Document title: Voldesc.sfd for NDADS DE MAGA_AVG datatype Project: DE NDADS Datatype: MAGA_AVG Super-EID: DOCUMENT There may be other documents also identified by this super-EID. NDADS filename: MAGA_DE_VOLDESC.SFD TRF entry B46598.txt in NSSDC's controlled digital document library. Feb. 1998. Document text follows: ---------------------- CCSDXZLM001SMARK0001CCSDXVNM0002SMRK0001 LOG_VOL_IDENT: 81-070A-01B-001-1 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 1000 COMPUTER_MANUFACTURER: DIGITAL EQUIPMENT CORPORATION OPERATING_SYSTEM: MICROVMS 4.7 COMPUTER_SYSTEM: MICRO VAX II TECHNICAL_CONTACT: JAMES B. BYRNES CODE 694 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION GODDARD SPACE FLIGHT CENTER GREENBELT, MD 20771 PHONE: 301-286-3076 TRANSFER_SOFTWARE: SOAR 3.0 PREV_VOL_IDENT: NONE CCSDXVNM0002EMRK0001CCSDYDNM000200NSSDabcdSMRK0003 SOURCE_OF_DATA: DYNAMICS EXPLORER A, MAGNETOMETER INSTRUMENT SCIENTIFIC_CONTACT: DR. JAMES A. SLAVIN CODE 696 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION GODDARD SPACE FLIGHT CENTER GREENBELT, MD 20771 PHONE: 301-286-5839 SOURCE_CHARACTERISTICS: A. DESCRIPTION_OF_SPACECRAFT: The Dynamics Explorer 1 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-1 spacecraft was placed in a high elliptical orbit whereas the DE-2 spacecraft had an orbit with low ellipticity. Instruments aboard the DE-1 spacecraft were: magne- tometer (MAGA), plasma wave instrument (PWI), spin-scan auroral imager (SAI), retarding ion mass spectrometer (RIMS), high-altitude plasma instrument (HAPI), and hot plasma compostion instrument (EICS - energetic ion compo- sition spectrometer). These instruments are often identified by their acronyms, and acronyms are used in this directory. B. ORBIT_INFORMATION: Because the Delta launch vehicle did not complete a full burn, the DE-1 satellite was placed in a lower than anticipated polar orbit, initially 23173 by 570 km. The orbital period was 409 min. The DE-1 and DE-2 sate- llites were launched by the same vehicle so that their orbits would be coplanar, allowing occasional two-point measurements along magnetic field lines. The DE-1 spacecraft spins at a rate of 10 rpm and the spin axis is perpendicular to the orbital plane. The apogee latitude precesses through 360 degrees in 3 years. The apogee was positioned over the north pole on September 8, 1981. C. PERFORMANCE: The DE-1 spacecraft has performed well since its launch on Aug. 3, 1981, and is still returning useful data at the present time. Power limitations force the duty cycle to be limited such that the instruments were not on conti- nuously. The initial average for the duty cycle was intended to be 50%. This value was changed according to the varying state of the satellite battery. TIME_SPAN_OF_THE_DATA: AUG-20-1981 TO PRESENT(FEB. 14, 1989) INSTRUMENT_ATTRIBUTES: A. FLUXGATE_SENSOR: The DE magnetometers were triaxial fluxgate sensors. When a saturable core immersed in an ambient magnetic field was driven into alternating positive and negative saturation, a flux component at the second harmonic of the drive frequency was induced by the ambient field. This flux, which was proportional to the magnitude of the field, was sensed, synchronously de- tected, integrated, and fed back to the sensing coil, wound solenoidally about the core sample. The coil axis defined the direction of sensitivity for that magnetic axis and the field generated by the feedback current nulled the ambient field in that direction. A closed loop system was form- ed in which the sensitivity and stability were determined primarily by the value and stability of the feedback transfer function, which included a voltage-to-current transducer and the solenoidal coil constant. B. ELECTRONICS: The dynamic range of the fluxgate sensor was 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 +/- 6200 nT required 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. C. THERMAL_CONTROL: Even with the use of graphite fiber reinforced plastic, the sensitivity of the sensors was temperature dependenct. A thermostatically controlled heater was incorporated to control the sensor temperature. The heater was driven by the spacecraft unregulated bus so that it could be left on bet- ween data acquisition periods on the power limited spacecraft. OBJECTIVE_OF_THE_INSTRUMENT: Deduction of field-aligned currents from the magnetic field observations with high resolution in DE-A AND DE-B was one of the most important obj- ectives of the magnetometer experiments. The low altitude (DE-B) magnetic field observations would provide the most dependable means of detecting field-aligned currents. A comparison of the DE-B magnetometer data with measurements of precipitated charged particles would yield information on the current carriers. Combined with the electric field measurements and with the ionospheric conductivity distribution deduced from the particle measuremnts, the magnetometer data would allow the construction of a model for the field-aligned currents. The combination of field-aligned current measurements and neutral atmosphere observations such as neutral wind ob- servations woulkd provide an opportunity for investigating the processes of the atmosphere-mafnetoshpere coupling. OUTPUT_PARAMETERS: BX,BY,BZ IN CALIBRATED SPACE CRAFT COORDINATES. PERFORMANCE_OF_THE_INSTRUMENT: NORMAL. DATA_PROCESS_CYCLE: TIME SYNCHRONOUS SAMPLING. DATA_SET_NAME: DAILY DATA FILES HISTORY: MAGNETOMETER A DAILY DATA FILES STILL BEING ASSEMBLED (FEB. 15,1989). PARAMETERS: The daily data files contains four words: time, BX, BY, and BZ spacecraft coordinates. RESOLUTION: Each file contains high resolution data (62.5 milliseconds data). CCSDYDNM000200NSSDabcdEMRK0003NSSDXZLMiiiiSMRK0004CCSDXKNM0002SMRK0005 LOG_VOL_COVERAGE: YYYY-MM-DD TO YYYY-MM-DD TYPES_OF_DATA_FILES_CONTENTED: Spacecraft coordinates daily files only NAMING_CONVENTION: Each daily file contains one full day's data. Hence, the date of the data is the name of the file. For example, file:D81286.DAT contains all the valus for year:1981, date:281. FILE_NAME_LIST: D81226.DAT D81335.DAT D82330.DAT ... 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: UTILITY.FOR CCSDXRLM0003EMRK0008NSSDXALMiiiiEMRK0004CCSDXZLM0001EMARK001