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GSA Search and Download Instructions

This page describes how to search and download the baseline calibrations from the GSA. This includes: 

  1. Flats for a range of nights, one or more filters. The standard flat field frames for GSAOI calibration are taken as dome flats. Optionally, twilight flats are available for the broad band filter suite (Z, J, K, Ks, and Kp) and GCAL flats (on and off) may also be available for the narrow band filters except the CO 2.360µm.
    1.  domeflats (ON and OFF)
    2. Twilight flats
    3. Gcal flats
  2. Darks for a given exposure time and/or read mode
  3. Photometric standards for a given observing night, one or more filters
  4. Information on other calibrations (taken from a programme - which may be public, which are not)
  5. Identifying frames with ROI (Region of Interest) read-out.

GSA PAGES CHANGED 2013-08-01:

Please note that as of August 01, 2013, the layout of the GSA pages at CADC has changed from what is shown in the pictures below. The functionality remains the same, and the instructions and links in this page have been updated to reflect the new structure. We will update the pictures soon.

The Complete Catalogue GSAOI Standard Query Form:

The Standard Query form for GSAOI is shown in the picture below. A short definition for each field is available by selecting the link in the field name. Help with the form itself, and with the different query constraints can be accessed under the Help menu in the left (Form Help)

GSAOI Standard query form

 

The first two sets of option (Retrieval Options and Target Information) are standard for all Gemini facility instruments. The user, however, must be aware that the Integration Time field is a meta-generated database entry, and corresponds to the total time on-source for the data frame. As such, its definition varies from instrument to instrument (for example, in the Near-IR, Integration time = Exposure time x coadds). IMPORTANT: for GSAOI, the coadds are actually AVERAGED, NOT SUMMED. So the total number of ADU (or e-) in a frame has alredy been divided by the number of coadds. This is relevant for photometric calibration: the integration time on source is EXPTIME x COADDS, but the exposure time to obtain e-/sec/pixel is EXPTIME only (in other worlds, a frame of 20sec x 3 coadds correspond to 60sec on source, but to obtain the flux per unit of time (seconds), the final processed image should be divided by 20, not 60). 

The Instrument Constraints set of options contains two fields that are GSAOI specific: GEMSASTR and GWFSCFG. In addition, users should keep in mind that, for GSAOI, the LNRS keyword actually reflects the number of non-destructive (low noise) reads instead of the number of Fowler samples (as is for most of the remaining near-IR instruments in the GSA). This way, LNRS = 2 correspond to 1 Fowler sample (1 read at the start, 1 at the end), while 8 Fowler samples would be LNRS=16.

A note on the Region of Interest (CCDSEC): some early sets of dome flats (Dec 2012-Feb 2013) were taken with two different sections: full frame and  a 1024 subarray (see the Identifying frames with ROI section below for an explanation on the sub-array formats). Since then, the GSAOI Gemini/IRAF package has been updated to use full-frame calibrations for all the formats. The different ROI modes are not available in the public OT component, and are currently used for the photometric standards (non-AO).

The GEMSASTR keyword represent the astrometric correction requested in the GeMS configuration. Currently only the Regular mode is being supported.

The GWFSCFG keyword is another meta-generated database entry, and is meant to represent the guide star configuration used in the observation. GSAOI+GeMS use up to four natural guide stars, which can be selected in any combination between 3 Canopus (optical) WFS and 3 GSAOI ODGW (near-IR). The best AO correction is obtained with the full set of four, either 3 CWFS + 1 ODGW or 1 CWFS + 3 ODGW. To simplify, the modes were called 3+1 or 1+3, respectivelly (and subsequently 2+1, 1+1, 1+2). Guiding without an ODGW is possible (3+0, 2+0, 1+0) as is guiding with the PWFS1 only (and therefore no AO correction).

 


Searching for DOMEFLATS in the GSA:


This example assumes a search is being done for dome flats for a programme with observations in filters [FeII], J, and H, spread over the dates of 2013-02-13 to 2013-03-31.

