THEMIS plays a role in developing and testing advanced observational techniques and instrumentation, mostly in the field of solar physics, particularly in the field of spectropolarimetry and adaptive optics.

The telescope specializes in spectroscopy and spectropolarimetry, analyzing the electromagnetic spectrum and the polarization of the light to infer multiple properties of the object that is observed, such as its composition, its physical caracteristics and its magnetic field.

THEMIS provides detailed information about the Sun's magnetic field in the lowest layers of the solar atmosphere (the photosphere and chromosphere), as well as around planets.

THEMIS can realize a high spectral resolution observations and possess unique capabilities to measure the full Stokes parameters (the set of values that describe the polarization state of the light which is received by THEMIS), providing a complete characterization of the target magnetic field. Its design minimizes instrumental polarization, ensuring highly accurate measurements of magnetic field.

The main objectives of THEMIS in solar physics are:

THEMIS is dedicated to investigating the magnetic field of the Sun, which drives much of the solar activity, including sunspots, filaments and protuberances, solar flares, and solar eruptions. THEMIS enables the measure of the three direction of the magnetic field vector with high precision, providing insights into the processes governing the magnetic field's generation, dynamics and role in solar activity.

THEMIS investigates transient events and dynamic processes in the Sun's atmosphere, including wave propagation, plasma flows, and instabilities. It aims to understand the coupling between different layers of the solar atmosphere and how energy is transported from the interior to the outer corona.

By monitoring long-term changes in solar magnetism, THEMIS contributes to understanding the solar cycle, including the 11-year activity cycle/22-year magnetic cycle and its impact on space weather. This research helps model how solar activity influences the Earth's magnetosphere and climate.

By improving our understanding of the Sun's magnetic activity and its role in driving solar phenomena, THEMIS contributes valuable data for space weather prediction and understanding the Sun-Earth connection.

While the THEMIS Solar Telescope is primarily designed and optimized for studying the Sun, it does have the capability to observe planets and other objects of the solar system in particular those who are closer to the Sun than Earth such as Mercury, Venus and some comets during their perihelion.

Observation of such objects with night telescope is challenging. Being in relatively close apparent proximity to the Sun on the celestial sphere, their observations must either be done during daylight, time during which night telescopes are not designed to operate, or during twilight, hence with an important remaining sky’s brightness leading to a reduced constrast. In addition, at twilight, these objects are usually close to the horizon, their lights going through a longer depth in the Earth atmosphere and hence subject to more scattering, turbulence and in fine distortion of the image.

THEMIS thus offers inequivalent graound-based observational capabilities of these near-Sun objects.

THEMIS specializes in solar spectropolarimetry, that can be applied to study the magnetic properties of other objects, including planets, if they reflect or emit sufficient polarized light.

THEMIS's high spectral resolution can allow detailed observations of the atmospheres of planets, including scattering phenomena in their atmospheres. and the measurement of chemical compositions via spectroscopy.

THEMIS operating primarily during daylight to observe the Sun it can observe bright planets like Venus, Jupiter, or Mars, which are visible in the daytime sky. These observations can provide insights into planetary albedo (reflectivity) and polarization of light scattered by planetary atmospheres or surfaces.