PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM RECORD_BYTES = 80 OBJECT = TEXT PUBLICATION_DATE = 2016-05-06 NOTE = "Software Interface Specification for the MESSENGER Radio Science Occultation Summary (OCCSUM) file. Formatted for display or printing with up to 78 constant width characters per line." END_OBJECT = TEXT END Johns Hopkins University Applied Physics Laboratory Space Department Software Interface Specification MESSENGER Radio Science Reduced Data Record Archive For Radio Occultation Summaries (OCCSUM) Files prepared by Mark Perry JHU/APL Laurel, MD 22073 240-228-0699 Version 1.2 25 February 2016 Document Review This document and the archive it describes have been through PDS Peer Review and have been accepted into the PDS archive. Mark Perry, MESSENGER RS Instrument Scientist, has reviewed and approved this document. This document has been reviewed according to PDS policy. Susan Ensor, MESSENGER Science Operations Center Lead, has reviewed and approved this document. Document Change Log |====================================================================| |REVISION|REVISION| SECTION | REMARKS | | NUMBER | DATE | AFFECTED | | |--------+--------+------------+-------------------------------------| | 0.1 |02/09/07| All | Adapted from SIS for MGS Radio | | | | | Science Occultation Summary File | |--------+--------+------------+-------------------------------------| | 0.3 |05/25/12| All | Corrected typos, added review | | | | | statement, version and date. | | | | | Distribution for Peer Review | |--------+--------+------------+-------------------------------------| | 0.5 |05/25/12| All | Corrected typos and publication date| |--------+--------+------------+-------------------------------------| | 0.6 |05/26/12| All | Update distribution list, & product | | | | | release date in sample label. | |--------+--------+------------+-------------------------------------| | 0.7 |05/31/12| All | Submitted for PDS Peer Review | |--------+--------+------------+-------------------------------------| | 0.8 |12/14/12| All | Incorporated comments from PDS | | | | | review. | |--------+--------+------------+-------------------------------------| | 0.9 |01/07/13| All | Minor additional revisions, update | | | | | to sample PDS label and data prod.; | | | | | Removed RECORD_BYTES from label; | | | | | Minor formatting changes. | |--------+--------+------------+-------------------------------------| | 0.91 |01/25/13| All | Minor revisions from review. Updated| | | | | sample label. | |--------+--------+------------+-------------------------------------| | 0.92 |02/15/13| Multiple | Addressed additional issues from the| | | | | review. Additional fields added to | | | | | the product file and one removed. | |--------+--------+------------+-------------------------------------| | 1.0 |09/05/13| Multiple | Miscellaneous minor mods from peer | | | | | review. | |--------+--------+------------+-------------------------------------| | 1.1 |09/05/13|Doc chg log | Fixed typo in date of revision 0.92.| |--------+--------+------------+-------------------------------------| | 1.2 |02/25/16|Multiple | Updates for final release | |====================================================================| Acronyms and Abbreviations APL Johns Hopkins University Applied Physics Laboratory ASCII American Standard Code for Information Interchange CSV Comma Separated Values dB Decibel DSN Deep Space Network GSFC Goddard Space Flight Center JPL Jet Propulsion Laboratory kHz Kilohertz km Kilometers MESSENGER MErcury Surface, Space ENvironment, GEochemistry, and Ranging MET Mission elapsed time NAIF Navigation and Ancillary Information Facility NASA National Aeronautics and Space Administration NAV Navigation Subsystem/Team OCCSUM Occultation Summary data file PDS Planetary Data System RF Radio frequency RS Radio Science RSR Radio Science Receiver, at JPL/DSN RSS Radio Science Subsystem RSSG Radio Science System Group at JPL SOC MESSENGER's Science Operation Center SPICE Spacecraft, Planet, Instrument, Camera-matrix, Events (a software library and toolkit provided by JPL) SIS