TSIS-1 SIM L3 V04 Solar Spectral Irradiance

NASA's Total and Spectral Solar Irradiance Sensor -1 (TSIS-1) operates on the International Space Station. TSIS-1 provides absolute measurements of the total solar irradiance (TSI) and spectral solar irradiance (SSI), important for accurate scientific models of climate change and solar variability. TSIS-1 is comprised of two instruments, the Total Irradiance Monitor (TIM), and the Spectral Irradiance Monitor (SIM).

This repository archives Version 4 (V04) of the TSIS-1 SIM Level 3 (L3) data release, and contains SSI in two cadences, 12-hour and 24-hour.

In this release, the degradation corrections have been reprocessed including the Channel C scan from April 2020. A key improvement includes applying a biannual, exposure-based degradation rate rather than a constant rate, resulting in irradiance changes up to ~350 ppm in the UV later in the mission. The diode background signal calculation was also improved to better filter poor values. Two problematic wavelengths (1846.259 nm and 2138.012 nm) were removed from the standard grid to resolve irregular spacing issues that led to frequent Level 3 data gaps. A Doppler magnitude correction has been added, with a maximum effect of ±70 ppm. Additionally, users are advised that temperature extremes—linked to orbital geometry—have introduced instrumental effects during three specific high-temperature periods. Corrections for these effects are under development and will be included in future releases along with updated uncertainties.

See the attached release notes or the TSIS SIM Data Products Release Notes page (https://lasp.colorado.edu/tsis/data/ssi-data/sim-ssi-release-notes/) for further details, and instructions for obtaining the latest TSIS-1 SIM L3 data release.

Data is archived in ASCII, netCDF, and IDL SAVfile format.