3. Glossary


Package distributed with the DRAGONS meta-package. astrodata is used to open datasets and provide an uniform interface to the data and the metadata (eg. headers) regardless of whether the file on disk is a FITS file or some other format, whether it is a GMOS file or NIRI file. The Recipe System relies critically on astrodata.


Not to be confused with astrodata, this is the base class for instrument-specific AstroData classes, and the one most users and developers will interact with at a programmatic level.


A descriptor is a high-level access to essential dataset metadata (eg. headers) through a uniform, instrument-independent interface. E.g., ad.gain(). A descriptor is a method on an AstroData instance.


Data Reduction for Astronomy from Gemini Observatory North and South.

A suite of packages comprising astrodata, gemini_instruments, the recipe_system, geminidr, and gempy, which together provide the full functionality needed to run recipe pipelines on observational datasets. DRAGONS can be referred to as a framework.


A DRAGONS package comprising various functional utilities, some generic, some Gemini-specific.


A function defined within a data reduction instrument package that performs actual work on a dataset. Primitives observe controlled interfaces in support of re-use of primitives and recipes for different types of data, when possible. For example, all primitives called flatCorrect must apply the flat field correction appropriate for the data, and must have the same set of input parameters. This is a Gemini Coding Standard; it is not enforced by the Recipe System.


A function defined in a recipe library (module) which defines a sequence of calls to primitives. A recipe is a simple python function that receives an instance of the appropriate primitive class (primitive set) and executes the primitive sequence defined in the recipe function. Users can pass recipe names directly to reduce.

Recipe System

The DRAGONS framework that automates the selection and execution of recipes and primitives. The Recipe System defines a set of classes that uses attributes on an astrodata instance to locate recipes and primitives appropriate to the dataset.


The command line interface to the Recipe System.

tags [or tagset]

Represents a data classification. When loaded with AstroData, a dataset will be classified with a number of tags that describe both the data and its processing state. The tags are defined in astrodata packages, eg. the Gemini package is gemini_instruments.