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Based on BeiDou-2 constellation navigation, properties of a relatively new
method, unscented Kalman filter and the most classical method, batch least
squares method are discussed. First, the research progresses of these two estimation
methods are summarized, and then the principles of unscented Kalman filter
and batch least squares method are brief...
Context in source publication
Context 1
... BeiDou-2 is a Chinese constellation of con- sists 35 satellites, which include 5 geostationary orbit satellites, and 30 non-geostationary satel- lites (27 in medium Earth orbit and 3 in inclined geosynchronous orbit), that will offer complete coverage of the globe. The geometry is expressed in inertial reference system as Figure 1, where ρ is the range vector from the navigation satellites to the satellite to be solved, r is the radius vector locating the satellite to be solved, BD r is the radius vector locating the navigation satellite. The fundamental observation is given by The measurement data used in this paper is only the range ρ . ...
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Citations
... 6 Binning is a procedure where the camera and/or software combines groups of pixels into a single pixel: for example, 1x1 binning means there is no grouping, 2x2 binning takes a rectangle of four contiguous pixels and combines them into a single pixel; this increases the effective pixel size and sometimes helps the signal-to-noise ratio. 7 WCS stands for World Coordinate System. An elaborate set of FITS conventions has been defined to specify the physical, or world, coordinates to be attached to each pixel of an Ndimensional image. ...
... EKF and UKF procedure: Least-squares from t 0 to t central , EKF/UKF from t central to t k . Modified from[7]. ...
Satellites orbiting around the Earth are used for many purposes; they can be of
different types, military or civilian, and they are employed in many areas and disciplines
including space science, navigation, meteorology, climate research, telecommunication
and many others. The interest for space and its possible commercial
exploitation has continued to grow and the number of new satellites has increased
year after year, in particular in the last decades. The growth in space satellite
activities has influenced the number of inactive and debris objects, that it is increasing
contextually. These bodies not only represent a pollution problem but
they also are a huge risk for active satellites. In fact an in-orbit collision may
cause a cascade effect, meaning that each collision creates more debris that in
turn can cause further collisions. For these reasons, mitigation strategies have
been developed by the international community in order to limit the density of
artificial space objects, like the ESA (European Space Agency) Space Situational
Awareness (SSA) program, able to provide Europe with timely and precise information
on space environment. Inside the SSA program, the Space Surveillance and
Tracking (SST) segment is targeted at tracking and maintaining the information
on all orbiting objects. To perform these observation tasks, nowadays, radar or
optical systems are used: both methods have benefits and disadvantages and have
different ideal applications.
This thesis fits in the field of SSA and SST. In particular, the main goal is
to develop and test techniques to process optical telescope images and to retrieve
information about multiclass uncatalogued satellites’ tracklets, in order to perform
an initial orbit determination and to predict their future position in space. For this
purpose, both simulated and real optical images of space objects of the four main
classes (LEO, MEO, GEO and HEO) are used, and different techniques to estimate
the orbit are studied and compared; in this way performances and criticalitites are
identified and discussed.
