Global warming imposes us to reflect on the way we carry research, embarking on the obligation to minimize the environmental impact of our research programs, with the reduction of our travel footprint being one of the easiest actions to implement, thanks to the advance of digital technology. The X-ray Integral Field Unit (X-IFU), the cryogenic spectrometer of the Athena space X-ray observatory of the European Space Agency will be developed by a large international consortium, currently involving 240 members, split over 13 countries, 11 in Europe, Japan and the United States. The travel footprint associated with the development of the X-IFU is to be minimized. For that purpose, a travel footprint calculator has been developed and released to the X-IFU consortium members. The calculator uses seven different emission factors and methods leading to estimates that differ by up to a factor of 5 for the same flying distance. These differences illustrate the lack of standards and regulations for computing the footprint of flight travels and are explained primarily, though partly, by different accounting of non- CO2 effects. When accounting for non-CO2 effects, the flight emission is estimated as a multiple of the direct CO2 emission from burning fuel, expressed in CO2-equivalent (CO2eq), with a multiplication factor ranging from 2 to 3. Considering or ignoring this multiplication factor is key when comparing alternative modes of transportation to flying. The calculator enables us to compute the travel footprint of a large set of travels and can help identify a meeting place that minimizes the overall travel footprint for a large set of possible city hosts, e.g. cities with large airports. The calculator also includes the option for a minimum distance above which flying is considered the most suitable transport option; below that chosen distance, the emission of train journeys are considered. To demonstrate its full capabilities, the calculator is first run on one of the largest scientific meetings; the fall meeting of the American Geoscience Union (AGU) gathering some 24000 participants and the four meetings of the lead authors of the working group I of the Intergovernmental Panel on Climate Change (IPCC) preparing its sixth assessment report. In both examples, the calculator is used to compute the location of the meetings that would minimize the travel footprint. Then, the travel footprint of a representative set of X-IFU related meetings is estimated to be 500 tons of CO2eq per year (to place this number in perspective, it is equivalent to 2 billion kilometers driven by an average passenger vehicle). Of this amount, each annual consortium meeting accounts for 100 tons, being located at a site of minimum emission and for a minimum distance for flying of 700 km. Actions to reduce the X-IFU travel footprint are being implemented, e.g., the number of large consortium meetings has been reduced to one per year and face-to-face working meetings are progressively replaced by video conferences. As the on-line travel footprint calculator may be used to all scientific collaborations and meetings, the calculator and its methodology described in this paper are made freely available to the science communitycommunity ( https://travel-footprintcalculator.irap.omp.eu ).

中文翻译：

---

估计、监控和最小化与 Athena X 射线积分场单元开发相关的旅行足迹

全球变暖迫使我们反思我们进行研究的方式，承担起尽量减少研究项目对环境影响的义务，由于数字技术的进步，减少我们的旅行足迹是最容易实施的行动之一. 欧洲航天局雅典娜空间 X 射线天文台的低温光谱仪 X 射线积分场单元 (X-IFU) 将由一个大型国际财团开发，目前有 240 个成员，分布在 13 个国家，11 个欧洲、日本和美国。与 X-IFU 开发相关的旅行足迹将被最小化。为此，我们开发了一个旅行足迹计算器并发布给 X-IFU 联盟成员。该计算器使用七种不同的排放因子和方法，得出相同飞行距离的估计值相差高达 5 倍。这些差异说明缺乏计算飞行旅行足迹的标准和法规，主要但部分是通过对非二氧化碳影响的不同核算来解释的。在考虑非 CO2 影响时，飞行排放量估计为燃烧燃料产生的直接 CO2 排放量的倍数，以 CO2 当量 (CO2eq) 表示，乘法因子范围为 2 到 3。考虑或忽略此乘法因子在将替代交通方式与飞行进行比较时，这是关键。该计算器使我们能够计算大量旅行的旅行足迹，并可以帮助确定一个会议地点，以最大限度地减少大量可能的城市东道国（例如拥有大型机场的城市）的整体旅行足迹。该计算器还包括最小距离选项，在该距离之上飞行被认为是最合适的运输选项；在所选距离以下，考虑火车行程的排放。为了展示其全部功能，该计算器首先在最大的科学会议之一上运行；美国地球科学联盟 (AGU) 秋季会议聚集了大约 24000 名参与者，政府间气候变化专门委员会 (IPCC) 第一工作组主要作者的四次会议准备了第六次评估报告。在这两个例子中，该计算器用于计算会议地点，以最大限度地减少旅行足迹。然后，一组具有代表性的 X-IFU 相关会议的旅行足迹估计为每年 500 吨二氧化碳当量（从这个数字来看，相当于一辆普通乘用车行驶 20 亿公里）。其中，每年的财团会议占 100 吨，位于排放量最小的地点，飞行距离最短为 700 公里。正在实施减少 X-IFU 差旅足迹的行动，例如，大型财团会议的数量已减少到每年一次，面对面的工作会议逐渐被视频会议取代。由于在线旅行足迹计算器可用于所有科学合作和会议，