Cosmic Origins Spectrograph Instrument Handbook for Cycle 17

2.1 SM4 and the Installation of COS

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COS will be installed into HST during Servicing Mission 4 (SM4), now scheduled for launch in August, 2008.

There are some critical aspects of the performance of COS that will not be known in detail until COS is installed into HST and fully calibrated. The information presented in this Handbook (sensitivities, for example), is based on data from tests performed on the ground and represents our current best understanding of COS. Proposers for Cycle 17 are unlikely to receive updated information before the proposal deadline, but they are urged to check the STScI Web pages before submission. Any such updates should be posted no later than one month before the proposal deadline.

Once executed, SM4 will be followed by a period of Servicing Mission Observatory Verification (SMOV), during which HST's science instruments are activated, tested, and characterized. The successful conclusion of critical SMOV tests leads to an instrument being available for science observations. Because of its detectors, COS needs several weeks to outgas before high voltages can be turned on (in order to avoid arcing), followed by several additional weeks of engineering activities.

We cannot predict exactly when COS will start to be available to General Observers in Cycle 17 because of uncertainty in the launch date for SM4 and in the activities needed to certify COS for science use. For planning purposes we are assuming that COS will be available for all of Cycle 17, once it has completed initial turn-on and SMOV.