S1D-Rama

Why this exists

Many analyses need a single 1D spectrum, but reduced echelle products are naturally 2D (order × pixel). S1D-Rama provides a transparent, script-level implementation of the APERO order-merging logic used to build 1D spectra.

What this does

Input

An s2d FITS file (*t.fits) from which S1D-Rama extracts:

• 2D flux image per order
• 2D wavelength map per order
• 2D blaze function per order

Output

FITS binary table extension named S1D with the following columns:

Algorithm

APERO-style order merging in seven steps:

1. Build target 1D wavelength grid (uniform in velocity).
2. Build edge taper weights per order so order ends fade in/out smoothly.
3. Multiply flux and blaze by the edge taper.
4. Spline each order onto the target 1D grid.
5. Combine overlapping orders using the blaze as weight.
6. Normalize by total weight in each wavelength bin.
7. Write merged vectors to FITS.

Velocity correction

S1D-Rama automatically reads the barycentric Earth radial velocity (BERV) and target systemic velocity from the FITS header and computes a rest-frame flux on the common wavelength grid.

Quick start

1 · Clone and enter the repo

git clone https://github.com/eartigau/s1drama
cd s1drama

Already have the repo?

git pull --ff-only

2 · Install dependencies

Requires: numpy ≥ 1.26, scipy ≥ 1.11, astropy ≥ 6.0, matplotlib ≥ 3.8, PyYAML ≥ 6.0.

python3 -m venv .venv
source .venv/bin/activate
python -m pip install --upgrade pip
python -m pip install -r requirements.txt

conda create -n s1drama python=3.12 -y
conda activate s1drama
python -m pip install --upgrade pip
python -m pip install -r requirements.txt

python -m pip install -r requirements.txt

3 · Run on your FITS file

python mk1d.py --make-plots data/NIRPS.2023-08-29T01:33:35.188t.fits

Process many files with a wildcard (quote to let Python expand it):

python mk1d.py "data/*.fits"

Force reprocessing of already-existing outputs:

python mk1d.py --force "data/*.fits"

Expected products

products/s1d/NIRPS.2023-08-29T01:33:35.188t_s1d_apero.fits
docs/figures/NIRPS.2023-08-29T01:33:35.188t_fig1_e2ds.png
docs/figures/NIRPS.2023-08-29T01:33:35.188t_fig2_edge_taper.png
docs/figures/NIRPS.2023-08-29T01:33:35.188t_fig3_s1d.png
docs/figures/NIRPS.2023-08-29T01:33:35.188t_fig4_overlap_zoom.png

4 · Inspect output quickly

python - <<'PY'
from astropy.io import fits
p='products/s1d/NIRPS.2023-08-29T01:33:35.188t_s1d_apero.fits'
with fits.open(p) as h:
    print('HDUS', len(h))
    print('EXT1', h[1].name)
    print('COLS', h[1].columns.names)
    print('NROWS', len(h[1].data))
PY

Configuration

All tunables live in config/s1drama.yaml. This file controls:

• FITS extension names (flux / wave / blaze)
• Output directory and filename suffix
• Merge constants (wavelength limits, binning, blaze threshold, edge smoothing)
• Plot defaults

Supply an alternative config at runtime:

python mk1d.py --config config/s1drama.yaml data/your_file.fits

CLI reference

python mk1d.py --help

Figures

Fig 1 — Input 2D flux image per echelle order

Fig 2 — Example order-edge taper for smooth blending at order boundaries

Fig 3 — Final merged 1D spectrum and merge weight as a function of wavelength

Fig 4 — Zoom on the overlap between orders 59–61. Color-coded order spectra are shown together with the merged S1D. The lower panel shows each order's weight fraction, making the transition at order boundaries explicit and demonstrating the seamless handoff in overlap regions.

Fidelity vs. full APERO pipeline

S1D-Rama reproduces the merge logic from APERO's e2ds_to_s1d function. It is intentionally a standalone implementation and does not run the full APERO reduction chain (calibrations, extraction, telluric recipes, database interactions, etc.).

References & attribution

Please cite APERO (Cook et al. 2022) when this method is used in scientific work.