The next generation of high-precision astrometry is rapidly approaching thanks to ongoing and upcoming missions like Euclid, LSST, and RST. We present a new tool (available at https://github.com/KevinMcK95/gaia_roman_astrometry) to simulate the astrometric precision that will be achieved when combining Gaia data with Roman images. We construct realistic Roman position uncertainties as a function of filter, magnitude, and exposure time, which are combined with Gaia precisions and user-defined Roman observing strategies to predict the expected uncertainty in position, parallax, and proper motion (PM). We also simulate the core Roman surveys to assess their end-of-mission astrometric capabilities, finding that the High Latitude and Galactic Bulge Time Domain Surveys will deliver Gaia-DR3-quality PMs down to G=26.5 mag and G=29.0 mag, respectively. Due to its modest number of repeat observations, we find that the astrometry of the High Latitude Wide Area Survey (HLWAS) is very sensitive to particular choices in observing strategies. We compare possible HLWAS strategies to highlight the impact of parallax effects and conclude that a multi-year Roman-only baseline is required for useful PM uncertainties (<100 mas/yr). This simulation tool is actively being used for ongoing Roman proposal writing to ensure astrometric requirements for science goals will be met. Subsequent work will expand this tool to include simulated observations from other telescopes to plan for a future where all surveys and datasets are harnessed together.

翻译：随着欧几里得、LSST和RST等当前及未来任务的推进，下一代高精度天体测量时代正快速来临。本文提出一种新工具（可通过https://github.com/KevinMcK95/gaia_roman_astrometry获取），用于模拟结合盖亚数据与罗马望远镜图像时将实现的天体测量精度。我们构建了符合实际观测条件的罗马望远镜位置不确定度函数，该函数与滤光片类型、星等及曝光时间相关，并结合盖亚测量精度与用户自定义的罗马观测策略，以预测位置、视差和自行运动的预期不确定度。通过模拟罗马核心巡天项目，我们评估了其任务终期的天体测量能力，发现高纬度时域巡天和银河系核球时域巡天将分别提供星等G=26.5和G=29.0以下、达到盖亚-DR3质量水平的自行运动数据。由于重复观测次数有限，高纬度广域巡天（HLWAS）的天体测量结果对观测策略的具体选择极为敏感。通过比较不同HLWAS策略方案，我们揭示了视差效应的影响，并得出结论：为获得有效的自行运动不确定度（<100 mas/年），必须建立跨多年的纯罗马望远镜观测基线。该模拟工具正被积极应用于罗马望远镜的提案撰写，以确保科学目标的天体测量要求得以满足。后续工作将扩展该工具的功能，纳入其他望远镜的模拟观测数据，为统筹整合所有巡天与数据集的未来观测规划提供支持。