Atmospheric monitoring missions aim at products like O<sub>3</sub>, H<sub>2</sub>O, NO<sub>2</sub>, SO<sub>2</sub>, BrO, CH<sub>4</sub>, CO, CO<sub>2</sub> as well as aerosols and cloud information. Depending on the application area (Ozone Monitoring, Green House Gas Monitoring, Tropospheric Composition and Air Quality, Chemistry Climate Interaction etc.) total or tropospheric columns as well as profile information is required. The user community of these data as well as their central requirements w.r.t. the payload aspects will be described. A large range of relevant passive instrument types is available, in particular imaging spectrometer, sounder and polarisation measuring systems in the UV-VIS, SWIR and TIR spectral range. Differences between instruments for dedicated missions are highlighted and evolution of requirements is explained, also in comparison with relevant existing instrumentation partly in orbit today. Aspects of technology roadmaps for instrument implementation as well as synergetic effects of instrument combinations and according mission scopes are discussed.
CarbonSat is a proposed Earth observation mission, which was selected in 2010 as one of two candidates for becoming the European Space Agency’s (ESA) eighth Earth Explorer (EE8). It is currently undergoing parallel feasibility studies (phase A) performed by two industrial consortia. CarbonSat aims at a better understanding of the natural and anthropogenic sources and sinks of the two most important anthropogenic greenhouse gases CO<sub>2</sub> and CH<sub>4</sub>, which will contribute to a better understanding of climate feedback and forcing mechanisms. To achieve these objectives the instrument will quantify and monitor the spatial distribution of carbon dioxide (CO<sub>2</sub>) and methane (CH<sub>4</sub>). It will deliver global data sets of dry air column-averaged mixing ratios of these gases with high precision (1 - 3 ppm for CO<sub>2</sub> and 6 - 12 ppb for CH<sub>4</sub>) and accuracy (0.5 ppm for CO2 and 5 ppb for CH<sub>4</sub>). The measurements will provide global coverage every 12 days above 40 degrees latitude at a spatial resolution of 2 x 3 km<sup>2</sup>. The retrieval products are inferred from observations of Earth radiance and solar irradiance at high to medium spectral resolution (0.1-0.55 nm) in the Near Infrared (747-773 nm) and Short Wave Infrared (1590- 1675 nm and 1925-2095 nm) spectral regions. The combination of high spatial resolution and global coverage requires a swath width larger than 180 km for three spatially co-aligned push-broom imaging spectrometers. The targeted product accuracy translates into stringent radiometric, spectral and geometric requirements for the instrument. This paper presents the system requirements derived from the demanding mission objectives and reports preliminary results of the feasibility studies. It highlights the key components of the instrument, focusing on the optical conceptual design, and addresses the identified critical performance aspects.
Since 2002-03-01 the spectrometer SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) is in a sun-synchronous polar orbit around the Earth aboard the new European environmental satellite ENVISAT. SCIAMACHY measures during its lifetime concentrations and distributions of atmospheric trace gases such as O<sub>3</sub>, BrO, OClO, ClO, SO<sub>2</sub>, H<sub>2</sub>CO, NO<sub>2</sub>, CO, CO<sub>2</sub>, CH<sub>4</sub>, H<sub>2</sub>O, N<sub>2</sub>O, metals, clouds, and aerosols. The quality of these data products depends both on the calibration of the instrument and the detailed knowledge of the instrument's status and behaviour at any time during the whole mission. To achieve this a comprehensive monitoring concept has been developed and implemented. This paper gives a brief overview of the instrument and the calibration and monitoring concepts. Results of the performance monitoring activities from nominal operations of the instrument show that SCIAMACHY in general is in good shape. The radiometric calibration of the instrument could be enhanced by a thorough revision of the on-ground calibration. An ice-layer buildup is observed on the IR detectors, which shall be compensated by a throughput correction factor.
The Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) is a contribution to the ENVISAT-1 satellite, which has been launched in March 2002. The SCIAMACHY instrument measures sunlight transmitted, reflected and scattered by the Earth's atmosphere or surface simultaneously from the UV to the SWIR spectral region (214 - 2380 nm) in nadir, limb, and occultation viewing geometry. SCIAMACHY allows the characterisation of the composition of the Earth atmosphere from the ground to the mesosphere. This paper gives an overview of the SCIAMACHY instrument and its in-flight detector, spectral and radiometric performance. Furthermore first results on trace gas retrieval from limb and nadir measurement mode will be summarised.
