Ulysses HISCALE Pages
2.3 HISCALE Level 1 Files
HISCALE Level 0 processing is done by the procedure called ARCGEN (for Archive
Generator), which uses the EDR, SEDR, and the auxiliary file IDF.DAT (for Instrument
Description file). For those familiar with the JPL SPICE system, the IDF.DAT file plays
the role of the I file in SPICE. ARCGEN and the command procedures that control its
execution during production are designed to process HISCALE EDR for 24 hour periods
synchronized on SCET days. The output file labeling scheme uses the day number in the file
names. ARCGEN writes two different file types populated with .RAT records (standing for
count rates) and .PHA (standing for pulse height analysis). The .PHA files have two record
types, one with the digitized pulse heights and the other type with the MFSA outputs. MFSA
stands for M and F spectrum accumulator, and these records report the readouts of HISCALE
on-board accumulations of digitized pulse heights from the M, M', F, and F' detectors into
32 energy channels for each angular sector. The MFSA repeat cycle is 1024 seconds long.
There are several important programming strategies that were employed to simplify the
HISCALE data at the ARCGEN step:
- Each ARCGEN output record has an identically defined header block, regardless of record
type or length. The record types are self-labeling within this universally defined record
- The .RAT records are defined so that they can have the same structure for all time
resolutions from the highest to lowest. Because the original file media for HISCALE
outputs were to be 1/2" large reel 6250 bpi magnetic tapes, the .RAT records were
defined to include the sectors rates for 10 spin groups. A spin group is two spins when
Ulysses operates at the highest bit rate (1024 bps) and is 4, 8, or 16 spins as the
telemetry rate is divided by successive factors of two. The principal reason that 10 spin
groups were lumped together was to yield large records to minimize the tape overhead of
inter record gaps and data overhead in the headers.
- The .PHA and .MFSA records also have count rates included. These rates are
time-synchronous with the PHA and MFSA cycles so that the pulse height analysis results
can be reliably converted to absolute fluxes.
- Because detector pitch angles with respect to the magnetic field are central to analysis
and interpretation of charged particle observations, space is reserved in the HISCALE
record headers for this information. Because of operational constraints on the
availability of the magnetic field vectors (kindly furnished by the HED team), ARCGEN
usually writes its output records with the pitch angle information vacant because of the
unavailability of the magnetic data. Later, when magnetic field files are available, the
procedure MAGMERGE computes this information and places it in the correct spin group of
the archive records.
- When .RAT data are averaged (by LANAVG) to longer intervals the averaged rates are all
placed in the space reserved for spin group #1 and placed in files with extension .AVG.
These .AVG records are created as an expedient intermediate step and are not intended for
final archiving. A median filtering procedure is also available for the creation of
averages of HISCALE data, provided that the averaging interval is long enough to include
at least 10 repetitions of each data item. This median filtering procedure, called QCA
(for Quality Controlled Averaging) writes records to a file labeled with extension .QCA.
Because of the serious effects that telemetry noise can have on long HISCALE averages, it
is strongly recommended that only QCA-based long averages be used for intervals of hourly
or longer time resolution. The .AVG or .QCA records can be condensed by a 10:1 factor, if
necessary, by a procedure called COMPRESS which places average rates in all 10 spin group
slots of the record.
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Updated 5/12/09, T. Hunt-Ward