PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "Elizabeth D. Duxbury & James R. Murphy, 1998-10-06." OBJECT = DATA_SET DATA_SET_ID = "MPFL-M-ASIMET-2-EDR-SURF-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "MPFL MARS ATM STRUCT INST AND MET PKG RAW SURFACE V1.0" DATA_SET_COLLECTION_MEMBER_FLG = "N" DATA_OBJECT_TYPE = TABLE START_TIME = 1997-07-04T21:11:55.216Z STOP_TIME = 1997-09-27T04:54:42.300Z DATA_SET_RELEASE_DATE = 1998-01-04 PRODUCER_FULL_NAME = "JOHN T. SCHOFIELD" DETAILED_CATALOG_FLAG = "N" DATA_SET_DESC = " Data Set Overview ================= Mars Pathfinder bounced down and rolled to a stop on the surface of Mars on July 4, 1997. It landed in an ancient floodplain in the Ares Vallis region of Chryse Planitia at 19.17 degrees North latitude, and 33.21 degrees West longitude. The total duration of the mission was 83 sols. Surface meteorology data were collected by the MET instrument on 76 of these sols (sols 17, 31, 43, 45, 46, 48, and 51 contain no meteorology data). MET data are organized into science and housekeeping data records. Each record is composed of 12 parameters, which for all intents and purposes are measured simultaneously. The science data record consists of surface pressure (two instrument sensitivity ranges), atmospheric temperature at three vertical locations on the MET mast (referred to as TOP, MIDDLE, and BOTTOM), atmospheric temperature as measured by the Descent Thermocouple located near the top of the MET mast, and wind speed and direction at the top of the MET mast. See [SEIFFETAL1997] for a complete description of the instruments. The housekeeping data record consists of various instrument voltages, currents, and reference temperatures. At the time of writing (Sept. 1998), we had not yet derived reliable wind speeds and directions from the data received from the Martian surface. We continue to re-calibrate the wind sensor, and hope to have the wind results released soon. The parameters contained in the science data record are the measured atmospheric pressure obtained with the two instrument sensitivity ranges (6-10 and 0-12 millibars). Also included are the three temperatures measured along the MET mast, as well as the temperature measured by the Descent Thermocouple. We have also included in this data set the measured temperatures of each of the six wire segments which comprise the wind sensor. These temperatures, and their spatial variation around the sensor's central cylinder, are the data from which wind speed and direction will be derived. The housekeeping data consist of several reference voltage measurements from which the stability of instrument power supplies and sensor constant current sources can be determined. Additionally, the thermocouple reference junction temperature, the internal temperature of the wind-sensor cylinder, the temperature of the pressure sensor, and the temperature of the MET circuit board are measured. All science and housekeeping parameters are derived from sampled digitized voltages. The time intervals during which data were collected are referred to as sessions. Each session is characterized by a session number, a duration, and science and housekeeping data record sampling rates. Session numbers during the mission ranged from 39 (~ 7 AM LST on Sol 1) to 1430 (Sol 83). Session durations varied in duration from 184 seconds to 89052 seconds. This latter duration, used on 5 occasions, produced what we have referred to as 'Presidential MET Sessions', during which data were continually collected at a 0.25 Hz rate for an entire sol. The science data record sampling rate used during the mission varied per the specifications of the ASI/MET science team. It ranged from 0.25 Hz (a single point measurement of each variable once every four seconds) to 2 Hz (2 point measurements per second). For more info, see [SEIFFETAL1997, SCHOFIELDETAL1997]. Parameters ========== The data downlinked from the spacecraft are digital numbers derived from measured voltages. Digitization is to 14 bits, compared with the 10 bit resolution available to the Viking meteorology instruments. These numbers are stored in the Experiment Data Record (EDR) files, whereas the Reduced Data Records (RDR), contain results in scientific units (millibars, Kelvin, etc.). EDR values are converted to volts and subsequently scientific units using calibration information. During the nominal mission (sols 1-30), the nominal MET observation strategy was 51 equally spaced 3 