Detection probability of an incoming photon flux and effective area for various X-ray instruments as a function of energy. Top panel: Detection probability as a function of energy for GOES 1-8 Å (red), GOES 0.5-4 Å (blue), STIX imaging (solid black), STIX spectroscopy (dashed black), and RHESSI (gray). Bottom panel: Effective area as a function of energy for the same instruments. The plot includes the effect of the attenuators in RHESSI (thin attenuator in dashed gray; thin plus thick attenuators in dotted gray) and STIX (dotted black). The dashed black line represents the STIX effective area multiplied by a factor of 12.8 (=(0.28[AU])⁻²), which corresponds to the increased sensitivity at perihelion.