Document title: VOLDESC.SFD for NDADS DE VEFI MAGB datatype Project: DE NDADS Datatype: VEFIMAGB Super-EID: DOCUMENT There may be other documents also identified by this super-EID. NDADS filename: VEFIMAGB_VEFIVOLDESC.SFD TRF entry B46575.txt in NSSDC's controlled digital document library. Feb. 1998. Document text follows: ---------------------- CCSDXZLM0001SMARK001CCSDXVNM0002SMRK0001 LOG_VOL_IDENT: USANASANSSDDEB2-0001A LOG_VOL_INITIATION_DATE: 1990-02-15 LOG_VOL_CLOSEING_DATE: 1992-01-21 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_MFGR: DIGITAL EQUIPMENT CORPORATION OPERATING_SYSTEM: MICROVMS COMPUTER_SYSTEM: MICRO VAX II TECHNICAL_CONTACT: CARMEN LIEBRECHT CODE 696.0 BUILDING 2, ROOM 205 NASA, GODDARD SPACE FLIGHT CENTER GREENBELT, MARYLAND 20771 SPAN DE696::VEFI TEL: (301)286-4629 TRANSFER_SOFTWARE: SOAR PREV_VOL_IDENT: None CCSDXVNM0002EMRK0001CCSDXSNM0002SMRK0003 DATA_SOURCES: DYNAMICS EXPLORER B, VECTOR ELECTRIC FIELD INSTRUMENT. SCIENTIFIC_CONTACT: DR. NELSON C. MAYNARD AIR FORCE GEOPHYS. LAB/PHG HANSCOM AFB, MA 01731 SPAN AFGL::MAYNARD TEL: (617)377-2431/32 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, 81 and the DE-2 satellite reentered the atmosphere on Feb. 19, 1983, with the last contact the day before. TIME_SPAN_OF_THE_DATA: 15-AUG-81 TO 16-FEB-83 INVESTIGATION_OBJECTIVES: The objective of this experiment was to monitor the DC and AC magnetospheric electric fields as measured from DE-2. INSTRUMENT_ATTRIBUTES: A. DESCRIPTION_OF_INSTRUMENT: This experiment utilized dual axis double floating probes, each having a 21.4 meter baseline, to measure the AC and DC electric field components in the satellite orbit plane. The AC data was in the form of spectrometer channel RMS outputs. Three spectrometers, A, B, and C monitored the data in the Fourier domain from 4 to 1000, 4 to 1000, and 1000 to 512000 Hz. The A and B spectromemters, though identical, could be connected to different antennas for comparisons. More information is available, please refer to N. C. Maynard et al. Space Science Instr., Vol 5, no. 4, 1981, edited by R. A. Hoffman. B. OPERATIONAL_MODE: The VEFI instrument measured the DC electric field at a resolution of 16 samples per second (2 samples per second data has also been submitted), fast variation peaks at a programmable resolution of 1, 2, or 4 samples per second (not submitted) and the variational electric fields at a programmable resolution of 1 peak and 1 average reading of each channel per second or 2 readings (peaks or average) of each channel per second (only the average has been submitted). C. PARAMETERS_MEASURED: The VEFI instrument measured the following parameters: 1. Vector DC electric field. 2. Fast variation peaks. 3. Variational electric fields: a. Comb filter bank A (8 channnels): 4-8, 8-16, 16-32, 32-64, 64-128, 128-256, 256-512 and 512-1024 Hz. b. Comb filter bank B (8 channnels): 4-8, 16-32, 45-64, 64-128, 181-256, 256-361, 361-512, and 512-1024 Hz. c. Comb filter bank C (4 channnels): 1.02-4.09, 4.09-16.0, 16.0-64.0, and 128-512.0 kHz. D. PERFORMANCE_OF_THE_INSTRUMENT: The antenna pair perpendicular to the orbit plane did not deploy. This experiment had few errors in the DC mode. AC measurements may, at times, contain spacecraft generated electromagnetic interference (EMI) and other problems which are discussed under DATA_SET_QUALITY. E. RESOLUTION: The resolution of the DC data archived is 16 samples per second for the high resolution data set, and 2 samples per second for the averaged data set. The resolution of the AC data archived depends on the mode of the spectrometer and can be or 2 samples per second (each data point in the data set archived has a time tag, therefore would be users need not to worry about instrument modes). As for the frequency resolution , all the frequency bands are characterize by a 6th order Butterworth response with the frequencies of the band edges defined at the -6db points. PARAMETERS: The following parameters have been archived: A. High resolution DC electric field (16 points per second) along the X and Y axes in spacecraft coordinates (X direction is along the spacecraft velocity vector and Y is vertically upward from September through March and vertically downward from March throug September). B. Averaged DC electric field (2 points per second) along the X and Y axes in spacecraft