Significance Climate change and air pollution caused by fossil-energy-related CO 2 and NO x emissions is a capstone societal issue. A critical barrier to an international treaty aimed toward controlling emissions is the inability to verify inventories and reduction of emissions claimed by individual nations following implementation of new technologies. We demonstrate for the first time, to our knowledge, that simultaneous remote observations of CO 2 , NO 2 , and CO regional column enhancements can be made with high fidelity and frequency. These can then be used to identify emissions from power plants and to distinguish them from other sources. Our findings represent a significant advancement in remote sensing monitoring methodology and can be used to develop an enforceable, transparent, and equitable climate treaty.
The Multispectral Thermal Imager (MTI) is a technology test and demonstration satellite whose primary mission involved a finite number of technical objectives. MTI was not designed, or supported, to become a general purpose operational satellite. The role of the MTI science team is to provide a core group of system-expert scientists who perform the scientific development and technical evaluations needed to meet programmatic objectives. Another mission for the team is to develop algorithms to provide atmospheric compensation and quantitative retrieval of surface parameters to a relatively small community of MTI users. Finally, the science team responds and adjusts to unanticipated events in the life of the satellite. Broad or general lessons learned include the value of working closely with the people who perform the calibration of the data as well as those providing archived image and retrieval products. Close interaction between the Los Alamos National Laboratory (LANL) teams was very beneficial to the overall effort as well as the science effort. Secondly, as time goes on we make increasing use of gridded global atmospheric data sets which are products of global weather model data assimilation schemes. The Global Data Assimilation System information is available globally every six hours and the Rapid Update Cycle products are available over much of the North America and its coastal regions every hour. Additionally, we did not anticipate the quantity of validation data or time needed for thorough algorithm validation. Original validation plans called for a small number of intensive validation campaigns soon after launch. One or two intense validation campaigns are needed but are not sufficient to define performance over a range of conditions or for diagnosis of deviations between ground and satellite products. It took more than a year to accumulate a good set of validation data. With regard to the specific programmatic objectives, we feel that we can do a reasonable job on retrieving surface water temperatures well within the 1°C objective under good observing conditions. Before the loss of the onboard calibration system, sea surface retrievals were usually within 0.5°C. After that, the retrievals are usually within 0.8°C during the day and 0.5°C at night. Daytime atmospheric water vapor retrievals have a scatter that was anticipated: within 20%. However, there is error in using the Aerosol Robotic Network retrievals as validation data which may be due to some combination of calibration uncertainties, errors in the ground retrievals, the method of comparison, and incomplete physics. Calibration of top-of-atmosphere radiance measurements to surface reflectance has proven daunting. We are not alone here: it is a difficult problem to solve generally and the main issue is proper compensation for aerosol effects. Getting good reflectance validation data over a number of sites has proven difficult but, when assumptions are met, the algorithm usually performs quite well. Aerosol retrievals for off-nadir views seem to perform better than near-nadir views and the reason for this is under investigation. Land surface temperature retrieval and temperature-emissivity separations are difficult to perform accurately with multispectral sensors. An interactive cloud masking system was implemented for production use. Clouds are so spectrally and spatially variable that users are encouraged to carefully evaluate the delivered mask for their own needs. The same is true for the water mask. This mask is generated from a spectral index that works well for deep, clear water, but there is much variability in water spectral reflectance inland and along coasts. The value of the second-look maneuvers has not yet been fully or systematically evaluated. Early experiences indicated that the original intentions have marginal value for MTI objectives, but potentially important new ideas have been developed. Image registration (the alignment of data from different focal planes) and band-to-band registration has been a difficult problem to solve, at least for mass production of the images in a processing pipeline. The problems, and their solutions, are described in another paper.
Recent calculations of the Martian obliquity suggest that it varies chaotically on timescales longer than about 10 7 years and varies between about 0 and 60°. We examine the seasonal water behavior at obliquities between 40 and 60°. Up to several tens of centimeters of water may sublime from the polar caps each year, and possibly move to the equator, where it is more stable. CO 2 frost and CO 2 ‐H 2 O clathrate hydrate are stable in the polar deposits below a few tens of meters depth, so that the polar cap could contain a significant CO 2 reservoir. If CO 2 is present, it could be left over from the early history of Mars; also, it could be released into the atmosphere during periods of high obliquity, causing occasional periods of more‐clement climate.
In modeling the thermal emissivity of a rough surface, such as wind-driven waves on a lake or ocean, it is customary to treat the surface as a collection of individual facets, each of which is flat but tilted with respect to the horizontal. By considering a one-dimensional cross-section through the rough surface, the authors derive a purely geometrical constraint on the statistical distribution of shadowed facet slopes that should be satisfied by any model of surface emissivity that includes the effect of self-shadowing. The purpose is not to develop a single shadowing model, but to provide a condition that any valid shadowing model should satisfy. Although the emphasis of the presentation is theoretical, some practical ramifications will also be discussed.
Lunar eclipse temperature measurements are sensitive to rock populations because surfaces with abundant exposed rock have much higher mean thermal inertias than surfaces dominated by fine powders . When the Moon passes into the I :arth's shadow, the abrupt reduction in insolation causes surfacc elements to cool at rates which are ILnctions oftheir thermal inertia . The rock population is a lunction of the exposure of a surface unit, originally composed of solid igneous rock or impact mclt, to the impact flux of modest sized projectiles. With time, a competent surface such as a lava flow field or an impact melt sheet will be comminuted by the impact flux reducing the ratio of coarse to fine particles . In principle, thermal measurements taken during lunar eclipse can be used as a measure of the relative age of surface units .
The QuickBird commercial imaging satellite is a pushbroom system with four multispectral bands covering the visible through near-infrared region of the spectrum and a panchromatic band. 6972 detectors in each MS band and 27888 detectors in the pan band must be calibrated. In an ideal sensor, a uniform radiance target will produce a uniform image. Unfortunately, raw imagery generated from a pushbroom sensor contains vertical streaks caused by variability in detector response, variability in electronic gain and offset, lens falloff, and particulate contamination on the focal plane. Relative radiometric correction is necessary to account for the detector-to-detector non-uniformity seen in raw imagery. A relative gain is calculated for each detector while looking at a uniform target such as an integrating sphere during ground calibrations, diffuser panel, or large desert target on-orbit. A special maneuver developed for QuickBird called the "Side-Slither" technique is discussed. This technique improves the statistics of a desert target and achieves superior non-uniformity correction in imagery. The "Side-Slither" technique is compared to standard techniques for calculation of relative gain and shows a reduction in the streaking seen in imagery.
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