Software Interface Specification SPK Spacecraft ephemeris kernel UTC Universal Coordinated Time Contents 1 General Description 1.1 Overview 1.2 Scope 1.3 Applicable Documents 1.4 System Siting 1.4.1 Data Sources, Transfer Methods, and Destinations 1.4.2 Generation Method and Frequency 1.5 Assumptions and Constraints 1.5.1 Usage Constraints 1.5.2 Priority Phasing Constraints 1.5.3 Explicit and Derived Constraints 1.5.4 Documentation Conventions 2 Interface Characteristics 2.1 Hardware Characteristics and Limitations 2.1.1 Special Equipment and Device Interfaces 2.1.2 Special Setup Requirements 2.2 Volume and Size 2.3 Labeling and Identification 2.4 Interface Medium Characteristics 2.5 Failure Protection, Detection, and Recovery Procedures 2.6 End-of-Line Conventions 3 Detailed Interface Specifications 3.1 Data production 3.2 Structure and Organization Overview 3.3 Detached PDS Label 3.3.1 Label Header 3.3.2 Label Body 3.4 Data File 4 Appendix A. Example OCCSUM Label 1 General Description 1.1 Overview This Software Interface Specification (SIS) describes Radio Science Occultation Summary (OCCSUM) data files from the MESSENGER Mission. OCCSUM files are created at the Johns Hopkins Applied Physics Lab (APL) and contain results of processing MESSENGER radio occultation data to obtain the shape of Mercury's surface. OCCSUM files contain summaries of results from one or more radio occultations. Section 3.1 contains information on how the data are produced. The MESSENGER mission is managed by APL for the National Aeronautics and Space Administration (NASA). 1.2 Scope The format and content specifications in this SIS apply to all phases of the MESSENGER Mission for which the OCCSUM was produced. 1.3 Applicable Documents [1] Srinivasan, D.K, Perry, M.E., Fielhauer, K.B., Smith, D.E., Zuber, M.T, The Radio Frequency Subsystem and Radio Science on the MESSENGER Mission Space Science Review, 131, 557-571, 2007. [SRINIVASANETAL2007] [2] Zuber, M.T., Aharonson, O., Aurnou, J.M., Cheng, A.F., Hauck, S.A., Heimpel, M.H., Neumann, G.A., Peale, S.J., Phillips, R.J., Smith, D.E., Solomon, S.C., Stanley, S., The Geophysics of Mercury: Current Status and Anticipated Insights from the MESSENGER Mission, Space Science Review, 131, 105-132, 2007. [ZUBERETAL2007B] [3] Perry, M. E., Kahan, D. S., Ernst, C. M., Solomon, S. C., Zuber, M. T., Smith, D. E., Phillips, Srinivasan, D.K., R. J., Oberst, J., Asmar, S. W., Measurement of the radius of Mercury by radio occultation during the MESSENGER flybys, Planetary and Space Science, 59, 1925-1931, 2011. [PERRYETAL2011] [4] Planetary Science Data Dictionary, JPL D-7116, Rev. F, October 20, 2008. Available: http://pds.jpl.nasa.gov/tools/dictionary.shtml. [Accessed 2012 September 10]. [5] Planetary Data System Standards Reference, JPL D-7669, part 2, version 3.8, 27 February 2009. [6] Perry, M.E., G.A. Neumann, R.J. Phillips, O.S. Barnouin, C.M. Ernst, D.S. Kahan, S.C. Solomon, M.T. Zuber, D.E. Smith, S.A. Hauck II, S.J. Peale, J. Margot, E. Mazarico, C.L. Johnson, R.W. Gaskell, J.H. Roberts, R.L. McNutt, Jr., J. Oberst, The low-degree shape of Mercury, Geophysical Research Letters, 42, 2015, 10.1002/2015GL065101. [PERRYETAL2015] 1.4 System Siting 1.4.1 Data Sources, Transfer Methods, and Destinations OCCSUM files are created by the MESSENGER Radio Science Team. OCCSUM files are distributed electronically via the Planetary Data System (PDS). 1.4.2 Generation Method and Frequency Each recorded occultation is analyzed and a summary line is added to an accumulating OCCSUM file when the analysis produces a radius estimate that has an uncertainty of 500 m or less. At each delivery of MESSENGER data to the PDS, starting with delivery 9 in March 2013, the OCCSUM file version Vnn was archived at the PDS. 1.5 Assumptions and Constraints 1.5.1 Usage Constraints None. 1.5.2 Priority Phasing Constraints None. 1.5.3 Explicit and Derived Constraints None. 1.5.4 Documentation Conventions 1.5.4.1 Data Format All data are provided as ASCII text. Floating point (real) numbers are represented in ASCII using the FORTRAN-style "E" or "F" formats. Fixed point and integer numbers are represented using the FORTRAN-style "I" format. 