UCL Department of Space and Climate Physics


Known Issues

SAS processing failures

Occasionally the ODF might be corrupted, in which case the data cannot be used in the catalogue. There are also occasional failures in the astrometric solution. If the astrometry has failed it could lead to large positional errors, so the data are not included. 

Bright sources missing

On rare occasions, the detection of quite bright sources (13-14th magnitudes) failed at the initial detection stage. Although such sources were detected at a later stage (when processing the mosaiced images), they were not included in the catalogue because the processing of the mosiced images does not include the coincidence-loss correction. As a result, some bright sources are missing from the catalogue (improvements of the source detection task is foreseen).

Faint sources detected in mosaic images

Some of the very low count rate sources, identified in stacked and mosaiced images for SUSS2, do not have any coincidence correction, and those added with SUSS2.1 have an incorrect coincidence correction. Please note however, this does not affect the photometry by more than 1-2% because the sources are faint. A file (SUSS2.1-mosaic_detections.zip) with a list of the affected sources is available to download. The number of affected sources is as follows:

V: 127285     B: 37967     U: 114985     UVW1: 244497     UVM2: 35095     UVW2: 19635 

Source numbering 

On some rare cases, the same catalogue source number might be assigned to very close sources (separated from each other by 2-3 arc seconds). This misidentification is unavoidable, so the users should be cautious when comparing observations of the same source made on different dates.

In addition, occasionally we find more than one SRCNUM corresponding to the same IAUNAME. This is to do with the way the source matching is performed and will be corrected in the next version of the catalogue. 

Bad fields

Occasionally very high, incorrect, count rates or count rate errors are encountered. These are usually associated with very crowded fields or with fields and data with other problems.