Figure 30

Figure 6.1: A drawing for the measurement concept chosen of the Deep Space Gravity Probe (from [106], drawing courtesy of Alexandre D. Szames). The formation-flying approach relies on actively controlled spacecraft and a set of passive test-masses. The main objective is to accurately determine the heliocentric motion of the test-mass by utilizing the 2-step tracking needed for common-mode noise rejection purposes. The trajectory of the spacecraft will be determined using standard methods of radiometric tracking, while the motion of the test mass relative to the spacecraft will be established by laser ranging technology. The test mass is at an environmentally quiet distance from the craft, ≥ 250 m. With occasional maneuvers to maintain formation, the concept establishes a flexible craft to test mass formation.