 

  • Go to the GSA main access page: http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/gsa/
  • On the left pane, select Search Complete Catalogue under the GSA queries menu.

 


GSA top page
  • Select GSAOI on the right hand list and click Continue to query form.

 

GSAOI Standard Query 

 

  • Define the query:
    • 1. Under Retrieval Options, select
      • Order by: Original File Name
      • Return: 500 rows
  • 2. Under Target Information:
    • Define what you are looking for:
      • Target Name: ==Domeflat
      • Resolver: Gemini Name
  • Define where you want to look for it (in this case the baseline calibration programmes):
    • Science Program: use the drop down menu to set it to Contains (case insensitive), then type GS-CAL2013 in the field.
  • Now define the date interval over which to search:
    • UT Date: 2013-02-01..2013-04-15
    • Unselect the Release Date, Observation Type, and Observation Class items to generate a cleaner table. The GEMASTR and GWFSCFG constraints also can be unselected.
  • 3. Click the Search button to execute the search.

 

GSAOI Query Domeflats 1

The resulting table will contain ALL domeflats taken in the period 2013-02-01 to 2013-04-15. The next step is to select the filters of interest (Z, J and H) and then click Download Datasets. The use of the "==" qualifier (requiring an exact match) for the target name helps to avoid the query timing out.

To restrict the search to only one filter, say H, follow steps 1 and 2 as described above, but add one more constraint:

2.5. Under Instrument Constraints, set:

 

  • Filters: ==H_G1103

 

GSAOI Domeflats query 2


Note that the "Filters" field uses the image header content, and is a combination of the two filter positions (for GSAOI, one is a colour filter, the other is always Clear -- which the GSA search has been programmed to ignore). The exact name of each filter can be extracted from the image header under the keywords FILTER1 or FILTER2. Alternativelly, an unconstrained seach can be done using the unique identifier provided as the Gemini Filter Name in the Instrument filter table. In this case, the query would use:

2.5 Under Instrument Constraints, set:

 

  • Filters: G1103

This will search for the string G1103 within the filter name (it is the equivalent to *G1103*). Alternativelly, one can search for the J filter:

 

  • Filters: J_G1102
or
  • Filters: G1102

or, for an exact match:

 

  • Filters: ==J_G1102

And it will look like this:

 

GSAOI Domeflats query 3

 

And if one actually tries the query above, the result is:

Query result J domeflats

 

As with many of the narrow band filters, the [FeII] filter name is simplified in the header:

 

  • Filters: FeII_G1118
or
  • Filters: G1118

or, again (note that the FeII filter is in wheel 2):

 

  • FIlters: ==FeII_G1118

 

DOMEFLATS OFF (projector lamps turned off, only ambient light/heat reaching the instrument).

To search for "dome flats off", simply replace the Target name above by  (note the capitals for the exact search).

 

  • Target Name: ==Domeflat OFF

 

Flats OFF are taken with the telescope pointing to the same position in the dome (there is no "white screen") as the "ON" flats, but the projector lights turned off. They should correspond to thermal emission from telescope structure/ambient only. As far as we could determine, the flats OFF do not contain any spatial structure. The counts are at the noise (dark) level in Z, J and H (and all narrow band filters in these wavelegths), and reaches 1000-2000 ADU in K (lower in Ks and K').  The only narrow band filter in the K band that presents some level of counts above noise is the  CO Δv=2 at 2.360μm.

 


Searching for TWILIGHT FLATS in the GSA:

To search for twilight flats, follow the same instructions as above, but use:

2. Under Target Information:

 

  • Target Name: ==Twilight

And it will look like:

 

GSAOI Twilight query 1

 


IMPORTANT
: for both Domeflats and Twilight flats, the naming convention is relevant. Please verify the spelling and capitalization: domeflat or twilight (all lower case) will not work if using the exact match (==) query.

 



Searching for GCAL FLATS in the GSA:

 

GCAL flats are not part of the baseline calibration set, but can be taken upon request if defined in the PhaseII. These frames use the facility calibration unit GCAL and therefore will be obtained with the telescope pointing at the same position as the science target but the light will not be passing through the GeMS (AO) optical bench. True usefulness of the GCAL flats (vs Domeflats) is still to be determined.

