The TESIS is a set of solar imaging instruments developed by the Lebedev Physical Institute of the Russian Academy of Science, and launched aboard the Russian spacecraft CORONAS-PHOTON in January 30, 2009. The main goal of the TESIS is to provide complex observations of solar active phenomena from the transition region to the inner and outer solar corona with high spatial, spectral and temporal resolution in the EUV and Soft X-ray spectral bands. The TESIS includes five unique space instruments to observe the inner and outer solar corona from 0.2 to 4 solar radii in spectral band 290-320 A. With the advanced capabilities of its instruments, the TESIS will help better understand the physics of solar flares and high-energy phenomena and provide new data on parameters of solar plasma in the temperature range 105 - 107 K. The TESIS experiment started in the deep minimun between the 23rd and the 24th cycles of solar activity and planned to continue through all the razing phase of new cycle till 2012-1013.

TESIS main tasks

• The study of mechanisms of solar wind generation and coronal heating.
• The development of methods for space weather forecasting.
• The study of the production and evolution of high-temperature plasmas in the corona.
• The analysis of processes of magnetic energy accumulation and release before and during flares.

TESIS Scientific Instruments

The TESIS includes five space instruments:

• MgXII Imaging Spectroheliometer (MISH) with spherical bent crystal mirror, for observations of the Sun in the monochromatic MgXII 8.42 A line
• EUV Spectoheliometer (EUSH) with grazing incidence diffraction grating, for the registration of full solar discs in monochromatic lines of the spectral band 280–330 A
• Two Full-disk EUV Telescopes (FET) with multilayer mirrors covering the band 130-136 A and 290-320 A
• Solar EUV Coronagraph (SEC), based on the Ritchey-Chretien scheme, to observe the inner and outer solar corona from 0.2 to 4 solar radii in spectral band 290-320 A
• X-ray photometer-spectroheliometer SphinX, designed by the Space Research Center of the Polish Academy of Science

Each of the instruments can operate independently or simultaniously with other TESIS instrumentation.

MgXII Imaging Spectroheliometer (MISH)

Optical scheme Soft X-ray spectroheliometer with Bragg's bent crystal mirror (quartz) Bragg's angle 82o.08 Spectral range Resonance doublet of H-like ion  Mg XII (8.418 A and 8.423 A) Focal length 1376 mm Aperture 71*103 mm Field of View 1o.15 (Full disk) Spatial resolution 2 arc. sec./pix Temporal resolution from 1 sec (partial field of view) to 10 sec (full disk) Detector Backside-CCD 2048*2048 pix CCD pixel size 13.5*13.5 micron

The MISH is an imaging spectroheliometer for the registration of monochromatic images of the Sun in the narrow spectral region, which covers a resonance doublet of the H-like ion MgXII with wavelengths 8.418 and 8.423 A.

The spectroheliometer consists of the following optical elements:

• entrance window with shutter;
• filter;
• focusing bent quartz crystal mirror;
• detector (CCD).

Optical scheme of the MISH is based on the Bragg's X-ray diffraction with the almost normal incidence (Bragg's angle is 82^o.08). The X-ray radiation is focused on the CCD detector of 2048×2048 pixels by a bent spherical mirror made from quartz [1010] crystal. The blocking of visible light is provided with two filters - at the entrance window (aluminated mylar) and  aluminium filter coated on the CCD.

The angular size of a CCD pixel is on the order of 2 arc. sec. The MISH field of view is equal to 1^o.15 and covers the sun and above-limb regions with the aim to observe high-altitude hot structures in the corona. This will allow to investigate not only hot plasma near the solar limb, but also hot structures at high altitudes.

Thanks to the partial field of view mode, long-term high-cadence (less than 10 s) observations are also possible.

The MISH spectroheliometer is the only instrument registering images of hot coronal plasma with temperatures about 10 MK.

