HST Call for Proposals

The OS lists the main characteristics of the observations that you propose to obtain. In general you must include in the OS all the configurations, modes, and spectral elements that you propose to use, and (except for SNAPs) all the targets that you propose to observe. Configurations or targets that are not specified in the Phase I proposal, but are included in Phase II, may delay the program implementation, and may be disallowed. Note the following:

•	For Long-Term Proposals, the OS should include information for all the proposed observations, not just those requested in Cycle 24.

•	Parallel observations must be included in the OS, and marked as such using the relevant special requirement flags (see Section 8.16.11 and Table 8.1).

•	Target acquisition observations (see Section 5.2 of the HST Primer) need not be included in the OS, unless they are themselves used for scientific analysis.

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Normal calibration observations that are often or routinely taken (e.g, fringe flats) need not be included in the OS. However, the OS should include any special calibration exposures of internal sources or external targets (see Section 4.3). Special internal calibrations should be listed separately from external calibration exposures. When these special calibrations require additional orbits, that should be specified and the orbits included in the total allocation. The need for these calibrations should be justified in the ‘Description of the Observations’ (see Section 9.2).

	All exposures of a given target made with a particular instrument may be summarized in a single observation block; observations of the same target with a second instrument (e.g. coordinated parallels) must be specified in a separate observation block.

If you are proposing polarimetric observations with ACS, then set this keyword to ‘yes’. There is no polarimetry keyword in the proposal PDF file, but this sets the appropriate flag in the Phase I submission.

Flag	Use this flag for
Coordinated Parallel	All of the exposures specified in this observation block are to be done in Coordinated Parallel mode (see Section 4.2.1).
Pure Parallel	All of the exposures specified in this observation block are to be done in Coordinated Parallel mode (see Section 4.2.2).
CVZ	Continuous Viewing Zone observations (see Section 4.1.1).
Duplication	Observations which duplicate or might be perceived to duplicate previous or upcoming exposures (see Section 5.2.1).
Target of Opportunity - Disruptive	Target-of-Opportunity observations with turn-around time shorter than 3 weeks (see Section 4.1.2).
Target of Opportunity - Non-disruptive	Target-of-Opportunity observations with turn-around time longer than 3 weeks (see Section 4.1.2).

Flag

Use this flag for

Coordinated Parallel

All of the exposures specified in this observation block are to be done in Coordinated Parallel mode (see Section 4.2.1).

Pure Parallel

All of the exposures specified in this observation block are to be done in Coordinated Parallel mode (see Section 4.2.2).

CVZ

Continuous Viewing Zone observations (see Section 4.1.1).

Duplication

Observations which duplicate or might be perceived to duplicate previous or upcoming exposures (see Section 5.2.1).

Target of Opportunity - Disruptive

Target-of-Opportunity observations with turn-around time shorter than 3 weeks (see Section 4.1.2).

Target of Opportunity - Non-disruptive

Target-of-Opportunity observations with turn-around time longer than 3 weeks (see Section 4.1.2).

Setting this requirement means there are no scheduling constraints on the Observation Block.

Set this requirement when all exposures defined in the Observation Block are affected adversely by geocoronal Lyman-alpha background emission, and therefore need to be obtained when HST is in Earth shadow. This requirement complicates scheduling and reduces HST observing efficiency, and must therefore have adequate scientific justification in the Phase I proposal. SHADOW is generally incompatible with CVZ. This requirement should not be used if low continuum background is required: in that case use LOW SKY instead.

Set this requirement when all exposures defined in the Observation Block are affected adversely by scattered light (e.g zodiacal light and earthshine), and therefore need to be obtained with minimal sky background. The continuum background for HST observations is a function of when and how a given target is observed. Observations can be scheduled when the sky background is within 30% of its yearly minimum for the given target, which is done by restricting the observations to times that minimize both zodiacal light and earthshine scattered by the Optical Telescope Assembly (OTA). To minimize the zodiacal light, the scheduling algorithm places seasonal restrictions on the observations; to reduce the earthshine, the amount of time data is taken within an orbit is reduced by approximately 15%. The former complicates scheduling, while the latter reduces the observing efficiency of HST. Therefore, using the LOW SKY restriction must have adequate scientific justification included in the Phase I proposal. With this restriction, the zodiacal background light for low-ecliptic latitude targets can be reduced by as much as a factor of 4. Avoiding the earthshine at the standard earth-limb avoidance angle (see Section 2.3 of the HST Primer) can make a similar difference. LOW SKY is generally incompatible with CVZ.

Setting this requirement means that all exposures defined in the Observation Block MUST be observed at the exact same ORIENT. This requirement is only meaningful if the observations are to occur in multiple visits (e.g. Number of Iterations is greater than 1, or if the Total Orbits is greater than 5).

Enter the ORIENT range that all the exposures defined in the Observation Block must be observed within. If multiple ORIENT ranges are acceptable, then enter all values.

Enter the range of dates that all exposures defined in the Observation Block must be observed within. If multiple BETWEENs are acceptable, then enter all values.