Document title: Data set description of the PI-provided DE WATS 2-second data Project: DE NDADS Datatype: WATS_2S_ASCII EID: DOCUMENT Super-EID: DOCUMENTS There may be other documents also identified by this super-EID. NDADS filename: TRF entry: b47612.txt in NSSDC's controlled digital document library, Dec. 1998. Document text follows: ---------------------- CCSDXZLM0001SMARK001CCSDXVNM0002SMRK0001 LOG_VOL_IDENT: USANASANSSDDEB4_0001 LOG_VOL_CLOSING_DATE: YYYY-MM-DD LOG_VOL_FILE_STRUCTURE: FILES-11 TAPE_DENSITY=6250 BPI TAPE_TRACKS=9 TAPE_LENGTH=2400 INCHES COMPUTER_MFGR: DIGITAL EQUIPMENT CORPORATION OPERATING_SYSTEM: VAX/VMS 5.4 COMPUTER_SYSTEM: MICRO VAX II TECHNICAL_CONTACT: DR. L. E. WHARTON CODE 914 NASA/GSFC GREENBELT, MD 20771 PHONE: 301-286-3486 SPAN: DEIO::WHARTON PREV_VOL_IDENT: NONE CCSDXVNM0002EMRK0001CCSDYDNM0002SMRK0003 DATA_SET_NAME: NEUTRAL VELOCITY AND TEMPERATURE DATA_SOURCES: DYNAMICS EXPLORER B, WIND AND TEMPERATURE SPECTROMETER (WATS) INVESTIGATOR_CONTACT: MR. N. W. SPENCER CODE 910 NASA/GSFC GREENBELT, MD 20771 PHONE: 301-286-5001 SPAN: PACF::SPENCER SOURCE_CHARACTERISTICS: A. DESCRIPTION_OF_SPACECRAFT: The Dynamics Explorer 2 spacecraft was one of two satellites launched for the Dynamics Explorer program. The two spacecraft were launched together into coplanar polar orbits for the purpose of studying coupling between the magnetosphere, ionosphere, and the atmosphere. The DE-2 spacecraft was placed in a low elliptical orbit whereas the DE-1 orbit was highly elliptical. Instruments aboard the DE-2 spacecraft were: magnetometer, vector electric field instrument, neutral atmosphere composition spectrometer, wind and temperature spectrometer, Fabry-Perot interferometer, ion drift meter, retarding potential analyzer, low altitude plasma instrument, and Langmuir probe. B. ORBIT_INFORMATION: Because the Delta launch vehicle did not complete a full burn the DE-2 satellite was placed in a lower than anticipated polar orbit, initially 1012 by 309 km. The orbital period was 98 min. The DE-1 and DE-2 satellites were launched by the same vehicle so that their orbits would be coplanar, allowing occasional two-point measurements along magnetic field lines. The DE-2 spacecraft spun once per orbit and the spin axis was perpendicular to the orbital plane so that one axis of the satellite always was aligned with the center of the earth. C. PERFORMANCE: The DE-2 spacecraft performed well through its lifetime. Power limitations forced the duty cycle to be limited to an average which was originally targeted at 30%. The lifetime of the spacecraft was shorter than anticipated because of the less than nominal performance of the launch vehicle. The launch was on Aug. 3, 1981 and the DE-2 satellite reentered the atmosphere on Feb. 19, 1983, with the last contact the day before. TIME_SPAN_OF_THE_DATA: 8-AUG-81 TO 18-FEB-83 INVESTIGATION_OBJECTIVES: The WATS objective was to provide up to 2 s resolution measurements of the neutral temperature and vertical and zonal velocity with emphasis on the variability driven by interactions in the atmosphere, ionosphere, and magnetosphere system. INSTRUMENT_ATTRIBUTES: A. DESCRIPTION_OF_INSTRUMENT: The Wind and Temperature Spectrometer (WATS) was a quadrupole mass spectrometer employing an electron beam ion source operating in the closed mode and a discrete dynode multiplier detector operating in the counting mode. The gas inlet orifice to the gold plated antechamber was pointed along the orbit path during normal spacecraft despun operations. Two rectangular baffles were swept in front of the orifice to provide temperature and velocity information. The vertical baffle gave the velocity in the satellite y axis direction and the horizontal baffle gave the velocity in the z axis while both baffles gave temperature information. The mass selection, instrument voltage levels, baffle offsets, etc. could be changed on command allowing a large variety of modes. See Spencer et al., The Wind and Temperature Spectrometer on Dynamics Explorer, Space Science Instrumentation, 5, 417 to 428, 1981. B. OPERATIONAL_MODE: The instrument was commanded in a given mode for