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Putting together FLAMIGOS-2 Observations

This page contains useful information for configuring F2 observations which should help reduce the number of iterations on the Phase II file between the PI and the NGO. It also contains an overview of the required OT observations and components for programs of different types. Before submitting your Phase II program to Gemini, use the F2 Phase II checklist to eliminate common mistakes.

Contents

 


 

F2 Templates

Initially each program contains a template set of observations based on the examples of the OT instrument libraries. The PI should apply these templates to the observations. Please follow this template link with updated template information.

Required OT observations and components

For each type of program, there are different requirements to which OT observations and components the user has to define in the Phase II. The table below gives an overview over the requirements. "Required" means that a Phase II will not be accepted without this type of observation or component being defined. "As needed" means that the user can add this type of observation or component as needed by the science goals of the program. Use the F2 OT library as a source of template and example observations.

Ar arcs mixed with the science data, i.e. taken at night, and any special standard stars are charged towards the program's allocated time. Baseline standard stars, telluric stars, GCAL flats, twilight flats, baseline Ar arcs, and mask images are not charged (see the NIR Baseline Calibrations for more details). The time for the acquisition observations is already included in the science observation overhead. No additional time is charged. However, the acquisition observations have to be defined as separate observations in the Phase II.

Each "Observe" command is given an Observe Class (see more details about Classes).

The details of each of the required observations and components are explained in the sections below.

Observation or Component

Program Type Class
Imaging (details)
Pre-imaging for MOS
MOS (details) Longslit (details)
Science Obs. Required Required Required Science
Offset Comp. As needed As needed As needed N/A
GCAL flats Do not add Required
Mix w/ science
Required
Mix w/ science
Nighttime
Partner
Calibration
Twilight flats Do not add As needed
Separate observation
As needed
Separate observation
Daytime
Calibration
Ar arcs N/A Required
Baseline: Separate observation
Required
Baseline: Separate observation
Daytime
Calibration
Charged if mixed w/ science Charged if mixed w/ science Nighttime
Program
Calibration
Acquisition Obs. N/A Required
Separate observation
Required
Separate observation
Acquisition
If for baseline standard If for baseline standard Acquisition
Calibration
Mask image N/A Required
Separate observation
N/A Daytime
Calibration
Baseline standard stars Do not add Required
Separate observation
Required
Separate observation
Nighttime
Partner
Calibration
Telluric stars
N/A Required Required Partner
Calibration
Special standard stars
Charged
As needed
Separate imaging observation
As needed
Separate longslit observation
Follow requirements for longslit
As needed
Separate longslit observation
Follow requirements for longslit
Nighttime
Program
Calibration

Calculation of overheads

Detailed information about overheads for acquisitions (and re-acquisitions), as well as readout and configuration times can be found on the Overheads page. PIs can now use the calculated planned execution times in the OT as reasonable approximations of the actual time that will be required, with the exception that reacquisitions must be included when integrations times are long. If you do not take this into consideration, it is likely that your Phase II will be overfull. Gemini queue observers will stop executing your program when the allocated time has been depleted, regardless of whether or not there are still unexecuted observations.

If your observation classes are set correctly, the OT will not add any planned time for GCAL flats, twilight flats, baseline Ar arcs, telluric observations or other daytime calibrations (e.g. mask images and Darks). The support staff from your National Gemini Office and your Gemini Contact Scientist will work with you if you have questions about your OT calculated program execution time.

Program Organization

It is recommended that groups be used as much as possible to keep the Phase II organized. Some recommended organizational practices are:

 

  1. Group science observations with their associated acquisition observation(s).
  2. Organize all the time for long observations (more than 2 hours) into a single observation.
  3. Place the required telluric observation (both the before and after the science observation) in the same group as the science observations.
  4. Place all daytime calibrations in a folder called Calibrations
  5. Place time constraints (dates/times, temporal spacing of observations) within the Scheduling Note and within the Timing Windows under Observing Constraints.
  6. Group names within a program should be unique.

 

Imaging observations

All imaging observations should have a dither sequence. The choice of offset will depend on the nature of the science target such that small offsets are suggested for uncrowded and sparse fields and large offsets are recommended for extended and/or crowded fields. We include these two examples in the OT templates. In any event, we recommend that the first offset position should always have p=0, q=0.

GCAL imaging flat observations should be included in the Phase II. So please see this GCAL configurations table for recommended GCAL configurations and exposure times. At this point, we anticipate that the flats not listed will be dome flats. The Gemini staff would take care of preparing suitable dome flats if needed.

Long-slit observations

GCAL flats should be mixed with your science observations. For long observations, add one flat for every 1-2 hours of science exposure time. For observations shorter than one hour, add one flat. Make sure you get flats for all spectral configurations. GCAL flats within these guidelines have class 'Nighttime Partner Calibration' and are not charged to the program. Any additional GCAL flats should have class 'Nighttime Program Calibration' will be charged to the program. Refer to the GCAL configurations for recommended GCAL configurations and exposure times (examples are available in the F2 OT Library).

