DOI: 10.25810/mas9-nj91
title: TSIS-1 SIM L3 V12 Solar Spectral Irradiance

description: 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 12 (V12) of the TSIS-1 SIM Level 3 (L3) data release, and contains SSI in two cadences, 12-hour and 24-hour. The TSIS-1 SIM L3 V12 data release contains data from 2018-03-14 to 2025-01-18.

V12 is an "off-cycle" release due to anomalies with the SIM Digital Signal Processor (DSP) and Electrical Substitution Radiometers (ESRs). On Sept. 03, 2023, the TSIS-1 SIM Digital Signal Processor (DSP) stopped responding to ground commands. Command and control of the DSP was restored on Oct. 21, 2023. However, the post-anomaly checkout showed issues with the electric substitution radiometers (ESRs) in certain configurations. Due to these issues, there are temporal and wavelength gaps in V12 data longward of 1620 nm after Oct. 21, 2023, where the ESR data do not meet accuracy standards.

The Sept 2023 DSP anomaly prevented the planned October 2023 semi-annual Channel C scans from being obtained. As a result, users should expect slightly higher noise after Apr. 04, 2023 (the latest Channel C observations) in the V12 L3 data release. Additionally, the V12 degradation corrections differ significantly from previous versions due to increased solar activity during the Solar Cycle 25 maximum. TSIS-1 SIM data users are encouraged to review the V12 release notes for complete details.

V13 restores full wavelength coverage of TSIS-1 SIM SSI data from 200--2400 nm with wavelength-dependent spectral corrections for most Electric Substitution Radiometer (ESR) data taken after the Digital Signal Processor (DSP) and ESR anomalies of Sept-Oct 2023. On Sept. 03, 2023, the TSIS-1 SIM DSP stopped responding to ground commands. Command and control of the DSP was restored on Oct. 21, 2023. However, the post-anomaly checkout showed issues with the electric substitution radiometers (ESRs). After a transition period of several months,  the SIM ESRs have reached a steady state at all wavelengths, but with an irradiance offset of up to 0.7%.  V13 includes wavelength-dependent spectral corrections that correct most of the ESR data taken since the anomalies. The correction of the remaining ESR data, less than 2% of the ESR data taken from October 2023 to January 2025, will be addressed in a future TSIS-1 SIM L3 data release. The 1-sigma irradiance uncertainties associated with these corrections are included in the ADDITIONAL_UNCERTAINTY column of the data product.

Additionally, V13 degradation corrections differ significantly from previous versions due to the loss of accuracy of the SIM ESR Channel-C (ESRC) configuration, and increased solar activity during the Solar Cycle 25 maximum. MEASUREMENT_PRECISION is now reported on a per-wavelength basis (Instead of wavebands).  TSIS-1 SIM data users are encouraged to review the V13 release notes for complete details.

See the attached TSIS_SIM_V12_Release_Notes.pdf 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.