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Hubble Space Telescope Primer for Cycle 25 > Appendix A: Orbit Calculation Examples > A.5 WFC3 Examples

A.5 WFC3 ExamplesThe WFC3 IR channel is used to obtain images of a target in filters F110W and F160W. Assume that the ETC has shown that exposure times of 10 minutes for F110W and 20 minutes for F160W are adequate for the science goals. These exposure times can be achieved with the up-the-ramp MULTIACCUM sequences SPARS50 (11.7 min) and SPARS100 (23.4 min), respectively. Also assume an orbital visibility^{1}of 54 minutes. A summary of the orbit calculations is shown in Table A.6.

Table A.16:

2 × 1.0 = 2.0 For the purposes of this example, the following conditions are adopted: (1) the exposure time necessary to reach the desired signal-to-noise ratio is 80 minutes. (2) The orbital visibility for each orbit is 58 minutes. (3) Assume that cosmic ray removal will be done using the drizzlepac package; therefore the exposure will not be broken into sub-exposures. (4) One 20 minute exposure is obtained at each pointing in a four-point dither, taken over two orbits.The orbit calculation for this visit is shown in Table A.17. Note that for a two arcsec offset maneuver, the three dither offsets will take 0.5 minutes each.

Table A.17:

2 × 2.1 = 4.2 2 × 0.5 = 1.0

Hubble Space Telescope Primer for Cycle 25 > Appendix A: Orbit Calculation Examples > A.5 WFC3 Examples