Visualise response and Planck spectrum fits

plot_response.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python
+"""Plot the instrument's relative spectral response R(lambda) from responsivity.csv.
+
+Shows the calibrated response curve (counts per unit irradiance, normalised to a
+median of 1 over the fit band). The curve is defined only where the calibration
+is valid; outside that band responsivity.csv holds NaN and nothing is drawn.
+
+Usage: python plot_response.py [responsivity.csv] [--png fig.png]
+"""
+import argparse
+
+import numpy as np
+import matplotlib
+matplotlib.use("Agg")
+import matplotlib.pyplot as plt
+
+from response import load_csv
+
+p = argparse.ArgumentParser(description=__doc__,
+                            formatter_class=argparse.RawDescriptionHelpFormatter)
+p.add_argument("responsivity", nargs="?", default="responsivity.csv")
+p.add_argument("--png", default="response.png")
+args = p.parse_args()
+
+wl, r = load_csv(args.responsivity)
+good = np.isfinite(r)
+lo, hi = wl[good].min(), wl[good].max()
+
+fig, ax = plt.subplots(figsize=(9, 5))
+ax.plot(wl, r, lw=1.8, color="C3")
+ax.set_xlabel("wavelength (nm)")
+ax.set_ylabel("relative responsivity R(λ)\n(median 1 over the band)")
+ax.set_title(f"Instrument spectral response, calibrated {lo:.0f}-{hi:.0f} nm")
+ax.set_ylim(bottom=0)
+ax.grid(alpha=0.3)
+fig.tight_layout()
+fig.savefig(args.png, dpi=130)
+print(f"calibrated band {lo:.0f}-{hi:.0f} nm, peak R={np.nanmax(r):.2f} at "
+      f"{wl[np.nanargmax(r)]:.0f} nm")
+print(f"wrote {args.png}")