Absolute Gravity Lab. Three Micro-G-LaCoste absolute gravimeters are operated in an environmentally-controlled basement at the observatory. One system (FG5-X) is owned by the Observatory and two other (FG5) instruments are on long-term loan from NERC's National Oceanographic Centre, Liverpool. Measurements of the local acceleration due to gravity are accurate to 2 microGal (10
-8 ms
2).