Background

The Total and Spectral Solar Irradiance Sensor-1 (TSIS-1) is a NASA heliophysics mission operating on the International Space Station. One of its two instruments, the Total Irradiance Monitor (TIM), measures Total Solar Irradiance (TSI): the total radiant power from the Sun received per unit area, integrated over the full solar spectrum. TIM uses four active-cavity electrical substitution radiometers (referred to here as cavities A, B, C, and D). Cavity A (id: 77) is the primary science cavity, while observations from the other cavities are used to characterize and correct changes in the primary cavity caused by long-term solar exposure.

The formal TSIS-1 TIM public science products are Level-3 6-hour and daily (24-hour) TSI averages. They are derived from higher-cadence measurements made approximately every 50 seconds. The Level-3 products report solar irradiance corrected to a mean Sun–Earth distance of 1 astronomical unit (AU). Clean solar observations in this demo dataset are therefore near 1362 W/m². The dataset also includes measurements made while the Sun is blocked by the Earth so the instrument is pointed to deep space, which are near 0 W/m², as well as observations between these extremes. Intermediate values can occur as the spacecraft moves into or out of eclipse, the Earth partially enters the instrument field of view, or the instrument is otherwise not in a nominal direct-solar observing state. These observations are useful for understanding the raw measurement stream but are flagged and are not treated as valid TSI measurements for the Level-3 product.

This demo contains approximately five days of Level-2-cadence TIM data, from 2026-07-23 through 2026-07-27, and is intended to provide a small but realistic scientific dataset for the coding exercise. It is a subset of internal processing data rather than a formally released TSIS-1 science product.

For additional background, see the LASP TSIS-1 Total Solar Irradiance Data page.

Data Files

The same dataset is available in two formats in this repository. You may use whichever is more appropriate for your implementation.

SQLite Database

tsis1_tim_coding_test.sqlite

The SQLite database contains three related tables and can be queried directly using SQL.

CSV files

• tsis1_tim_coding_test__INSTRUMENTMODES.csv
• tsis1_tim_coding_test__TIMCORRECTEDIRRADIANCEDATA.csv
• tsis1_tim_coding_test__TIMLEVEL3QUALITYFLAGS.csv

Each CSV file is the direct export of its equivalent table in the SQLite database.

Tables and Important Fields

INSTRUMENTMODES

This is a lookup table describing the instrument configuration associated with an observation.

Field	Description
INSTRUMENTMODEID	Numeric identifier used to join to the observation tables.
PROJECT	Project or mission name.
INSTRUMENT	Instrument name.
CHANNEL	TIM servo-loop/channel identifier.
MODE	For the records used by this demo, identifies the active TIM cavity: A, B, C, or D.
DESCRIPTION	Human-readable description of the instrument mode.

TIM has two servo loops: cavities A/D form one loop and B/C form the other. Only one cavity in each pair can be active at a time. Both loops operate concurrently, so simply comparing the number of records for different cavities does not necessarily indicate how many valid solar observations each cavity contributed.

TIMCORRECTEDIRRADIANCEDATA

This table contains the approximately 50-second-cadence irradiance observations.

Field	Description
MICROSECONDSSINCEGPSEPOCH	Observation time, represented as microseconds since the GPS epoch.
INSTRUMENTMODEID	Links the observation to INSTRUMENTMODES.
VERSION	Processing/data version.
IRRADIANCE	Corrected irradiance in W/m².
IRRADIANCETYPE	Simplified classification describing the type of observation.

IRRADIANCETYPE values are:

Value	Name	General Meaning
0	OTHER	Observation that does not fall into one of the primary categories.
1	SOLAR	Valid direct-solar observation.
2	DARK	Dark/eclipsed observation.
3	DARK_EARTH	Dark observation affected by an Earth view.
4	GAIN_MODE	Instrument gain/calibration mode.

For exploration and visualization, SOLAR and DARK are the most straightforward categories to compare. For example, plotting irradiance over time will show solar observations clustered around ~1362 W/m² and dark observations near zero.

TIMLEVEL3QUALITYFLAGS

Despite its name, this table contains quality information at the same Level-2 cadence as the irradiance observations. The flags are used when deciding which measurements can contribute to the Level-3 products.

Field	Description
MICROSECONDSSINCEGPSEPOCH	Observation time.
INSTRUMENTMODEID	Instrument mode/cavity associated with the observation.
VERSION	Processing/data version.
QUALITYFLAGS	Integer bit field containing zero or more data-quality flags.

For this exercise, you do not need to interpret the individual quality-flag bits.

The important distinction is:

• QUALITYFLAGS = 0 : no quality flags are present
• QUALITYFLAGS != 0 : one or more quality conditions are present

In this demo dataset, observations with QUALITYFLAGS = 0 correspond to observations classified as IRRADIANCETYPE = 1 (SOLAR). The irradiance type can therefore be thought of as a simplified representation of the more detailed quality information.

When using SQL, the irradiance and quality tables can be associated using the combination of: MICROSECONDSSINCEGPSEPOCH, INSTRUMENTMODEID, and VERSION.

The equivalent merge can be performed when using the CSV files.