To help you in analysing and processing further the LWS data we recommend
that you make use of the two packages especially developed for this
purpose: ISAP and LIA.
The user is also refered to the LWS data reduction recipes.
The recipes are available from:
https://www.cosmos.esa.int/web/iso 
ISO Explanatory Library LWS
The recipes are structured as worked examples for the following AOT types:
This is a software package that was specifically written for LWS and SWS data. The package was written jointly by the LWS Instrument Team, the SWS Instrument Team and IPAC. It can read in the product files and write as ouput FITS files, ASCII files or IDL save files. This package requires an IDL licence and the IDL path should also include the IDL astronomy library which is available at:
http://idlastro.gsfc.nasa.gov/
The routines in ISAP have been tailored to reduce LWS data. ISAP allows the user to flag or delete data points that are clearly wrong (due to undetected glitches for instance) and to perform most of the basic operations for spectral analysis like averaging scans with different averaging routines, scaling the detectors to make smooth spectra, rebinning spectra to a standard wavelength scale, adding a constant, averaging spectra, subtracting a background spectrum from a spectrum, measuring line intensities and fitting line profiles, as well as some LWS specific operations like defringing the data.
A full set of documentation, including cookbooks for reducing each observation type is available with ISAP.
ISAP can be downloaded from the ISO website in IPAC:
http://www.ipac.caltech.edu/iso/ ISAP
or
https://www.cosmos.esa.int/web/iso ISO Data Analysis Software ISAP
This package is written as a set of IDL routines, to be used together with ISAP. The routines are written to allow users to inspect, reprocess and recalibrate their LWS data with the possibility of interactively customizing the various data reduction stages to their particular set of data. It also allows some extra functionalities, like the interactive FP responsivity correction. LIA is a joint developement of the ISO-LWS Instrument Team at Rutherford Appleton Laboratories (RAL, UK - the PI Institute) and the Infrared Processing and Analysis Center (IPAC/Caltech, USA).
As of June 2003 the current version of LIA is version 10.1. LIA can be downloaded from the UKIDC web site:
http://www.ralspace.stfc.ac.uk/RALSpace/
or
http://www.cosmos.esa.int/web/iso ISO Data Analysis Software LIA
A full set of documentation is available at this web site.
If you need further help with LIA, you can contact the UK ISO
National Data Centre ( isouk@rl.ac.uk).
The following lists the routines included in LIA together with a short description.
INSPECT_SPD: Displays SPD results before and after
the application of the standard deglitching algorithm. A
two panel plot with a Graphical User Interface (GUI)
appears on the screen. The user
can display the data in LWS instrument time key (ITK)
units, or in seconds from the start of the observation.
The display can be zoomed to look in more detail at the
effects of the glitches. Various glitch statistics are reported.
INSPECT_IPD:
Displays illuminator flash sequence data for closed
flashes. The dark currents as measured at the start of each
closed flash are also displayed. The user can get an
impression here whether the calculated dark currents are
in line with the latest best estimates from the PV
phase/Handover flashes. Dark currents in flux units are also
listed.
INSPECT_DRIFT:
Displays the SPD results before and after the detector
responsivity drift correction is applied. Only suitable for
displaying grating LWS01 data.
INSPECT_ABS: Displays the absolute responsivity
correction factors (the ratio of closed illuminator flash
data referenced to the illuminator flash data at the time
of flux calibration observation).
INSPECT_RSRF:
Displays the SPD data (LSPD file), the Relative Spectral
Response Function (RSRFs in the LCGR file) and the AAR
data (LSAN - the LWS Auto-Analysis results file) in
wavelength units. A two panel plot with a GUI appears on the
screen. The upper panel shows the LSPD and the RSRF
(normalised to the LSPD data at the grating rest position).
Only suitable for grating AOTs, i.e. LWS01 and LWS02.
This routine is expected to be useful for verifying the
existence, or otherwise, of some of the more interesting
features present in the LSAN file. INSPECT_RASTER:
Displays the pointing directions for raster
observations, as well as for single pointings.
IA_DARK:
Dark Current (DC) subtraction. The estimate and subtraction of
the DC is a critical point particularly for faint sources and for
FP observations in general; in these cases signal received is
at the detector noise level and hence an incorrect DC
subtraction may lead to negative photocurrents; as these are
later divided by the instrumental transmission profiles
(RSRF) the resulting calibrated spectrum will
be potentially difficult to interpret.