each of 4 consecutive 2 second slots and this sequence of modes repeated every 8 seconds. The instrument had an ion and a RPA mode but these were considered experimental test modes and only data from the neutral non-retarding mode are included in the data files. A typical mode sequence was two horizontal and two vertical measurements. Sometimes the RPA mode was substituted for one of the vertical measurements. In this case the data points would be 4 seconds apart instead of the usual 2 seconds. Each baffle mode could be for one of two masses which were usually selected to be O2 and N2. C. MEASURED_PARAMETERS: The measured parameters were density (intended only as a backup to NACS data), temperature, and velocity. The z and y axis velocities are converted into zonal and vertical velocities respectively. Sometimes a mode sequence contained measurements for both O2 and N2 but usually N2 was selected at low altitudes and O2 was selected at high altitudes. All the measured parameters are for only the one mass selected. It is assumed that most of the measured O2 in the instrument comes from recombined ambient O. In the data files mass 32 is to be interpreted as mass 16. D. PERFORMANCE_OF_THE_INSTRUMENT: The WATS instrument returned usable data from shortly after launch until the spacecraft reentered the atmosphere (Feb. 19, 1983). This was occasionally interrupted by very brief periods in which the spacecraft was placed in a spinning mode. Data during these periods are used for instrument diagnostics such as the flight-path angle response curve. While the ion and RPA modes returned statistically significant data, the experimental curves varied from the expected forms and no data was produced. E. RESOLUTION: The data records are 2 seconds apart except for the case of a slot such as the RPA mode which produced no data. Then the data records are 4 seconds apart. Temperature is produced by both baffles but the velocity in a given direction is only obtained when the appropriate baffle is deployed. The mode with two horizontal and two vertical slots would give a temperature resolution of 2 seconds and a repeating vertical or zonal velocity sequence with 2 second and then 6 second gaps. PARAMETERS: The eleven parameters included in each data record are: Word Parameter 1 Date in YYDDD, YY = last 2 digits of the year, DDD=day number 2 Universal time of the data in milliseconds 3 Mode, 3 or 4 = horizontal and 5 or 6 = vertical 4 Outin, 1=baffle going out and 0=going in 5 Mass in AMU, usually 28 or 32 6 Density in number per cc 7 Temperature in degrees Kelvin 8 Velocity in spacecraft coordinates in meters per second 9 T1, T2, slot position, mode 10 (C+B)/8, C/8 11 Velocity in corotating Earth frame in meters per second Parameter explanations: T1 and T2 are the times the baffle crosses the first or second optical position sensor. The slot position is the number (1 through 4) of the four slot measurement cycle. The slot position should have no effect on the data except for transients from a mode in a previous slot. This ocured when the RPA mode was included in slot 3 and the resulting transient distorted the curve in slot 4 causing an error in the temperature. C and B in word 10 are the count level and the background level. The background, B, is the total count level change resulting from both absorption and desorption of the measured gas in the metallic surfaces of the instrument. It can be both positive and negative as the absorption process could either add or subtract particles from the instrument chamber. The velocity in word 8 or 11 is horizontal for mode 3 or 4 and vertical for mode 5 or 6. Word 11 is obtained by rotating from satellite coordinates to geographical coordinates, assuming that the ram wind is zero. DATA_SET_QUALITY: Data quality below 500 km for the temperature and 800 km for the velocity is generally quite good. Quality deteriorates at higher altitudes as oxygen and molecular nitrogen approach their background values. Usually mass 16 (measured as 32) was used for wind and temperature above 300 km because its concentration is higher at the higher altitudes and mass 28 was used below 