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HST Cycle 25 Phase II Proposal Instructions > Chapter 6: Parallel Science Exposures > 6.3 Coordinated Parallel Containers

6.3 Coordinated Parallel Containers
Text Proposal File
In the text proposal file format, coordinated parallel exposures are indicated with the exposure-level special requirement:
PAR <parallel-exp-list> WITH <primary-exp-list>
This designates a set of one or more parallel exposures which will execute in parallel with a set of one or more primary exposures in the same visit. The PAR WITH special requirement must be specified on the first exposure in the <primary-exp-list>. Exposures in the <parallel-exp-list> have to appear immediately after the exposures in <primary-exp-list>. Parallel exposure numbers must follow this sequence as well.
The APT User Interface.
A Coordinated Parallel Container designates a set of one or more parallel exposures (<parallel-exp-list>) that will execute in parallel with a set of one or more primary exposures (<primary-exp-list) in the same visit. The SI used in the first exposure defines the primary SI (and therefore defines the <primary-exp-list>). All other exposures that use the same SI will also be considered primary.
All exposures using a different SI will be considered parallel. Parallel exposures using the same SI will be executed in the order specified in the container. The first parallel exposure which uses a given instrument will be executed as early as possible, but not before the first primary exposure.
6.3.1 Instrument Configuration
The exposures in <primary-exp-list> and <parallel-exp-list> are limited to the following instrument configurations and modes:
 
STIS/FUV-MAMA1
COS/FUV4
TIME-TAG5 or ACCUM
TIME-TAG5 or ACCUM
1
In order to protect the STIS MAMA detectors from inadvertent overillumination, these configurations may be used as 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 MAMA primary observations.
2
FGS may only be used as primary, never parallel.
3
ACS exposures cannot be used in both the <primary-exp-list> and the <parallel-exp-list>, and all ACS exposures in the <parallel-exp-list> must use the same configuration.
4
In order to protect the COS FUV and NUV detectors from inadvertent overillumination, these configurations may be used as the coordinated parallel observation 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 COS primary observations.
5
COS Time-tag exposures are limited to a single one in a parallel exposure or as the primary exposure of a coordinated parallel.

All exposures in <primary-exp-list> must have the same Instrument Configuration (Config) and the same Aperture or Field of View (Aperture). No exposure in <parallel-exp-list> may use the same SI as the primary exposures.
6.3.2 Targets
Coordinated parallels may specify fixed, generic, or solar system targets; the special target ANY; or internal targets. However, the pointing of HST will be determined only by the primary exposures. Any pointing conditions to be applied on the primary+parallel combination must be specified on the primary exposures via exposure-level special requirements, or on the visit as a whole via visit-level special requirements. All external exposures in a given <primary-exp-list> must have the same pointing. This generally means the same target, aperture, and POS TARG (see the discussion of optional parameters below).
If a parallel exposure specifies a fixed target, it should be a different target from the primary ones and should appear in the Target List. In this case, an ORIENT special requirement is required to ensure that the parallel target is in the aperture. It is the observer’s responsibility to verify that the specified orientation will place the parallel target in the aperture; STScI will not check the geometry. Contact your Program Coordinator if you need assistance.
If the parallel target is diffuse and the orientation does not matter, or if there is no parallel target as such and the intent is just to sample whatever the parallel aperture happens to fall on, you should select the ANY target (which should not appear in your Target List).
6.3.3 Special Requirements
The following exposure-level special requirements are disallowed for both primary exposures (any exposure in a <primary-exp-list>) and parallel exposures:
MAXimum DURation [<time or percentage>]
MINimum DURation [<time or percentage>]
The following exposure-level special requirements are allowed for primary exposures, but not for parallels:
PHASE <number1> TO <number2>
POSition TARget <x-value>, <y-value>
REQuires EPHEMeris CORRection <id>
REQuires UPLINK
SAME POSition AS <exposure>
Allowed without restriction:
SEQuence <exposure-list> NON-INTerruptible (replaced by the Exposure Group Container in APT; see Section 5.19)
No parallel exposure may appear in the <exposure-list> of an RT ANALYSIS FOR Special Requirement, or be the <exposure> referenced by a SAME POS AS special requirement.
6.3.4 Optional Parameters
The Number_Of_Iterations must be set to 1 for any COS exposure in a coordinated parallel container.
6.3.5 Ordering Restrictions and Interpretations
In Coordinated Parallel Containers, the SI used in the first exposure defines the “primary” SI.
If the exposures in the <parallel-exp-list> contain exposures that use different SIs, an attempt will be made to execute each set of exposures with the same SI in parallel with the other sets. All exposures within a given set must be contiguous in the container. Within a set, exposures will be executed in the order they appear.
Due to readout conflicts and limits on the number of SIs which may execute simultaneously, parallel exposures sometimes have to be delayed. If a parallel exposure conflicts with an exposure in its primary list, the parallel will be delayed. If two parallel exposures using different SIs conflict, the exposure which appears later in the container will be delayed.
Following a set of exposures in a Parallel Container, subsequent exposures not in the container will be delayed until after all the primary and parallel exposures have completed.
Text Proposal File
In the Text Proposal File, the exposures in the <parallel-exp-list> of a PAR WITH special requirement must appear immediately after the exposures in <primary-exp-list>.
6.3.6 Efficiency Considerations
Within a set of coordinated-parallel exposures, the ground system will not break up sequences of exposures that are too long to fit in an orbit, as it does for non-coordinated-parallel exposures. Each group of exposures with the same SI must be short enough to fit in one orbit. If it is necessary to take coordinated-parallel data over multiple orbits, a separate Parallel Container – with a new set of exposures – should be specified for each orbit.

HST Cycle 25 Phase II Proposal Instructions > Chapter 6: Parallel Science Exposures > 6.3 Coordinated Parallel Containers

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