In this step, you place all of your exposures (science and non-science, alike) into orbits, including tabulated overheads, and determine the total number of orbits required. Refer to Chapter 8 when performing this step. If you are observing a small target and find your total time request is significantly affected by data-transfer overheads (which will be the case only if you are taking many separate exposures under 339 seconds with the WFC), you can consider the use of CCD subarrays to lessen the data volume. Subarrays are described in Section 7.3.1 (WFC), Section 7.3.2 (HRC), and in Section 8.2.1.
At this point, if you are happy with the total number of orbits required, you're done! If you are unhappy with the total number of orbits required, you can adjust your instrument configuration, lessen your acquisition requirements, or change your target signal-to-noise or wavelength requirements, until you find a combination which allows you to achieve your science goals.
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