GCAL flats can be obtained for all broad and narrow band filters EXCEPT H, K, Ks, K' and CO 2.36mu. If a search on GCAL flats turns up frames in these filters, users should be aware that they have been most likely taken for engineering or instrument monitoring purposes and should not be used for science data reduction. As of this stage of commissioning, domeflats and/or twilight flats should be preferred over GCAL for all filters.

This example assumes a search is being done for GCAL Flats for a programme with observations in the Z filter, spread over the dates of 2013-02-01 to 2013-04-15.

 

  • Go to the GSA main access page: http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/gsa/
  • On the left pane, select Search Complete Catalogue under the GSA queries menu.

 

GSA top page
  • Select GSAOI on the right hand list and click Continue to query form

GSAOI Standard Query 

 

  • Define the query:
    • 1. Under Retrieval Options, select
      • Order by: Original File Name
      • Return: 500 rows
  • 2. Under Target Information:
    • It is best not to constraint the target name. GCAL flats are searched by observing class, rather than name.
    • Define where you want to look for it
      • Again, the programme ID is best left unconstrained. GCAL flats are nighttime partner calibrations, and as such, not subject to proprietary period. An unconstrained search may turn up other flats using the same configuration (although not pointing at the same position). If specific calibrations are required, then use the same Programme ID as the science data.
    • Now define the date interval over which to search:
      • UT Date: 2013-02-13..2013-03-31
      • Unselect the Release Date, and Observation Class items to generate a cleaner table. The GEMASTR and GWFSCFG constraints also can be unselected.
  • 3. Click the Search button to execute the search.

 

GSAOI Query GCAL flats 1

The resulting table will contain ALL GCAL flats taken in the period 2013-02-01 to 2013-04-15. The next step is to select the filters of interest (Z) and then click Download Datasets.

To restrict the search to return only the desired filter (Z_G1101), follow steps 1 and 2 as described above, but add one more constraint:

2.5. Under Instrument Constraints, set:

 

  • Filters: ==Z_G1101

Note that the "Filters" field uses the image header content, and is a combination of the two filter positions (for GSAOI, one is a colour filter, the other is always Clear -- which the GSA search has been programmed to ignore). The exact name of each filter can be extracted from the image header under the keywords FILTER1 or FILTER2. The use of the "==" qualifier (requiring an exact match) for the filter configuration helps to avoid the query timing out.

Alternativelly, an unconstrained seach can be done using the unique identifier provided as the Gemini Filter Name in the Instrument filter table. In this case, the query would use:

 

2.5 Under Instrument Constraints, set:

 

  • Filters: G1101

This will search for the string G1101 within the filter name (it is the equivalent to *G1101*).

 


Searching for Darks in the GSA:


This example assumes a search for darks in the period 2013-02-01 to 2013-03-30, with the following configuration: Very Faint Object readout mode, 30sec exposure time, 3 coadds. The examples will go from the more generic search to the very specific one.

 

  1. 1. Search for all darks in a certain time period.
  2. 2. Search for all darks in a certain time period using Very Faint Object read mode.
  3. 3. Search for all darks in a certain time period with 60sec exposure time, 3 coadds and Very Faint Object read mode.

Reminder: For GSAOI, the LNRS keyword actually means the number of Low Noise Reads, and NOT the number of Fowler samples. This means that LNRS=2 is 1 read at the start of the exposure and one at the end, thus 1 Fowler sample, while LNRS=16 is 8 reads at the start and 8 at the end, thus 8 Fowler samples.

Example 1: Search for darks based on observing dates alone.

 

  • Go to the GSA main access page: http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/gsa/
  • On the left pane, select Search Complete Catalogue under the GSA queries menu.

 

GSA Top page

  • Select GSAOI on the right hand list and click Continue to query form.

