giant.catalogs¶
This package provides access to star catalogs for doing stellar OpNav and calibration in GIANT.
Description¶
A star catalog in GIANT is primarily responsible for telling us the location of stars in the inertial frame (at a specific date), the uncertainty on that position (if available), and the magnitude of the star (or how bright it is). This data is then packaged into a Pandas DataFrame with specific columns from which GIANT can determine this information.
To get this information, we can use an existing star catalog, like the Tycho 2 and UCAC4 catalogs, or we can use
the provided GIANT catalog, which is a merging of the Tycho 2 and UCAC4 catalogs into an efficient SQL format. For
most OpNav scenarios the default GIANT catalog is sufficient, as it includes stars down to about 18th visual magnitude
and is very efficient for querying data, making stellar OpNav and calibration proceed faster. In some cases, you may
have other requirements for your catalog (perhaps dimmer stars or you would like to use a different magnitude for your
stars) in which case you can rebuild the GIANT catalog using the script build_catalog. Just be
aware that rebuilding the catalog will require you to download the UCAC4 and Tycho 2 catalogs to your computer,
which can take up significant space and can take a long time to download.
Use¶
Star catalogs in GIANT are accessed through a class, which queries the data from wherever it is stored (normally
locally on your machine.) Typically, you will use the method query_catalog() with filtering options
for right ascension, declination, and magnitude. This will then return a pandas dataframe with the requested data with
columns of GIANT_COLUMNS, which can then be used however you need. Some catalogs may also provide a method
to return the full dataset for each star (what the full data set it varies from catalog to catalog). You will need
to see the documentation for the particular catalog you care about if you need this information.
If you need to project the queried stars to get their location on an image, then you can use
project_stars_onto_image(), from the catalogs.utilities package, which will give you the location of
the stars in pixels.
If you want to add a new star catalog as a source for GIANT, then first reach out to the developers. We may already
be working on it. If this doesn’t work out, you can also see the meta_catalog module documentation for more
details on how to define your own catalog class.
In addition to the Catalog classes provided in this package, there is also the catalogs.utilities module
which provides utilities for unit/epoch/representation conversions and applying proper motion to star tables. These are
generally useful functions so you may occasionally find yourself using tools from this module as well.
Modules
This module defines the abstract base class (abc) for defining GIANT star catalogs that will work for Stellar OpNav and camera calibration as well as the column definitions for the dataframe used to contain stars in GIANT. |
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This module defines the interface to the GAIA star catalog. |
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This module defines the interface to the Tycho 2 star catalog. |
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This module defines the interface to the UCAC4 star catalog. |
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This module provides a class for interfacing with the USNO GNC (Guidance Navigation and Control) star catalog. |
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This submodule provides utility constants and functions for working with star data in GIANT. |
