Cookbook for NFI Scientific Data Analysis
Currently, any Guest Observer receives a tape (Final Observing Tape,
containing reformatted telemetry data of his/her observation. BeppoSAX
team provides all the needed software to reduce such data and
produce final scientific products (images and pseudo-images, light curves,
spectra etc.) for each BeppoSAX instrument.
As described elsewhere, BeppoSAX scientific
data can be reduced using two different software packages, which reflect also
into two different phylosophies:
LECS and MECS allow position (X,Y), time (T) and energy (E) of
each photon to be recorded. PDS and HPGSPC provide information
on time and energy for each
detected photon, if used, as most of the time, in direct modes,
since they do not have imaging capabilities.
So we may say that the result of an observation
is a vector in a four (two) dimentional space
(actually this space can have even
higher dimension, since each photon is characterized by further
(risetime or burstlenght information, veto information etc etc.)
which are do not strictly concern scientific analysis).
- SAXDAS produces linearized and screened event
list and housekeeping files from the FOT in
standard FITS/OGIP format.
Final scientific products have then to be "extracted" using, for istance,
In the near future it will also be possible
copy the event and housekeeping files through the network
from the SDC WWW site. It will be therefore possible to avoid the burden
of performing the reduction procedure "at home"
- XAS accumulates
final scientific products directly from the FOT
files (eventually stored on a disk area); all corrections and selections are performed during the accumulation loop.
in XAS we accumulate direclty spectra or time series, nevertheless,
the original data are still a four dimentional vector.
After (or simultaneously, as in the case of XAS) data reduction, the
observer always performs the following three operations:
Whatever software the observer uses to reduce the data
she/he produceds a final (projected) product of same sort,
which has to be analyzed and interpreted.
projection of the original four (two) dimensional vector into a one
dimesional array or a two dimentional image;
binning or grouping, or summing of the data to achieve gaussian
statistics in each newbin or/and to improve the signal to noise ratio;
scientific analysis (spectral fit, correlation and/or Fourier
tecniques, foldings, source
detection etc.) of the projected and binned final product.
The analysis of the scientific products can be in principle fully performed with
FTOOLS and XANADU package.
Please send questions/problem reports to: firstname.lastname@example.org