Document title: Documentation for the NDADS DE IDM_ASCII datatype Project: DE NDADS Datatype: IDM_ASCII Super-EID: DOCUMENT There may be other documents also identified by this super-EID. NDADS filename: IDM_FORMAT_DE.SFD TRF entry: B46559.txt in NSSDC's controlled digital document library, Feb. 1998. Document text follows: ---------------------- CCSDYDNM000200NSSD0055SMARK001 TYPE_OF_FILE_NAME: IDM FILES RECORD_TYPE_NAMES: IDM_1 RECORD_TYPES: RECORD_TYPE_NAME: IDM_1 MAXIMUM_RECORD_TYPE_LENGTH: 4100 BYTES FIELD_NAME: DATE FIELD_MNEMONIC: DATE FIELD_DESCRIPTION: Year and day number of the year of the record in the form YYDDD. (e.g. 81264 is day 264 of year 1981.) FIELD_RESOLUTI0N: 1 day FIELD_RANGE: MINIMUM_VALUE: 81215 MAXIMUM_VALUE: 83049 FIELD_IDIOSYNCRACIES: None FIELD_SYNTAX: VI4 FIELD_NAME: TIME FIELD_MNEMONIC: TIME FIELD_DESCRIPTION: The universal time (UT) time of the day in milliseconds (ms) of the start of the 8 second block of data contained in the record. All the fields describing satellite location are calculated for this time. FIELD_RESOLUTI0N: 1 ms FIELD_RANGE: MINIMUM_VALUE: 0 MAXIMUM VALUE: 86399999 FIELD_IDIOSYNCRACIES: None FIELD_SYNTAX: VI4 FIELD_NAME: Geographic latitude FIELD_MNEMONIC: Glat FIELD_DESCRIPTION: The geographic latitude of the spacecraft in degrees. FIELD_RESOLUTI0N: 0.0001 degrees FIELD_RANGE: MINIMUM_VALUE: -90.0 degrees MAXIMUM_VALUE: 90.0 degrees FIELD_IDIOSYNCRACIES: See RECORD_TYPE_ALGORITHMS FIELD_SYNTAX: VR4 FIELD_NAME: Geographic longititude FIELD_MNEMONIC: Glon FIELD_DESCRIPTION: The geographic longititude of the spacecraft in degrees. FIELD_RESOLUTI0N: 0.001 degrees FIELD_RANGE: MINIMUM_VALUE: -180.0 degrees MAXIMUM_VALUE: 180.0 degrees FIELD_IDIOSYNCRACIES: See RECORD_TYPE_ALGORITHMS FIELD_SYNTAX: VR4 FIELD_NAME: Invariant latitude FIELD_MNEMONIC: Ilat FIELD_DESCRIPTION: The invariant latitude of the spacecraft in degrees. FIELD_RESOLUTI0N: 0.0001 degrees FIELD_RANGE: MINIMUM_VALUE: 0.0 degrees MAXIMUM_VALUE: 90.0 degrees FIELD_IDIOSYNCRACIES: See RECORD_TYPE_ALGORITHMS FIELD_SYNTAX: VR4 FIELD_NAME: Magnetic local time FIELD_MNEMONIC: Mlt FIELD_DESCRIPTION: The magnetic local time of the spacecraft in hours. FIELD_RESOLUTI0N: 0.0001 hours FIELD_RANGE: MINIMUM_VALUE: 0.0 hours MAXIMUM_VALUE: 24.0 hours FIELD_IDIOSYNCRACIES: See RECORD_TYPE_ALGORITHMS FIELD_SYNTAX: VR4 FIELD_NAME: Altitude FIELD_MNEMONIC: Alt FIELD_DESCRIPTION: The altitude of the spacecraft in km. FIELD_RESOLUTI0N: 0.01 km FIELD_RANGE: MINIMUM_VALUE: 200. km MAXIMUM_VALUE: 1012. km FIELD_IDIOSYNCRACIES: See RECORD_TYPE_ALGORITHMS FIELD_SYNTAX: VR4 FIELD_NAME: Spacecraft Velocity FIELD_MNEMONIC: Scvel FIELD_DESCRIPTION: The geocentric velocity of the spacecraft in m/s FIELD_RESOLUTI0N: 1.0 m/s FIELD_RANGE: MINIMUM_VALUE: 7000. m/s MAXIMUM_VALUE: 8000. m/s FIELD_IDIOSYNCRACIES: See RECORD_TYPE_ALGORITHMS FIELD_SYNTAX: VR4 FIELD_NAME: Number of TIME-VELOCITY pairs in IDM_1 record FIELD_MNEMONIC: Nrec FIELD_DESCRIPTION: This is an integer giving the number times the Vtime and Vion fields will be repeated in the record. FIELD_RESOLUTI0N: 1 FIELD_RANGE: MINIMUM_VALUE: 4 MAXIMUM_VALUE: 508 FIELD_IDIOSYNCRACIES: None FIELD_SYNTAX: VI4 FIELD_NAME: Time of ion velocity measurement