IA_DRIFT:
Responsivity Drift (RD) correction. It is well known that the
LWS detectors present a temporal drift in responsivity . Its
removal is based on the evaluation of the time series of
averages of spectral scans; the obvious requirement is that
the scan range and the source's intrinsic signal does not vary.
The sole case in which this requirement is met is with single
pointing L01 AOTs (fortunately the majority of LWS observations).
IA_ABSCORR:
Absolute Responsivity Correction (ARC) factors. ARCs are the
values used to scale the detector responsivities to the
values measured when the LWS primary calibrator (Uranus) was
observed, and on which the instrumental transmission profiles
of the instrument have been derived.
FP_PROC (for FP data only):
An interactive tool which produces calibrated
LSAN files for FP observations. It can handle both L03
and L04 AOTs and allows important functions such as i)
realignment of scans in an L03 AOT; ii) correction for
incorrect grating positioning in an L04 AOT; or iii)
reprocessing using either a default or a user supplied set of
dark currents (for this reason FP_PROC also belongs
to the third routine class - see below). GUI_FPMF An interactive tool to perform FP multi-Gaussian
fitting of a single blended line.
DEFRINGE(L01, L03 and L04): This tool is written for
interactive defringing
of LWS data. It requires an LSAN file containing data
which has been averaged across each separate detector
(for L01 AOT) or mini-scan (for L03 AOT), or line
(for L04 AOT). This is because the fringes change with
wavelength and therefore
the routine removes the fringing by detector (L01), mini-scan
(L03) or line (L04).
If the data is not averaged in this manner, the GUI
will not work.
SHORT_AAL (for Grating data only):
utilitity to recalibrate an L01 or
L02 observation. It essentially performs wavelength and flux
calibration using interactively reprocessed data (see above)
as input. It can also perform a general reprocessing
(without using the interactve routines) using default
settings which are different from those used by the OLP.
There are a number of keywords which need to be used when
calling SHORT_AAL, depending on which of the interactive
routines have previously been used. FP_PROC
(for FP data only, same routine as in second class):
utilitity to recalibrate an L03 or L04 observation. It
essentially performs wavelength and flux calibration using
interactively reprocessed data (see above) as input. It
can also perform a general reprocessing (without using the
interactive routines) using default settings which are
different from those used by the OLP. It also allows
interactive manipulation of the data (for this reason
FP_PROC also belongs to the second routine class,
see above).
A number of keywords should be used when calling
FP_PROC, depending on which of the interactive
routines have previously been used.
In LIA Version 10 FP_PROC was extensively modified
to include
non-prime data, extend the grating profiles, improve the
throughput coefficients and remove side-order contamination.
CORRECT_SPECTRUM - corrects an averaged, de-fringed
off-axis point
source spectrum to the flux and spectral shape that would be seen had the
source been observed on-axis.EXTENDED_FLUX - re-calibrates an averaged, de-fringed spectrum of an
extended source to flux per steradian or MJy/sr. The routine corrects the
flux and spectral shape and corrects for the effective beam of the
instrument. However, the re-calibration assumes a smooth extended source,
which rarely applies in practice.
SS_CORR - corrects for strong-source effects, which occur in
detectors LW1 to LW4 (see Section 5.7). The routine produces a
corrected LSPD file, that the user has to process through SHORT_AAL to
create the corrected LSAN file for further analysis.
Two different sets of correction
coefficients are available, based on models of Mars and Saturn respectively.
The resulting spectra need to be checked to see which coefficients give the
better result.
Further work is currently being undertaken to determine a uniform approach
for applying this correction, to eliminate the need to select coefficients
or perform subsequent processing. In the meantime, users who require
assistance with applying this correction to their data should contact
experts at the UK ISO Data Centre (see Section 6.10).
GR_TRANSIENT - applies a transient correction for grating
data only.
The GUI-based routine, to be included in a future version of LIA, will perform the
transient
correction on L01 grating data, starting at SPD level.
The responsivity drift correction and deglitching are carried out prior to
the transient correction being applied.
The routine applies the transient correction using the Fouks-Schubert
method as described in Section 6.9.
The routine looks for the three tunable parameters 
,
and E that minimize the quadratic differences between forward
and backward scans. The output is one forward and one backward scan, that the
user can compare to one another to see how well the correction performed.
The starting values for and are given in
Table 6.2. For E the starting value is 1.0.
NIR_LEAK - work has been completed on correcting
the LWS data known to be affected by the the near-infrared
light leak, with corrected data imported to the ISO Data Archive. A LIA
routine may however be released for performing this correction in a
future version.