Automated typing of LRIS (BLUE and RED) frames

Version History

Version

Author

Date

PypeIt

1.0

Debora Pelliccia

6 Sep 2023

1.13.1.dev

1.1

Debora Pelliccia

10 Aug 2024

1.16.1.dev

Basics

The general procedure used to assign frames a given type is described here: Frame Types.

LRIS frame typing

The primary typing of LRIS frames is performed by pypeit.spectrographs.keck_lris.KeckLRISSpectrograph.check_frame_type(). This function checks the values of various header keywords against a set of criteria used to classify the frame type. The same criteria are used for keck_lris_red, keck_lris_red_orig, keck_lris_red_mark4, keck_lris_blue, and keck_lris_blue_orig, unless otherwise noted. The header cards required for the frame-typing and their associated keyword in the PypeItMetaData object are:

fitstbl key

Header Key

exptime

ELAPTIME (TELAPSE for keck_lris_red_mark4)

hatch

TRAPDOOR

decker

SLITNAME

lampstat01

See below

lampstat01 is defined using a combination of header keywords, which include LAMPS, MERCURY, NEON, ARGON, CADMIUM, ZINC, HALOGEN, KRYPTON, XENON, FEARGON, DEUTERI, FLAMP1, FLAMP2, FLIMAGIN, FLSPECTR. Since LRIS header keywords have changed over time, the exact combination of keywords used to define lampstat01 varies depending on the available header keywords.

The criteria used to select each frame type are as follows:

Frame

hatch

lampstat01

decker

exptime

science

'open'

'off'

!= 'GOH_LRIS'

>61s

standard

'open'

'off'

!= 'GOH_LRIS'

>1s & <61s (LRIS RED) or <900s (LRIS BLUE)

bias

'closed'

'off'

!= 'GOH_LRIS'

<1s

slitless_pixflat

'open'

'off'

== 'direct'

<60s

pixelflat

'closed'

'Halogen' or '2H'

!= 'GOH_LRIS'

<60s (LRIS RED) or <300s (LRIS BLUE)

pixelflat

'open'

'on'

!= 'GOH_LRIS'

<60s (LRIS RED) or <300s (LRIS BLUE)

trace

'closed'

'Halogen' or '2H'

!= 'GOH_LRIS'

<60s (LRIS RED) or <300s (LRIS BLUE)

trace

'open'

'on'

!= 'GOH_LRIS'

<60s (LRIS RED) or <300s (LRIS BLUE)

illumflat

'closed'

'Halogen' or '2H'

!= 'GOH_LRIS'

<60s (LRIS RED) or <300s (LRIS BLUE)

illumflat

'open'

'on'

!= 'GOH_LRIS'

<60s (LRIS RED) or <300s (LRIS BLUE)

arc

'closed'

!= 'Halogen', '2H', 'on', 'off'

!= 'GOH_LRIS'

Not used

tilt

'closed'

!= 'Halogen', '2H', 'on', 'off'

!= 'GOH_LRIS'

Not used

Note that PypeIt employs commonly used value of exptime to distinguish frame type; however, if needed, the user can specify a different value by using the exprng parameter in the PypeIt Reduction File; see also Frame Types.

The science and standard frames have identical selection criteria, except for the exptime value. In order to better distinguish between the two types, the RA and DEC header keywords are also used to assign the standard type to frames with RA and DEC values that are within 10 arcmin of one of the standard stars available in PypeIt (see Flux-calibration Standards).

The criteria used to select arc and tilt frames are identical; the same is true for pixelflat, trace, and illumflat frames. It’s important to note that PypeIt is able to correctly assign the pixelflat, trace, and illumflat types to the internal and dome flat frames, and it tries to do the same for the twilight flats, by selecting frames that looks like science frames and include the following words in the OBJECT or TARGNAME header keywords: ‘sky’, ‘blank’, ‘twilight’, ‘twiflat’, ‘twi flat’. This way of identifying twilight flats is not robust, therefore the user should always check the frame types assigned and manually change them if needed in the PypeIt Reduction File.

Note, also, that if both pixelflat and slitless_pixflat frames are identified, the pixelflat assignment will be removed so that the slitless_pixflat frames will be used for the flat fielding.

Finally, note that a LRIS frame is never given a pinhole or dark type.

Testing

Requirement PLL-16 states: “As a user, I expect the pipeline to automatically classify my data.”

PypeIt meets this requirement as demonstrated by the tests at ${PYPEIT_DEV}/unit_tests/test_frametype.py. There is one test per spectrograph:

  • test_lris_blue()

  • test_lris_blue_orig()

  • test_lris_red()

  • test_lris_red_orig()

  • test_lris_red_mark4()

Here is an example of how to run the tests:

cd ${PYPEIT_DEV}/unit_tests
pytest test_frametype.py::test_lris_blue -W ignore

The tests requires that you have downloaded the PypeIt PypeIt Development Suite and defined the PYPEIT_DEV environmental variable that points to the relevant directory. The algorithm for all these tests is the same and is as follows:

  1. Find the directories in the PypeIt Development Suite with Keck LRIS data (separately for keck_lris_blue, keck_lris_blue_orig, keck_lris_red, keck_lris_red_orig, keck_lris_red_mark4).

  2. For each directory (i.e., instrument setup):

    1. Make sure there is a “by-hand” version of the pypeit file for this setup where a human (one of the pypeit developers) has ensured the frame types are correct.

    2. Effectively run pypeit_setup on each of the instrument setups to construct a new pypeit file with the automatically generated frame types.

    3. Read both the by-hand and automatically generated frame types from these two pypeit files and check that they are identical. This check is only performed for the calibration frames, not any science or standard frames.

Because this test is now included in the PypeIt Unit Tests (GitHub CI), this frame-typing check is performed by the developers for every new version of the code.