FIELD_MNEMONIC: Vtime FIELD_DESCRIPTION: The universal time (UT) time of the day in milliseconds (ms). of the following ion velocity measurement (Vion). FIELD_RESOLUTI0N: 1 ms FIELD_RANGE: MINIMUM_VALUE: 0 MAXIMUM VALUE: 86399999 FIELD_IDIOSYNCRACIES: None FIELD_SYNTAX: VI4 FIELD_NAME: Ion velocity measurement FIELD_MNEMONIC: Vion FIELD_DESCRIPTION: The component of the ion velocity parallel to the y-axis (approximately vertical, a positive value indicates an upward velocity) or the z-axis (approximately horizontal) of the spacecraft rounded to the nearest 1 meter/second. The first two digits to the right of the decimal point are not data values, but indicators of data quality and the mode of operation of the IDM. In the most common mode of operation, two velocity measurements are made along one axis during a minor telemetry frame (1/4 second). Normally, only the first of these is included in these files. This means that the data points for each axis will be equally spaced in time. If the first point is determined to be bad (fill or "flyer") then the second point will be used. If the first digit after the decimal point is even then the first data point in the minor frame has been used. If odd, the second. In addition, velocity measurements taken during times of low ion density (Ni) are not as reliable. The first digit after the decimal indicates this as follows: 0 or 1 ; Ni > 2.0E4, velocity measurements are good. 2 or 3 ; 2.0E4 > Ni > 7.0E3, averaging several data points is recommended 4 or 5 ; Ni < 7.0E3, data are unreliable. The second digit after the data point indicates the axis of the measurement. If the second digit after the decimal point is even, then the associated velocity measurement is along the horizontal (z) axis. If odd, the measurement is of the vertical (y-axis) velocity. Some modes of operation of the IDM may result in unequal time spacing of the data points or sections of data where only one axis is sampled. Use of the time tags and the axis flag is therefore always recommended. Caution should be exercised when using the data near the beginning or the end of a file. There are often periods of several (up to 10) 8-second blocks where the satellite instrumentation and/or telemetry is in the process of being turned on or off. As a result any large value (>4000 m/s) for the ion velocity measurements at such times is probably incorrect. FIELD_RESOLUTI0N: 1 m/s FIELD_RANGE: MINIMUM_VALUE: -5000. m/s MAXIMUM_VALUE: 5000. m/s FIELD_IDIOSYNCRACIES: See RECORD_TYPE_ALGORITHMS FIELD_SYNTAX: VR4 RECORD_TYPE_FIELD_RELATIONSHIPS: The order of the fields in an IDM_1 record is as follows: DATE, TIME, Glat, Glon, Ilat, Mlt, Alt, Nrec, 1st Vtime, 1st Vion, 2nd Vtime, 2nd Vion, ......, Nrec-th Vtime, Nrec-th Vion. Each record nominally contains 8 seconds of data. RECORD_TYPE_ALGORITHMS: The real fields of an IDM_1 record are initialized with a fill value of 9999999.0 and subsequently the geophysical values are inserted. Thus if there is no data available for a given parameter that particular field will contain the fill data value. MISCELLANEOUS_TYPE_OF_FILE_ATTRIBUTES: IDM files are sequential with a single type of variable length record (IDM_1). CCSDYDNM000200NSSD0055EMARK001