 

GSAOI Standard query

 

  • 1. Under Retrieval Options, select
    • Order by: Original File Name
    • Return: 500 rows
  • 2. Under Target Information:
    • Leave Target Name blank. Darks are searched by observation type, not name.
    • Since darks are daytime calibrations, in this case it is best not to restrict the kind of programme being searched on. This way, you may be able to find extra darks taken for other queue programmes.
    • Define the date interval over which to search:
      • UT Date: 2013-02-01..2013-03-30
    • Select Observation Type = Dark (from the drop down menu)
    • You may want to unselect the Science Program, Release Date, Observation Class, and Filters items to generate a cleaner table. The GEMASTR and GWFSCFG constraints also can be unselected.
  • 3. Click the Search button to execute the search.

 

GSAOI Darks query 1

The resulting table will contain ALL darks taken in the period 2013-02-01 to 2013-03-30. The next step is select the exposure time/coadds/read mode of interest, then click Download Datasets.

 

Example 2: Search for darks in a given period of time, for a specific read mode (very faint object)

 

  • Follow the same instructions as the previous example for steps 1 and 2.
  • 3. Under Instrument Constraints, select:
    • LNRS: ==16
    • You may want to unselect the Science Program, Release Date, Observation Class, and Filters items to generate a cleaner table. The GEMASTR and GWFSCFG constraints also can be unselected.
  • 4. Click the Search button to execute the search.

 

GSAOI Darks query 2


The resulting table will contain the darks taken in the period 2013-02-01 to 2013-03-30, and using the Very Faint Moder readout (LNRS=16) . The next step is select the exposure time/coadds of interest, then click Download Datasets. The use of the "==" qualifier (requiring an exact match) for the LNRS helps to avoid the query timing out.

Example 3: Search for darks in a given period of time and using very faint object mode, for a specific exposure time (60sec) and coadds (3)

 

  • Follow the same instructions as the previous examples for steps 1 and 2.
  • 3. Under Instrument Constraints, select:
    • EXPTIME: 60.
    • COADDS: ==3
    • LNRS: ==16
    • You may want to unselect the Science Program, Release Date, Observation Class, and Filters items to generate a cleaner table. The GEMASTR and GWFSCFG constraints also can be unselected.
  • 4. Click the Search button to execute the search.

 


GSAOI Darks Query 3

 

The resulting table will contain the darks taken in the period 2013-02-01 to 2013-03-30, with exposure time 60 sec, three cooads, and using the Very Faint Moder readout (LNRS=16). The next step is select the frames of interest if it is the case, then click Download Datasets. The use of the "==" qualifier help to avoid the query timing out.

 



Searching for Photometric Standards in the GSA:

This example assumes a search for Photometric Standards for the night of 2013-03-21 UT (file prefix S20130321S, Calibration programme ID GS-CAL20130321), all available filters. Please see the description of the photometric standard observations in the Baseline Calibrations page in order to understand when and how they are observed.

 

  • Go to the GSA main access page: http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/gsa/
  • On the left pane, select Search Complete Catalogue under the GSA queries menu.

 

GSA Top page

 

  • Select GSAOI on the right hand list and click Continue to query form.

 

GSAOI Standard query
  • 1. Under Retrieval Options, select
    • Order by: Original File Name
    • Return: 500 rows
  • 2. Under Target Information:
    • Leave Target Name blank.
    • Define where you want to look for it (in this case the baseline calibration programme for that specific night):
      • Science Program: use the drop down menu to set it to Matches (case sensitive), then type GS-CAL20130321 in the field. Note that the query will require an exact match, so capitalization is relevant.
    • Select Observation Type = Object (from the drop down menu)
    • Select Observation Class = partnerCal (from the drop down menu)
    • You may want to unselect the Datalabel and Release Date items to generate a cleaner table. The GEMASTR constraint can be unselected as well.
    • We expect to be routinely observing the GSAOI Baseline Photometric standards guiding with either PWFS1 or CWFS3. So, if the search above returns spurious frames, one extra option is to select GWFSCFG = PWFS1 or "1+0" (from the drop down menu), in order to further restrict the query. 
    • If looking for standards over a time interval (for example, 20130321UT +/- 5days), use:
      • Science Program: Contains (case insensitive) and type GS-CAL2013 in the field
      • UT Date: 2013-03-16..2013-03-26
  • 3. Click the Search button to execute the search.

