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Hubble Space Telescope
New Mandatory Keyword for COS Observations Describing whether Targets are Point Sources or Extended

Starting with Cycle 23, COS observers are required to define their targets as EXTENDED = "YES" or "NO" at the target description level. This new field is required for COS observations only. This change is intended to provide an indication as to whether the source extent might be large enough to affect the reliability of the default pipeline extraction which is currently optimized for point source targets. In the future this keyword may also be used to allow the pipeline to use an alternate extraction procedure better suited to extended sources. Both COS FUV and NUV observations of targets with FWHM larger than about 0.6 arcsec or radius larger than 0.35 arcsec should be considered as extended. "YES" should be selected for such targets and "NO" for targets of smaller angular extent. The field should be left blank if the target is not being observed by COS. If this new target-level description keyword is not provided, APT will trigger a warning message asking the PI to define it, and any proposals submitted without a value specified for all COS targets will be sent back to the PI to be corrected. See the COS STAN articles from February and March 2015 for further details. Note that the old exposure-level EXTENDED keyword, set via the "optional parameters" prior to Cycle 23, is still present in APT but has been deprecated. As a result, the exposure-level EXTENDED keyword should no longer be selected for any exposure starting in Cycle 23.