EUV spectroheliometer (EUSH)

Instrument Slitless EUV spectroheliometer with grazing incidence diffraction grating and multilayer parabolic mirror Spectral range 280 - 330 A Focal length 600 mm Aperture 5*80 mm Field of view 1o.24 (Full disk, contracted along dispersion axis) Main spectral lines lines of ions: HeII, SiIX, SiXI, FeXIV-FeXVI, MgVIII, NiXVIII, CaXVII, AlIX, FeXXII and other Angular resolution 4.4 arc. sec./pix (perpendicular to dispersion axis) and 1.5 arc. min./pix (along dispersion axis) Temporal resolution 30 - 600 sec Detector Backside-CCD 2048*2048 pix CCD pixel size 13.5*13.5 micron

The EUSH is an imaging spectroheliometer operating in the band 280-330 A. This covers HeII, SiIX, SiXI, FeXII-FeXVII, MgVIII, NiXVIII, CaXVIII, AlIX, FeXXII and other spectral lines formed at temperatures from 5*10⁴ to 2.0*10⁷ K.

The spectroheliometer consists of the following optical elements:

• filter;
• diffraction grating;
• multilayer parabolic mirror;
• detector (CCD)

Full-disk EUV Telescopes (FET)

Instrument Two hershel telescopes with multilayer parabolic mirrors Spectral range 130 - 136 A (telescope 1) and 290 - 320 А (telescope 2) Focal length 1600 mm Aperture diameter 100 mm Field of view 1o.0 (full disk) Angular resolution 1.7 arc. sec./pix Temporal resolution 1 - 10 sec Detector Backside-CCD 2048*2048 pix CCD pixel size 13.5*13.5 micron

The FET includes two normal-incidence Hershel telescopes with multilayer mirrors.

The telescopes consist of the following optical elements:

• entrance window with shutter;
• filter;
• artificial moon (telescope 2);
• multilayer mirror;
• detector (CCD);

The first telescope operates in the 130-136 A spectral region with FeXX 132.84 A and FeXXIII 132.91 A lines. The images obtained by the telescope will provide data on spatial distribution and dynamics of very hot coronal plasma with temperature higher than 10⁷ K.

The second telescope covers the 290-320 A spectral region centered at the HeII 303.8 A line. Intense emission in the HeII 303.8 A line is mainly produced in the transition layer with a temperature lower than 10⁵ K.

The telescopes may operate simultaneously or in a sequence depending on the operating mode.

In both instruments, the Sun's image is formed by parabolic mirrors with multilayer coatings. Visible light is blocked by thin-film pre-filers placed after the entrance window at the front panel and by similar filters coated on the CCD surfaces. The enctrance window of HeII-telescope is equipped with an artificial moon. This allows us to observe the corona from 0.2 to 4 solar radii by inclining the mirror with a pointing and focusing mechanism.

The image detectors of the FET are backside-CCDs of 2048x2048 pixels. The fields of view cover the hole Sun. The angular resolution of both telescopes is on the order of 1.7 arc. sec./pixel. The temporal resolution depends on the operating mode: for full frame images it is 10 seconds, while partial-frame images may be registered with up to 1 second time resolution

Solar EUV Coronograph (SEC)

Instrument Coronograph based on Ritchey-Chretien telescope Spectral range 290 - 320 А Focal length 600 mm Aperture Circular  diameter 85 mm (outer) and 25 mm (inner) Field of view 2o.5 (solar corona from 0.7 to 4 solar radii above the surface) Angular resolution 5 arc. sec./pix Temporal resolution 100 - 600 sec Detector Backside CCD 2048*2048 pixels CCD pixel size 13.5*13.5 micron

The SEC is a solar coronograph based on the Ritchey-Chretien scheme. The SEC operates in the spectral band 290 A centered at the lines SiXI 303.3 A and Hell 303.8 A. Its field of view is 2.5^o covering the inner and outer corona through from solar limb from 0.7 to 4 solar radii.

The SEC consists of the following optical elements:

• filters
• primary mirror
• secondary mirror
• detector (CCD)