Everitt - GPB

- Geodesic effect
	- Einstein: 6571 pm 1 (marc/yr)
	- 4-gyro:   6578 pm 9
		- systematics < 97 (cautious)
		- readout 0.12

- annoying successfulness of Newtonian dynamics
	- GM/c^2 R very small (2 10^-6 Sun, 7 10^-10 Earth)
	- Einstein's 2.5 tests (Mercury perihelion, light deflection, redshift)

- NASA's contributions
	- laser ranging
	- GPA (gravitational redshift around Earth)
	- radar time delay (Doppler tracking?)
	- GPB

- GPB challenge
	- gyroscope: 10^7 better than best navigation
		- possible by space + cryogenics
	- telescope: 10^3 better than star trackers
	- gyro readout: calibrate to 1 in 10^5

- [...] some complex modeling required [...]

- STEP