2.5	SNAP and TOO Programs with COS

The COS photon-counting detectors can be harmed by exposure to bright light. Because all COS observations must be checked at STScI by an Instrument Scientist to confirm that both the intended target and all nearby objects lie within safe-brightness limits, the total number of targets accepted for all COS and STIS MAMA SNAP programs will be limited to 150 per cycle.

For similar reasons, when planning Target of Opportunity (TOO) observations COS observers must ensure that sufficient time is available to allow for STScI screening of targets for compliance with safety limits. Ultra-rapid TOOs, (< 2 days), are not allowed with COS. No COS observations will be performed until the bright object screening can be completed. This process can be greatly accelerated by preliminary discussions with the assigned Contact Scientist to clarify the information that the observer will need to provide to STScI and the criteria that will be used to determine if the target is safe to observe.

For more information on these and other policies pertaining to HST observing, please see the Call for Proposals.