CFH12k Queued Observing Programme: Preliminary Description.


7. The Tier 2 Proposal.

 Many changes will be made to CFHT's modus operandi to accommodate the queued observing programme. We propose that one of these be the introduction of a two tier proposal process. First, a near-conventional proposal oriented around the scientific justification which will be submitted to the TACs, and second, a description of the accepted observing programme providing all the information required by the observing queue to execute it.

This section defines the form of the second tier proposal.

The second tier proposal will be an explicit statement of each accepted programme's needs. This will take the form of a set of keyword-value pairs assembled by each investigator which completely describes the needs of his or her programme and which defines the use of the I-time as allocated by the TAC. CFHT will provide the mechanism by which the investigator will compile the required information, most likely as a set of web forms or ASCII templates. CFHT will also develop a database engine which will parse the provided information into a database on the front end and will be capable of identifying, from this database, the small set of optimum observations to be taken at any given time once the observing queue is started. The submission mechanism will allow for the grouping of observations when appropriate.

The final format will be formalised to be handled automatically and will include considerable detail not described here. Nevertheless, we expect only the most general parameters will be explicitly described by the templates, any other information pertinent to the observations should be written into the "Comment" fields.

The original inspiration for this scheme was the HET phase II proposal language (Gaffney, 1997, private communication, and http://rhea.as.utexas.edu/~niall/adass97/).

7.1. The Proposal Definition.

7.1.1. Proposal Templates

 A programme will be defined by a series of templates which specify:

      1. the fields to be observed,
      2. the constraints on the observations,
      3. the instrument configuration,
      4. the specific observation parameters. These templates are defined as follows:
        Field Template

        		Defines a field to observe.

        		 RunId

        		 1st tier proposal RunId

        		 name

        		 Unique name for template

        		 RA

        		 Right Ascension of centre of field

        		 Dec

        		 Declination of center of field

        		 Epoch

        		 Epoch of coordinates

        		 Finder_chart_URL

        		 URL of finder chart, if available.

        		 Calibration_flag

        		 Is this a calibration field?

        		 Comment

        		 Freestyle comment

        Constraints Template

        		Defines a set of observing constraints

        		 RunId

        		name

        		Sky_brightness

        		 Maximum allowable sky brightness

        		 Seeing_band

        		 Upper seeing band (arcsec)

        		 Transparency

        		 Lower transparency limit (%)

        		 Comment

        Instrument Template:

        		Defines instrument configuration

        		 RunId

        		name

        		Filter

        		 Filter to use

        		 Bin_factor

        		 CCD Bin factor to use

        		 Raster

        		 CCD raster to use

        		 Comment

        Observation Template:

        		Defines observation parameters

        		 RunId

        		name

        		Integration_time

        		 Total integration time

        		 Comment

7.1.2. Observation Groups

 The individual templates are brought together by an observation group. This operates like a simple macro and associates all the necessary parameters for obtaining a group of observations. Each group is assigned a unique identifier within the queue (ID).

An observation group may refer to only one field. A group is treated as a single entity by the queue; that is, if multiple exposures are defined within a group, their status within the group is determined by their total integration and readout times. The telescope may only be repointed in order to generate dithered images on the same field while a group is executed.

An observation group may only refer to one constraints template. That is, all the exposures within the group are subject to the same airmass, sky brightness, transparency and seeing constraints.

Multiple observation and instrument templates may appear within a single group. Thus the investigator may schedule, for example, dithered V and I images within the same field. However, in order to maintain the flexibility of the queue and increase the chances that a programme will be executed and completed, it is in the investigators' interests to make groups as small as possible.

The observation group definition is:
Observation group:

RunID

name

Comment

ForField:

 Field_Template_name

 AccordingTo:

 Constraint_Template_name

 DitherGrid

 Sequence of dithering for exposures in group (arcsec)

Using:

 Instrument_Template_name

 Execute:

Observation_Template_name

 Repeat:

 Repeat_factor

Using:

 Instrument_Template_name

 Execute:

Observation_Template_name

 Repeat:

 Repeat_factor

 .....

End_Group

7.2. Sample Tier 2 Proposal.

This section presents a sample Tier 2 observing proposal the specific example is deliberately very simple.

A short observing programme has been accepted by the Telescope Allocation Committee who have granted the investigator 3 hrs of I-time. In that time, the investigator wishes to obtain images of a single field centered on the north Galactic pole in V, from 18th to 26th magnitude with a signal-to-noise ratio in the anticipated point-source photometry of 20. The investigator also wishes to generate shift-and-add superflats from his data and so will dither his images, and he chooses to accept the preferred CFHT airmass limit of 1.5 for the field.

The investigator also has the following information:
Camera pixel scale

 0.21 arcsec pixel-1

Dark sky brightness at CFHT (V)

 50 photons sec-1 arcsec-2

CFH12k CCD readout noise

 5 electrons pixel-1

CFH12k readout time, full frame, unbinned

 2 min

Poisson noise from the sky will dominate the readout noise by a factor of 10 in approximately 2 minutes. It is assumed that any other noise sources such as dark current, and coherent interference noise are also dominated by sky in this time. A V=18 star reaches the half-saturation level of the detector in 20 seconds (in 0.5" arcsec seeing).

The investigator calulates that the following total integration times will be needed to acheive the required signal-to-noise.

Seeing conditions

Integration time

0.4"

 1.26

0.5"

 1.90

0.6"

 2.67

0.7"

 3.58

0.8"

 4.63

The investigator then elects to require a seeing of 0.55-0.64 arcsec for his observations, and breaks his 3 hours of I-time up as follows:



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