Caveats

Below gives a list of the known caveats for the current version of ESASky:

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CAVEATS OF THE DATA

There are some caveats on the data currently provided by ESASky:

  • Data are regularly updated in the application and some important datasets might still be missing. Data are complete up to the dates described in the ESASky help pages.
  • The Herschel Data Distribution provides combined Standalone Browse Products per observation with either the three wavelengths for the SPIRE maps or two for the PACS maps. This makes it currently impossible to send a Herschel observation to Virtual Observatory tools like e.g. Aladin.

 

CAVEATS OF THE CATALOGUES

The current catalogues functionality on ESASky has the following caveats:

  • For the XMM-Newton Serendipitous Source catalogue, only sources with QUALITY=GOOD are shown.

Please note that some catalogues may display rounded or truncated values in ESASky; however, all the original digits are kept when the catalogue tables are downloaded or loaded into a VO application through SAMP.

 

CAVEATS of the all-sky views (hips)

IMPORTANT The HiPS are intended for visualization only. They are not science-ready products and should not be used to perform scientific data analysis.

The all-sky views (HiPS) currently available on ESASky have some known caveats:

  • The current HiPS maps have fixed flux cuts and pixel intensity stretching for high and low intensities. As a consequence, if strong flux level differences exist between different observations, it is often not possible to find an automated way that would allow good static visualisation of all the data. For XMM-Newton and INTEGRAL, the scaling of the input data to the same background level provided a good representation of all the images in the HiPS. In other cases this approach did not work well and we proceeded with re-scaling of the standardised images based on the Planck flux scale (ISOCAM, AKARI, Herschel-SPIRE). This alternative processing was not successful for Herschel-PACS, where we implemented individual pixel cuts and stretching to each image before adding it to the HiPS all sky map.  There is still room for improvements and we are currently exploring more flexible scheme.

  • Herschel RGB HiPS maps: because of the way the Herschel images were standardised and stretched for the all sky HiPS maps, the pixel distribution does not have a physical meaning and as a consequence the RGB maps are not representative for the actual characteristics of the emitting regions (temperature). Even more difficult to produce is a representative RGB HiPS for PACS and SPIRE combined. That is why we do not provide such a HiPS map in this version. We are exploring alternative ways to produce meaningful RGB maps for Herschel for the next release.

  • HiPS from ongoing missions (HST, XMM-Newton, INTEGRAL) do not contain all the observational data available in the archives, but only the public data up to the HiPS map creation date indicated in the HiPS information page. These HiPS maps will be periodically replaced with newer ones adding more recent observations to the previous HiPS.