1.5.4.2. Time Standards Within the data files, all times are reported in Universal Coordinated Time (UTC) as strings of 21 ASCII characters. The format is "yyyy-dddThh:mm:ss[.fff]", where "-", "T", ":", and "." are fixed delimiters; "yyyy" is the year "20nn"; "ddd" is a three-digit day of year (1 to 366); "T" separates the date and time segments of the string; "hh" is hour of day; "mm" is the minutes of hour (00-59); "ss" is the seconds of hour(00-59); and (optional) "fff" is milliseconds; and "[]" denotes that sub-second precision is optional. 1.5.4.3 Coordinate Systems The OCCSUM uses the Mercury-centered fixed body coordinate system. 1.5.4.4. Limits of This Document This document applies only to OCCSUM data files. 1.5.4.5. Typographic Conventions This document has been formatted for simple electronic file transfer and display. Line lengths are limited to 80 ASCII characters, including line delimiters. No special fonts or structures are included within the file. Constant width characters are assumed for display. 2 Interface Characteristics 2.1 Hardware Characteristics and Limitations 2.1.1 Special Equipment and Device Interfaces OCCSUM files were created at MESSENGER's Science Operation Center (SOC) using ASCII formats. They are stored in electronic form at the SOC and PDS servers. OCCSUM files are comma separated variable (CSV) text files. They contain no binary data. Character values are enclosed in double quotes per PDS requirements. 2.1.2 Special Setup Requirements None. 2.2 Volume and Size OCCSUM products have increasing length, depending on the number of occultation events included in the file. The file size is the product of the record length times the number of events included in the file. For 168 occultations (the number in the first data release) and a maximum data record length of 192 bytes, the maximum OCCSUM file size would have been 168*192+302 (the maximum header length) or 32,558 bytes. The first data file actually had 32,049 bytes. The final file has 117,426 bytes. 2.3 Labeling and Identification The OCCSUM file is named MESS_RS_OCC_Vnn.CSV where nn is the version number 01 through 99. With each delivery, a new version of the OCCSUM file was delivered with a new version number. Each new version contains the data from the previous one with possible improvements as well as new material. Each OCCSUM file is accompanied by a detached PDS label, which is a file in its own right. The label file has the name MESS_RS_OCC_Vnn.LBL. 2.4 Interface Medium Characteristics OCCSUM products are electronic files. 2.5 Failure Protection, Detection, and Recovery Procedures None. 2.6 End-of-Line Conventions End-of-Line in the OCCSUM products and labels is indicated by PDS- Standard (i.e., ASCII 0x0D 0x0A) characters. 3 Detailed Interface Specifications 3.1 Data production The occultation measurements of Mercury's radius are based on data acquired using the RSR open-loop receiver. The Radio Science System Group (RSSG) at JPL extracts the time-dependent RF power as MESSENGER passes behind and past Mercury as viewed from Earth [1,2,3]. The best-performing extraction algorithm is a short-term periodogram using a windowed FFT with 50% overlap. Normally, the FFT is filtering 4 Hz around the carrier. Other extraction algorithms used are a normal FFT and a software phased-locked loop (PLL). These latter algorithms produced lower signal margins (FFT) or more distortion (PLL) for the lowest signal levels, but sometimes produced the best results for the strongest transmissions. When analyzing with multiple algorithms, the archived value is the one with the lowest uncertainty as measured by the quality of the diffraction fit. Future releases of occultation data may use other algorithms; when those Solutions are included in the archive, they are identified in the Accompanying RSRDR_DS.CAT. The received RF power follows the predictions of edge diffraction, where the power is one quarter (-6dB) of the unocculted power at apparent geometric occultation, which is the time when the source, edge, and