minute measurement sessions per Sol. For each session science data records were sampled at a rate of 0.25 Hz. Interspersed with these sessions were longer (15 minute, one hour, entire sol) sessions often sampled at a higher rate (1 Hz). The purpose of this strategy was to characterize the full diurnal cycle throughout the sol, as well as higher frequency fluctuations at a variety of times during the sol. These times were spread over a number of sols to remain within data downlink constraints. Thus, we planned to characterize the diurnal cycle at 'low-frequency' (51 times each sol), and then over the period of ~10 sols to accumulate information at higher sampling frequencies so that every hour of the day would have such sampling. Continuous sampling for a complete sol at 0.25 Hz (a 'Presidential MET Session') was first conducted on Sol 25 and subsequently on sols 32,38,55, and 68. These are the only sols during the extended mission (sols 31-83) when MET data were collected outside the hours of 0900 - 1500 LST. Data are stored on a session-by-session basis. Thus, data for a particular sol are included in multiple files, for sols 1-49. On later sols, single sessions were specified to cover the duration of spacecraft activity on that sol (nominally 9 AM to 2:30 PM). Thus, from sol 50 (Session 1398) through sol 83 (Session 1430), data for each sol are contained in a single data file (session). Session numbers ranged from 39-1430, but no data for sessions 1330, 1338, 1340, 1341, 1362, 1370, 1376, 1379, 1384, 1385, 1386, 1387, 1389, 1390 were returned. Thus, there are no files for these sessions. Processing ========== The following process was used to create the MET Surface Experiment Data Records: 1) The individual packets of binary data were constructed into single-session data files. 2) The 14-bit binary numbers were converted to ASCII numbers. 3) Time-related values which were measured in RTIs (Real Time Interrupts, where 125 milliseconds = 1 RTI) were converted to seconds. 4) SCLK values were calculated for cases where the first packet was missing from a session. The above files are those that were distributed by the Multimission Image Processing Laboratory (MIPL) during the mission. After the mission, a timing error was discovered in the telemetry data and all of the SCLK values were recalculated. Further details of the timing error are described below in the section on Ancillary Data. Finally, the data were converted to PDS format, by separating the science and housekeeping records into distinct files, converting the tab-delimited fields to fixed-width fields, and exchanging the multiple packet headers for a single session header. (The original packet headers have been retained in a separate file called 'PKT_HDRS.TAB'; see Ancillary Data, below.) The real time processing of the MET Surface EDRs was performed at the Jet Propulsion Laboratory's Multimission Image Processing Laboratory using the VICAR suite of data processing programs. For questions concerning the creation of the data products, please contact: Address: Allan Runkle M/S 168-414 Jet Propulsion Laboratory 4800 Oak Grove Drive Pasadena, CA 91109 Phone: (818) 354-6006 Email: Allan.Runkle@jpl.nasa.gov For science related questions about the data, please contact the ASI/MET Facility Instrument Science Team Lead: Address: Tim Schofield M/S 169-237 Jet Propulsion Laboratory 4800 Oak Grove Drive Pasadena, CA 91109 Phone: (818) 354-2517 Email: John.T.Schofield@jpl.nasa.gov Data ==== All of the data in this data set are contained in ASCII tabular files with detached PDS labels. Science and housekeeping data have been split into separate files, stored in the directories SURF_EDR/SCIDATA and SURF_EDR/HKPDATA, respectively. Beneath that, the data files are separated by session number into fourteen directories labeled SE00XXS through SE14XXS (for the science data) and SE00XXH through SE14XXH (for the housekeeping data). Individual filenames are constructed as follows: SE0559S.TAB 1234567.890 1: The first character will always be an 'S', representing Surface data. 2: The second character will always be an 'E', signifying the raw data (Experiment Data Record). The corresponding calibrated data (ie., Reduced Data Record) can be found in the SURF_RDR directory, in a file with the same name, except that the 'E' will be an 'R'. 3-6: The next four characters provide the session number of the data file. 7: The seventh character will be either an 'S' or an 'H'. 