IDA Contents

The ISO Data Archive offers access to all ISO data with the following list of features:

Default Dataset

For every ISO observation, a default dataset has been declared among the different products available (Pipeline or HPDP). This is the “best dataset” recommended that can be directly retrieved from this Archive Interface.

Pipeline Products

Every observation is run through an automatic data-analysis pipeline called Off-Line Processing, or OLP, to produce three sets of data products, namely:

The ISO Handbook describes the various types of analysis that are performed.

Detailed technical descriptions of the contents and formats of data product files are given in the corresponding sections of the ISO Handbook.

The type and sophistication of analysis performed for each product set is instrument dependent. Products are classified further in the Archive according to the following scheme:

Raw Data Products
These are essentially unpacked telemetry in which no data reduction has taken place and thus form the starting point for data analysis performed by OLP or the user's own system. PHT ERD is an example.
Basic Science Data Products
These data have been processed further to an intermediate level (with the use of calibration files where necessary), often containing physical units. They are ready for assembly into structures of astronomical significance. This assembly can be done by OLP or, independently, by observers themselves. For example, the final result of the LWS pipeline is the LSAN file that contains a tabulation of flux in physical units measured during the observation. Scientific conclusions can be drawn when this assembly is complete.
Fully Auto-processed Science Data Products
These data include a set of coherent, instrument-independent measurements of images or spectra designed to get as close as possible by automatic means, to what could be produced by an astronomer using an interactive analysis system. Where possible, products follow FITS standard conventions to ease further analysis by standard high-level tools such as IDL or MIDAS. They allow the user to carry out initial survey programmes, or to assess the relevance of a given observation to their scientific work. However, the limitations must be emphasised of such an automatic procedure, which takes no account of the individual circumstances of an observation and involves no scientific judgement. Significantly better results are likely to be possible using an interactive system. Nevertheless, the CAM pipeline for example produces individual FITS image in the CMAP file, which are combined, where appropriate, into mosaics in the CMOS file. It then gives a tabulation of sources detected in the images in the CPSL file and gives individual source spectra, as appropriate, in the CSSP file.
For the spectrometers, LWS and SWS, the AAR products contain basic science data. For CAM and PHT, these are the SPD products. An overview of the files per product level for each instrument can be found in the list of files per product level. Each observation has a Data Quality Report including the quality information available.

The pipeline products undergo a scientific validation to establish confidence in the processing and calibration of the products. An overview of the calibration status and the accuracies of the pipeline products are given in the ISO Handbook. The scientific validation per AOT summarizes the current overall status.

Browse Products from the Pipeline Products
An independent software generates a number of data sets for users from the standard pipeline products:

Survey Products
These are fully reduced standard data sets, either FITS images, or ASCII FITS tables, for survey-type work. It must be emphasised that, although these products contain fully reduced data, the processing is done in a standard and automatic way, which does not involve any scientific judgement. These products may serve for statistical or survey-type analysis of large samples.

Icons and Postcards
These are static representations in GIF-format of the survey products. Icons are small images intended to give an impression of the data: photometry, an image or a spectrum. Postcards are essentially enlarged icons with annotations added to give users an impression of the flux levels and wavelengths covered. Icons and postcards facilitate a quick-look scan of the data to identify which data need to be retrieved. These browse products should never be used for scientific work.

A short description follows of the main, instrument-dependent, characteristics of the browse products.



CAM Survey Products

These products are the equivalent of the AAR, giving the image from the CMOS file (when it exists) and CMAP (if it does not).



CAM Icons and Postcards

The postcard is the image of the survey product, projected in RA, DEC coordinates. It contains a grey-scale coded wedge to indicate flux levels. The icon is a small version of the CMAP/CMOS image shown in detector coordinates. The mean image of all wavelengths is displayed for CAM spectral observations (CAM04); the spectrum shown is that of the innermost 10x10 pixels. Up to four multi-filter or multi-PFOV measurements (for a given observation) are shown inside the corresponding icon.



LWS Survey Products

The following processing steps are applied to the standard AAR LSAN file:

  1. remove all data points with bad status
  2. clip outliers
  3. remove individual scans which are inconsistent with the majority of the scans
  4. average the remaining scans for each detector
It should be noted that the resulting spectrum is not stiched together nor is it averaged across detectors. Also, no defringing is applied.



LWS Icons and Postcards

Postcard and icon are spectra. Only the spectrum of the central point is presented for raster maps.



PHT Survey Products

The survey product is the equivalent of AAR. No survey product is derived for polarization observations.



PHT Icons and Postcards

Depending on the observing mode, postcards and icons are:



SWS Survey Products

The following processing steps are applied to the standard AAR file:

  1. remove all data points with bad or unreliable status
  2. flatfield the data such that all detectors are scaled to the same level
  3. clip outliers using sigma clipping
  4. rebin the data to a grid with the nominal resolution



SWS Icons and Postcards

Postcard and icon are spectra which are presented in a mosaic form when the observation contains more than one wavelength range.

Highly Processed Data Products (HPDP)

The Off-Line Processing Pipeline copes well with a number of instrumental artifacts in an automatic fashion. The final products can however be improved by processing them further, in particular by means of the Interactive Analysis software packages, as documented in the ISO Handbook.

Many ISO papers are based on a systematic reduction of archive data, producing 'Highly Processed Data Products' (HPDP). These products include DATA (images, spectra etc.), which have been processed beyond the pipeline and/or using new, refined algorithms and therefore have been improved to any degree compared to the pipeline products, as well as any resulting CATALOGUES and ATLASES.

Projects have been undertaken by the ISO Data Centre, in collaboration with the national instrument data centres, for systematic data reduction of specific instrument modes, that produce homogeneous sets of HPDP.

Browse Products have also been generated from the HPDPs which are default dataset.


ISO VO Compatible Products

The Survey Products are in most cases the ISO VO compatible products. They are generated from the standard pipeline AAR file or from the Highly Processed Data Products.

Only in the case of CAM, specific VO compatible products have been generated, which are different from the standard Survey Products. CAM products that are accessible from VO have been also produced based on the pipeline products.

VO products can be displayed from the ISO Data Archive using direct access to VO Tools as VOSpec (for spectra) and Aladin (for images).