Since the very beginning of astronomy the location of objects on the sky has been a fundamental observational quantity that has been taken for granted. While precise two dimensional positional information is easy to obtain for observations in the electromagnetic spectrum, the positional accuracy of current and near future gravitational wave detectors is limited to between tens and hundreds of square degrees, which makes it extremely challenging to identify the host galaxies of gravitational wave events or to detect any electromagnetic counterparts. Gravitational wave observations provide information on source properties that is complementary to the information in any associated electromagnetic emission. Observing systems with multiple messengers thus has scientific potential much greater than the sum of its parts. A gravitational wave detector with higher angular resolution would significantly increase the prospects for finding the hosts of gravitational wave sources and triggering a multi-messenger follow-up campaign. An observatory with arcminute precision or better could be realised within the Voyage 2050 programme by creating a large baseline interferometer array in space and would have transformative scientific potential. Precise positional information of standard sirens would enable precision measurements of cosmological parameters and offer new insights on structure formation; a high angular resolution gravitational wave observatory would allow the detection of a stochastic background and resolution of the anisotropies within it; it would also allow the study of accretion processes around black holes; and it would have tremendous potential for tests of modified gravity and the discovery of physics beyond the Standard Model.

自从天文学开始以来，物体在天空上的位置一直是理所当然的基本观测量。尽管很容易获得精确的二维位置信息以进行电磁光谱的观测，但是当前和不久的将来的重力波探测器的位置精度仅限于数十到数百平方度，这使识别星系的主星系极具挑战性。引力波事件或检测到任何电磁对应物。引力波观测可提供有关源特性的信息，可与任何相关的电磁辐射中的信息互补。因此，具有多个信使的观测系统的科学潜力远大于其各个部分的总和。具有更高角分辨率的重力波探测器将大大增加寻找重力波源的主体并引发多信使后续运动的前景。通过在太空中创建大型基线干涉仪阵列，可以在Voyage 2050计划中实现具有弧度分钟精度或更高精度的天文台，这将具有变革性的科学潜力。标准警报器的精确位置信息将能够精确测量宇宙学参数，并提供有关结构形成的新见识；高角度分辨率引力波天文台将能够检测出随机背景，并能分辨其中的各向异性；它还可以研究黑洞周围的积聚过程；