observer are aligned along the same RF path. The diffraction pattern defines carrier power variations in the absence of system noise. The team at APL fits that pattern to the available data. The time that the fitted diffraction pattern falls to 6 dB below the normal (unocculted) power is the derived time of geometric occultation [3]. The uncertainty in the fit of the diffraction pattern to the data is the uncertainty in the time. The low-power cases produce poor-quality fits and the time uncertainty is no better than the data resolution. Improved algorithms for processing the RF power reduced time uncertainty in the low-power cases, and the improved results are archived in the later versions of the product. The positions of MESSENGER, Mercury, and the DSN antenna, based on the time of occultation as observed at Earth, provide the radius of Mercury at the point where the RF path grazes a smooth sphere centered at Mercury's center of mass. This is the raw_measured_radius parameter. Local topography, which is not included in these analyses, determines the actual occulting edge, which may be displaced both radially and horizontally from the smooth- sphere location. For each occultation result, the data set includes the direction of the RF path, which is useful for researchers interested in investigating the effects of local topography. The 170 occultation measurements of radius that overlap with MLA data are an average of 5 meters higher than the MLA data with a dispersion of 130 meters. The time-based uncertainty is the uncertainty in the time of occultation multiplied by the perpendicular speed, and the data set only includes occultations where this uncertainty is 500 meters or less. Since many of the egress events had large time uncertainties, there are more ingress events in the archive than egress events. The following SPICE kernels are the auxiliary data used to produce the initial archive of occultation results. The SPK file used to process the data is one of the parameters in the archived occsum file. MESSENGER ephemeris is based on and referenced to Mercury's center of mass. The uncertainty in Mercury's center of mass with respect to Earth is negligible for radius measurements derived from occultations. Occultation analyses are based on reconstructed ephemerides. The following SPICE kernels or later versions of them are used in processing. Spacecraft ephemeris: an SPK with .bsp extension that is identified in the data record Leap-seconds file: naif0011.tls Earth topography: earth_topo_050714.tf Earth ephemeris: earth_000101_160220_151129.bpc DSN ephemeris: earthstns_itrf93_050714.bsp Planetary constants: pck00010_msgr_v21.tpc During most occultations, MESSENGER transmits using its low-gain antennas, so the signal margin is low. For ingresses, the bandwidth of the open-loop receiver at the DSN can be narrowed to 1 kHz because data are collected in the coherent (2-way) mode and downlink frequency is predicted accurately. During an occultation, the transponder uses an internal oscillator for a frequency reference. The instability of this oscillator precludes knowledge of its frequency to better than 1 kHz, so, at egress, the transmissions are one-way (non-coherent) and the bandwidth of the RSR receiver capturing the transmitted power is widened to 4 kHz. For most egresses, the wider bandwidth increases the noise to a level that precludes determination of the egress time to an accuracy necessary for useful measurements of Mercury's radius. Consequently, most of the analyzed occultations are ingresses. The OCCSUM file contains most of MESSENGER's occultations that were ingresses with tangent points in the southern hemisphere; these radius measurements supplement the altimeter data that are available only north of the equator. The occultations with northern- hemisphere locations were analyzed primarily to validate the analysis procedures and to independently assess accuracy. During most of the orbit phase of the mission, there are two or three occultations per 24 hours. The occultations are periodic, and there are gaps of one to two months without Earth occultations. MESSENGER uses X-band channel #27, 7.177 GHz uplink and 8.432 GHz downlink. Reference 3 contains additional information on producing radius measurements from RF occultations. 