Document title: VOLDESC.SFD for NDADS DE VEFI data Project: DE NDADS Datatype: VEFIMAGB NDADS Datatype: MAGB_GMS_62MS_V Super-EID: DOCUMENT There may be other documents also identified by this super-EID. NDADS filename: VEFIMAGB_MAGBVOLDESC.SFD NDADS filename: MAGBVOLDESC.SFD TRF entry B46573.txt in NSSDC's controlled digital document library. Feb. 1998. Document text follows: ---------------------- CCSDXZLM0001SMARK001CCSDXVNM0002SMRK0001 LOG_VEL_IDENT: USANASANSSDDEB1-0001A LOG_VOL_INITIATION_DATE: YYYY-MM-DD LOG_VOL_CLOSING_DATE: YYYY-MM-DD VOLUME_DIAMETER: 12 INCHES LOG_VOL_CAPACITY: 1 GB/LOGICAL_VOL LOG_VOL_FILE_STRUCTURE: FILES-11 VOLUME_DRIVE_MFGR_AND_MODEL: OPTIMUM 1000M WITH 1.6 CONTROLLER COMPUTER_MFGR: DIGITAL EQUIPMENT CORPORATION OPERATING_SYSTEM: MICROVMS 4.4 COMPUTER_SYSTEM: MICRO VAX II TECHNICAL_CONTACT: JAMES B. BYRNES CODE 694 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION GODDARD SPACE FLIGHT CENTER GREENBELT, MD 20771 SPAN DE696::U4JBB PHONE 301-286-3076 TRANSFER_SOFTWARE: SOAR 4.0 PREV_VOL_IDENT: NONE CCSDXVNM0002EMRK0001CCSDYDNM000200NSSDabcdSMRK0003 DATA_SOURCES: DYNAMICS EXPLORER B, MAGNETOMETER INSTRUMENT SCIENTIFIC_CONTACT: DR. JAMES A. SLAVIN CODE 696 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION GODDARD SPACE FLIGHT CENTER SPAN DE696::U6JAS PHONE 301-286-5839 DESCRIPTION_OF_SPACECRAFT: The Dynamics Explorer 2 spacecraft was one of two satellites in the Dynamics Explorer program. The two spacecraft were launched together into coplanar polar orbits for the purpose of studying coupling between the mag- netosphere, 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(MAG-B), vector electric field instrument(VEFI), neutral atmosphere composition spectrometer (NACS), wind and temperature spectrometer(WATS), Fabry-Perot interferometer (FPI), ion drift meter(IDM), retarding potential analyzer(RPA), low altitude . plasma instrument(LAPI), and Langmuir probe(LANG). 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 two-point measurements along magnetic field lines. The DE-2 spacecraft was nadir oriented (i.e. one side always pointing toward the center of the earth). PERFORMANCE: The DE-2 spacecraft performed well throughout its lifetime. Available power limited the instrument duty cycle to an average of thirty percent. The lifetime of the spacecraft was shorter than anticipated because of the less than nominal performance of the launch vehicle. DE-2 was launched on Aug. 3, 1981 and reentered the atmosphere on Feb. 19, 1983. ( Final data pass on Feb. 18, 1983). TIME_SPAN_OF_THE_DATA: 15-AUG-81 TO 16-FEB-83 INVESTIGATION_OBJECTIVES: The study of field-aligned currents using the DE-1 and DE-2 magnetic field measurments was the primary objective of the magnetometer investi- gation. Comparison of the magnetometer data with measurements of precipitating charged particles yielded information on the current carriers. Combined with the electric field measurements and ionospheric conductivity distributions deduced from the particle measuremnts, the magnetometer data allowed the construction of global models for ionospheric and field-aligned currents. The combination of field-aligned current measurements and neutral atmosphere observations provided an opportunity for investigating atmosphere-magnetosphere coupling and assessing the total rate of energy transfer into the upper atomsphere. INSTRUMENT_ATTRIBUTES: A. DESCRIPTION_OF_INSTRUMENT: The DE magnetometers utilize triaxial fluxgate sensors. When a saturable core immersed in an ambient magnetic field is driven into