Tiny Ionospheric Photometers on FORMOSAT-3/COSMIC: On-orbit performance

摘要

The Tiny Ionospheric Photometer (TIP) sensors aboard the Constellation Observing System for Meterology, Ionosphere and Climate (COSMIC, also called FORMOSAT-3) spacecraft comprise a suite of six nadir-viewing ultraviolet photometers for characterizing the Earth's nightside ionosphere. The TIP instruments complement the ionospheric capabilities of the GPS occultation experiment (GOX) by characterizing horizontal ionospheric density gradients. These photometers target 01 135.6 nm emission produced by ionospheric O~++e recombination and measure ionospheric structure with a spatial resolution of 10-30 km. The TIP instrument design had to solve several design challenges in order to achieve its intended science and mission requirements within operational constraints imposed by the spacecraft and budget constraints. The photometers have a simple design which excludes OI 130.4 nm emission and achieves a sensitivity of approximately 500 counts/s/Rayleigh at 135.6nm. The satellites initially orbited in the same plane at 500 km, then over the course of 13 months they were individually raised to their final 800 km orbits in six planes separated by 24° in right ascension. These maneuvers provided opportunities for cross-calibration among the sensors, for multipass observations as the satellites orbit together early in the mission, and for observations at different spatial resolutions as the spacecraft operate at different altitudes. In this paper we evaluate on-orbit sensor performance of the TIP sensors, and discuss improvements for follow-on missions.