The Triple-angle Ionospheric PhotoMeter (Tri-IPM), an airglow and aurora monitoring payload onboard the Fengyun-3E (FY-3E) satellite, is designed for high-sensitivity observations of far-ultraviolet airglow during twilight from the ionosphere‒thermosphere system. This compact, nadir-viewing instrument features three probes (A, B, and C) oriented at 0°, −30°, and 30° relative to the nadir direction, enabling multiangle detection of OI 135.6 nm and N2 Lyman–Birge–Hopfield (LBH) band (147.5–162.5 nm) emissions. With a spatial resolution of ~30 km × 14 km and a responsivity exceeding 2 counts/s/R, the Tri-IPM achieves high-precision measurements while maintaining a red-leak suppression ratio of ~109 to minimize spectral contamination. This paper presents the design principles, ground calibration, and preliminary on-orbit performance of the Tri-IPM. On-orbit tests demonstrate excellent agreement between the observed airglow radiances, their spatial distributions, and the solar zenith angle dependencies of the theoretical models. Furthermore, the results exhibit strong consistency with observations from the Global-scale Observations of the Limb and Disk (GOLD) mission, validating the instrument’s reliability. By providing high-sensitivity, high-resolution global observations of far-ultraviolet (FUV) twilight airglow, the Tri-IPM advances research on ionospheric–thermospheric dynamics and enhances space weather monitoring capabilities. Its integrated on-orbit calibration ensures long-term data accuracy, making it a valuable tool for both scientific studies and operational space environment surveillance.
Fu et al. (Fri,) studied this question.