300 km because it has less distortion from the gas-surface interaction. The statistical error is given by ST/T = 1.3 / SQRT(C) and SV = 260 / SQRT(C) m/s where ST is the standard deviation of the temperature, T is the temperature, C is the counts as given in word 10, and SV is the standard deviation of the velocity. For a count level of 10000 the error of the temperature would be 1.3% and the error of the velocity would be 2.6 meters per second. Added to the statistical error are systematical errors such as an uncertainty of about 24 m/s in the velocity due to errors in sensing the angle of the baffle arm and an error of about 3% due to uncertainties in the baffle sweep rate. The oxygen gas surface interaction causes an error that increases the oxygen temperature about 3% and adds or subtracts about 100 m/s to the oxygen velocity when the baffle is moved in or out. Since some of the systematic errors are large and can be corrected a correction algorithm is provided. Since the correction procedure involves spectral distortion and loss of resolution it should not be used when only the spectrum or ac variations are of interest. DATA_PROCESSING_OVERVIEW: A. DATA_PROCESSING_CYCLE: The telemetry data were converted into density temperature and velocity in spacecraft coordinates and stored both in the Mission Analysis Files (MAF) and a tape archive. Since the MAF data would occasionally be lost the tape archive was the primary data base. A directory of the tape data base was maintained and compared to the MAF directory. Whenever data files appeared in the MAF directory that were not in the tape directory they were copied onto the tape data base. B. HISTORY: Data was processed under the control of an automated program which scanned the available telemetry, found the files that had not been processed and continuously submitted jobs to process the data. Thus the data base was checked for completeness as the processing progressed. To avoid reprocessing telemetry that produced no data an entry was placed in the directory with a flag indicating that it produced no data. When the first attempt of processing the data was completed all the telemetry that produced no data was reprocessed. This procedure was then repeated. Still considerable gaps in the reduced data remained due to the fact that the DE Sigma-9 failed to promote about 10% of the requested segments of telemetry. These data gaps were identified and the telemetry was processed to fill them in. Finally contiguous data segments were combined into one file and redundant or overlapping data segments were eliminated. In the final data set the velocity in the geographic corotating coordinate system was calculated and added to the data words. DATA_USAGE: The WATS temperature and transverse velocity combined with the NACS density and the FPI ram wind are the five fundamental neutral transport variables of fluid dynamics. They are used to study the neutral dynamics of the upper atmosphere and combined with the same five ion transport variables and the electric and magnetic field provide the set of variables necessary to study the ion-neutral dynamics. A program to correct the WATS data is provided. The data provided on the tapes is named c*.dat. After running the correction program the files will be named d*.dat, as described in the format descriptor TYPE_OF_FILE_DESCRIPTION, by the correction program. To correct the data execute: WATSCOR Then as prompted: Enter allocated dev with [ ] This would be the device, a disk or tape, followed by the account name upon which the data resides. A return indicates the current directory. Next as prompted: Enter file name with * An entry like "C*.dat" would correct all the WATS data on the device. The output files will be of the form "D*.dat". The correction program will distort the spectrum of the data and will introduce a loss of resolution. For studies requiring only the AC variations like gravity wave analysis it should not be used. For analysis requiring a correct DC level such as the ion-neutral momentum or energy balance the correction program should be used. An interactive program to read the directory called: