The Sub-Millimetre Radiometer (SMR) on board the Odin satellite performs limb sounding measurements of the middle atmosphere to detect molecular emission from different species. Carbon monoxide (CO) is an important tracer of atmospheric dynamics at these altitudes, due to its long photochemical lifetime and high vertical concentration gradient. In this study, we have successfully recovered over 18 years of SMR observations, providing the only dataset to date being so extended in time and stretching out to the polar regions, with regards to satellite-measured mesospheric CO. This new dataset is part of the Odin/SMR version 3.0 level 2 data. Much of the level 1 dataset – except the October 2003 to October 2004 period – was affected by a malfunctioning of the phase-lock loop (PLL) in the front end used for CO observations. Because of this technical issue, the CO line could be shifted away from its normal frequency location, causing the retrieval to fail or leading to an incorrect estimation of the CO concentration. An algorithm was developed to locate the CO line and shift it to its correct location. Nevertheless, another artefact causing an underestimation of the concentration, i.e. a line broadening, stemmed from the PLL malfunctioning. This was accounted for by using a broader response function. The application of these corrections resulted in the recovery of a large amount of data that was previously being flagged as problematic and therefore not processed. A validation study has been carried out, showing how SMR CO volume mixing ratios are in general in good accordance with the other instruments considered in the study. Overall, the agreement is very good between 60 and 80 km altitude, with relative differences close to zero. A positive bias at low altitudes (50–60 km) up to +20 % and a negative bias up to −20 % at high altitudes (80–100 km) were found with respect to the comparison instruments.

中文翻译：

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Odin / SMR中层一氧化碳长期测量的恢复和验证

奥丁卫星上的亚毫米辐射计（SMR）对中层大气进行肢体探测，以检测不同物种的分子发射。一氧化碳（CO）由于具有较长的光化学寿命和较高的垂直浓度梯度，因此在这些海拔高度是重要的大气动力学示踪剂。在这项研究中，我们已经成功地恢复了18年的SMR观测值，这是迄今为止唯一一个时间如此扩展并延伸到极地地区的数据集，涉及卫星测量的中层CO。 Odin / SMR 3.0版第2级数据。除2003年10月至2004年10月这一时期外，许多1级数据集都受到用于CO观测的前端锁相环（PLL）故障的影响。由于此技术问题，CO线可能会偏离其正常的频率位置，从而导致检索失败或导致对CO浓度的错误估计。开发了一种算法来定位CO线并将其移动到正确的位置。但是，由于PLL的故障，会导致另一个导致浓度低估的伪像，即线条变宽。这是通过使用更广泛的响应函数来解决的。这些更正的应用导致恢复了以前被标记为有问题并因此未处理的大量数据。已经进行了一项验证研究，显示了SMR CO体积混合比总体上与研究中考虑的其他仪器基本吻合。总体，在60至80公里的高度之间，该协议非常好，相对差异接近于零。在低海拔（50–60 km）直至 相对于比较仪器，在高海拔（80–100 km）处发现+ 20  ％的负偏压和高达-20％的负偏压。