IONOSAR

关于森林地上生物量及其变化的知识对于量化地球碳循环和气候的变化具有根本重要性，对于评估森林资源及其为人类提供的服务也至关重要。就世界大多数地区而言，特别是热带森林，关于生物量的信息目前非常有限，比例非常粗略，而且有很大和无法量化的误差。因此，更好地处理这些森林中的生物量是了解森林如何促进气候变化和支持联合国关于保护森林措施的谈判的重要组成部分。为了满足这一迫切需要，由英国和法国科学家领导的一个国际小组向欧洲航天局提出了BIOMASS卫星使命，用于地球探测器核心任务的第三个周期。在竞争性评估中，该特派团首次被选为拟进一步研究的29个特派团中的6个特派团之一，并于2009年3月被选为A阶段研究的其余3个特派团之一。如果一切顺利，BIOMASS将在2011年通过进一步评估，并将于2016-17年推出。在为期五年的使命期间，它将以符合国家规模清查和碳通量计算需要的准确度和空间分辨率绘制全世界地面生物量的地图，并绘制森林生物量的变化。这些数据对于改善我们对当前和未来碳循环的评估至关重要，并对水循环和人类对生物圈的使用产生重要影响。该使命还有几个重要的次要目标，包括收集有关极地冰、土壤湿度、海洋盐度和干旱地区地下结构和古水文学的新信息。BIOMASS利用了一个新的机会，因为在2003年之前，由于可能干扰军事系统，它使用的长雷达波长（68厘米）无法用于地球观测。然而，在2003年，国际电信联盟开放了这个波长用于对地球成像。这是一个关键的发展，因为在这种长波长下对森林的测量对生物量非常敏感。然而，沿着长波长雷达的特殊能力而来的是特殊的问题。特别是，BIOMASS使用的雷达信号必须穿过电离层，这可能会以各种方式影响它们。因此，确保BIIOMASS的选择和成功的关键步骤是制定应对这些影响的策略。这种策略的一部分是仔细选择轨道，因为电离层随着位置、一天和一年中的时间以及太阳上的条件而变化很大。因此，我们可以选择一个减少影响的轨道;要做到这一点，需要对电离层行为有广泛的了解，部分研究将致力于积累这种知识，并将其与雷达性能联系起来。然而，很明显，在某些条件下，我们需要纠正数据的方法，大部分研究将致力于开发和测试方法。它的终点将是一套程序，告诉我们如何在BIOMASS遇到的任何电离层条件下准确测量森林生物量和高度，从而确保使命能够实现其雄心勃勃的科学目标。

Knowledge about forest above-ground biomass and how it is are changing is of fundamental importance in quantifying how the Earth's carbon cycle and climate behave, and is also crucial in assessing forest resources and the services they provide to mankind. For most parts of the world, in particular the tropical forests, information on biomass is currently very limited, at very coarse scales, and subject to large and unquantified errors. Getting a better handle on the biomass in these forests is therefore an essential part of knowing how forests contribute to climate change and supporting UN negotiations on measures to protect them. In response to this urgent need, an international team led by UK and French scientists proposed the BIOMASS satellite mission to the European Space Agency for the third cycle of Earth Explorer Core missions. In competitive assessments, this was first selected to be one of six missions out of 29 proposed for further study, and in March 2009 was one of the remaining three selected for Phase A Study. If all goes well and BIOMASS passes a further assessment in 2011, it will launch in 2016-17. Over the five-year mission lifetime, it will map the full range of the world's above-ground biomass with accuracy and spatial resolution compatible with the needs of national scale inventory and carbon flux calculations, and will map changes in forest biomass. These data are crucial for improving our assessments of the current and future carbon cycle, and have important ramifications for the water cycle and human use of the biosphere. The mission also has several important secondary objectives, including gathering new information on polar ice, soil moisture, ocean salinity, and sub-surface structures and palaeo-hydrology in arid areas. BIOMASS takes advantage of a new opportunity, since before 2003 the long radar wavelength it uses (68 cm) was unavailable for Earth Observation because of possible interference with military systems. However, in 2003 the International Telecommunication Union opened this wavelength for imaging the Earth. This was a key development, since measurements of forests at this long wavelength are very sensitive to biomass. However, along with the special capabilities of long wavelength radar come special problems. In particular, the radar signals used by BIOMASS have to travel through the ionosphere, which can affect them in a variety of ways. Hence a key step in ensuring the selection and success of BIIOMASS is to develop strategies for dealing with these effects. Part of this strategy is to choose the orbit carefully, because the ionosphere varies enormously with position, time of the day and year, and conditions on the Sun. So we can choose an orbit that reduces the effects; to do this requires extensive knowledge about ionospheric behaviour, and part of the research will be devoted to building up this knowledge and relating it to radar performance. However, it is clear that there are conditions under which we will need ways to correct the data, and much of the research will be devoted to developing and testing methods to do this. Its end point will be a set of procedures that tell us how make accurate measurements of forest biomass and height under whatever ionospheric conditions BIOMASS encounters, and thus ensure the mission can deliver its ambitious science goals.