PARallel <parallel-exp-list> WITH <primary-exp-list>
(replaced by Coordinated Parallel Containers in the APT User Interface)This special requirement specifies that the exposures in <parallel-exp-list> will execute in parallel with a sequence of exposures in <primary-exp-list>.
In the Text Proposal File, both <primary-exp-list> and <parallel-exp-list> must be replaced by either a single exposure number, or a range of exposure numbers separated by a hyphen. See
Section 6.3 on page 93 for more details.
Specifies that the current science exposure must be made available to the observer for analysis in real time. (See the
Call for Proposals for a discussion of real-time observing.) Any science exposures whose execution depends upon a decision based on the real-time analysis should have
RT ANALYSIS specified. The
REQuires UPLINK Special Requirement may also be used with
RT ANALYSIS to establish the ground-to-spacecraft link. The current exposure will be available for analysis at least 16 minutes (for fixed targets) prior to that uplink; for moving targets the time is 24 minutes.
This Special Requirement is a limited resource and should only be used when necessary. Justification for its necessity should be included in the
Real_Time_Justification text.
Note that the exposures in the <exposure-list> must be in the same visit as the current exposure, and
RT ANALYSIS may not be used if the exposure uses patterns or if Number_of_Iterations > 1.
Indicates that a real-time command uplink is needed to execute this exposure. An uplink will be scheduled prior to the current exposure. This Special Requirement should be used with
RT ANALYSIS to replace the capability formerly available with
INTeractive ACQuisition (obsolete) and it should specifically identify which exposures need an uplink, assuming that the uplink already provided is not sufficient. This Special Requirement can also be used without
RT ANALYSIS if the information which needs to be uplinked is not dependent on real-time analysis of HST data. Usage of this Special Requirement is considered a limited resource and should only be used when necessary. Justification for its necessity should be included in the
Real_Time_Justification text.
REQuires EPHEMeris CORRection <id>
Indicates that a correction for position errors due to moving-target and/or HST ephemeris uncertainty may be needed to execute the exposure. This Special Requirement is only valid for exposures with moving targets. The offset will be uplinked during an available (“generic”) uplink prior to the earliest exposure that uses it. The pointing correction may require a minute or two of target visibility time.
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When observing an object within about 1 AU of the Earth. In this case, the uncertainty in the position of HST accumulated between the time the schedule is built and the time it is executed can cause the observation to miss the target. (The HST ephemeris is inaccurate by as much as 60 seconds, which translates into a positional error on the moving target). The offset can be easily calculated by STScI personnel in this case.
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With moving targets, the maximum target ephemeris uncertainty must be specified in the solar-system target list (see
Section 4.3.6 on page 66). STScI will be unable to schedule corrections larger than the maximum offset derived from this uncertainty, so too small an uncertainty may limit the usefulness of the
REQ EPHEM CORR procedure. However, offsets larger than about 1 arcminute may make scheduling difficult. If your observation requires a correction this large, contact your Program Coordinator.
The <id> is an alphanumeric string of up to six characters in length. Exposures with the same
REQ EPHEM CORR ID (whether in the same visit or in different visits) will use the same offset and must be taken at the same orientation. If exposures in different visits use the same ID, the visits involved are all subject to the same scheduling restrictions as
SAME ORIENTation AS <visit>. The
SAME ORIENT Special Requirement is implied across such a set of visits, and need not be specified directly.
Requests that the current exposure be taken when the total background light is no more than 30% greater than the yearly minimum value of the
zodiacal background for that target. To minimize Earth shine, the exposure will also be taken when the target is at least 40 degrees from the bright Earth. This limits visibility time to about 48 minutes per orbit. Efficiency and schedulability are reduced with this Special Requirement, but to a much lesser degree than with
SHADOW. This Special Requirement may not be combined with
SHADOW or used in a
CVZ visit
PHASE <number1>
TO <number2>
Requests that the exposure start in the specified phase range (<number1> to <number2>) of a periodic variation. <number1> and <number2> should be between 0.0 and 1.0. The
PERIOD <time> ZERO-PHASE (HJD) <date> used in the calculation should have been already entered at the visit level. With short periods, the phase range (difference between <number1> and <number2>) should be made as wide as possible to make scheduling easier.
Please note that there is no need to repeat the PHASE Special Requirement for multiple exposures within the same Visit (unless you are attempting to specify different phases for those exposures). Instead, specify
PHASE for only the first exposure in the Visit. If the phase window you specify is short, you may need to adjust
PHASE for the first exposure so that the subsequent ones start before the phase window ends.
SEQuence <exposure-list> NON-INTerruptible
(replaced by Exposure Group Containers in the APT User Interface)Specifies that exposures defined in the <exposure-list> be observed without gaps due to Earth occultation or SAA passages. Gaps between exposures may still be necessary to allow time for activities which are necessary to set up for the next exposure, such as pointing changes, readouts of the SI buffers, and SI reconfigurations. This requirement must be included for a series of FGS exposures which are to be executed within the same orbit.
In the Text Proposal File, the exposure list must be a range of numbers separated by a hyphen, such as SEQ NON-INT 55-60.
Note: If this requirement is placed on
one exposure (e.g.,
SEQ 20 NON-INT) and
Number_of_Iterations > 1, the sequence of subexposures will not be split.
Requests that the current exposure be taken while HST is in the umbral shadow of the Earth. It is primarily useful when contamination by geocoronal emission (Lyman alpha, OI 1304е, etc.) must be minimized. However, it does not minimize
zodiacal light, which is the principal source of background at wavelengths longer than 3500е (see the
LOW-SKY Special Requirement).
Exposures using this Special Requirement are limited to about 32 minutes per orbit (including overheads). Scheduling may only be feasible for a small percentage of the year. This Special Requirement is a limited resource and should only be used when necessary; most usages of
SHADOW will have been approved by the TAC during the Phase I review process. This Special Requirement may not be combined with
LOW-SKY or used in a
CVZ visit.