Ar arcs taken during the day as baseline calibrations. These calibrations are not charged to the program, but the PI has to define them in the Phase II. Define these observations as separate from the science observations and set the class to 'Daytime Calibration'. Make sure the instrument configuration matches the science observation. If you copy the science observation in order to edit it for the Ar arc, make sure to remove the guide star from the target component, remove any science exposures, and change the class. Arcs taken as part of a science longslit observations should have class 'Nighttime Program Calibration' and will be charged to the program. Refer to the for recommended GCAL configurations and exposure times. Also, complete examples are available in the F2 OT Library).

Acquisition observations need to be defined for each longslit target. No extra time is charged for these observations, as the overhead for setting up is already included in the science observation. However, the acquisition observations should be defined as separate observations in the Phase II. In general, we recommend to set up the acquisition sequences such that they include " sky " observations used to perform a sky subtraction during the nighttime acquisition. Only if the object is brighter than H=12 we consider that the " sky " observations are not needed. An acquisition observation for a longslit target should have the following instrument configuration:

 

Same target, guide star and PA as for the science observation
F2 filter closest to the spectroscopic filter
1) For Bright targets (H < 12):
Add a F2 sequence with at least 3 steps
Step1 - FPU: Imaging (none); Detector read mode: Bright Object; Exposure time: 5 sec 
depending of the brightness of the target.
Step2 - FPU: Same longslit as for science; Detector read mode: Bright Object ;
Exposure: 10 sec. This step is used to measure the slit center and in the templates 
includes a small offset. This offset shifts the target away from the slit center. 
This is done so that light from the target does not interfere with the slit center measurement.
Step3 - FPU: Same longslit as for science; Detector read mode: Bright Object;
Exposure: 5 sec depending of the brightness of the target. 
2) For faint sources (H > 12):
Add a F2 sequence with at least 5 steps
Step1 - FPU: Imaging (none); Detector read mode: Bright Object; Exposure time: 10 sec 
depending of the brightness of the target; offsets: small offset in q for sky subtraction.
Step2 - FPU: Imaging (none); Detector read mode: Bright Object; Exposure time: 10 sec 
depending of the brightness of the target; offsets: back to the target with p=0 and =0.
Step3 - FPU: Same longslit as for science; Detector read mode: Bright Object;
Exposure: 10 sec. This step is used to measure the slit center and in the templates 
includes a small offset. This offset shifts the target away from the slit center. 
This is done so that light from the target does not interfere with the slit center measurement.
Step4 - FPU: Same longslit as for science; Detector read mode: Bright Object;
Exposure: 10 sec depending of the brightness of the target; offsets: small offset 
is applied in q. This observation will be used to perform a sky subtraction of the 
next " on-source " observation.
Step5 - FPU: Same longslit as for science; Detector read mode: Bright Object;
Exposure: 10 sec depending of the brightness of the target. 

Class: Acquisition

The science observations should include offsets. As it is the case for imaging, the choice of offset depends on the nature of the source. Thus, for sparse sources we recommend small offsets ( < 15 arcsec) whereas we recommend larger offsets (> 300 arcsec) for crowded and/or extended sources.

Twilight flatfields are only taken for longslit observations of extended targets. No extra time is charged for these observations. However, the twilight flatfields should be defined as separate observations in the Phase II. Make sure the instrument configuration matches the science observation. If you copy the science observation in order to edit it for the twilight flatfield, make sure to remove the guide star from the target component, then edit the science exposures to have only one exposure with 30sec exposure time and class 'Daytime Calibration'. If doing small wavelength dithers to fill in the chip gaps then only one wavelength setting will have a twilight flatfield taken, so you need to select the wavelength at which you want the twilight flatfield. If there are no twilight flats in the submitted Phase II for a longslit programs, it will be assumed that they are not needed.

Standard Stars

Imaging standards sufficient to obtain flux calibration at the 5% level are base calibrations and are taken by Gemini staff. If better calibration is needed then observations for additional standards must be included in the Phase II. The class should be 'Nighttime Program Calibration' and the time will be charged to the program. The PIs should also consider that given the F2 FOV at least a handful of " 2MASS " sources are probably included in the science observations.

Telluric standards used to cancel telluric (atmospheric) absorption features in the data are baseline calibration and are not charged to the program. Observations for these baseline telluric standard need to be defined in the Phase II including one observation that can be executed " before " and " after " the science observation. All telluric standards are taken in longslit mode using the same slit as for longslit science observation or the longslit closest in width to the width of the MOS slitlets. The observations needed are:

  1. Longslit acquisition with class 'Acquisition Calibration.' The longslit acquisition sequence for all telluric stars use the Bright Object read mode to image the field, measure the slit center, and to confirm if the target is within the slit.

  2. Spectroscopic observation with class 'Nighttime Partner Calibration'. Please select an exposure time long enough to obtain good signal-to-noise (i.e., 120 seconds). For longslit the instrument configuration should match the science observations.
  3. Daytime arcs with class 'Daytime Calibration'. All other guidelines for daytime arcs apply.

Additional spectroscopic standards --- absolute flux standards, velocity standards, line-strength standards, etc.--- must also be defined. If absolute flux calibration is desired then the 8-pix longslit should be used.