 

GSAOI Photometric standards query 1

 

The resulting table will return all frames corresponding to nighttime calibrations (Observation Class = Partner Cal) that are not Darks or GCAL Flats (Obsevation Type = Object). At the time of writing, the only thing left should be the standards. If not, the CWFSCFG = PWFS1 (or 1+0) should do the trick.

The next step is select the frames of interest (e.g., for a given filter), then click Download Datasets

Here is an example of the result, for the night of 2013-02-28:

 

Query result for PhotStds

 


 

Searching for Calibrations other than the Baseline set:

 

1. Darks taken upon request for a specific a queue programme will be public (as these frames are Daytime Calibrations). The search described above will include those. Pending further evaluation on the stability of the dark frames, the team is considering the possibility of obtaining a "library" of darks covering different exposure times/read modes. If that is the case, those will be picked by the above searches. If we decide to go that way, this page will be updated with specific information.

2. Although they are not in the baseline set, and will be taken only if requested, GCAL Flats taken during the night will be public.

3. Any other nighttime calibration obtained upon request (PSF standard fields, special calibration fields, etc) will be subject to the standard proprietary period (18 months).

4. There is currently no provision to make available through the GSA any other ancillary information from GeMS (e.g., ODGW streams). These need to be requested by the user and arrangements made directly with the Gemini Contact Scientist.

5. Anything else that I haven't figured out yet, but I'm sure the users will.

 




Searching for Calibrations using ROI (Region Of Interest) readout:

 

The GSAOI detectors allow for three different Region of Interest (ROI) read out configurations: Full frame, ARRAY and CENTRAL.  Only Full Frame is currently available in the external (public) OT, with the smaller ROIs still being evaluated for commissioning. The main advantage of the ROIs is to shorten the minimum exposure time (by reducing the readout overhead), thus allowing for observation of brighter targets. On the other hand, they have several practical drawbacks for the observation definition (smaller FOV, variable size gaps). 

As of the current stage of commissioning, it is believed that full frame calibrations (flats of all kinds, darks) can be used to process frames taken using any of the smaller ROIs. The GSAOI Gemini package has been designed to properly derive the overlapping region and to avoid combining frames obtained with different ROIs. 

The Full Frame ROI results in each of the detectors being read in full (2048 x 2048 pix), and the final mosaic is 4090 x 4090 pix, plus the gaps:

 

GSAOI full frame

 

The ARRAY NxN mode  - where N = 64, 128, 256, 512 or 1K - consists in reading a NxN sub-array centered in each of the four detectors (left panel in the figure below shows ARRAY 1K). In this mode, the size of the gaps is variable.  The CENTRAL NXN mode - where N=64, 128, 256, 512, 1K or 2K - consists in reading a NxN sub-array centered in the middle of the mosaic (right panel in the figure shows CENTRAL 1K). In this mode, the size of the gaps is the same as for full frame.

 

GSAOI ROI ARRAY and CENTRAL 1K

 

In the GSA search page, the ROI mode can be identified, or searched for, using the CCDSEC keyword. This keyword is present in each extension, and any of the extensions can be searched, but if left unconstrained, the output table will show the value of CCDSEC in extension [1] (Detector #1 - the bottom-right one in the mosaic). Note that while in ARRAY mode the CCDSEC will be the same for all extensions, this is not the case in CENTRAL mode.

The search below shows an example for a set of ROI DOMEFLATS, using ARRAY 1K, CENTRAL 1K, CENTRAL 512 and ARRAY 512. In full frame mode, CCDSEC will always correspond to the full detector ([1:2048,1:2048]).

 

GSAOI ROI Search 1


The resulting output/download table will be the following:

 

GSAOI ROI Search 2