Model of WSO-UV telescope during "Space Week" in Madrid, May 2011
|Mission type||Space telescope|
|Operator||Russian Astro Space Center|
|Payload mass||2,840 kg (6,261 lb)|
|Start of mission|
|Launch date||23 October 2025 (proposed)|
|Rocket||Angara A5 / DM-03|
|Launch site||Vostochny Site 1A|
|Wavelengths||115 to 315 nm|
The Spektr-UV, also known as World Space Observatory-Ultraviolet (WSO-UV), is a proposed ultraviolet space telescope intended for work in the 115 nm to 315 nm wavelength range. Launch had initially been planned for 2007, but has since been continually delayed; as of March 2020, the launch is planned for October 2025 atop an Angara A5 rocket from Vostochny Cosmodrome.
The main instrument of the observatory is a 1.7-metre Ritchey–Chrétien telescope. The telescope will be equipped with the following instruments:
WSO-UV Spectrographs Unit (WUVS) (Russia/Japan)
The WUVS spectrographs assembly consists of four channels:
- Vacuum Ultraviolet Echelle Spectrograph, VUVES (Russia)
The FUV high-resolution spectrograph (VUVES) provides echelle spectroscopy capabilities with high resolution (R ~ 50 000) in the 115–176 nm range.
- Ultraviolet Echelle Spectrograph, UVES (Russia)
The NUV high-resolution spectrograph (UVES) provides echelle spectroscopy capabilities with R ~ 50 000 in the 174–310 nm range.
- Long-Slit Spectrograph, LSS (Russia)
The Long-Slit Spectrograph (LSS) provides low resolution (R ~ 1000), long slit spectroscopy in the 115–305 nm range. The spatial resolution is better than 0.5 arcsec(0.1 arcsec as the best value).
- UV Spectrograph for observation of Earth-like Exoplanets, UVSPEX (Japan)
"Many Earth-sized planets have been discovered and some appear to lie in the habitable zone. Moreover, several Earth-sized planets were recently detected around low temperature stars near the solar system. However, it is difficult to characterize them as Earth-like or Venus-like. Transit spectroscopy for exoplanetary atmosphere has been performed to characterize larger exoplanets but it requires very high accuracy because of their small size...
High sensitivity (photon counting) is required for M-type star faint in UV. Spectral resolution of 0.5 nm is enough for separating major emission lines of exospheric atoms. The spectral resolution will be achievable by spectrometers in the main WUVS block, however, it is difficult to measure the weak stellar emission from M-type stars without a photon-counting detector. To realize exoplanet transit observations in oxygen spectral lines with the desired accuracy, we equip the WSO-UV telescope with the UVSPEX spectrograph...
The spectral resolution is better 0.5 nm to separate O I line from other spectral lines. The spectral range is to exceed the wavelengths from 115 nm to 135 nm to detect at least H Lyman alpha 121.6nm to O I 130 nm. The throughput is better 0.3% accounting more than four terrestrial exoplanets distanced at 5 pc. To achieve these requirements, a simple spectrograph design is proposed, containing the slit, the concave (toroidal) grating as a disperse element and the imaging photo-detector. This optical concept is conventional and used in the other space missions for UV spectroscopy. Spectrometer slit is aligned at primary focus of the telescope from off-axial sub-FoV. Slit width is 0.2 mm, corresponding to 5 arc-sec. The concave grating is laminar type with groove density of 2400 grooves per mm. It has a toroidal shape with the curvature radii of 266.4 mm in horizontal direction and of 253.0 mm in vertical direction. The effective area has nearly O 25 mm and the focal length is ~250 mm. The surface is coated by Al + MgF2 to increase the reflectance, and diffraction efficiency of ~29% can be achieved."
WSO-UV Field Camera Unit (FCU) (Russia/Spain)
The FCU has two channels, each fed by an independent pick off mirror:
- Field Camera Unit FUV channel (FCU/FUV) (Russia/Spain)
The far UV (FUV) channel has capabilities for high resolution imaging.
MCP detector, scale 0,047 arcsec/pixel in 115–190 nm range
- Field Camera Unit UVO channel (FCU/UVO) (Russia)
The UV-optical (UVO) channel is designed for wide field imaging.
CCD detector, scale 0,146 arcsec/pixel in 185–810 nm range
Stellar Coronograph for Exoplanet Direct Imaging, SCEDI (NAOJ, Rikkyo University, Japan)
"For research on exoplanets, a team of Russian (IKI RAS, INASAN) and Japanese (NAOJ, Rikkyo University) scientists proposed a new tool - Stellar coronograph for direct images of exoplanets
(Stellar Coronograph for Exoplanet Direct Imaging, SCEDI). Decision for the inclusion of this regime in the project should be confirmed in 2019, after the completion of the outline design stage of the FCU and
after receiving financing by the Japanese side.
Obtaining direct images of exoplanets located at a sufficient distance from the parent star is unique possibility of researching such out of transit objects.
Observations using a coronograph aboard a space observatory working out of Earth’s turbulent atmosphere, receiving light from a two-meter class telescope with diffraction-quality optics, make it possible to study even non transit exoplanets, the sizes of which approximately correspond to the size of the Earth, in the habitable zone of its star."
-HIRDES (High-Resolution Double Echelle Spectrograph): R~55000 spectroscopy of point sources in the 102–320 nm range (Germany) Germany exit Spektr-UV programm due to financial problems, Russia replaced HIRDES with WUVES.
-ISSIS (Imaging and Slitless Spectroscopy Instrument for Surveys) being developed to carry out UV and optical diffraction limited imaging of astronomical objects. The ISSIS incorporates three channels: High Sensitivity Far-UV Channel: 120–200 nm; Channel for Surveys (FUV): 120–600 nm, optimized for 120–270 nm; Channel for Surveys (UVO): 120–600 nm, optimized for 270–600 nm (Spain). Due to financial problems Spain canceled ISSIS, and limited participation in Spektr-UV programm to ground segment and supply of detectors for FCU.Russia replaced ISSIS with FCU.
In October 2012, tests of antennas for the space telescope were completed.
Spektr-UV is an international project is led by Russia (Roscosmos). At present the international cooperation includes three basic participants: Russia (will provide the telescope, spacecraft, launch facilities, ground segment); Spain (FCU detectors, ground segment); Japan (UVSPEX).