gaia¶
This module defines the interface to the GAIA star catalog.
Catalog Description¶
The GAIA is a (nearly) complete sky survey of over 1.8 billion stars with 1.46 billion including proper motion solutions. It is generally very accurate for both positions and magnitudes and is mostly complete between magnitudes 3 and 20.
To access the GAIA catalog, GIANT uses the astroquery TAP+ interface
(https://astroquery.readthedocs.io/en/latest/gaia/gaia.html) to retrieve the information from the web. Since the
catalog is still in development this is the best way to ensure you have the most current solutions. Alternatively,
if you need more speed or are working in an environment where you cannot access the web, you can use the function
build_catalog() to download a subset of the catalog to a local HDF5 file and then point the class to this file.
Use¶
The GAIA catalog can be used anywhere that a star catalog is required in GIANT.
It is stored on the internet in a TAP+ service which allows querying the results and returning them to the machine.
Since the GAIA catalog is still being revised as more data becomes available, GIANT by default queries to this service
rather than having a local copy of the catalog (also the catalog is huge!!!). As mentioned previously, if this
doesn’t work for you for whatever reason, you can use the build_catalog() function to download a local copy of
the catalog in GIANT format and then provide the catalog_file argument to the class constructor to use this rather
than live queries.
Once you have initialized the class, then you can access the catalog as you would any
GIANT usable catalog. Simply call query_catalog() to get the GIANT records for the stars as a
DataFrame with columns according the GIANT_COLUMNS.
Note that the epoch for the astrometry solutions in the GAIA catalog changes with each new release. GIANT tracks these for you and handles them appropriately, but be aware of this if you are using the catalog data directly. Also note that since in GIANT we primarily care about stars for attitude/calibration purposes, we filter out stars from the GAIA catalog which have questionable solutions or for which there is missing data. If you need access to everything in the catalog consider the astroquery api discussed previously. For more information about the GAIA catalog refer to https://www.cosmos.esa.int/web/gaia-users/archive.
Classes
This class provides access to the GAIA star catalog. |
Function
Blends groups of stars together into a single "apparent" star as viewed by a camera. |
|
Build a local GIANT catalog: |
|
This identifies possible star pairs based on separation angle. |
Constants
This specifies the GAIA data release to use when querying the TAP+ service. |
|
This specifies the default location of the HDF5 database file that contains the data for this catalog. |
