Herschel observing will be conducted autonomously without real-time interaction. This means that observers are not expected to be present at the HSC while their observations are carried out.
All observations have to be specified in full detail by the proposers using HSpot well in advance to the time when the observations will actually be executed. For a variety of reasons including efficiency, sky coverage and instrument operation constraints, Herschel mission planning will distribute the available observing time among accepted proposals on a 'per observation' (AOR) basis. This is the way other space-based facilities like the Spitzer Space Telescope and the Hubble Space Telescope (HST) operate, and it was also the case of Herschel's precursor, the Infrared Space Observatory (ISO).
Similarly, it must be emphasised here that - for operational reasons - no guarantees can be given that any particular observation (AOR in the case of Herschel) within an accepted proposal will, in fact, be executed, although every attempt will be made to achieve this objective. Note that no grades are assigned to individual AORs accepted for execution. This means that the final scheduling sequence will be based solely on maximising the telescope observing efficiency.
Slew times between observations are charged over all AORs as a flat 3 minutes overhead. This overhead time is automatically applied to all non-time constrained observations entered through HSpot.
However, time constrained observations can also be defined using HSpot. These are:
All observations entered in HSpot using the timing constraints window.
All observations entered in HSpot using the Group/Follow-on constraints, with the exception of concatenations
Observations requesting an orientation constraint or a chopper avoidance angle.
Time constrained AORs reduce the flexibility of scheduling and the overall observing efficiency. For this reason they are further penalised, in terms of overhead charges, with a 10 minutes slew overhead in HSpot, instead of the 3 minutes applicable to non-constrained AORs. Programmes with heavily constrained AORs will need to be accompanied by a compelling justification.
Concatenated observations are charged 3 minutes overhead per AOR, unless observing the same target (no slew, see also below), then only 3 minutes overhead for the entire chain is charged.
If a concatenated chain is time constrained, then the overhead charge is 10 minutes for the first AOR, and 3 minutes for each following AOR, unless observing the same target, then only 10 minutes for the entire chain is charged.
Concatenation between 2 AORs is permitted:
For scientific reasons as motivated in the proposal.
For nearby targets. Two targets are nearby if they are separated in the sky by less than 1 degree. A target can be celestial (fixed position) or a solar system object (moving position).
Using the same sub-instrument only: the applicable 'sub-instrument' definitions are:
The PACS photometer and spectrometer are separate 'sub-instruments';
The SPIRE photometer and spectrometer are separate 'sub-instruments';
The SPIRE PACS parallel mode is a separate 'sub-instrument';
The seven HIFI LO bands are separate 'sub-instruments';
In order to preserve the overall science efficiency of the observatory, duplicate observations will in general not be permitted. Checks for potential duplications (see the Herschel Duplication Policies document) between your planned observations and already approved AORs contained in the so-called 'Reserved Observation List' will be made by the HSC during the technical review of submitted proposals.
The 'Reserved Observation List', available in the HSC web page, contains all observations of the GT and OT Key Programmes and of the GT1 proposals previously approved by the HOTAC that cannot be duplicated by any OT1 programme. The list can be inspected by OT1 proposers using the Herschel Reserved Observations Search Tool (HROST).
This tool enables you to search all the AORs included in the current Reserved Observations List in a simple fashion through a java-based web interface (requires Java 1.6 or higher). Once you start the application you can make queries by entering a position in the sky and a search radius as input and the tool will return as output a summary description of all AORs in the database overlapping your search area. Potential duplications found using this tool can be further investigated in detail using HSpot. You can access and download those AORs of your interest by using the option 'View accepted proposals' under the 'File' menu in HSpot.
The HOTAC will be informed of the existing duplications in each round of submissions and will assign priorities (and allocate time eventually) based on scientific arguments, if considered necessary. Otherwise, the duplicated observations will be blocked and the PI's of those proposals containing duplicated AORs will be contacted by the HSC. They will be informed about the identified duplications and recommended to adapt their observing programmes in the most efficient way to maximise the scientific return of the mission.
This may imply the coordinated distribution of the duplicate observations among the proposals affected, saving time which can be used for including additional observations or deeper exposures of other targets; or sharing the data, if an agreement is reached by the corresponding PIs in this sense, increasing the synergies and/or complementarities between the observations originally proposed. Decisions adopted by the affected PIs must be communicated to the HSC before the observations are released for scheduling.