3.2 Structure and Organization Overview The OCCSUM is a file generated by analysis software at APL. It conforms to Planetary Data System standards [5]. Each OCCSUM file is accompanied by a detached PDS label. The OCCSUM file is an accumulating file, so each delivery contains both previous data and new data. The older solutions are subject to revision, so researchers should use the most recent version. 3.3 Detached PDS Label The detached PDS label has two parts -- a header and body. The header contains information about the origin of the file and its general characteristics such as record type and size. The body is a complete bit-level definition of the OCCSUM file. Each OCCSUM detached PDS label is constructed of ASCII records. The last two characters in each record are the carriage-return (ASCII 13) and line-feed (ASCII 10) characters. 3.3.1 Label Header The structure of the label file header is illustrated in Figure 4-2. An example of a complete label file is given in Appendix A. |====================================================================| | | | Figure 4-2. Label Header - Standard Keyword and Value Pairs | | | |====================================================================| | | | | PDS_VERSION_ID = PDS3 | | | LABEL_REVISION_NOTE = "2012-JHU/APL MESSENGER Ver. 1" | | | PRODUCT_VERSION_ID = "01" | | | RECORD_TYPE = STREAM | | | FILE_RECORDS = nnn | | | ^HEADER = ("MESS_RS_OCC_V01.CSV",1) | | | ^SPREADSHEET = ("MESS_RS_OCC_V01.CSV",2) | | | INSTRUMENT_NAME = "RADIO SCIENCE SUBSYSTEM" | | | INSTRUMENT_ID = "RSS" | | | INSTRUMENT_HOST_NAME = "MESSENGER" | | | TARGET_NAME = "MERCURY" | Standard | | DATA_SET_ID = "MESS-H-RSS/MLA-5-SDP-V1.0" | Keywords | | MISSION_NAME = "MESSENGER" | and | | INSTRUMENT_HOST_ID = "MESS" | Values | | PRODUCT_ID = "MESS_RSS_OCC_V01" | | | PRODUCT_TYPE = OCC | | | PRODUCER_ID = "MESSENGER RS TEAM" | | | PRODUCT_CREATION_TIME = YYYY-DDDThh:mm:ss | | | START_TIME = YYYY-DDDThh:mm:ss.fff | | | STOP_TIME = YYYY-DDDThhh:mm:ss.fff | | | DESCRIPTION = " ... " | | | | | |====================================================================| Keyword-value pairs in Figure 4-2 are defined below: PDS_VERSION_ID The version of the Planetary Data System for which these data have been prepared (set to "PDS3" by agreement between MESSENGER and PDS). LABEL_REVISION_NOTE A notation of the source and version of the label file. PRODUCT_VERSION_ID An integer value (range 01..99) in string form that indicates the version of the product file. The version number is incremented each time a new OCCSUM product is delivered to the PDS. RECORD_TYPE The type of record. Set to "STREAM" to indicate that logical records are of variable-length text. FILE_RECORDS The number of records in the OCCSUM file; instance dependent. ^HEADER Pointer to the OCCSUM file associated with this label and the record number of the first record defined as header. The structure of the file name is described in section 2.3. ^SPREADSHEET Pointer to the OCCSUM file associated with this label and the record number of the first data record. The structure of the file name is described in Section 2.3. INSTRUMENT_NAME Name of the instrument; set to "RADIO SCIENCE SUBSYSTEM". INSTRUMENT_ID Acronym identifying the instrument. "RSS" in this case. INSTRUMENT_HOST_NAME Name of the spacecraft; set to "MESSENGER". TARGET_NAME Name of the planet; set to "MERCURY". DATA_SET_ID Identifier for the data set of which this OCCSUM product is a member. Set to "MESS-H-RSS/MLA-5-SDP-Vn.m", where "Vn.m" indicates the version number of the data set, starting from "V1.0". MISSION_NAME Identifies the mission; set to "MESSENGER". INSTRUMENT_HOST_ID The identifier of the spacecraft carrying the instrument. Set to "MESS". PRODUCT_ID A unique identifier for the product within the data set; identical to the file basename (i.e., the file name excluding the ".CSV" extension) given in the ^SPREADSHEET pointer. PRODUCT_TYPE