243 research outputs found
Systematic ranging and late warning asteroid impacts
We describe systematic ranging, an orbit determination technique especially
suitable to assess the near-term Earth impact hazard posed by newly discovered
asteroids. For these late warning cases, the time interval covered by the
observations is generally short, perhaps a few hours or even less, which leads
to severe degeneracies in the orbit estimation process. The systematic ranging
approach gets around these degeneracies by performing a raster scan in the
poorly-constrained space of topocentric range and range rate, while the plane
of sky position and motion are directly tied to the recorded observations. This
scan allows us to identify regions corresponding to collision solutions, as
well as potential impact times and locations. From the probability distribution
of the observation errors, we obtain a probability distribution in the orbital
space and then estimate the probability of an Earth impact. We show how this
technique is effective for a number of examples, including 2008 TC3 and 2014
AA, the only two asteroids to date discovered prior to impact
Innovative methods of correlation and orbit determination for space debris
We propose two algorithms to provide a full preliminary orbit of an
Earth-orbiting object with a number of observations lower than the classical
methods, such as those by Laplace and Gauss. The first one is the Virtual
debris algorithm, based upon the admissible region, that is the set of the
unknown quantities corresponding to possible orbits for objects in Earth orbit
(as opposed to both interplanetary orbits and ballistic ones). A similar method
has already been successfully used in recent years for the asteroidal case. The
second algorithm uses the integrals of the geocentric 2-body motion, which must
have the same values at the times of the different observations for a common
orbit to exist. We also discuss how to account for the perturbations of the
2-body motion, e.g., the effect.Comment: 18 page
Innovative observing strategy and orbit determination for Low Earth Orbit Space Debris
We present the results of a large scale simulation, reproducing the behavior
of a data center for the build-up and maintenance of a complete catalog of
space debris in the upper part of the low Earth orbits region (LEO). The
purpose is to determine the performances of a network of advanced optical
sensors, through the use of the newest orbit determination algorithms developed
by the Department of Mathematics of Pisa (DM). Such a network has been proposed
to ESA in the Space Situational Awareness (SSA) framework by Carlo Gavazzi
Space SpA (CGS), Istituto Nazionale di Astrofisica (INAF), DM, and Istituto di
Scienza e Tecnologie dell'Informazione (ISTI-CNR). The conclusion is that it is
possible to use a network of optical sensors to build up a catalog containing
more than 98% of the objects with perigee height between 1100 and 2000 km,
which would be observable by a reference radar system selected as comparison.
It is also possible to maintain such a catalog within the accuracy requirements
motivated by collision avoidance, and to detect catastrophic fragmentation
events. However, such results depend upon specific assumptions on the sensor
and on the software technologies
Interstellar Object Uncertainty Evolution and Effect on Fast Flyby Delivery and Required Delta-V
Interstellar objects (ISOs) are small bodies that can travel through our
solar system from other star systems. When present in our solar system, they
represent an opportunity to study the properties and origins of these objects,
as well as the potential for cross-pollination of material between star
systems. With current propulsion technology, rendezvous with these objects is
likely infeasible, and thus the maximum science return results from a rapid
response flyby and impactor. However, while trajectories to ISOs may be
feasible, their potentially high ephemeris uncertainties and high-speed
hyperbolic orbits present significant challenges to navigation. In this paper
we assess these challenges by modeling the uncertainties of reachable synthetic
ISOs as a function of time, as derived by measurements from ground
observatories and an approaching spacecraft. From these uncertainties we derive
the final delivery accuracy of fast flyby spacecraft to the ISO and required
statistical delta-v for navigation. We find that these two challenges can lead
to hundreds of meters-per-second or even kilometers-per-second of required
statistical delta-v for navigation, reduce delivery accuracy to hundreds of
kilometers, and make autonomous navigation a requirement
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