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Hubble Space Telescope Primer for Cycle 25 > Appendix A: Orbit Calculation Examples > A.3 FGS Example

A.3 FGS ExampleThe FGS is used to observe a binary star named Binary01, as well as five reference stars (ref1, ref2, ref3, ref4, ref5). All stars are in the same FGS field of view, and can therefore be observed in one visit (see Section 6.2.2). Stars ref4 and ref5 have magnitude V = 14.6, and all the other targets have 13.0 < V < 14.0. To enable the removal of drift and jitter in the post observation analysis of the data, the Binary01 is observed in POS mode several times (twice in this example) and the reference stars are each observed twice. The desired exposures are listed in Table A.10,

• Therefore, a preliminary observing strategy can be created by the user to fit the observations in one orbit, as shown in Table A.12.

Table A.10:

20 scans of 40 sec each (see Table 6.7) for Binary01

Table A.11:

Table A.12:

Hubble Space Telescope Primer for Cycle 25 > Appendix A: Orbit Calculation Examples > A.3 FGS Example