Cosmic Origins Spectrograph Instrument Handbook for Cycle 17

2.5 Limitations on Proposing to Use COS

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2.5.1 The COS GTO program

The COS Instrument Definition Team (IDT) is responsible for the development, management, and scientific oversight of COS prior to launch. The COS IDT has approximately 550 orbits of guaranteed observing time with the instrument. The IDT observing time will occur primarily in Cycle 17, with a portion of the time remaining for observations in Cycles 18 and 19. Key personnel on the COS IDT include:

• Principal Investigator: James Green (University of Colorado)
• Project Scientist: Cynthia Froning (University of Colorado)
• Co-Investigators: Dennis Ebbets (Ball Aerospace), Sara R. Heap (GSFC), Claus Leitherer (STScI), Jeffrey Linsky (University of Colorado), Blair D. Savage (University of Wisconsin-Madison), J. Michael Shull (University of Colorado), Oswald Siegmund (University of California-Berkeley), Theodore P. Snow (University of Colorado), and John T. Stocke (University of Colorado).
• Primary Contractor: Ball Aerospace, Boulder CO.

As GTOs, the COS IDT is permitted to have exclusive access to the targets they will observe, and General Observers may not propose to observe those targets with COS. The COS GTO target list may be found on the MAST web page: http://archive.stsci.edu.

2.5.2 SNAPshots with COS

COS' detectors are photon counters and can be harmed by exposure to bright light. All COS observations must be checked at STScI by an Instrument Scientist to confirm both that the intended target is within safe limits for brightness and that no potentially too-bright objects exist nearby. Because of the time needed to do this, in Cycle 17 our first priority will be GO observations, and COS SNAPshots will only be permitted if the objects to be observed lie within fields observed by GALEX.

2.5.3 Non-point sources uses of COS

COS was optimized for faint point sources (objects less that 0.1 arcsec in diameter) because such objects are the primary targets proposed by COS' Investigation Definition Team (IDT). The COS IDT specifically avoided compromising FUV throughput for the sake of making COS a more general purpose instrument since STIS is intended to fulfill that need.

Nevertheless, COS is very powerful and can be applied to many scientific investigations. There may be applications to extended or structured sources, but in general at a significant cost in the resolution or purity of the spectrum. With only a few exceptions, this document is written for point-source observing, with the intent of adding information on other uses once we can assess them after launch.