Jim Shell, Novarum Tech, LLC
Keywords: high area-to-mass (HAMR) objects, photometry, solar radiation pressure
Abstract:
Resident space object mass is a fundamental property and a key object characterization attribute. Estimating the debris mass from fragmentation events provide insight into the root causes and symmetry of these events by considering the conservation of momentum. Mass estimates of debris also enable an understanding if similar failure mechanisms were responsible for debris-generating events from common object types.
Deriving object mass from observational data and object astrodynamics properties is a valuable technique as it may be applied to the space object population at scale. Historical techniques have predominantly focused on deriving non-conservative force components from propagation perturbations resulting from drag and solar radiation pressure. These non-conservative force components enable an estimation of an object’s area-to-mass ratio. In turn, the signature of objects provides a size estimate of these objects. Taken together, a mass estimate is made possible.
Efforts to date estimating mass have largely focused on low earth orbit objects and used drag and radar cross section to estimate object sizes. However, there are now space object catalogs such as the JSC Vimpel catalog, which contain numerous high-altitude objects and the explicit inclusion of area-to-mass estimates coupled with optical signatures. High perigee objects with negligible drag enable improved area-to-mass determination from the solar radiation pressure perturbations. Given that an object albedo is constrained from zero (fully absorptive) to one (fully reflective) enables a range of area-to-mass estimates. Like the application of radar cross section to derive object sizes, photometric signature data may be processed to derive an effective object area based upon similar albedo constraints. From the area-to-mass derived from solar radiation perturbations and inferred optical size, a mass estimation technique is enabled for high altitude objects. The higher the area-to-mass of an object, the better the mass estimate fidelity.
The development of the technique will be provided, along with an examination of specific breakup events and what may be inferred from the mass distribution from individual debris objects. Uncertainties in the estimation process are also provided which may then be validated against some “truth” sources where the mass of some objects are reliably know.
Past fragmentation events are analyzed using this analytical approach, where specific mass distributions and trends are observed. These mass distributions, coupled with the kinematic analysis of energetic events such as breakups and hypervelocity impacts, reinforce breakup models and inform the root cause of energetic events. Three different Centaur V breakup events are explored in detail, with the mass distributions supporting a hypothesis that a common root cause event was responsible for all three events. These Centaur V events (2014-055B, 2009-047B, 2018-079B), occurring within a one year time period, are significant given their debris constitutes the most numerous population in geo-transfer orbit (GTO). The debris mass distribution for the three Centaur V events is found to peak at ~0.02 kg per debris object.
Empirically-derived mass estimates of orbital debris enables the validation and improvement of orbital debris breakup and hypervelocity impact models. This in turn, better informs debris collision risk and impact damage assessments.
Date of Conference: September 19-22, 2023
Track: Space Debris