G-Sample is designed for sample collection missions to identify the presence and quantity of sample material gathered by spacecraft equipped with end effectors. The software method uses a maximum-likelihood estimator to identify the collected sample's mass based on onboard force-sensor measurements, thruster firings, and a dynamics model of the spacecraft. This makes sample mass identification a computation rather than a process requiring additional hardware.
Simulation examples of G-Sample are provided for spacecraft model configurations with a sample collection device mounted on the end of an extended boom. In the absence of thrust knowledge errors, the results indicate that G-Sample can identify the amount of collected sample mass to within 10 grams (with 95-percent confidence) by using a force sensor with a noise and quantization floor of 50 micrometers. These results hold even in the presence of realistic parametric uncertainty in actual spacecraft inertia, center-of-mass offset, and first flexibility modes.
Thrust profile knowledge is shown to be a dominant sensitivity for G-Sample, entering in a nearly one-to-one relationship with the final mass estimation error. This means thrust profiles should be well characterized with onboard accelerometers prior to sample collection. An overall sample-mass estimation error budget has been developed to approximate the effect of model uncertainty, sensor noise, data rate, and thrust profile error on the expected estimate of collected sample mass.
This program was written by John Carson of Caltech for NASA's Jet Propulsion Laboratory.
This software is available for commercial licensing. Please contact Karina Edmonds of the California Institute of Technology at (626) 395-2322. Refer to NPO-44403.
This Brief includes a Technical Support Package (TSP).
Dynamic Method for Identifying Collected Sample Mass
(reference NPO-44403) is currently available for download from the TSP library.
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Overview
The document presents the G-SAMPLE (Dynamic Method for Identifying Collected Sample Mass), a novel in-flight dynamical method developed by NASA's Jet Propulsion Laboratory (JPL) for identifying the presence and quantity of sample material collected during space missions. This method addresses the challenge of accurately determining sample mass without the need for additional flight hardware, such as cameras, which are typically used for visual identification.
G-SAMPLE employs a maximum-likelihood estimator that utilizes onboard force sensor measurements, thruster firings, and a dynamics model of the spacecraft to compute the collected sample mass. This algorithmic approach allows for the identification of both the presence and the quantity of sample material, making it a significant improvement over existing methods that rely solely on visual identification, which cannot quantify the mass.
The document outlines the performance of G-SAMPLE, indicating that it can estimate the amount of collected sample mass to within 10 grams with 95% confidence, provided that the force sensor has a noise and quantization floor of 50 micrometers. The results are robust even in the presence of realistic uncertainties related to spacecraft inertia, center-of-mass offset, and flexible modes. However, the accuracy of mass estimation is highly sensitive to the characterization of thrust profiles, which should be well-defined using onboard accelerometers prior to sample collection.
Additionally, the document includes an error budget that approximates the effects of model uncertainty, sensor noise, data rate, and thrust profile errors on the expected estimates of collected sample mass. This budget is crucial for mission design, as it helps in understanding the potential variances in mass estimation.
Overall, G-SAMPLE represents a significant advancement in the field of sample collection for space missions, providing a computational solution that enhances efficiency and reduces the need for additional hardware. The method's reliance on existing onboard sensors and its ability to deliver accurate mass estimations make it a valuable tool for future aerospace endeavors.
For further inquiries or detailed information, the document provides contact details for JPL's Innovative Technology Assets Management.
