PDS_VERSION_ID = PDS3
RECORD_TYPE = STREAM
OBJECT = TEXT
PUBLICATION_DATE = 1999-08-16
NOTE = "This file describes the structure of the
PWS waveform data files."
END_OBJECT = TEXT
END
Each PWS waveform data file (binary) in this data set consists of fixed
length records. Each data file has an attached ASCII header file that
describes the contents of the data file in a PDS label like
(keyword=value) format. Unfortunately these attached labels do not comply
with the PDS standards and the information they contain is unreliable
sometimes. The ASCII header includes carriage returns and line feeds to
facilitate display on multiple platforms. These line terminator
characters are not record delimiters! The header is padded with space
characters so that the header will align with the binary data record
length. There are no record delimiters. In some configurations, the
header may be a single record and in others it may span multiple (J) records.
The PDS label file uses the nomenclature:
^TEXT = ("60563600.DAT", 1)
^TABLE = ("60563600.DAT", 4)
^TIME_SERIES = ("60563600.DAT", 5)
to indicate that the ASCII header (text) begins in record 1 of the file
60563600.DAT, the EDR header (a table) begins in record 4, and the data
(a time series) series data begin in record 5.
The length of the records is dependent on the instrument mode
and the spacecraft telemetry format that was used during data acquisition.
There are four (4) instrument modes:
0 = SURVEY, 1 = 10 kHz, 2 = 80 kHz, and 3 = 1 kHz
and four (4) telemetry formats:
LPW, MPW, MPP, and HPW
used to acquire PWS waveform data.
APID Inst Mode Tel-fmt Rec-Length Blocks/Rec Samples/Block
(bytes)
----------------------------------------------------------------------
PWH1 1,2,3 LPW 465 1 870
PWH2 1,2,3 MPW 670 10 128
PWH3 1,2 MPP 1630 10 320
PWH3 3 MPP 1080 10 210
PWH4 1,2 HPW 7910 10 1576
PWH4 3 HPW 1080 10 210
PWH5 1,2,3 LPW 4350 10 864
Immediately following the ASCII header is a binary "EDR" header record.
The EDR header is described by the PDS format file EDRHDR.FMT and in a
more human-readable format in EDRHDR.TXT. Once again, this header record
is padded to the data record length, however, the EDRHDR never spans more
than a single record. The EDRHDR contains information about the data
including the instrument mode and telemetry format id. Other useful
information such as the number of file records, the file start/stop time
and spacecraft clock values are also stored in the EDR header.
Following the EDR header are some number (K <= 91) data records. Each
data record consists of a 30 byte header and either one (1) or ten (10)
blocks of data. Each data block is a time series of 4-bit waveform
samples where the time between samples is determined by the instrument
mode (frequency). Each data row contains data acquired within a single
spacecraft minor frame (2/3 second). If multiple data blocks exist within
the minor frame, they occur on the real-time interrupt (RTI) boundaries,
of which there are ten (10) per minor frame. The start time of each time
series is the RTI time associated with the data block. Not all data
blocks contain data. This is especially true in the APID = PWH5
data files. The number of waveform samples in a data block is listed in
the table above. Although there are flag values in the various headers
that indicate whether or ot data is present in each data block, these
values are also unreliable. If a data block contains non-zero values,
they can be assumed to be valid. The "Row Prefix" header contains the
time of the minor frame, and
Row
+-------------------------------------------------------------+
1,J | PDS Label like header (ignore) |
+ +
| |
+ +
| |
+-------------------------------------------------------------+
J+1 | EDR Header - value of J+K located in byte 51 of this header|
+-------------------------------------------------------------+
J+2 |Row Prefix | I1 | I2 | I3 | I4 | I5 | I6 | I7 | I8 | I9 | I10|
+-------------------------------------------------------------+
J+3 | . | . | . | . | . | . | . | . | . | . | . |
+-------------------------------------------------------------+
. | . | . | . | . | . | . | . | . | . | . | . |
+-------------------------------------------------------------+
. | . | . | . | . | . | . | . | . | . | . | . |
+-------------------------------------------------------------+
. | . | . | . | . | . | . | . | . | . | . | . |
+-------------------------------------------------------------+
. | . | . | . | . | . | . | . | . | . | . | . |
+-------------------------------------------------------------+
J+K |Row Prefix |RTI0|RTI1|RTI2|RTI3|RTI4|RTI5|RTI6|RTI7|RTI8|RTI9|
+-------------------------------------------------------------+
/\ / \ / \
/ \ / \ / \
/ \ / \ / \
/ \ / \ / \
Contains / \ / \
Row Start / \ / \
time / \ +-------------+
/ \ Time start time of data within
/ \ an item is the time of the RTI
/ \ within the minor frame. RTI's
/ \ are numbered 0-9 (modulo 10
+--------------------------+ counter) An RTI is
|1|2|3|... |N| approximately 1/15 second.
+--------------------------+
I = "item" or block number 1<=I<=10
J = # of header "records" 1<=J<=6
K = # of data records plus 1 (edr header) 2<=K<=92
N = # of waveform samples per data block 128<=N<=1576
3150 samples per second for 1kHz data,
25200 samples per second for 10kHz data,
201600 samples per second for 80kHz data.
The PDS labels which describe the data use the phrase "ITEMS = 10. In
this picture, Ix (item x) and RTIx (real-time interrupt x-1) are used
interchangeably.