Session
Next on the Pad
Location
Salt Palace Convention Center, Salt Lake City, UT
Abstract
ODIN (Optomechanical Distributed Instrument for Inertial sensing and Navigation) is a gyroscope-free inertial measurement unit based on a cube of six monolithic fused silica wafers which complete a twelve-axis sensing capability, i.e., three linear, three angular, and six centripetal acceleration measurements. ODIN will fly as a secondary payload on the GRATTIS (Gravitational Reference Advanced Technology Test in Space) mission, slated for launch in February of 2027, led by the University of Florida and funded by the NASA InVEST program. By the end of the GRATTIS mission, it is expected that ODIN will reach an exit TRL-7.
The primary objective of ODIN in the GRATTIS mission is to demonstrate the technology in a space environment. A secondary objective of ODIN is to demonstrate the noise floor of the optomechanical accelerometers by subtracting signal from the six centripetal acceleration measurements. The signals which need to be subtracted are centripetal acceleration and gravitational gradient as the two quantities are inexorably linked. It is expected that the ODIN accelerometers are sensitive enough to be affected by the gravitational gradient terms up to degree and order 2 which appear at the orbital frequency (~0.176 mHz for a 500 km orbit). Centripetal acceleration can be subtracted with initial conditions on angular velocity obtained from star trackers and from the measurements of angular acceleration recovered from ODIN. Gravitational gradient terms up to degree and order 2 are well known and static and can therefore be subtracted from the six centripetal acceleration measurements with sufficiently accurate position and attitude information. Furthermore, the sum of diagonal elements can be utilized to eliminate gravity gradients in the instance that sufficiently accurate position or attitude data cannot be attained.
Each wafer of ODIN contains two linear, low-frequency, optomechanical resonators oriented 90° apart with a fundamental mode around 8 Hz, this design builds upon our previously developed TRL-5 optomechanical accelerometers. The resonators consist of a test mass (~4 grams) suspended by 100 μm thick flexures whose displacement is measured with a laser heterodyne interferometer with precision at the sub-picometer level. This displacement is converted to acceleration by the transfer function of the mechanical resonator. It is estimated that the noise of ODIN at 1 mHz is at 10-9 m/s2/√Hz in linear acceleration and 50 μrad/√Hz in angular measurements – performance levels on par with GRACE (Gravity Recovery and Climate Experiment) instruments. However, ODIN’s low cost, size, weight and power (CSWaP) allows for simplified mission architecture (an important step in facilitating constellations of satellite gravimetry satellites), spacecraft miniaturization, or utilization as a redundant instrument. Furthermore, ODIN differs from other satellite gravimetry compatible accelerometers in that the readout is optical instead of electrostatic and in that a mechanical resonator facilitates a large dynamic range allowing for flight at lower altitudes.
We will present here status on the development of ODIN, the goals for the mission, and expected performance.
Document Type
Event
ODIN: Optomechanical Distributed Instrument for Inertial Sensing and Navigation
Salt Palace Convention Center, Salt Lake City, UT
ODIN (Optomechanical Distributed Instrument for Inertial sensing and Navigation) is a gyroscope-free inertial measurement unit based on a cube of six monolithic fused silica wafers which complete a twelve-axis sensing capability, i.e., three linear, three angular, and six centripetal acceleration measurements. ODIN will fly as a secondary payload on the GRATTIS (Gravitational Reference Advanced Technology Test in Space) mission, slated for launch in February of 2027, led by the University of Florida and funded by the NASA InVEST program. By the end of the GRATTIS mission, it is expected that ODIN will reach an exit TRL-7.
The primary objective of ODIN in the GRATTIS mission is to demonstrate the technology in a space environment. A secondary objective of ODIN is to demonstrate the noise floor of the optomechanical accelerometers by subtracting signal from the six centripetal acceleration measurements. The signals which need to be subtracted are centripetal acceleration and gravitational gradient as the two quantities are inexorably linked. It is expected that the ODIN accelerometers are sensitive enough to be affected by the gravitational gradient terms up to degree and order 2 which appear at the orbital frequency (~0.176 mHz for a 500 km orbit). Centripetal acceleration can be subtracted with initial conditions on angular velocity obtained from star trackers and from the measurements of angular acceleration recovered from ODIN. Gravitational gradient terms up to degree and order 2 are well known and static and can therefore be subtracted from the six centripetal acceleration measurements with sufficiently accurate position and attitude information. Furthermore, the sum of diagonal elements can be utilized to eliminate gravity gradients in the instance that sufficiently accurate position or attitude data cannot be attained.
Each wafer of ODIN contains two linear, low-frequency, optomechanical resonators oriented 90° apart with a fundamental mode around 8 Hz, this design builds upon our previously developed TRL-5 optomechanical accelerometers. The resonators consist of a test mass (~4 grams) suspended by 100 μm thick flexures whose displacement is measured with a laser heterodyne interferometer with precision at the sub-picometer level. This displacement is converted to acceleration by the transfer function of the mechanical resonator. It is estimated that the noise of ODIN at 1 mHz is at 10-9 m/s2/√Hz in linear acceleration and 50 μrad/√Hz in angular measurements – performance levels on par with GRACE (Gravity Recovery and Climate Experiment) instruments. However, ODIN’s low cost, size, weight and power (CSWaP) allows for simplified mission architecture (an important step in facilitating constellations of satellite gravimetry satellites), spacecraft miniaturization, or utilization as a redundant instrument. Furthermore, ODIN differs from other satellite gravimetry compatible accelerometers in that the readout is optical instead of electrostatic and in that a mechanical resonator facilitates a large dynamic range allowing for flight at lower altitudes.
We will present here status on the development of ODIN, the goals for the mission, and expected performance.