RDIR is provided. It reads the directory file DIR.DAT and lists the file names and times for which there exists data in the data base. An optional output file name containing this list may be input to the program. The directory file is placed on each of the three WATS tapes and is the directory only for the given tape. To avoid confusion, in the case of loading online more than one WATS tape, an identical directory named WATSnDIR.LIS, where n is the tape number, is placed on the tape. For example, if all three tapes are placed online the combined directory must be constructed by the VAX/VMS command: COPY WATS1DIR.LIS,WATS2DIR.LIS,WATS3DIR.LIS DIR.LIS The three types of specification allowed are: Orbit number Orbit number range Time range. These inputs are described during execution when the program requests them. A program to read the data is called: WATSREAD The user, when he is prompted, inputs the name of the WATS data file to be read and then the name of a file that the data is to be written into. The purpose of this program is to format the data. DATA_ORGANIZATION: The WATS data are contained in sequential files with each contiguous segment of data in a separate file. The files are binary and consist of eleven 4 byte words with the first 5 integers and the last 6, except for word 9 and 10, real numbers. The eleven parameters included in each data record are: Word Parameter 1 Date in YYDDD, YY = last 2 digits of the year, DDD=day number 2 Universal time of the data in milliseconds 3 Mode, 3 or 4 = horizontal and 5 or 6 = vertical 4 Outin, 1=baffle going out and 0=going in 5 Mass in AMU, usually 28 or 32 6 Density in number per cc 7 Temperature in degrees Kelvin 8 Velocity in spacecraft coordinates in meters per second 9 T1, T2, slot position, mode 10 (C+B)/8, C/8 11 Velocity in corotating Earth frame These parameters are explained in INSTRUMENT_ATTRIBUTES SECTION C. MEASURED_PARAMETERS. The blocksize is 2024 bytes and the recordlegnth is 44 bytes. Word 9 consists of four 1 byte unsigned integers and word 10 consists of two 2 byte unsigned integers. The data are contained on 3 6250 BPI 2400 foot 9 track tapes. CCSDYDNM000200NSSDABCDEMRK0003NSSDXZLMIIIISMRK0004CCSDXKNM0002S MRK0005 LOG_VOL_TIME_COVERAGE: 1981-08-08 to 1983-02-18 NAMING_CONVENTION: The data files are named CONS.DAT where ON is the orbit number and S is a one digit number with no significance except when there are more than one segment of data per orbit number. Then S will increase for segments of data later in time. For example, C14712.DAT would be the file for orbit number 1472 segment number 2. These data files are combined into three backup files named WATS1.BCK, WATS2.BCK, AND WATS3.BCK and are placed, in backup format, on three tapes labeled WATS1, WATS2, AND WATS3 respectively. FILE_TIME_COVERAGE: The times of the data segments are contained in the directory file DIR.DAT. It is a formatted ASCII file which contains: Orbit number, (beginning and end) (Date, Time, Latitude, Longitude, Local Time) with Date and Time as described in DATA_ORGINIZATION, Latitude and Longitude in degrees and Local Time in hours. The Fortran format is given by: Format(A6,2(I6,I9,F9.1,F7.1,F5.1)) The directory for tape #1 is: 00770 81220 57240718 -39.4 145.2 1.5 81220 60290695 40.2 -47.5 13.5 00790 81220 67438740 64.0 102.6 1.5 81220 69596700 -79.2 93.7 1.5 01699 81226 77223203 77.4 55.8 1.1 81226 79387195 -66.1 46.8 1.1 01880 81228 16119398 66.5 -50.9 1.0 81228 16741391 24.8 -53.5 1.0 01900 81228 27359353 81.5 82.2 13.0 81228 28493335 23.9 -102.6 1.0 01980 81228 74599387 80.6 64.7 1.0 81228 76389392 -39.2 57.3 1.0 02050 81229 29263344 82.0 -106.9 0.9 81229 31053340 -37.8 -114.3 0.9 02070 81229 40999564 82.1 -155.9 0.9 81229 42789571 -37.7 -163.3 0.9 02090 81229 52743560 81.8 155.1 0.9 81229 54525566 -37.5 147.7 0.9 02100 81229 58583577 83.6 130.6 0.9 81229 60389582 -37.2 123.2 0.9 . . . PREV_LOG_VOL_COVERAGE: NONE CCSDXKNM0002EMRK0005CCSDXRNM0003SMRK0006 NESTING= L REF= FORMAT.SFD CCSDXRNM0003EMRK0006CCSDXRLM0003SMRK0007 ADI= NSSDefgh CLASS= I NESTING= N SCOPE= EACH REF=N*.* CCSDXRLM0003EMRK0007NSSDXZLMiiiiEMRK0004CCSDXZLM0001EMARK001