The global carbon dioxide observation satellite (TanSat) mission of China is introduced. Two instruments carried by
TanSat including carbon dioxide (CO2) spectrometer with high spectral resolution, termed the TanSat CO2 Spectrometer
(TSCS), and the Cloud and Aerosol Polarize Instrument (CAPI) will make global measurements of atmospheric CO2 with
the high precision of 1% and resolution of 1 km approximately. In this paper, we aim at quantifying the error associated
with aerosol and albedo over China utilizing the new designed parameters of TanSat. Firstly, the latest specifications of
TSCS are analyzed through the observing simulations as well as the retrieval experiments over some areas in China, where
space-based measurements of CO<sub>2</sub> confront the huge challenge induced by atmospheric aerosols which optical depth can
ascend up to more than 1 at wavelengths of 550 nm at certain atmospheric conditions. MODIS aerosol and albedo products
are used in the synthetic measurements. The impacts of both aerosol scattering and surface albedo on CO2 retrieval
accuracy are investigated by applying different retrieval implementation. The errors are estimated for nadir observation
over land with typical solar zenith angle 30° and 60°. Comparisons amongst the three approaches suggest that correctly
treatment of aerosol scattering is necessary to account for the impacts of multiple scattering in order to meet the
requirement of TanSat mission. The development of retrieval algorithm will be continued to the launch of TanSat in late
With the stable increase of carbon dioxide (CO<sub>2</sub>) concentrations, space based measurements of CO<sup>2</sup>
concentration in lower atmosphere by reflected sunlight in near infrared band has become a hot
research topic at present. Recently, the instruments sensitive to total CO<sub>2 </sub>column data in near-surface
have become available through the SCIAMACHY instrument on ENVISAT and TANSO-FTS on
GOSAT. The developing hyper spectral CO<sub>2</sub> detector in China carried by TANSAT will be launched
in late 2015. Hyper spectral CO<sub>2 </sub>detector is designed to provide global measurements of CO<sub>2</sub> in
lower troposphere. It employs high resolution spectra of reflected sunlight taken simultaneously in
near-infrared CO2 (1.61μm and 2.06μm) and O2 (0.76μm) bands.
Associating climate change with the observation requirements of carbon sources and sinks, the
feasibility of making CO2 column concentration measurements with high-resolution and
high-precision is studied by high resolution atmosphere radiation transfer model. The effects of key
specifications of the hyper spectral CO<sub>2 </sub>detector such as spectral resolution, sampling ratio and
sign-to-noise ratio (SNR) on CO<sub>2 </sub>detection are analyzed combining the scientific requirements of
CO<sub>2 </sub>measurements of China.
The typical characteristics of hyper spectral CO2 detector on TANSAT are grating spectrometer
and array-based detector. To achieve the column averaged atmospheric CO2 dry air mole fraction
(XCO<sub>2</sub>) precision requirements of 1×10<sup>-6</sup>-4×10<sup>-6</sup>, hyper spectral CO<sub>2</sub> detector should provide high
resolution at first to resolve CO<sub>2</sub> absorption lines from continuous spectra of reflected sunlight.
Compared to a variety of simulated spectral resolutions, the spectral resolution of hyper spectral CO<sub>2</sub>
detector on TANSAT can resolve CO<sub>2</sub> spectral features and maintain the moderate radiance
sensitivity. Since small size array detector-based instruments may suffer from undersampling of the
spectra, the influences of spectral undersampling to CO<sub>2 </sub>absorption spectra are studied, the results
indicate that sampling ratio should exceed 2 pixels/FWHM to ensure the accuracy of CO<sub>2 </sub>spectrum.
Signal-to-noise ratio is one of the most important parameters of hyper spectral CO<sub>2</sub> detectors to
ensure the reliability of CO<sub>2 </sub>signal. SNR requirements of CO<sub>2</sub> detector to different detection
precisions are explored based on the radiance sensitivity factors. The results show that it is difficult
to achieve the SNR to detect 1×10<sup>-6</sup>-4×10<sup>-6 </sup>CO2 concentration change in the boundary layer by solar
shortwave infrared passive remote sensing, limited by the instrument development at present.
However, the instrument SNR to detect 1% change in the CO<sub>2</sub> column concentration is attainable.
The results of this study are not only conductive to universal applications and guides on developing
grating spectrometer, but also helpful to have a better understanding of the complexity of CO<sub>2</sub>
GPS technology provides a new powerful approach for measuring atmospheric water vapor. In this paper the experiment of observing integrated atmospheric water vapor or the precipitable water (PW) using ground-based GPS receivers performed in southwestern region of China is presented. Zenith total delay (ZPD) data are collected in a GPS network consisting of 10 stations. Time series ofwater vapor in one hour bins for 10 months is retrieved. The results of 3 stations in southwestern region affected by many monsoons show that the water vapor has large variability in spatial and temporal scales. The water vapor derived from GPS is compared with retrievals from the radiosondes. The GPS PW agrees well with data from radiosondes which indicates GPS PW are correct at this locations. The difference of PW from them is larger when the humidity is higher and more variable in summer. The results of comparison with the NCEP reanalysis PW data show that they are consistent with each other. In the mountain areas where observations are few PW from GPS can be used to validate the PW from numerical model analyses. Finally long-term monitoring water vapor using ground-based GPS is discussing.