IONOSAR

了解森林地上生物量及其变化情况，对于量化地球的碳循环和气候行为至关重要，对评估森林资源及其为人类提供的服务也至关重要。对于世界大多数地区，特别是热带森林，目前关于生物量的信息非常有限，规模非常粗略，容易出现大的和无法量化的误差。因此，更好地掌握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它们的措施的谈判的重要组成部分。为了应对这一迫切需求，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第三周期地球探测器核心任务的生物质卫星任务。在竞争性评估方面，该特派团最初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，生物质能在2011年通过进一步评估，它将在2016-17年度推出。在为期五年的飞行任务期间，它将绘制符合国家比例尺清单和碳通量计算需要的精度和空间分辨率的世界地上生物量的全部范围图，并绘制森林生物量的变化图。这些数据对于改进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利用具有重要影响。该飞行任务还有几个重要的次要目标，包括收集关于极地冰、土壤湿度、海洋盐度以及干旱地区的地下结构和古水文学的新信息。生物质能利用了一个新的机会，因为在2003年之前，它使用的长雷达波长(68厘米)无法用于对地观测，因为可能会干扰军事系统。然而，2003年，国际电信联盟开放了这一波长，用于对地球进行成像。这是一项关键的发展，因为在如此长的波长上测量森林对生物量非常敏感。然而，伴随着长波雷达的特殊能力，也带来了特殊的问题。特别是，生物质使用的雷达信号必须通过电离层传输，这可能会以各种方式影响它们。因此，确保选择BIIOMASS并取得成功的一个关键步骤是制定应对这些影响的战略。这一战略的一部分是仔细选择轨道，因为电离层随着位置、一天和一年的时间以及太阳的条件而变化很大。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，部分研究将致力于建立这种知识并将其与雷达性能联系起来。然而，很明显，在某些情况下，我们将需要方法来修正数据，许多研究将致力于开发和测试方法来做到这一点。它的终点将是一套程序，告诉我们如何在生物量遇到的任何电离层条件下准确测量森林生物量和高度，从而确保任务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.