STScI

Phase 2 Proposal Instructions for Cycle 10

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6.3 Coordinated Parallels

Coordinated parallel exposures are indicated by the exposure-level special requirement:

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. Parallel exposures using the same SI or NICMOS detectorwill be executed in the order specified on the Visit/Exposure Logsheet. The first parallel exposure which uses a given instrument or NICMOS detector will be executed as early as possible, but not before the first primary exposure.

The PARallel WITH special requirement must appear on the first exposure in the <primary-exp-list>. Exposures in the <parallel-exp-list> must appear on the Visit/Exposure Logsheet immediately after the exposures in <primary-exp-list>. Parallel exposure numbers should follow this sequence as well.

6.3.1 Instrument Configuration

The exposures in <primary-exp-list> and <parallel-exp-list> are limited to the following instrument configurations and modes:
Configuration Operating Mode
WFPC2 IMAGE
STIS/FUV-MAMA1 ACCUM
STIS/NUV-MAMA1 ACCUM
STIS/CCD ACCUM
FGS POS
ACS/WFC2 ACCUM
ACS/HRC2 ACCUM
ACS/SBC2,3 ACCUM


1In order to protect the STIS MAMA detectors from inadvertent overillumination, they may be used as coordinated parallels only if an exact spacecraft orientation (ORIENTation) is specified, the coordinates of the parallel field are determined, and the parallel target or field passes the same bright-object screening applied to MAMA primary observations.
2ACS 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.
3In order to protect the ACS SBC detector from inadvertent overillumination, the ACS/SBC configuration may be used for coordinated parallels only if an exact spacecraft orientation (see ORIENTation <angle1> TO <angle2>) is specified, the coordinates of the parallel field are determined, and the parallel target or field passes the same bright-object screening applied to SBC primary observations.

 

All exposures in <primary-exp-list> must have the same Instrument Configuration (Config) and the same Aperture or Field of View (Aperture). Except for the NICMOS, No exposure in <parallel-exp-list> may use the same SI as the primary exposures. NICMOS parallel exposures may use the same SI but only in a different configuration.

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), except for NICMOS background patterns (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 ORIENTation special requirement is required to ensure that the parallel target is in the aperture. It is the observerÕs 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, a generic target specification should be used. If there is no parallel target as such, and the intent is just to sample whatever the parallel aperture happens to fall on, the ANY target (which should not appear in the Target List) should be used. Generic targets or target ANY should only be used in one of these three cases:

  1. The exposure is PARALLEL WITH or SAME POS AS another exposure (so that the pointing is determined by the other exposure), or
  2. The visit is a pure parallel (in which case the target will be matched against already-scheduled observations), or
  3. The visit is ON HOLD (as with Targets of Opportunity, for example). In this case the target should be replaced by a fixed target when the ON HOLD is removed.

Coordinated parallels and their primaries may not use the WFPC2 UVFLAT or VISFLAT internal targets.

6.3.3 Special Requirements

All the fields on the Visit/Exposure Logsheet should be filled out as for primary exposures. However, the following exposure-level special requirements are disallowed for both primary exposures (any exposure in a <primary-exp-list>) and parallel exposures:
EXPAND
MAXimum DURation [<time or percentage>]
MINimum DURation [<time or percentage>]
RT ANALYSIS

 

The following exposure-level special requirements are allowed for primary exposures, but not for parallels:

END ORBIT

LOW-SKY
PHASE <number1> TO <number2>
POSition TARget <x-value>, <y-value>
REQuires EPHEMeris CORRection <id>
REQuires UPLINK
SAME POSition AS <exposure>
SAVE OFFSET <id>
SHADOW
USE OFFSET <id>

 

The following exposure-level special requirements are allowed without restriction:
NO SPLIT
SEQuence <exposure-list> NON-INTerruptible
SAA CONTOUR (WFPC2 only)

 

No parallel exposure may appear in the <exposure-list> of an RT ANALYSIS FOR Special Requirement, or be the <exposure> referenced by a SAME POSition AS special requirement.

6.3.4 Optional Parameters

The WFPC2 READ=NO option is not allowed, because the WFPC2 CCDs are erased during delays between exposures to avoid cosmic-ray effects.

For ACS coordinated parallels, no automatic image exposures will be scheduled when in conjunction with HRC prism observations. In this case the usual default of AUTOIMAGE=YES does not apply, and the AUTOIMAGE optional parameter may not be specified.

The parameters used with patterns for NICMOS may be used for coordinated parallels subject to the following restrictions and interpretations:

  1. Only a single NICMOS exposure in the PARallel WITH Special Requirement may use a pattern. This exposure must be the only exposure in <primary-exp-list>. Background pattern parameters may not be used on a parallel exposure, because they involve pointing changes.
  2. All NICMOS parallel exposures will be taken at each pattern position. Any parallel exposures using other SIs will also be taken at each pattern position.
  3. Only a single NICMOS exposure in the PARallel WITH special requirement may use a pattern, and no other exposure in the list may use the same configuration. This exposure must be either the only exposure in <primary-exp-list> or the first exposure in <parallel-exp-list>.
  4. Background pattern parameters may be used on a parallel exposure only if OFFSET=FOM and the primary exposures use an SI other than NICMOS.
  5. All other NICMOS parallel exposures will be taken at each pattern position. If the exposure using the background patterns is the primary, parallel exposures using other SIs will also be taken at each pattern position.
  6. If OFFSET=FOM, each sequence of NICMOS exposures in <parallel-exp-list> using a different detector must take no longer to execute than the exposure with OFFSET=FOM.

Within a PARallel WITH special requirement, the NICMOS CAMERA-FOCUS, optional parameter may be used only by one NICMOS detector, referred to as the Òprimary detector.Ó If the primary exposures use the NICMOS, the primary detector is the one used in those exposures. Otherwise, the primary detector is determined by the configuration used for the first NICMOS exposure in <parallel-exp-list>.

Within a PARallel WITH special requirement, the NICMOS FOMXPOS, FOMYPOS optional parameters may be used only by one NICMOS detector, referred to as the Òprimary detector.Ó If the primary exposures use the NICMOS, the primary detector is the one used in those exposures. Otherwise, the primary detector is determined by the configuration used for the first NICMOS exposure in <parallel-exp-list>.

6.3.5 Ordering Restrictions and Interpretations

The exposures in the <parallel-exp-list> of a PARallel WITH special requirement must appear on the Visit/Exposure Logsheet immediately after the exposures in <primary-exp-list>.

If the <parallel-exp-list> contains exposures which use different SIs or NICMOS detectors, an attempt will be made to execute each group of exposures with the same SI or NICMOS detector in parallel with the other groups. All exposures within a given group must be contiguous on the logsheet.Groups of parallel exposures using different NICMOS detectors must be contiguous on the logsheet. Within a group, exposures will be executed in the order in which they appear on the logsheet.

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-exp-list>, the parallel will be delayed. If two parallel exposures using different SIs or NICMOS detectors conflict, the exposure which appears later on the logsheet will be delayed.

Following a set of exposures in <primary-exp-list> and <parallel-exp-list>, subsequent exposures not part of either list will be delayed until after all primary and parallel exposures have completed.

Example 1: Three WFPC2 exposures parallel with three STIS exposures

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 or NICMOS detector must be short enough to fit in one orbit. If it is necessary to take coordinated-parallel data over multiple orbits, a separate PARallel WITH special requirement Ð with a new <primary-exp-list> and <parallel-exp-list> Ð should be specified for each orbit.


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