Surface Contamination of Some Materials of the Space Station ‘MIR’

Abstract

About 60 samples of various materials exposed to low Earth orbit (LEO) conditions for 997 days on board the orbital space station ‘Mir’ were investigated. The aim was to determine the properties of the contamination layers formed during LEO exposition. The following methods were used: optical and scanning electron microscopy, local x-ray microanalysis, secondary ion mass spectrometry in fast atom bombardment ionization mode, electron spectroscopy for chemical analysis, temperature programmed desorption mass spectrometry, x-ray phase analysis, spectral reflectance, solar absorbance and relative emittance measurements. Two effects were observed for all samples: the formation of contamination deposits and the erosion of the substrate–original surface. The relative contribution of both effects changes depending on the sample type and on exposure conditions. The deposit thickness varies on the sample surface over a very wide range (at least five decimal orders of magnitude), changing from values exceeding 100 μm to values of less than 2 nm (possibly these regions do not contain any deposit at all). The main element of contamination is silicon; the others are potassium and calcium. Evidence of a chemical reaction between the Teflon FEP substrate and the contamination was observed.

Contaminations of inner surface of magnesium fluoride windows in the ‘Expose-R’ experiment on the International Space Station

“…Indeed, alpha-line of Lyman series of atomic hydrogen (121.6 nm; photon energy 10.7 eV) dominates in the spectrum of Solar VUV radiation. Moreover, radiation with wavelength 121.6 nm induces photoionization of macromolecules with their subsequent transformations similar to those induced by other types of ionizing radiations (Dorofeev & Skurat 1982; Barbashev et al 1992; Skurat & Dorofeev 1994; Van Eesbeek et al 1994; Skurat et al 1997; Skurat et al 2001; Skurat & Samsonov 2001; Skurat 2003). However, a substantial difference of absorbed radiation doses is observed in gamma-radiolysis, bombardment by fast electrons and VUV irradiation (see, for example, (Skurat 2003)).…”

“…Previous studies demonstrated that, main components of contaminating deposits on outer surfaces of orbital stations contain the chemical groups SiO x ( x ≤ 2) and carbon-containing groups (identified by X-ray photoelectron spectroscopy (XPS)) formed from volatile organosilicone compounds of intrinsic outer atmosphere (Skurat et al . 2001, 2011, 2013). Their origin and chemical composition are not completely understood and therefore are the objects of research.…”

Atomic spectrometry update. X-ray fluorescence spectrometry

“…Sun et al, 53 in a contribution to heterogeneous catalysis, used XRMF to measure the adsorption of metal salts by porous gamma-alumina beads. Skurat et al 54 examined about 60 samples from the space station 'MIR' to assess the degree of surface contamination that had occurred in low Earth orbit. X-ray microfluorescence was one of a number of techniques used to assess surface contamination and substrate erosion of the various materials by particles comprised predominantly of Si, with Ca and K. In another materials characterisation application, Istratov et al 55 reviewed the advantages and limitations of a number of novel and emerging techniques used to understand phenomena and defects that limit the lifetime of solar cells.…”