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ASCA distributions have a standard directory structure. This structure is
present on ASCA CD-ROM distributions and in the HEASARC ASCA archive.
The UK ASCA Archive uses the same basic structure, but with some modifications.
Therefore, those accustomed to the layout of the ASCA CD-ROMs are still advised to familiarise themselves the contents of this page.
Below we describe all of the files included in a single ASCA observation, organized
by data product type:
- UNScreened data files
- SCReened data files
- AUXiliary products
- HTML files
The HEASARC archive for each sequence contains the following additional
directories; 'telem', 'spectra', and 'lcurves', not present in the UK ASCA
Archive. The 'telem' directory contains the raw information as transmitted
on ground. The same information in a suitable format for the ASCA processing
software is included in the 'unscreened' directory. The 'spectra' and 'lcurves'
directories contain derived files for each detected source. These products
can be recreated as they are at HEASARC using the files in the 'screened'
The UNScreened data product contains the unfiltered event files.
- Example: ad10012000g200170h.unf
- Description: These files contain all of the useful data from
the telemetry files in a format readable by ascascreen, the FTOOLS,
These files contain all of the bad data which must be removed before
they will yield scientific results. If you wish to fine-tune the
selection criteria for reducing the data
(common for in-depth analysis),
you should start with these files.
For FTOOLS 3.6 or earlier you will need to run
ascascreen -e unf
to do this.
Separate files contain data taken with different instruments,
or when the spacecraft was in different states.
The event file list
gives a descriptive
list of each of these files.
The SCReened data product contains the filtered event files.
- Example: ad10012000g200170h.evt
These files are the result of passing the
unfiltered event files
through xselect with a standard set of choices for
throwing away bad data. The selection criteria used are described
processing documentation at HEASARC, and the specific criteria for each file
are given in the processing log.
The filtered event files are useful for your initial analysis of the
data or if you wish to apply stricter selection criteria than those
used to create these files.
All of the data products in an ASCA distribution
are derived from the screened event files.
- Name: ad[base].totexpo
- Example: ad51011020gis25670.totexpo
- Description: An exposure map summed over all the
filtered event files
and over both instruments of a given type
(i.e. both GIS2 and GIS3 or both SIS0 and SIS1).
The exposure maps give exposure times in seconds and do not account for
- Name: ad[base]_[all/lo/hi].totsky
- Example: ad51011020sis32002_hi.totsky
- Description: Counts image summed in the same way
as the exposure maps.
These files are divided into three energy ranges:
- `lo' means <2keV
- `hi' means >2keV
- `all' means all energies.
- Name: ad[base].gif
- Example: ad51011020gis25670.gif
- Description: Images produced from the `all' energy
summed sky images and the
using ximage. These images have been only minimally smoothed.
This data product contains miscellaneous files produced in processing.
The most useful of these are the filter files.
- Name: ft[date-base].mkf
- Example: ft930415_2053_0240.mkf
- Description: A time history of the condition of the
spacecraft and instruments. xselect uses this file to
filter out bad data from the science files. Filter files are essential
for data reduction.
There is one filter file for each
telemetry file. These are
sometimes referred to as "MKF" or "makefilter" files.
- Name: fa[date-base]
- Example: fa930415_2053.0240
- Description: Files specifying the pointing of the spacecraft
as a function of time. You will need these files if you want to run
the ascalin FTOOL to recalibrate your data.
There is one attitude file for each
- Name: ft[date-base].ghf
- Example: ft930415_2053_0240.ghf
- Description: A time history of the GIS gain derived from
measurements of the detector temperatures.
You will need these files if you want to run
the ascalin FTOOL to recalibrate your data.
There is one gain history file for each
- Name: frf.orbit.[version]
- Example: frf.orbit.160
- Description File containing the orbital elements for the
spacecraft at the time of the observation. Orbit files include
information all the way back to the start of the mission, so newer
orbit files will work for older observations.
- Name: ad[base].cal
- Example: ad51011020g200170.cal
- Description A PI spectrum extracted from the calibration source
in each GIS instrument. A single calibration spectrum is extracted
for each combination of energy and spatial binning in the sequence.
Usually there is only one spectrum per instrument. These spectra can
give a rough check on the GIS gain calibration (the spectrum should
peak near 5.9 keV), but note that the gain where the calibration
source is located is not as well calibrated as the gain at the
center of the detector.
A number of HTML files are generated by the processing, and contain information on everything done to produce the distributed files. The log of errors encountered is especially useful.
- Name: ad[sequence]_[ver]_hdr_page.html
- Example: ad10012000_001_hdr_page.html
- Description: A basic description of the observation
and processing. This is the "home page" for the
HTML pages generated in processing.
- Name: ad[sequence]_[ver]_file_info.html
- Example: ad51011020_056_file_info.html
- Description: A descriptive list of all the files in the
- Name: ad[sequence]_[ver]_event_info.html
- Example: ad51011020_056_event_info.html
- Description: A descriptive list of all
filtered and unfiltered
event files. This will answer the question, "How is this event file
different from that one?".
- Name: ad[sequence]_[ver]_index.html
- Example: ad51011020_056_index.html
- Description: An index to make accessing the
- Name: ad[sequence]_[ver]_errors.html
- Example: ad51011020_056_errors.html
- Description: A list of all errors encountered in processing.
These are usually checked by the processing team and do not indicate
serious problems with the data.
- Name: ad[sequence]_[ver]_joblog.html
- Example: ad51011020_056_joblog.html
- Description: A detailed log of everything done to produce
the distributed files. This can be useful for tracking down problems
which may have occurred in processing. This log is very verbose, so
the processing log index and the
processing error index can be helpful
for navigating this file.
- Name: ad[sequence]_[ver]_source_info.html
- Description: Lists the sources detected in the processing for
this observation. The quoted counts are the raw counts extracted from
a circle not corrected for vignetting or background.
Go back to ASCA Distribution Files