SUBMILLIMETRON project

Submillimeter Wave Cryogenic Telescope
for the International Space Station

Introduction
The objectives of the Submillmetron Project
Experiment configuration
Main parameters
Cryogenic Telescope parameters
Block diagram of the Cryogenic Telescope
Free flying spacecraft with the
Submillimeter Wave Cryogenic Telescope
picture (click to enlarge)


The Submillimetron is the international project of the space telescope for astronomical studies at submillimeter and millimeter wavelengths using facilities of the Russian segment of the International Space Station (ISS). The concept of Submillimetron telescope includes a 60 cm mirror telescope cooled to liquid helium temperature combined with a new type of supersensitive microbolometers arrays. This combination gives unique possibility to realize background limited sensitivity in the spectral minimum of the extraterrestrial background electromagnetic radiation around frequency 1 THz. This region is between peaks of galactic dust emission and extragalactic cosmic microwave background (CMB) measured by COBE satellite. The angular resolution about 1 arcmin and field of about 1o are similar to IRAS satellite survey, but more then order of magnitude better sensitivity about 10-18 W Hz-1/2 and another spectral region permits reveal in full sky survey sufficiently more new astrophysical objects. For following space missions Herschel (FIRST), Planck, IRIS these results will give useful complementary information of measurements with different angular resolution in another spectral regions. Next feature of the project is the concept of free flying instrument with periodic docking to ISS. Unlike to the usual concept of an autonomous mission this one gives possibility to combine low cost with reliability, refilling, repairment and maintenance. The initiative of the Project was done in Astro Space Center of the P.N. Lebedev Institute after discussions with NASA and JPL, supported later by the Russian Academy of Sciences. The proposal was undertaken to feasibility study in S.P. Korolev Rocket Space Corporation Energia (RSCE) and approved by the Russian Space Agency for the 2-d stage of ISS realization after years 2004 - 2005. The project is accepted for implementation by RSCE, which is responsible for the core of the ISS, its Russian Segment.

The objectives of the Submillmetron Project.

The objects of an astronomical study in submillimeter and infrared wavelengths are the "cold" components of the matter in the Universe (3oK radiation relic of Big Bang, extragalactic sources on the stage of star birth burst, dust in the Solar System, in the Galaxy).
The primary goals are:
  • a submillimeter wave full sky photometric survey,
  • studies of the spectral enegy distribution (SED) of astronomical sources and their variability,
  • determination of 105 - 106 brigtest objects of young Universe
    (between beginning of visible stucture formation and half of modern age),
  • investigations of clasters of galaxies (Zeldovich-Syunyaev effect),
  • search for spectral details in the CMB due to processes during "dark time" between the epochs of recombination and secondary heating,
  • study of the anisotropy and polarization of the cosmic microwave background (CMB) with efficient separation of foreground sources.
    The secondary goal is to provide a test bed to perform the technological experiments needed to develop follow-on projects.

    Experiment configuration

    The main configuration of the Submillimetron in the process of observation is free flying spacecraft (FFS) carrying telescope payload with deployed screens and fully active cryogenic systems. The FFS has docking equipment for work in conjunction to ISS on stages of delivery, deployment , and if necessary for refilling, repairment and maintenance. The FFS made on the base of Progress cargo-ship has also possibility to arrange auxiliary observing instruments, for example heterodyne instrument for high resolution spectrometry and interferometry with noncooling mirror up to 3.5 m. The orbit of the FFS can be distant enough from ISS to solve problems of contaminations and excessive infrared radiation and shadowing. Submillimtron telescope payload consists of Cryogenic Telescope with optics and cryogenics systems and Data Registration and Processing Unit with electronics and power supply systems.

    Orbit: circular orbit at an altitude of approximately 444 km with a 51.6o inclination.
    Delivery to initial ISS orbit: modified cargo-ship Progress

    Payload: the Submillimeter Cryogenic Telescope

    Data output: 1 Gbyte/day

    The Cryogenic Telescope parameters are:
    Diameter: D=0.6 m
    Optical system: two-mirror Cassegrain

    Cooling:

    Wavelengths:
    submillimeter bands: 0.2, 0.25, 0.35, 0.45, 0.55, 0.7, 0.9, 1.2, 1.7 mm.
    Spectral bandwidth: 20 - 40% of the central wavelength.

    Detector arrays:
    in submillimeter bands 1D arrays, 10-300 elements each.
    Sensitivity of the detectors 10-18 W/Hz1/2

    Angular resolution:
    submillimeter bands: 1-10 min of arc (diffraction limited)

    Sensitivity of the telescope (integration time = 1 s) in submillimeter bands: 3-12 mJy.




    Block diagram of the Cryogenic Telescope
    STR - Star Tracker,
              determines the pointing
              of the telescope;
    HeII – superfluid helium
               vessel T=2K,
               cooling of primary
               and secondary mirrors;
    FDB - Focal Dichroic
               Beam-splitters
               assembly;
    SBA - Submillimeter
               Bolometer Array;
    CAU - Cool Electronics Unit
               (amplifiers and
               control circuits);
    mKC - milli-Kelvin Cooler 
                (T<300 mK);
    TEA – Telescope Electronics
               Assembly,
    DRPU - Data Registration
                and Processing Unit.


    Last updated: 2002, Sept.24
    E-mail: f4agro@fy.chalmers.se