First acquisition date missing from timeseries.h5 when preparing OPERA time series for MintPy

[alhandwerger]

Description:

When using opera-utils to prepare OPERA time series products for MintPy, the resulting timeseries.h5 file is missing the first acquisition date in the stack.

The original OPERA time series stack includes an initial epoch with zero displacement (reference epoch). However, after running the MintPy preparation workflow via opera-utils, the first date is not included in timeseries.h5.

Impact:

Users cannot visualize the full temporal range of the OPERA time series.

The missing zero-reference epoch may cause confusion when interpreting cumulative displacement.

Example:

Here is first file in the stack
OPERA_L3_DISP-S1_IW_F30713_VV_20230405T141543Z_20230417T141543Z_v1.0_20250902T145245Z.nc

which has a reference date = 20230405, but N=0 for the mintpy timeseries.h5 time - 20230417 (see screen shot below)

@scottstanie @mgovorcin

[gracebato]

I think @scottstanie you just need to add the first date as zero values.