BUG - Failure to produce maps due to Pointing Sets epoch misaligning with SPICE data

[pleasant-menlo]

Description of the issue

For some repointings, the epoch associated with a pointing set falls before the SPICE coverage window begins for the DPS frame. For example, imap_ultra_l1c_90sensor-heliopset_20251128-repoint00062_v005.cdf has an epoch of 2025-11-28T10:02:11.600076, but the coverage window in imap_dps_2025_332_2025_334_001.ah.bc only starts at 2025-11-28T10:11:48.599.

Frame transformations for pointing sets are currently calculated at the exact epoch from the pointing set, which can cause the transformation to fail due to not having SPICE coverage. This prevents making maps that include this day of data.

Some options to address this:

1. Make the L1c pointing set epoch be the middle of the data collection window
2. Leave the L1c as is but use the middle of the pointing set time (epoch + epoch_delta/2) when computing transformations

Steps to reproduce the issue

To demonstrate the pointing set epoch falling outside of the SPICE coverage range, the following command can be run with the provided dependency file:

imap-cli --instrument ultra --data-level l2 --descriptor u90-ena-h-hf-nsp-full-hae-4deg-3mo --start-date 20251128 --version v000 --dependency imap_ultra_l3_u90-no-spice_20251128_v000.json

imap_ultra_l3_u90-no-spice_20251128_v000.json

Expected behavior (What should happen)

Running the command should result in generating a map containing a single pointing set's worth of data.

Actual behavior (What does happen)

Running the command results in failure to generate a map due to the following error:

spiceypy.utils.exceptions.SpiceNOFRAMECONNECT: 
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Toolkit version: CSPICE_N0067

SPICE(NOFRAMECONNECT) --

At epoch 8.1759620078309E+08 TDB (2025 NOV 28 10:03:20.783 TDB), there is insufficient information available to transform from reference frame -43901 (IMAP_DPS) to reference frame -43924 (IMAP_HAE). IMAP_DPS is a CK frame; a CK file containing data for instrument or structure -43901 at the epoch shown above, as well as a corresponding SCLK kernel, must be loaded in order to use this frame. Frame IMAP_HAE could be transformed to frame 1 (J2000). Failure to find required CK data could be due to one or more CK files not having been loaded, or to the epoch shown above lying within a coverage gap or beyond the coverage bounds of the loaded CK files. It is also possible that no loaded CK file has required angular velocity data for the input epoch, even if a loaded CK does have attitude data for that epoch. You can use CKBRIEF with the -dump option to display coverage intervals of a CK file.

pxform_c --> PXFORM --> REFCHG

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