This study is devoted to the development of a semi-analytical algorithm for the determination of the otpical thickness, the liquid water path and the effective size of droplets from spectral measurements of the intensity of solar light reflected from water clouds with large optical thickness. The algorithm is planned to be aplied to the data fromteh Scanning Imaging Absorption Spectrometer for Atmospheric Chartography, launched on March 1st, 2002 on board of the ENVIronmental SATellite. The probability of photon absorption by droplets in the visible and near-IR spectral regions is low. This allows us to simplify and modify well known asymptotic equations of the radiative transfer theory, taking into account the fact that the single scattering albedo is close to one. Modified asymptotic equations are used to develop the inverse algorithm. We also avoid the use of the Mie theory, applying parameterization and geometrical optics results with account for wave corrections. The main advantage of the method proposed lays in the fact that the equations derived not only provide a valuable alternative to the numerical radiative transfer solution. They are also much more simple than equations of a conventional asymptotic theory. This simplicity allows both the simplication of the cloud retrieval algorithm and, even more important, insight into various factors involved in cloud retrieval schemes.
SCIAMACHY (Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY) is a contribution to the ENVISAT-1 satellite, which is to be launched in spring 2000. The SCIAMACHY instrument is designed to measure sunlight transmitted, reflected and scattered by the Earth's atmosphere or surface. The instrument measures simultaneously from the UV to the NIB spectral spectral region (240 - 2380 nm). Observations are made in alternate nadir and limb viewing geometries and also for solar sunrise and lunar moonrise occultation. Inversion of the SCIAMACHY measurements will provide the following: the amount and distributions of some important trace gases O<SUB>3</SUB>, BrO, OClO, ClO, SO<SUB>2</SUB>, H<SUB>2</SUB>CO, NO<SUB>2</SUB>, CO, CO<SUB>2</SUB>, CH<SUB>4</SUB>, H<SUB>2</SUB>O, N<SUB>2</SUB>O, p, T, aerosol, and radiation flux profiles, cloud cover and cloud top height. Combination of the near simultaneous limb and nadir observations enables the tropospheric column amounts of O<SUB>3</SUB>, NO<SUB>2</SUB>, CO, CH<SUB>4</SUB>, H<SUB>2</SUB>O, N<SUB>2</SUB>O, SO<SUB>2</SUB>, and H<SUB>2</SUB>CO to be detected. SCIAMACHY will provide new insight into the global behavior of the troposphere and the stratosphere.
The scanning imaging absorption spectrometer for atmospheric chartography (SCIAMACHY), to be launched on the European polar platform ENVISAT at the end of 1999, will measure sun- and moonlight which is either transmitted, reflected or scattered by the Earth atmosphere. The double spectrometer is designed for the ultraviolet, visible and near IR wavelength region, covering that range with a resolution of 0.24 nm to 1.5 nm. It was conceived to improve our knowledge and understanding of a variety of issues of importance to chemistry and physics of the Earth atmosphere. Scientific objectives are to study ozone hole chemistry, troposphere- stratosphere exchange and tropospheric pollution. This will be achieved by a combined limb, nadir and occultation observation strategy. The SCIAMACHY instrument and operational concept is finalized approaching now the on- ground calibration phase. The planned wavelength and radiometric calibration measurements, including a detailed characterization of the instrument polarization behavior, will be fundamental for the required high data accuracy. Additionally the in-flight calibration and monitoring concept will allow a proper correction of instrument ageing effects. This study describes pre-flight and in-flight calibration the approaches to be employed to maintain a high radiometric and spectral accuracy of the SCIAMACHY measurements throughout its life are reported.
The scanning imaging absorption spectrometer for atmospheric cartography (SCIAMACHY) is a passive optical instrument applied for the remote sensing of the earth atmosphere. SCIAMACHY is the German/Dutch contribution to the first ENVISAT mission defined by ESA and will be launched on the Polar Platform in 1999. Dornier Satellitensysteme GmbH has the prime-contract by the German agency DARA and Fokker Space B.V the prime contract by the Dutch agency NIVR with participation of the Belgian institute BIRA. The primary scientific objective of SCIAMACHY instrument is to observe the atmosphere by measuring sun- and moonlight which is transmitted, reflected and scattered by the earth's atmosphere. Based on the atmospheric absorption of light in the 240 nm to 2385 nm bandwidth concentrations of ozone, greenhouse and trace gases will be determined. The instrument was conceived to improve our knowledge and understanding of a variety of issues of importance to chemistry and physics of the earth's atmosphere such as ozone hole chemistry, troposphere-stratosphere exchange and tropospheric pollution.