Glows L2 - Apply calibration

[vmartinez-cu]

This pull request implements the use of a time-dependent calibration factor for GLOWS L2 data processing, ensuring that photon flux and uncertainties are correctly converted to physical units (Rayleighs) using ancillary calibration data. The changes include updating data structures, processing logic, and tests to support calibration lookup and application.

Key changes:

GLOWS L2 Data Processing and Calibration

• The HistogramL2 and DailyLightcurve classes were updated to accept and use a calibration factor (counts per second per Rayleigh), which is required for correct photon flux and uncertainty calculations. The calibration factor is selected based on the mid-epoch of the observational day using a new static method, get_calibration_factor.

• The main glows_l2 processing function passes a calibration dataset through to the HistogramL2 data class.

Ancillary Calibration Data Handling

• The ancillary calibration file reader (convert_file_to_dataset) was refactored to store calibration times as coordinates and ensure the dataset is sorted by time, improving reliability when selecting calibration factors.

Testing Enhancements

• Test fixtures and test cases were updated to mock calibration datasets and verify that calibration factors are correctly selected and applied in flux and uncertainty calculations.

Closes #2886

[Copilot]

Pull request overview

This PR adds support for applying a time-dependent GLOWS L2 calibration factor (counts/s per Rayleigh) when converting daily lightcurve histogram rates and uncertainties into physical units (Rayleighs), using an ancillary “l2-calibration” dataset.

Changes:

• Plumbs a calibration dataset through glows_l2() → HistogramL2 → DailyLightcurve and applies it in flux/uncertainty calculations.
• Adds HistogramL2.get_calibration_factor() to select an appropriate factor based on the mid-epoch of the observation day.
• Refactors the GLOWS ancillary calibration .dat reader to store calibration times as coordinates and sort by time; updates/extends tests and fixtures accordingly.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
imap_processing/glows/l2/glows_l2.py	Passes calibration dataset into HistogramL2 during L2 generation.
imap_processing/glows/l2/glows_l2_data.py	Adds calibration-factor selection and applies calibration in DailyLightcurve flux math.
imap_processing/ancillary/ancillary_dataset_combiner.py	Refactors l2-calibration .dat ingestion to use start_time_utc as a coordinate and sorts by it.
imap_processing/tests/glows/conftest.py	Adds a mock calibration dataset fixture.
imap_processing/tests/glows/test_glows_l2.py	Updates tests to provide calibration dataset to glows_l2()/HistogramL2.
imap_processing/tests/glows/test_glows_l2_data.py	Adds coverage for calibration-factor selection; updates flux/uncertainty expectations with calibration.
imap_processing/tests/ancillary/test_ancillary_dataset_combiner.py	Extends calibration combiner test and asserts coordinate usage/sorting.

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