'S' signifies science data; 'H' signifies housekeeping data. 8-0: The file extension indicates which type of file it is. The only two options are 'LBL' (the PDS label file), or 'TAB' the ASCII table containing the data. As an example, the data from session 559 is stored in the following locations on the ASI/MET CD: SURF_EDR/SCIDATA/SE05XXS/SE0559S.TAB - raw data file SURF_EDR/SCIDATA/SE05XXS/SE0559S.LBL - PDS label for SE0559S.TAB SURF_EDR/HKPDATA/SE05XXH/SE0559H.TAB - raw housekeeping file SURF_EDR/HKPDATA/SE05XXH/SE0559H.LBL - PDS label for SE0559H.TAB SURF_RDR/SCIDATA/SR05XXS/SR0559S.TAB - calibrated data file SURF_RDR/SCIDATA/SR05XXS/SR0559S.LBL - PDS label for SR0559S.TAB SURF_RDR/HKPDATA/SR05XXH/SR0559H.TAB - calibrated housekeeping file SURF_RDR/HKPDATA/SR05XXH/SR0559H.LBL - PDS label for SR0559H.TAB The tabular files are formatted so that they may be read directly into many database management systems (DBMS) or spreadsheet programs on various computers. Each of the files contains two tables. The first is the header table, and is only a single record in length. The second table contains all of the data records for a session and varies in length. All fields in the tables are stored in columns of fixed width and are right justified. The records are of fixed length; since the header records are shorter than the data records, they have been padded with blank spaces at the end of the record. The last two bytes of each record contain the ASCII carriage return and line feed characters. This allows the tables to be treated as fixed length record files on computers that support this file type and as normal text files on other computers. The ancillary data file, PKT_HDRS.TAB, (described below,) is similar to the regular data files, except that it only contains a single table with 8,173 records, and the fields in the table are comma separated. The PDS labels are object-oriented. The object to which the labels refer (the tables) is denoted by a statement of the form: ^object = location in which the carat character ('^', also called a pointer in this context) indicates that the object starts at the given location. For an object located outside the label file (as in this case), the location denotes the name of the file containing the object, along with the starting record. For example: ^DATA_TABLE = ('SE0559S.TAB', 2) indicates that the DATA_TABLE object begins at record 2 of the file SE0559S.TAB, in the same directory as the detached label file. (Records are counted starting at 1, not 0.) When there is only a single object in the data file (as with PKT_HDRS.TAB), the record number may be dropped: ^TABLE = 'PKT_HDRS.TAB' The detached label files are stream format files, with a carriage return (ASCII 13) and a line feed character (ASCII 10) at the end of each record. This allows the files to be read by the MacOS, DOS, UNIX, and VMS operating systems. Ancillary Data ============== As mentioned above, a timing problem was discovered in the MET telemetry data after the mission. The root cause of the problem is not completely understood, but likely involved a software error in the counting of the housekeeping vs. science records with their varying sampling rates. However, the problem is sufficiently understood to correct the data. Most of the time, the housekeeping sensors were sampled every thirty-six seconds, while the science sensors were sampled every four seconds. (Each sample corresponds to a record within a packet.) However, at packet boundaries, the interval alternates between zero seconds at one boundary, and eight seconds at the next. In those cases where the science sampling rate was every two seconds, the packet boundary problem is only seen every seventeen packets; an interval of zero seconds is followed by an interval of four seconds. When the science sampling rate is every second, the problem recurs roughly every thirty packets, with an interval of zero seconds followed by an interval of two seconds. In general, the problem can be corrected by shifting the SCLK values of all the science data records in a packet following a zero second packet boundary. In all cases, the values should be shifted forward by an amount equal to the science sampling interval. None of the housekeeping data records were affected by this problem. Due to the necessity of correcting this problem and of calculating SCLKs in cases where the first packet in a session was missing, all of the SCLK values provided in the EDR files