alternating positive and negative saturation, a flux component at the second harmonic of the drive frequency is induced by the ambient field. This signal, which is proportional to the magnitude of the field, is sensed, synchronously detected, integrated, and fed back to the sensing coil, wound solenoidally about the core sample. The coil axis defines the direction of sensitivity for that magnetic axis and the field generated by the feedback current nulls the ambient field in that direction. A closed loop system is form- ed in which the sensitivity and stability are determined primarily by the value and stability of the feedback transfer function, which includes a voltage-to-current transducer and the solenoidal coil constant. ELECTRONICS: The dynamic range of the fluxgate sensor is set by the voltage controlled current source to nominally +/- 6000 nT, corresponding to an output vol- tage of +/- 5V. The dynamic range was extended to the +/- 62000 nT re- quired for the DE mission by a precision 4 bit digitally controlled current source which generates compensation fields in increments of nominally 8000 nT from -56000 to +56000 nT. THERMAL_CONTROL: Even with the use of graphite fiber reinforced plastic, the sensitivity of the sensors is weakly temperature dependent. A thermostatically con- trolled heater was incorporated to control the sensor temperature. The heater was driven by the spacecraft unregulated bus so that it could be left on between data acquisition periods on the power limited spacecraft. B. OPERATIONAL_MODE: The DE-2 magnetometer possesses only a single operational mode in which the ambent field is sampled 16 times per second whith a digital resolution of +/- 1.5 nT. C. MEASURED_PARAMETERS: BX, BY, BZ IN SPACECRAFT COORDINATES. D. PERFORMANCE_OF_THE_INSTRUMENT: Magnetometer performance was nominal throughout the life of the mission. E. RESOLUTION: Each file contains high resolution data (62.5 milliseconds data). PARAMETERS: The daily data files contains four words: universal time, BX, BY, and BZ (spacecraft coordinates). DATA_SET_QUALITY: Data set quality is excellent. Care must be taken to avoid mis-interpretation of field direction variations due to spacecraft attitude errors and dynamics. DATA_PROCESSING_OVERVIEW: A. DATA_PROCESS_CYCLE: TIME SYNCHRONOUS SAMPLING. B. HISTORY: FINAL MAGNETOMETER B CALIBRATED DAILY DATA FILES WERE ASSEMBLED IN 1989. DATA_USAGE: Although the DE-2 magnetometer data has been successfully used to construct geomagnetic field models up to order 9, more typical usage is to derive field-aligned current densities from gradients in B measured along the spacecraft orbit. DATA_ORGANIZATION: Flat files containing time-tagged magnetic field vectors at 62.5 msec resolution. DATA_SET_NAME: DAILY DATA FILES CCSDYDNM000200NSSDabcdEMRK0003NSSDXZLMiiiiSMRK0004CCSDXKNM0002SMRK0005 LOG_VOL_COVERAGE: YYYY-MM-DD TO YYYY-MM-DD TYPE_OF_FILE_TIME_COVERAGE: Spacecraft coordinates daily files only YYYY-MM-DDTHH:MM:SS TO YYYY-MM-DDTHH:MM:SS NAMING_CONVENTION: Each daily file contains one full day's data. The date of the data is the name of the file. For example, file:D81286.DAT contains all the values for year:1981, day:281. FILE_NAME_LIST: PREV_LOG_VOL_COVERAGE: NONE CCSDXKNM0002EMRK0005CCSDXRNM0003SMRK0006 NESTING: L REF: FORMAT.SFD CCSDXRNM0003EMRK0006CCSDXRLM0003SMRK0007 ADI: NSSDefgh CLASS: I NESTING: N SCOPE: EACH REF: [DATA]*.*;* CCSDXRLM0003EMRK0007CCSDXRLM0003SMRK0008 ADI: NSSEijkl CLASS: J REF: READ_ME_FIRST.DAT CCSDXRLM0003EMRK0008NSSDXALMiiiiEMRK0004CCSDXZLM0001EMARK001