The type or category of a product within a data set. Set to OCC. PRODUCER_ID The entity responsible for creation of the data product; set to "MESSENGER RS TEAM". PRODUCT_CREATION_TIME The time at which this OCCSUM file was created; expressed in the format "YYYY-DDDThh:mm:ss" where the components are defined in Section 1.5.4.2. START_TIME The time corresponding to the first entry in the OCCSUM file, given in the format "YYYY-DDDThh:mm:ss[.ff]" where the components are defined in Section 1.5.4.2. STOP_TIME The time corresponding to the last entry in the OCCSUM file, given in the format "YYYY-DDDThh:mm:ss[.ff]" where the components are defined in Section 1.5.4.2. DESCRIPTION A short description of the OCCSUM product. 3.3.2 Label Body The body of the PDS label completely defines both the format and the content of the OCCSUM file. An example of a complete label is given in Appendix A.1. The label contains a NAME and short descriptions of each field. The descriptions below are more detailed. All calculations account for light-time effects. RSR_FILE Name of the raw RSR data file used as the source of the RF power history. These files are stored at the MESSENGER RS PDS site in the raw-data archive. TRAJECTORY_FILE(SPK) Name of the MESSENGER ephemeris file that provided the position of MESSENGER during the occultation. These files are archived at the MESSENGER PDS site. INGRESS/EGRESS This is the type of occultation event, either an ingress (I) or egress (E) OCCULTATION_TIME The time of geometric occultation as observed at the DSN station. This is the time when the power is one quarter (-6dB) of the unocculted power. ORBIT_NUMBER The number of MESSENGER orbits about Mercury at the time of this occultation. Orbit zero begins at the first apoapsis, which is approximately six hours after the orbit insertion maneuver. An entry of zero (0) in the orbit block indicates a flyby occultation. DIRECTION_OF_RF_PATH The angle between local meridian (northward) and the direction of Earth at the occultation point, measured positive toward the east. The angle or bearing indicates the direction of signal propagation. An RF signal traveling from due west toward due east as it grazed the surface would have a direction of 90 degrees. PERPENDICULAR_SPEED The absolute value of the surface-normal component of the apparent velocity of MESSENGER with respect to Mercury's limb as viewed along the RF path from Earth at the time of occultation. This is the speed perpendicular to both the Earth line of sight and to the limb. When multiplied by the uncertainty in time, this perpendicular-speed parameter provides the time-based component of the uncertainty in the radius measurement. The uncertainty in this speed is less than one percent. TANGENT_LATITUDE At the time of geometric occultation, this is the latitude that the RF path would graze the surface of a smooth sphere centered at Mercury's center of mass. The radius of this sphere is the Raw_measured_radius parameter. TANGENT_LONGITUDE At the time of geometric occultation, this is the longitude that the RF path would graze the surface of a smooth sphere centered at Mercury's center of mass. RAW_MEASURED_RADIUS At the time of geometric occultation, this is the minimum distance between Mercury's center of mass and the RF path between MESSENGER and the DNS antenna in contact with MESSENGER. Calculations include light-time effects. TIME_UNCERTAINTY The uncertainty in the time of geometric occultation. This uncertainty is based on the least-squares fit of the RF power to the diffraction curve that represents the predicted RF power history. When the signal drops from the unocculted level to the noise level in one time step, there are too few data points to produce a good-quality fit to the diffraction pattern, and uncertainty is set to half the sampling resolution (TIME_RES), which was typically 0.25 seconds. TIME_RES The time step of the RF power data used to fit to the diffraction pattern in seconds. DECAY_SCALE The scale length of the diffraction pattern, Converted to seconds based on the velocities and geometry of MESSENGER, Mercury, and