Astrometric Solar-System Anomalies

Understand

There are at least four unexplained anomalies connected with astrometric data.

• Perhaps the most disturbing is the fact that when a spacecraft on a flyby trajectory approaches the Earth within 2000 km or less, it often experiences a change in total orbital energy per unit mass.
• Next, a secular change in the astronomical unit AU is definitely a concern.
• It is increasing by about 15 cm yr$^{-1}$.