6.1 Parallel Science Limitations

These restrictions are to ensure that parallels can be scheduled and executed safely and efficiently:

• Parallel observations have some special restrictions on the targets that may be specified; see 6.2 Pure Parallels and 6.3 Coordinated Parallel Containers for details.
• All scheduling constraints (pointing, orientation, and relative timing) that apply to coordinated primaries and parallels must be specified only on the primary exposure.
• No visit-level special requirements, and only a few exposure-level special requirements, are applicable to pure parallel visits.
• Exposures parallel with any instrument mode which permits interactive or autonomous motion of HST (e.g., interactive or onboard acquisitions) are not supported.
• Neither parallel exposures nor the primary of a coordinated parallel may have real-time (i.e., TDRS contact) requirements of any kind.
• In order to protect the ACS SBC detector from inadvertent overillumination, the ACS/SBC configuration may be used for coordinated parallels only if an exact ORIENT (e.g., ORIENT 20D to 20D) is specified. Also, the coordinates of the parallel field must be determined and the parallel target or field must pass the same bright-object screening applied to SBC primary observations.

These limitations are discussed further below.