Earth. PC/NO The downlink received carrier power (Watts) of The unocculted transmissions divided by the Noise power spectral density (Watts/Hz). ALGORITHM An integer that identifies the algorithm used to extract the carrier power from the RSR data: 0 = Fast Fourier Transform (FFT) 1 = Software Phase Locked Loop (PLL) 2 = Overlapping FFT S/C-TO-LIMB_DISTANCE At the time of occultation, the distance between MESSENGER and the occultation point at Mercury as calculated assuming a smooth sphere. LIMB-TO-DSN_DISTANCE At the time of occultation, the distance between the DSN station and the occultation point at Mercury as calculated assuming a smooth sphere. 3.4 Data File The OCCSUM data file contains a summary of occultation measurements from MESSENGER occultation events. The structure and content of each OCCSUM file are defined by the accompanying detached PDS label (see Section 3.3 and Appendix A). 4 Appendix A. Example OCCSUM Label A.1 Example Label The following is an example Occultation Summary (OCCSUM) Label. In Appendix A.2, the corresponding data file is shown PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "2016-JHU/APL MESSENGER" PRODUCT_VERSION_ID = "04" RECORD_TYPE = STREAM FILE_RECORDS = 637 ^HEADER = ("MESS_RS_OCC_V04.CSV",1) ^SPREADSHEET = ("MESS_RS_OCC_V04.CSV",303) INSTRUMENT_NAME = "RADIO SCIENCE SUBSYSTEM" INSTRUMENT_ID = "RSS" INSTRUMENT_HOST_NAME = "MESSENGER" TARGET_NAME = "MERCURY" DATA_SET_ID = "MESS-H-RSS/MLA-5-SDP-V1.0" MISSION_NAME = "MESSENGER" INSTRUMENT_HOST_ID = "MESS" PRODUCT_ID = "MESS_RS_OCC_V04" PRODUCT_TYPE = OCC PRODUCER_ID = "MESSENGER RS TEAM" PRODUCT_CREATION_TIME = 2016-055T00:00:00 START_TIME = 2008-014T19:10:29.700 STOP_TIME = 2015-116T15:24:09.850 DESCRIPTION = "This file contains a summary of MESSENGER radio occultation measurements of the radius of Mercury." OBJECT = HEADER HEADER_TYPE = SPREADSHEET RECORDS = 1 BYTES = 302 INTERCHANGE_FORMAT = ASCII DESCRIPTION = "The first record in the file contains a list of the column headings for the data in the following records. This header record is comma-delimited." END_OBJECT = HEADER OBJECT = SPREADSHEET ROWS = 636 ROW_BYTES = 188 FIELDS = 17 FIELD_DELIMITER = "COMMA" OBJECT = FIELD NAME = "RSR_FILE" FIELD_NUMBER = 1 BYTES = 31 DATA_TYPE = CHARACTER DESCRIPTION = "The name of the Radio Science Receiver file that contains the raw data for this occultation" END_OBJECT = FIELD OBJECT = FIELD NAME = "TRAJECTORY_FILE(SPK)" FIELD_NUMBER = 2 BYTES = 36 DATA_TYPE = CHARACTER DESCRIPTION = "Spacecraft mission ephemeris file name" END_OBJECT = FIELD OBJECT = FIELD NAME = "INGRESS/EGRESS" FIELD_NUMBER = 3 BYTES = 1 DATA_TYPE = CHARACTER DESCRIPTION = "Occultation event, ingress (I) or egress (E)" END_OBJECT = FIELD OBJECT = FIELD NAME = "OCCULTATION_TIME" FIELD_NUMBER = 4 BYTES = 21 DATA_TYPE = TIME DESCRIPTION = "The time, in UTC, of geometric occultation as observed at the DSN station. This is the time when RF power is one quarter (-6dB) of the unocculted power" END_OBJECT = FIELD OBJECT = FIELD NAME = "ORBIT_NUMBER" FIELD_NUMBER = 5 BYTES = 5 DATA_TYPE = ASCII_INTEGER DESCRIPTION = "Spacecraft orbit number for this occultation. Orbit one begins at the first apoapsis following the orbit-insertion maneuver. Orbit zero (0) indicates a flyby occultation." END_OBJECT = FIELD OBJECT = FIELD NAME = "DIRECTION_OF_RF_PATH" FIELD_NUMBER = 6 BYTES = 8 DATA_TYPE = ASCII_REAL UNIT = "deg" DESCRIPTION = "The angle between the local meridian and the direction of Earth at the occultation point, measured positive from local north toward local east. The angle or bearing indicates the direction of signal propagation. A RF signal traveling from due west toward due east as it grazed the surface would have a Direction_of_RF_Path of 90 degrees." END_OBJECT = FIELD OBJECT = FIELD NAME = "PERPENDICULAR_SPEED" FIELD_NUMBER = 7 BYTES = 5 DATA_TYPE = ASCII_REAL UNIT = "km/s" DESCRIPTION = "The component of the apparent velocity of MESSENGER with respect to Mercury's limb that is perpendicular to both the limb and the line of sight to Earth. When multiplied by the uncertainty in time, Perpendicular_speed