coordinates. C. Included in the same file with the DC averaged data is the integrated potential along the X axis in spacecraft coordinates. D. The averaged variational electric fields (1 or 2 points per second, usually 1) for all channels of each of the three spectrometers. E. Variational electric fields averaged at 16 second intervals for all channels of each of the three spectrometers. F. Some orbital parameters such as the altitude of the satellite, the geographic longitude and latitude, the magnetic local time and the invarient latitude have been included for each data point of each file except for the high resolution files. G. Other parameters such as the averaged electric field in topographical and LMG are derived but not included in this data set and can be requested from the principal investigator. DATA_SET_QUALITY: The DC electric field measurement (the component in the orbital plane) has a nominal accuracy of 4 mV/meter. There is a contact potential error correction applied to the DC data. The data entered in this data set are the best contact potential correction available at the time of the data submission, and conforms to the 4mV/m accuracy. The AC measurements have an accuracy of 2 percent of the value measured. Channel 1 of spectrometer A sometimes records anomalous high values without corresponding increases in channel 2, ignore this values. Also a limited number of AC data segments have had their gain misinterpreted during processing and the data values are off by three orders of magnitude, those identified for which the problem occurred for all three spectrometers during the whole segment have been removed, however those not identified or those for which a large portion of the data is good remain in the data set, caution should be observed. Spacecraft EMI was generally less than 15 micro- volts/meter. DATA_PROCESSING_OVERVIEW: A. DATA_PROCESSING_CYCLE: VEFI data were extracted from the DE-2 telemetry data and converted to geophysical units on the DE Science Data Processing System (DESDPS) Sigma-9 computer. Contact potentials, v x B electric field and co-rotation electric fields were subtracted from the DC electric field data. Two VEFI Mission Analysis Files ( MAFs ) were created routinely, the AC MAF containing the spectrometer data and the DCA MAF containing 8-point averages of the DC data. DC high resolution and intermediate MAF data files were created only for specific cases because the large amount of disk space and CPU time required to create them were not available on the DESDPS Sigma-9 computer. A more complete DC high resolution data set was created when the DE-2 telemetry data base became available on optical disk on the DE MicroVAX system. VEFI DC high resolution files were created for all the DE-2 TM data available on optical disk. Contact potentials, v x B electric filed, and co-rotation electric fields were substracted from the DC high resolution electric field data. A daily format (each file containing all data available for a given day) was chosen for compatibility with the DE-2 Magnetometer data. B. HISTORY: The data sets submitted to NSSDC are a subset of the current MAF data sets, and they have been reformatted to a more simplified format. Five types of files are included which contain the following data: 1. The average readings of most AC MAFs. Some AC MAFs have been excluded from this data set due to some data quality problems. If data is needed for a specific time not included in this data set, please contact the principal investigator. Also peak readings can be requested from the principal investigator. 2. The high resolution DC electric field in spacecraft coordinates. This data set was not part of the original archival plan. VEFI files were created on the DESDPS Sigma-9 at the time of the original archival plan and that computer did not have the resources to generate the whole high resolution data base (see DATA_PROCESSING_CYCLE). 3. The averaged DC electric field in spacecraft coordinates and the integrated potential portions of all DCA MAFs for which contact potential adjustment is possible. 