lsst::obs::test; Simple camera and data repository for testing

obs_test models a simple camera with one CCD and includes a data repository containing a few raw images and some associated calibration data.

obs_test is designed to be used for unit tests that require camera geometry and/or a small data repository.

Camera

The obs_test camera consists of a single CCD whose geometry matches a subregion of a single LSST CCD. The chosen LSST CCD is is near, but not at, the center of the LSST focal plane, in order to make the obs_test camera geometry nontrivial and to provide a bit of distortion. A subregion is used (rather than simply using an entire LSST CCD) in order to make the images smaller.

In detail, the obs_test CCD, sensor 0, corresponds to the following LSST CCD subregion:

• Raft R2,2 (the center raft)
• CCD/sensor S0,0 (the lower left CCD in the raft)
• Amplifiers/channels C0,0, C0,1, C1,0 C1,1, keeping only the 1000 pixels in Y nearest the center line of the CCD

obs_test CCD amplifiers map as follows to LSST CCD amplifiers:

• "00" = "C0,0"
• "10" = "C0,1"
• "01" = "C1,0"
• "11" = "C1,1"

The data ID keys that may be used to identify "raw" images and (except for "amp") "calexp" images are:

• amp: amplifier name: one of "00", "01", "10", "11" (not used for calexp)
• ccd: ccd number: always 0
• filter: filter name
• visit: exposure number

Like the LSST camera, the obs_test camera focal plane coordinates are rotated 90 degrees from pixel coordinates. (The focal plane coordinates are determined by the camera engineers, whereas CCD pixel coordinates are required to have x along rows and y along columns).

Data

The data directory includes the following:

• ReadMe.md: a file describing the data and how it was generated
• input: the data repository. This includes three raw images and associated flats, biases and defects.
• utils: scripts used to generate the data from lsstSim data

Unlike the LSST camera, but like most other cameras, obs_test raw images combine the data from all amplifiers into a single image.

Classes

Useful classes include:

• TestCamera: camera geometry for the obs_test camera. Unlike most obs_* packages this package builds its own camera geometry (by instantiating this class), rather than relying on the lsst.obs.base.CameraMapper to load camera geometry data from a persisted lsst.afw.cameraGeom.CameraConfig.
• TestMapper: camera mapper for the obs_test camera

Example

To obtain the camera geometry and a raw image:

import os.path
import lsst.utils
import lsst.daf.persistence
obsTestDir = lsst.utils.getPackageDir('obs_test')
input = os.path.join(obsTestDir, "data", "input")
butler = lsst.daf.persistence.Butler(root = input) # don't add to the input repo
rawImage = butler.get("raw", dict(visit=1))
cameraGeom = butler.get("camera")