Failure analysis on optical components is usually carried-out, on standard testing devices such as optical/electronic microscopes and spectrometers, on isolated but representative samples. Such analyses are not contactless and not totally non-invasive, so they cannot be used easily on flight models. Furthermore, for late payload or satellite integration/validation phases with tight schedule issues, it could be necessary to carry out a failure analysis directly on the flight hardware, in cleanroom.
The increase of performance of new optical instruments for science and Earth observation always leads to higher requirements in terms of contamination due to particle sedimentation in cleanrooms and deposition of chemical species in vacuum environment. Specific cleanliness control procedures are implemented in order to mitigate the risks of contamination on optical sensors and sensitive diopters, especially when used for UV applications. Such procedures are commonly carried out in cleanrooms and are described in both European ECSS-Q-ST-70-50C and NASA SN-C-0005D standards. UV light at 365 nm is often used for the inspection of optical sensitive surfaces to localize and to evaluate the amount of fluorescent particles, essentially coming from textile fibers. But other groups of compounds can be observed with a different spectral response and distribution, like adhesives and resins or even organic residues. Therefore, we could take advantage of this spectral information closely linked to specific molecules for partial identification of these materials before further investigation involving wipe on flight model and measurement in a laboratory.
Optical instruments for space applications with improved performances (smaller pixels and spectral range extension) are becoming more and more sensitive to chemical contamination and particle sedimentation. Outgassing under vacuum conditions causes dramatic flux losses, especially in the UV bandwidth. Furthermore, it is difficult to perform physicochemical analyses of contaminated surfaces on flight models, in a clean room. Conventional analytical techniques such as FTIR (Fourier Transform Infrared interferometer) need the tool to be in contact with the studied area, which is forbidden when working on satellites. In addition, it does not give any information about the distribution of the contaminants in the field of view. The probed area is large, mono-pixel, and the sensitivity of the instrument is too low for hundred nanometer thin film deposits. A first study has shown that we could benefit from using the UV/visible fluorescence spectra to partially identify contaminants and polymer materials. The shape of the fluorescence spectra of adhesives, paints and varnishes have specific signatures that could be recorded into a designated reference database. The location of the presence of these contaminants on such sensitive optics is also relevant. To acquire both these parameters, we designed a specific compact hyperspectral instrument to remotely acquire cube images (500x500 pixels) in a 5 degree field of view, and on a wide range of continuous wavelengths from UV at 320 nm up to the near infrared at 1000 nm. This paper will present the chosen trade-off between different critical optics for a new portable version of this instrument. It is dedicated to space and cultural heritage applications and the first results on an engineering prototype will be shown.
The development of new high power EUV sources and EUV space imaging requires optics having specific
properties which depend on applications and operating conditions. These both applications are very different in the
working multilayers environment. For the high power sources, multilayers are submitted to short pulses with high
energy peak whereas, for the space imaging, multilayers are submitted to continuous flux with low level. Moreover
photon energy and environment for both applications may be different. The environment may affect structure and top
layer contamination when optics are stored, handled, mounted on the final device and finally operating. Main
environmental parameters investigated are temperature and humidity variation.
One objective is the optimisation of multilayer coatings to offer the highest resistance under photonic, ionic
fluxes and temperature cycle. This means that interfacial diffusion between thin layers and degradation of the capping
layers have to be avoided or reduced. The present study relies with designing, depositing and testing different structures
of multilayer coatings in order to minimise the influence of the environment.
Multilayer coatings based on molybdenum, silicon and silicon carbide materials have been deposited by magnetron
sputtering on silicon and zerodur substrates. Samples were submitted to radiations emitted by an EUV source at
wavelength closed to 13.5 nm. Furthermore they were also submitted to thermal cycles and annealing under warm
humidity in the aim to simulate extremes storage or handling conditions as space mission's conditions.
The damages and the performance of the multilayers were evaluated by using grazing incidence reflectometry
at 0.154 nm and EUV reflectometry at the operating wavelength.
After a presentation of the multilayer design, deposition and metrology tools, we will describe the different
environmental effects on the coatings to take in care during EUV source exposure, handling and storage conditions.
First results on multilayers performances to EUV source exposure and space specification tests are presented. Main
damages studies were on annealing, thermal cycling and warm humidity.