4. The averaged DC electric field in spacecraft coordinates and the integrated potential portions of all DCA MAFs for which the contact potential adjustment was not performed. This data set is identical in format to the one just described but its accuracy could be lower than stated under DATA_SET_QUALITY. This data set was not part of the original archival set because of accuracy concerns but a decission was made later to include it for completeness. Although the files in this data set are in the same format and have the same contents as the DC files for which the contact potential has been adjusted, we placed this data set separate from the DCA data set in a subdirectory originally intended as a spare. 5. The 16 second averages of about half of all the available AC MAFs. This data set, also referred to as the ionospheric irregularities data base, consists of only one large file and it is the result of a study on statistical presentations of the VEFI AC data. The data included in this data set was all the VEFI AC data for which microfiche was available at the time the study was conducted; microfiche browsing was necessary to assure that all the data included in this study was good data. DATA_SET_NAME: VEFI DCHR files: Vector Electric Field Instrument DC high resolution daily files VEFI DCA files: Vector Electric Field Instrument DC average files for which contact potentials were adjusted. VEFI DCAN files: Vector Electric Field Instrument DC average files for which contact potentials were not adjusted. VEFI AC files: Vector Electric Field Instrument AC average files. VEFI AC16SECAVER file: Vector Electric Field Instrument AC 16 SECOND average file. DATA_USAGE: The regions of useful geographic coverage for this experiment are unlimited. This includes polar, auroral, subauroral, and equatorial geophysical domains. The quoted accuracy, 4 millivolts/meter, is appropriate for all regions. We have, with special geometrical trick, reduced the error to 2 millivolts/meter in the near-equatorial regions but that data set is not included in the submission because that study required very special precautions for interpretation. DATA_ORGANIZATION: Five types of files have been submitted: 1. VEFI DCHR daily files: contain the high resolution (16 samples per second) electric field in spacecraft coordinates (two components). 2. VEFI DCA files: contain the averaged (2 samples per second) DC electric field in spacecraft coordinates (2 components), altitude of the satellite, geographic latitude and longitude, magnetic local time, and invariant latitude. In addition, the first record contains the orbit number of the data, and the contact potentials used for the pass. Contact potentials have been adjusted for all files in this data set. 3. VEFI DCAN files: Same as 2 except no contact potential adjustments was performed for the files in this data set. 4. VEFI AC files: contain the spectrometer data for all channels of all 3 spectrometers, antenna to which spectrometer is connected, gain of the spectrometer, altitude of the satellite, geographic longitude and latitude, magnetic local time and invariant latitude. In addition, the first record of the file contains the orbit number. 5. VEFI AC16SECAVER file: contains about half of all VEFI spectrometer data averaged at 16 second intervals for all channels of all three spectrometers, invariant latitude, magnetic local time, geographic latitude, geographic longitude, altitude of the satellite and Kp. This data set consists of only one large file and will be included in the last optical platter. TYPE_OF_FILE_RELATIONSHIP: None. CCSDXSNM0002EMRK0003CCSDXKNM0002SMRK0005 LOG_VOL_COVERAGE: 1981-12-01 TO 1982-03-31 TYPES_OF_DATA_FILES_CONTENTED: AC, DCA, and DCAN files TYPE_OF_FILE_TIME_COVERAGE: A. AC FILES: 1981-12-01T00:00:00 1982-03-31T23:57:00 B. DCA FILES: 1981-12-01T09:26:00 1982-03-31T02:45: C. DCAN FILES: 1981-12-01T00:00:00 1982-03-31T23:57:00 NAMING_CONVENTION: The files in this data set have been named in the following manner: DCAYYDDDHHMMHHMM.DAT (DCA and DCAN files) ACYYDDDHHMMHHMM.DAT (AC files) VHRYYDDD.DAT (high resolution files) The file names start with the data type (DCA and AC) followed by: 1. YY: last two digits of the year of the start date of the data. 2. DDD: day of year of the start date of the data. 3. HH: hours of the start time of the data. 4. MM: minutes of the start time of the data. 5. HH: hours of the stop time of the data. 6. MM: minutes of the stop time of the data. The 16 second averaged file name is AC16SECAVER.DAT. 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