The Gravitational Reference Advanced Technology Test in Space

The GRATTIS mission aims to demonstrate the functionality and sensitivity of the Simplified Gravitational Reference Sensor (S-GRS), an advanced inertial sensor for future Earth geodesy missions. S-GRS measures and compensates for non-gravitational accelerations, enhancing the precision of spacecraft motion data due to Earth's gravity. It uses a cubic test mass inside an electrode housing for high-precision measurements, replacing the traditional grounding wire with a UV LED-based charge management system. Scheduled for launch in 2027, GRATTIS will feature two S-GRS units on a 160 kg microsatellite, enabling precise drag and angular acceleration measurements.

3D CAD model of a mechanical a embly with two view . The left view how the front ide with tructural component , upport rod , and internal machinery. The right view provide a top-down per pective, revealing the arrangement of equipment in ide a container-like tructure, including multiple boxe and panel connected by green upport rod . — **GRATTIS spacecraft and payload.** GRATTIS spacecraft and payload with the two-layer payload enclosure made semitransparent: S-GRS Heads are shown in yellow near the S/C center of mass with vent pipes in brown, SACUs are shown in blue, and PCUs are shown in green (credit: GRATTIS team)

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