provides the time-based uncertainty in the radius measurement derived from the occultation time." END_OBJECT = FIELD OBJECT = FIELD NAME = "TANGENT_LATITUDE" FIELD_NUMBER = 8 BYTES = 7 DATA_TYPE = ASCII_REAL UNIT = "deg" DESCRIPTION = "At the time of geometric occultation, this is the latitude that the RF path would graze the surface of a smooth sphere centered at Mercury's center of mass." END_OBJECT = FIELD OBJECT = FIELD NAME = "TANGENT_LONGITUDE" FIELD_NUMBER = 9 BYTES = 8 DATA_TYPE = ASCII_REAL UNIT = "deg" DESCRIPTION = "At the time of geometric occultation, this is the longitude that the RF path would graze the surface of a smooth sphere centered at Mercury's center of mass." END_OBJECT = FIELD OBJECT = FIELD NAME = "RAW_MEASURED_RADIUS" FIELD_NUMBER = 10 BYTES = 8 DATA_TYPE = ASCII_REAL UNIT = "km" DESCRIPTION = "At the time of geometric occultation, this is the minimum distance between Mercury's center of mass and the RF path between MESSENGER and the DSN antenna in contact with MESSENGER. Calculations include light-time effects." END_OBJECT = FIELD OBJECT = FIELD NAME = "TIME_UNCERTAINTY" FIELD_NUMBER = 11 BYTES = 5 DATA_TYPE = ASCII_REAL UNIT = "second" DESCRIPTION = "The uncertainty in the time of geometric occultation." END_OBJECT = FIELD OBJECT = FIELD NAME = "TIME_RES" FIELD_NUMBER = 12 BYTES = 5 DATA_TYPE = ASCII_REAL UNIT = "second" DESCRIPTION = "The time step of the RF power data used to fit to the diffraction pattern." END_OBJECT = FIELD OBJECT = FIELD NAME = "DECAY_SCALE" FIELD_NUMBER = 13 BYTES = 5 DATA_TYPE = ASCII_REAL UNIT = "second" DESCRIPTION = "The scale length of the diffraction pattern, converted to seconds based on the velocities and geometry of MESSENGER, Mercury, and the Earth." END_OBJECT = FIELD OBJECT = FIELD NAME = "PC/NO" FIELD_NUMBER = 14 BYTES = 6 DATA_TYPE = ASCII_REAL UNIT = "dB*Hz" DESCRIPTION = "Downlink received carrier power (Watts) of the unocculted transmissions divided by the noise power spectral density (Watts/Hz)." END_OBJECT = FIELD OBJECT = FIELD NAME = "ALGORITHM" FIELD_NUMBER = 15 BYTES = 1 DATA_TYPE = ASCII_INTEGER DESCRIPTION = "The integer identifies the algorithm used to extract the carrier power from the RSR data: 0= Fast Fourier Transform (FFT); 1= Software Phase Locked Loop (PLL); 2= Overlapping FFT" END_OBJECT = FIELD OBJECT = FIELD NAME = "S/C-TO-LIMB_DISTANCE" FIELD_NUMBER = 16 BYTES = 11 DATA_TYPE = ASCII_REAL UNIT = "km" DESCRIPTION = "At the time of occultation, the distance between MESSENGER and the smooth-sphere occultation point at Mercury." END_OBJECT = FIELD OBJECT = FIELD NAME = "LIMB-TO-DSN_DISTANCE" FIELD_NUMBER = 17 BYTES = 11 DATA_TYPE = ASCII_REAL UNIT = "km" DESCRIPTION = "At the time of occultation, the distance between the DSN station and the smooth-sphere occultation point at Mercury." END_OBJECT = FIELD END_OBJECT = SPREADSHEET END A.2 Example Data File An example OCCSUM data file corresponding to the label example in Section A.1 is given below. Lines are wrapped so as not to exceed 78 printable characters in this text document. "RSR_file","Trajectory_file(SPK)","Ingress/Egress","Occultation_time"," Orbit_number","Direction_of_RF_path","Perpendicular_speed","Tangent_latitude", "Tangent_longitude","Raw_measured_radius","Time_uncertainty","Time_res"," Decay_scale","Pc/No","Algorithm","S/C-to-limb_distance","Limb-to-DSN_distance" "mess_rs_20110820005_3b1_rsr.dat","msgr_20040803_20140821_od270sc_0.bsp",I, 2011-082T00:46:31.080,9,-95.664,0.901,-7.631,-6.742,2443.103,0.188,0.250,0.375 ,20.685,2,6.4261e+03,1.3473e+08 "mess_rs_20110821200_2b1_rsr.dat","msgr_20040803_20140821_od270sc_0.bsp",I, 2011-082T12:51:51.750,10,-95.675,0.866,-5.282,-9.579,2441.611,0.081,0.250,0. 387,19.948,2,6.3230e+03,1.3271e+08 "mess_rs_20110830027_3b1_rsr.dat","msgr_20040803_20140821_od270sc_0.bsp",I, 2011-083T00:57:08.840,11,-95.699,0.831,-3.070,-12.438,2441.297,0.117,0.250,0. 400,20.002,2,6.2250e+03,1.3070e+08 "mess_rs_20110841242_2b1_rsr.dat","msgr_20040803_20140821_od270sc_0.bsp",I, 2011-084T13:12:46.260,14,-95.813,0.732,3.030,-21.153,2441.579,0.115,0.250,0. 445,18.305,2,5.9526e+03,1.2481e+08