| RUSALKA experiment aimed to demonstrate the method to monitor CO2 and CH4 is now
prepared for the Russian segment of the International Space Station (ISS). Hardware will be
delivered to ISS in March 2009. The novel instrument is a high-resolution near-IR
spectrometer combining an echelle grating with an acousto-optic tunable filter (AOTF) for
separation of diffraction orders. A compact design with no moving parts within the mass
budget of 2 kg allows to reach the resolving power of 10000-20000 in the spectral
ranges of 1580 nm (CO2), 1640 nm (CH4), in 49 and 47 diffraction orders, and
of reference O2 bands 760 and 1270 nm, in 101 and 61 diffraction orders. Only
one diffraction order can be measured at a time, but thanks to flexibility of the
AOTF tuning, any order can be measured randomly and rapidly within the spectral
range. A spectrometer, based on this principle, SOIR (Solar Occultation InfraRed) is
operational on Venus Express ESA mission since 2005. RUSALKA investigation targets
precision measurements of CO2 and CH4 integral quantities, in nadir/oblique or
observing solar glint over the water surfaces. Test measurements are also planned
in solar occultation mode. Battery-powered RUSALKA package consists of the
spectrometer itself, standard photographic camera for context imaging, and adapters.
Measurements will be performed by crew members pointing manually the target areas. Such
measurements from ISS will allow to verify the method to be used in the future on
different satellite platforms. The small size of the instrument makes it ideal for
micro-satellites, capable to provide necessary pointing for glint or solar occultation
observations. The status and calibration of RUSALKA flight hardware will be discussed. |