TSIS-1 SIM L3 V02 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 2 (V02) of the TSIS-1 SIM Level 3 (L3) data release, and contains SSI in two cadences, 12-hour and 24-hour.

This version improves upon version 1 in several key ways. The updated degradation correction method now incorporates bi-annual Channel C scans, significantly improving long-term measurement trending, unlike version 1, which only used the initial first light scan. In version 2, no degradation correction is applied beyond 1050 nm due to low signal-to-noise at these wavelengths, though trends will continue to be monitored. A bug in the Doppler shift correction was fixed, along with a slight wavelength scale adjustment for better alignment with the Kurucz reference spectrum and improved inter-channel consistency, resulting in a net shift of 20–50 ppm. Diode responsivity temperature corrections were improved above 600 nm, particularly between 800–1000 nm, and adjustments were made between 300–400 nm to better match the ESR, though further refinement is ongoing due to limited ESR data. Additional fixes include a bug in the scattered light correction (affecting 200–220 nm), addition of a measurement stability uncertainty term, and a Level 3 processing bug fix that reduced excessive variance in the IR above 1700 nm.

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.