Document title: Readme.doc for NDADS DE RPA_ASCII datatype
Project: DE
NDADS Datatype: RPA_ASCII         
Super-EID: DOCUMENT                      
There may be other documents also identified by this super-EID.
NDADS filename: RPA_READ_ME_DE.DOC
TRF entry B46561.txt in NSSDC's controlled digital document library. Feb. 1998.
Document text follows:
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                 DE-2 Retarding Potential Analyzer data on NDADS
                 _______________________________________________

The Dynamics Explorer 2 Retarding Potential Analyzer (RPA) files contain
the ion temperature, the ion drift velocity along the sensor look direction,
and the ion composition and orbit parameters in ASCII format. The time 
resolution is typically 2 seconds. Data are given as daily files (typically 
a few 100 Kbytes each). NSSDC-developed software was used to read the RPA 
binary data and create ASCII files.  For more on DE-2, RPA, and the binary 
data, see RPA_VOLDESC_DE.SFD and RPA_FORMAT_DE.SFD.

The RPA files are requested with the DATA_TYPE = RPA_ASCII and the ENTRY_ID =
yyddd and are then staged as yydddhhmm_RPA_DE_2S_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 IDM files is 81218-83049
with most days represented.  

------------------------------------------------------------------------------
                   Format of yydddhhmm_RPA_DE_2S_V01.ASC Files
------------------------------------------------------------------------------

Each data record contains the following data (if there is no data for a given
parameter, a fill value of 9999999.0 is given):

date                                  (yyddd)
UT                                    (ms)
data quality (see below)
X component of ion velocity           (m/s)
Y component of ion velocity           (m/s)
Z component of ion velocity           (m/s)
ion temperature                       (K)
ion density                           (ions/cc)
spacecraft potential                  (volts)
O+ concentration                      (ions/cc)
H+ concentration                      (ions/cc)
He+ concentration                     (ions/cc)
molecular ions                        (ions/cc)
high mass                             (ions/cc)
sigma (RMS error of RPA analysis)     (%)
sweep type (see below)
geographic latitude                   (deg)
geographic longitude                  (deg)
invariant latitude                    (deg)
magnetic local time                   (hr)
altitude                              (km)

data quality - The data quality field contains a flag that describes the quality
of the RPA data.  A value greater than or equal to 0 indicates that the data has
passed the set of basic quality checks.  A negative value indicates that the RPA
data fails at least one check and is untrustworthy.  Following are the sequence
of checks. Tests are sequentially performed until a flag is assigned.

   Ni<8000 or Ni>6.E6                                    flag=-70
   Psi<-2 or Psi>0.5                                     flag=-60

   for INVARIANT LATITUDE<50
      Ti<500 or Ti>10000                                 flag=-50
      |Vx|>700 m/s                                       flag=-20
      Mols>O+                                            flag=-40
      H+>O+                                              flag=-30
      Vx=0                                               flag= 40
      Vx non zero
         Sum of light ions > 25% O+                      flag= 50
         Sum of light ions < 25% O+                      flag= 20
   set flag to 0 if one of the needed concentrations is unavailable.
   increase magnitude of flag by 5 if rms fit error > 10%

   for INVARIANT LATITUDE>50
      Ti<500 or Ti>200000                                flag=-50
        Ti>7000
          |Vx|<1000 and |Vz|<1000                        flag=-20
          Alt>600
            Mols>O+                                      flag=-40
            O+>Mols                                      flag= 30
          Alt<=600
            Mols>O+
              Vx>0                                       flag=-10
              Vx<=0                                      flag= 0
            O+>Mols                                      flag= 30
        Ti<=7000
          |Vx|>2000                                      flag=-20
          Mols>O+                                        flag=-40
          O+>Mols                                        flag= 60
   set flag to 0 if one of the needed concentrations is unavailable.
   increase magnitude of flag by 5 if rms fit error > 12%

sweep type -  The sweep type field contains a number (1 - 4) that represents the
type of RPA sweep used.  The sweep types are:
  
 1. Integral RPA curve obtained with voltage sweep from 0 to beyond 10 volts.
 2. Electronic derivative of RPA curve obtained with voltage sweep from 0 to
    beyond 10 volts.
 3. Integral RPA curve obtained with voltage sweep from 0 up to 8 volts.
 4. Electronic derivative of RPA curve obtained with voltage sweep from 0 to
    8 volts.