are calculated values, rather than the original values received in the telemetry. Given the possibility of an error in the correction of the timing problem, it was decided that the original SCLK values should be retained somewhere. Therefore, all of the original UNCORRECTED packet headers were stripped out of the original data files and concatenated into a single ancillary data file called 'PKT_HDRS.TAB'. This is a single ASCII tabular data file stored in the INDEX directory of the ASI/MET CD. The structure of the individual records in the file is almost identical to that of the header records in each of the data files, and is fully described by the PDS label included in the same directory. Software ======== The ASI/MET Surface EDR tables can be displayed on UNIX, Macintosh, and PC platforms as simple ASCII files, or using the PDS developed program, NASAView. This software is freely available from the PDS Central Node and may be obtained from their web site at http://pds.jpl.nasa.gov/. For more information or help in obtaining the software, contact the PDS operator at the following address: Address: Planetary Data System, PDS Operator Jet Propulsion Laboratory 4800 Oak Grove Drive Pasadena, CA 91109 Phone: (818) 354-4321 Email: pds_operator@jpl.nasa.gov WWW URL: http://pds.jpl.nasa.gov/ Media / Format ============== The ASI/MET Surface EDR data will be stored and distributed on compact disc-read only memory (CD-ROM) media. The CDs are formatted according to ISO-9660 and PDS standards. The data files do not include extended attribute records (XARs), and will therefore not be readable on some older VMS operating systems." CONFIDENCE_LEVEL_NOTE = " Review ====== The contents of this CD have been peer reviewed by the following people: Lyle Huber - PDS Atmospheres Node, New Mexico State University Julio Magalhaes - MPF ASI/MET Team, NASA Ames Research Center Jim Murphy - MPF ASI/MET Team & PDS Atmospheres Node, New Mexico State University Tim Schofield - MPF ASI/MET Team Lead, Jet Propulsion Laboratory Rob Sullivan - MPF Participating Scientist, Cornell University Betty Sword - PDS Central Node Data Engineer, Jet Propulsion Laboratory John Wilson - Non-MPF scientist, Geophysical Fluid Dynamics Laboratory/NOAA, Princeton University Data Coverage and Quality ========================= During pre-flight testing, the pressure sensor was tested at temperatures (190 K) that were significantly lower than its design limits (220 K), and much colder than it experienced within the spacecraft on the Martian surface. This extreme stressing of the sensor cast doubt upon the calibration which had been obtained prior to that point, and the schedule thereafter did not permit recalibration of the sensor in a controlled environment. During cruise to Mars, the ASI/MET system was periodically powered up and the pressure sensor signal, as well as its temperature, were measured. These measurements, together with measurements obtained during free fall and entry, provided a data set from which the variation of sensor zero-offset as a function of the temperatures experienced during cruise (270-280K) could be determined. It became clear that thermal stressing had changed the offset and increased its variation with temperature by a factor of 3. It was not possible to verify gains in flight, but laboratory testing on the flight spare sensor suggested that sensor stressing would not produce significant gain changes. The flight data, in addition to the pre-flight calibration data, have been used to determine pressure from the down-linked pressure sensor signals. The thermocouples appeared to work very well, and there is no reason to question the results from them. As stated above, the determination of wind speed and direction is ongoing, and a new wind data set will be issued following analyses of recent sensor recalibration work, and application of its results to wind-sensor data returned from the Martian surface." END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_TARGET TARGET_NAME = MARS END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = MPFL INSTRUMENT_ID = ASIMET END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = MPFL INSTRUMENT_ID = WINDSOCK END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "SEIFFETAL1997" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "SCHOFIELDETAL1997" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "VAUGHAN1995" END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET END