The scale of the solar system is slowly changing, likely increasing as a result of solar mass loss, with additional change possible if there is a secular variation of the gravitational constant, G. The measurement of the change of scale could provide insight into the past and the future of the solar system, and in addition a better understanding of planetary motion and fundamental physics. Estimates for the expansion of the scale of the solar system are of order 1.5 cm year−1 AU−1, which over several years is an observable quantity with present-day laser ranging systems. This estimate suggests that laser measurements between planets could provide an accurate estimate of the solar system expansion rate. We examine distance measurements between three bodies in the inner solar system -- Earth’s Moon, Mars and Venus -- and outline a mission concept for making the measurements. The concept involves placing spacecraft that carry laser ranging transponders in orbit around each body and measuring the distances between the three spacecraft over a period of several years. The analysis of these range measurements would allow the co-estimation of the spacecraft orbit, planetary ephemerides, other geophysical parameters related to the constitution and dynamics of the central bodies, and key geodetic parameters related to the solar system expansion, the Sun, and theoretical physics.
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机译：太阳系的尺度正在缓慢变化，可能由于太阳质量损失而增加，如果引力常数G发生长期变化，则可能会发生其他变化。尺度变化的度量可以提供对过去的了解。以及太阳系的未来，以及对行星运动和基本物理学的更好理解。太阳系规模扩展的估计量约为1.5 cm year -1 AU -1 ，在几年中，这是当今激光的可观测量测距系统。该估计表明行星之间的激光测量可以提供对太阳系膨胀率的准确估计。我们研究了内部太阳系中三个物体（地球的月球，火星和金星）之间的距离测量值，并概述了进行测量的任务概念。该概念涉及将载有激光测距应答器的航天器放置在每个物体周围的轨道上，并在几年的时间内测量三架航天器之间的距离。通过对这些距离测量值的分析，可以对航天器的轨道，行星历表，与中心体的构成和动力学有关的其他地球物理参数，以及与太阳系膨胀，太阳和理论有关的关键大地参数进行共同估计。物理。
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