Message xfr Sky Frequency File olf Open Loop File btm Biased Tracking Data Message bof Biased Open Loop File  Ionospheric Media Calibration (ION) files, Tropospheric Media Calibration (TRO) files, Earth Orientation Parameter (EOP) files, and weather (WEA) files are named, respectively, as follows:  sssttaaYYYY_DDD_yyyy_ddd.ion, sssttaaYYYY_DDD_yyyy_ddd.tro, sssttaaYYYY_DDD_yyyy_ddd.eop, sssttaaYYYYDDDyyyyddd_##.wea,  where: sss 3-character spacecraft identifier GRA GRAIL-A GRB GRAIL-B GRX both tt Target ID, e.g., LU : Moon (Lunar) aa Activity/Experiment ID, e.g. GF : gravity field YYYY start year DDD start day of year yyyy end year ddd end day of year ## DSN complex number   Files in the CALIB Directory : Files in the CALIB directory are those likely to have wide applicability in working with the raw data.  One file, GRAILCOMPONENTS.TXT is included in the CALIB directory. It describes the Spacecraft bus component model with dimensions and orientations, as well as the spacecraft components specular/diffuse reflectivity properties.   Software : Software for parsing, reducing, and analyzing data such as these has been developed at Stanford University, JPL, 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.

Overview : Data in this archival data set have been collected to support radio science investigations, in particular derivation of the gravity field of the Moon. These are similar to data collected using other spacecraft and are believed to be generally of good quality.   Review : This archive underwent PDS external review from August 31, 2012 to November 30, 2012.   Data Coverage and Quality : Data coverage in this dataset corresponds to individual tracking passes at the DSN. In some cases, supplemental RSR data were collected, in which GRAIL-A data were collected during GRAIL-B tracks or GRAIL-B data were collected during GRAIL-A tracks.  XFRs, TDMs, OLFs, BTMs, and BOFs were created from RSR data with specific parameters and software by the Radio Science Systems Group at JPL. Other software or parameters could be used. Based on the processing at JPL, data with signal-to-noise ratio less than 20 dB-Hz (sometimes higher) were excluded in order to eliminate noise that might be interpreted as signal.  Because DSN tracking occurred every day, the RSS EDR data set contains data from launch until end of mission, whereas the LGRS data sets only cover the periods when the LGRS was turned on. Gaps in DSN coverage are either due to normal DSN scheduling procedures or from occasional equipment problems. In either case, the data set contains all data collected at the DSN.  See mission phases in CATALOG/MISSION.CAT.   Limitations : The limitations in this data set follow from the coverage and quality of the data, as described above.