Examples

In the examples below, img is either a string with the filename of a Roman ASDF file or a Roman datamodel ImageModel.

1. To run TweakReg in a Python session with the default parameters:

   from romancal.tweakreg.tweakreg_step import TweakRegStep
   step = TweakRegStep()
   step.call([img])
   

   Note

   If the input is a single Roman DataModel, either step.call([img]) or step.call(img) will work. For multiple elements as input, they must be passed in as either a list or a ModelContainer.

2. To run TweakReg in a Python session on an association file with the default parameters:

   from romancal.tweakreg.tweakreg_step import TweakRegStep
   step = TweakRegStep()
   step.call("asn_file.json")
   

3. To run TweakReg on a Roman’s exposure with default astrometric parameters and save the absolute catalog data:

   from romancal.tweakreg.tweakreg_step import TweakRegStep
   step = TweakRegStep()
   step.save_abs_catalog = True # save the catalog data used for absolute astrometry
   step.abs_refcat = 'GAIADR3' # use Gaia DR3 for absolute astrometry
   step.catalog_path = '/path/for/the/abs/catalog' # save the Gaia catalog to this path
   step.call([img])
   

4. To run TweakReg using a custom source catalog with the default parameters:

   • make sure the source catalog is in one of the supported formats. The file content below is an example of a valid catalog (ascii.csv format):

     $ cat ref_catalog_1
     
     x,y
     846.1321662446178,945.839358133909
     664.7073537074112,1028.4613139252003
     1036.160742774408,642.3379043578552
     935.8827367579428,594.1745467413945
     1491.9672737821606,1037.4723609624757
     735.1256651803337,1410.2791591559157
     1358.2876707625007,651.7112260833995
     526.4715950130742,751.745104066621
     1545.082698426152,703.601696337681
     374.9609365496525,972.6561578187437
     1110.3498547121228,1644.2214966576498
     341.18333252240654,891.4733849441861
     820.0520846885105,312.0088351823117
     567.7054174813052,386.8883078361564
     1447.356249085851,1620.3390168916592
     1400.4271386280673,1674.3765672924937
     1681.9744852889235,571.6748779060324
     959.7317254404431,197.8757865066898
     1806.3360866990297,769.0603031839573
     487.1560001146406,257.30706691141086
     1048.7910126076483,85.36675265982751
     1075.508595999755,29.085099663125334
     

   • create catfile containing the filename of the input Roman datamodel and its corresponding catalog, one per line, as shown below

     $ cat /path/to/catfile/catfilename
     
     img1 ref_catalog_1
     img2 ref_catalog_2
     img3 ref_catalog_3
     

   The content of catfile will allow TweakReg to assign the custom catalog to the correct input Roman datamodel. In the example above, source catalog ref_catalog_1 will be assign to img1, and so on.

   Now we can execute the following:

   from romancal.tweakreg.tweakreg_step import TweakRegStep
   step = TweakRegStep()
   step.use_custom_catalogs = True # use custom catalogs
   step.catalog_format = "ascii.ecsv" # custom catalogs format
   step.catfile = '/path/to/catfile/catfilename' # path to datamodel:catalog mapping
   step.call([img])