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- Split center_position and observing_band fields
- Retaining image size data (the VO _xel fields)
- Add fields for spectral resolution, physical data description, and spacial region information
- Determination and acquisition of time-domain information.
Below is the proposed new table structure for Images and Image Products in the metadata database. There are 3 classes of columns below: initial columns, new columns, columns adapted from (previous_column). Depending on the design decisions and the behavior or CASA, some of these fields could be removed (t_xel, em_xel, pol_xel) if they they will be invariant.
Images Database Table:
| Column Name | VO Equivalent | Source | Comments |
|---|---|---|---|
| target_name | target_name | OBJECT Keyword | |
| center_ra (center_position) | s_ra | Center of Ra Axis | |
| center_dec (center_position) | s_dec | Center of Dec Axis | |
| field_of_view | s_fov | Average of NAXISn*CRDELn of the Spacial Axes | |
| spacial_region | s_region | Derived from Spacial Data | STC-S String Defined in the TAP (Dowler, et al 2010) |
| ra_element_count | s_xel1 | Relevent NAXISn Keyword | |
| dec_element_count | s_xel2 | Relevent NAXISn Keyword | |
| spacial_resolution | s_resolution | Average of CRDELn of the Spacial Axes | |
| image_stop_time | t_max | Temporal domain information for an image is dependent upon the observation(s) used in its generation. Some controlling process (Like Vlass Manager, whatever imaging pipeline we create, and any image manipulation software we use) will need to supply it. Since we are intending to store cubes as a collection of images, t_xel will can be removed and automatically returned as 1 for any individual image. | |
| image_start_time | t_min | ||
| image_integration_time | t_exptime | ||
| temporal_element_count | t_xel | ||
| frequency_min(observing_band) | em_min | Minimum of Spectral Axis | The spectral information is recoverable from the FITS header, and will identify the observing receiver(s), and total bandwidth processed for the image. |
| frequency_max (observing_band) | em_max | Maximum of Spectral Axis | |
| spectral_resolution | em_res_power | Spectral CRDELn Keyword | |
| spectral_element_count | em_xel | Spectral NAXISn Keyword | |
| image_units | o_ucd | BTYPE & BUNIT Keywords | Description of the physical quantity measured in the image |
| polarization_id | pol_states | Deduced from NAXISn Keyword | More clarity is required for polarization information, as the exemplar files (Vlass quicklook images) have limited information available. Some method of conveying information about images (in CTYPE/CUNIT keywords, or via outside information) is required to get anything other than an overly simplistic assumption (NAXISn = 1 means Stokes I and NAXISn = 4 means Full Stokes Parameters). |
| polarization_element_count | pol_xel | Relevent NAXISn Keyword | |
| telescope | instrument_name | TELESCOP Keyword | The observing instrument(s) |
| image_id | obs_id | automatically generated | Unique Identifier for the Image |
| file_id | automatically generated | link to information about the physical file | |
| max_intensity | These values are can be determined from the data portion of the image file in conjunction with the BSCALE & BZERO keywords. The library which is used for FITS interaction for ingestion can perform these calculations, but no information about the speed of results is yet available. | ||
| min_intensity | |||
| rms_noise | |||
| thumbnail | weblog, a PNG with identical name |
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| Column Name | VO Equivalent | Source | Comment |
|---|---|---|---|
| image_set_id | obs_id | automatically generated | Unique Identifier for the Image Set |
| project_code | Required to facilitate Ingestion | ||
| configuration | This will need to hold the entire list used for the imaging. | ||
| collection_name | obs_collection | ||
| calib_level | calib_level | As defined by the VO in their 0-4 system |
VO ObsCore Remaining Fields:
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