The guidelines are the same as for normal longslit observations except that the classes for the on-sky observes should be 'Nighttime Program Calibration'. The associated acquisition observations should have class 'Acquisition' and any GCAL flats are still 'Nighttime Partner Calibration'. The time will be charged to the program. Daytime arcs are always 'Daytime Calibration' and are not charged.

Observations that will be split over several nights

Some observations cannot be completed within one night and therefore will require multiple acquisitions. Exactly how such an observation will be split in several observations over several nights will normally be determined by the Gemini Staff at the time of scheduling the night's observations (see the overheads page for guidelines). The user should define such observations as one observation, and add a comment to explain which assumptions were made about the number of reacquisitions and the resulting overheads.

Observing conditions

The observing conditions are specified as percentiles in image quality, cloud cover, sky background (and water vapor). Refer to the observing conditions page for details about the meaning of these percentiles. If the percentiles do not give sufficient information to the queue observer about the observing conditions required for a given observation, the user should add a comment to the observation detailing the observing conditions, e.g. "Need fwhm better than 0.75 arcsec in r". Such comments cannot be used to request better observing conditions than approved by the time allocation process.

Baseline calibrations

F2 Baseline calibrations that are not specifically mentioned above should not be included in the Phase II programs prepared by the users.

MOS observations

Programs that contain MOS observations require masks designed from F2 pre-imaging taken for all separate fields. PIs with MOS programs are encouraged to submit designs as soon as possible.

MOS programs should contain the final Phase II information for the pre-imaging observations when it is first submitted. The MOS observations should also be included in the program. Small adjustments to the MOS observations are allowed when the mask design has been done. However, the pointing and PA of your target cannot be changed between the pre-imaging and the MOS observations. PIs with MOS programs will be contacted by Gemini when the pre-imaging data is available. Revised Phase II MOS programs and mask designs should be submitted asap. See mask deadlines (linked from the relevant semester's OT instructions page) for Classical runs. Mask designs should be submitted directly through the OT, instructions will be sent to you when your pre-imaging is available.

PIs with pre-imaging from previous semesters should use the mask naming scheme (below) for their current program. Upload the original pre-imaging through the OT so that masks can be checked. Please also include a note listing the previous program number.

The focal plane unit for the MOS observations should be specified as Custom Mask MDF, and the field for the name should contain your program ID and a running number for the mask within the program, e.g. for program GN-2014A-Q-20 the mask names should be GN2014AQ020-01 and GN2014AQ020-02 for the first and the 2nd mask, respectively. Note the leading zero on the program ID and mask numbers.

The total time used for both pre-imaging and MOS observations must not exceed the allocated time.

It is recommended that pre-imaging observations are dithered by 5 arcsec in both directions, e.g. 4 exposures in a square pattern with size 5 arcsec will work ok. Pre-imaging exposures should be taken in the broad band filter closest to the central wavelength coverage of the MOS observations.

GCAL flats should be mixed with your science MOS observations. For long observations, add one flat for every 1-2 hours of science exposure time (it is important to take GCALflats frequently for spectral observations at long wavelengths because of fringing, and less critical if observing in the blue). For observations shorter than one hour, add one flat. Make sure you get flats for all spectral configurations. GCAL flats within these guidelines have class 'Nighttime Partner Calibration' and are not charged to the program. Any additional GCAL flats should have class 'Nighttime Program Calibration' and will be charged to the program.

Ar arcs taken during the day are baseline calibrations. These calibrations are not charged to the program, but the PI has to define them in the Phase II. Define these observations as separate from the science observations and set the class to 'Daytime Calibration'. Make sure the instrument configuration matches the science observation. If you copy the science observation in order to edit it for the Ar arc, make sure to remove the guide star from the target component, remove any science exposures, and change the class. Arcs taken as part of a science MOS observations should have class 'Nighttime Program Calibration' and will be charged to the program. Refer to GCAL configurations for recommended GCAL configurations and exposure times (examples are available in the F2 OT Library).

Mask images are taken of all MOS masks before they are used for science. These calibrations are not charged to the program, but the PI has to define them in the Phase II. Define these observations as separate from the science observations. The instrument configuration should be as follows:

 

No guide star
J filter
Detector: Bright Object read mode
Class: Daytime Calibration
Define a GCAL flat using the appropriate information
from the following webpage.

 

For a complete example see the F2 OT Library.

Acquisition observations need to be defined for each MOS mask. No extra time is charged for these observations, as the overhead for setting up is already included in the science observation. However, the acquisition observations should be defined as separate observations in the Phase II. An acquisition observation for a MOS mask should have the following instrument configuration:

 

Same target, guide star and PA as for the science observation
F2 filter closest to the wavelength setting used 
FPU should be Custom MDF mask and the same mask as for the science observation
Exposure time: 30-90 sec depending on the brightness of the acquisition stars
Detector: Bright Object read mode
Add an "observe", and edit it to show 4 exposures with class Acquisition

 

Broad band filters cannot be used for MOS acquisitions. Narrow band filters should in general not be used for MOS acquisitions. See also the example in the F2 OT Library.