Document title: Readme.doc for NDADS DE-2 RPA_DUCT_ASCII datatype
Project: DE
NDADS Datatype: RPA_DUCT_ASCII     
Super-EID: DOCUMENT                      
There may be other documents also identified by this super-EID.
NDADS filename: DUCT_READ_ME_DE.DOC
TRF entry B46564.txt in NSSDC's controlled digital document library. Feb. 1998.
Document text follows:
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                        DE-2 DUCT data on NDADS
                   __________________________________

The Dynamics Explorer 2 DUCT ASCII files contain measurements of the total
ion concentration 64 times per second and the most important DE-2 orbit
parameters.  NSSDC-developed software was used to read the DUCT binary data
and create ASCII files.  For more on DE-2, DUCT, and the binary data, see
DUCT_VOLDESC_DE.SFD and DUCT_FORMAT_DE.SFD.

The DUCT files are requested with the DATA_TYPE = DUCT_ASCII and the
ENTRY_ID = yyddd and are then staged as yydddhhmm_DUCT_RPA_DE_250MS_V01.ASC;
yy is the year, ddd is the day of the year, hh is the hour, and mm is
the minute of the starting time of the data in the file.  The date range
for the DUCT files is 81215-83048 (3 Aug 81 - 17 Feb 83) with most days 
represented.  

----------------------------------------------------------------------
       Format of yydddhhmm_DUCT_RPA_DE_250MS_V01.ASC Files
----------------------------------------------------------------------

Each data record contains the following data.  If there is no data for the
first eight parameters, the field is filled with 9999999.0.  The wide band
filter fields are filled with 0.0 when no data is available.  Negative or
zero values in the ion density fields indicate that no data is available.

date                                  (yyddd)
UT                                    (ms)
number of ion density measurements [n]
geographic latitude                   (deg)
geographic longitude                  (deg)
invariant latitude                    (deg)
magnetic local time                   (hr)
altitude                              (km)

spectral power in freq. band #1       (1/Hz)		Uniformely
...
spectral power in freq. band #6       (1/Hz)		distributed
spectral power in freq. band #1       (1/Hz)
...							in time
spectral power in freq. band #6       (1/Hz)
spectral power in freq. band #1       (1/Hz)		over each
...
spectral power in freq. band #6       (1/Hz)		8 second
spectral power in freq. band #1       (1/Hz)
...							telemetry
spectral power in freq. band #6       (1/Hz)		frame

ion density #1                        (cm-3)	Uniformely distributed over
...						each 8 second telemetry frame.
ion density #n                        (cm-3)	(n is typically 512)
                     
Each data record spans several lines in the ASCII files.  The first line 
of each record contains the following data: date, UT, number of ion density
measurements, geographic latitude, geographic longitude, invariant latitude,
magnetic local time, and altitude.  The next four lines contain the 24 wide
band filter measurements, with 6 values on each line.  The remaining lines
contain the ion density measurements, with 6 values on each line.

A period of negative values in the ion density field often occurs for several
records at the beginning or ending of a file as the spacecraft is turned on or
off.  These negative values are not valid data.  Please see DUCT_FORMAT_DE.SFD
for a complete description of all the data fields.