ULTRA l1b add function to flag events that are within the earth keepout angle.

[lacoak21]

Change Summary

Overview

Add a function to flag events where the particle look direction is outside the Earth keepout angle. A lot of this PR is pulling out code from the function compute_culling_mask that @laspsandoval wrote and creating a new function compute_unit_target_vectors.

File changes

• imap_processing/spice/geometry.py
  • pull out code from compute_culling_mask and make a new function that can be used generally for other instruments
• imap_processing/ultra/l1b/ultra_l1b_culling.py
  • Compute the angle between the earth unit vector and each particle's look direction and flag events where the angle is less than the constant threshold given by the ULTRA IT team.

Testing

I wrote a test that uses the exact code that Bob uses in order to validate our functions. It can be found here https://github.com/demajistre/imap_processing/blob/dev/ultra_user/planets/ENA_planets.py

[Copilot]

Pull request overview

This pull request adds functionality to flag ULTRA L1b events where particle look directions fall within the Earth keepout angle. The changes extract reusable code from compute_culling_mask into a new general-purpose function compute_unit_target_vectors for computing unit vectors from IMAP to target bodies, and implements Earth angle filtering for individual particle events.

Changes:

• Extracted unit vector computation logic into a reusable compute_unit_target_vectors function in the SPICE geometry module
• Added get_valid_earth_angle_events function to filter L1b events based on Earth keepout angle
• Added Earth angle threshold constant for ULTRA 45 instrument

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 11 comments.

Show a summary per file

File	Description
imap_processing/spice/geometry.py	Adds compute_unit_target_vectors function to compute unit vectors from IMAP to target bodies (e.g., Earth)
imap_processing/ultra/l1c/ultra_l1c_culling.py	Refactors to use new compute_unit_target_vectors function, removing duplicate code
imap_processing/ultra/l1b/ultra_l1b_culling.py	Adds get_valid_earth_angle_events to flag events based on Earth keepout angle
imap_processing/ultra/constants.py	Adds EARTH_ANGLE_45_THRESHOLD constant (15 degrees in radians)
imap_processing/tests/spice/test_geometry.py	Adds test for compute_unit_target_vectors function
imap_processing/tests/ultra/unit/test_ultra_l1b_culling.py	Adds test validating get_valid_earth_angle_events against ULTRA IT team's implementation

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[lacoak21]

The is the code that was pulled from compute_culling_mask that Laura already tested and validated but I wrote a test for it just to be sure.