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Perturbations on Earth satellites and space junk from solar storms and space weather

Date: Monday, 15 May 2023

Venue: Room B3.02 (Zeeman Building)

Organiser: Dimitri Veras (Physics)

Programme [Abstracts are below]

12:00 - 1:00 Lunch in the Mathematics Common Room

1:00 - 1:40 David Jackson (Met Office, Exeter)

–Operational space weather forecasting

1:45 - 2:25 Giovanni Gronchi (University of Pisa, Italy)

–Initial orbit determination from one position vector and a very short arc of optical observations

2:30 - 3:10 Jennifer O'Kane and Simon George (Defence Science and Technology Laboratory, Portsdown West)

--Space weather impacts on the Low Earth Orbit environment

3:15 - 4:00 Tea in the Mathematics Common Room

4:00 - 4:40 David Themens (University of Birmingham)

–Space weather impacts on the ionosphere and its implications
for radio navigation and communications

4:45 - 5:25 Shambo Bhattacharjee (Naval Postgraduate School, California, USA)

–Rest-to-rest slew maneuvers and orbital perturbation


David Jackson

Operational space weather forecasting

The Met Office Space Weather Operations Centre (MOSWOC) provides 24/7 space weather alerts, warnings and forecasts for UK Government and a range of other affected users, including power grid and satellite operations, aviation, and GNSS users.

In this presentation a review of existing services will be presented, together with an assessment of challenges and ongoing research aimed at filling the gaps in the services that we offer. There shall be particular focus on the Space Weather Instrumentation, Measurement, Modelling and Risk (SWIMMR) programme, which is an integrated programme that transitions academic research into new operational products in a joined-up and focused manner.

There shall also be discussion on space weather impacts on the operation of low Earth orbiting satellites. Reasonable worst case scenarios shall be discussed, together with a review of existing and future operational services to support these users.

Giovanni Gronchi

Initial orbit determination from one position vector and a very short arc of optical observations

We address the problem of computing an asteroid orbit (OD problem) from one topocentric position vector ${\cal P}_1=(\rho_1,\alpha_1,\delta_1)$, where $\rho_1,\alpha_1$ and $\delta_1$ denote respectively the topocentric distance, the right ascension and the declination at epoch $t_1$, and a VSA of optical observations, giving an attributable ${\cal A}_2 = (\alpha_2,\delta_2,\dot{\alpha}_2,\dot{\delta}_2)$ at the mean epoch $\bar{t}_2$ of the VSA.

Using the algebraic conservation laws of the angular momentum, the Laplace-Lenz vector and the energy in the two-body dynamics, we can write the OD problem as a system of polynomial equations in the unknowns $\dot{\rho}_1$, $\dot{\alpha}_1$, $\dot{\delta}_1$, $\rho_2,\dot{\rho}_2$, $z_2$, where $z_2$ is an auxiliary variable.

We prove that the system is consistent (i.e. it generically admits solutions, at least in the complex field), and we can obtain a univariate polynomial $\mathfrak{u}$ of degree eight in the unknown range $\rho_2$ at epoch $\bar{t}_2$ to solve the OD problem. Through a symbolic manipulator, we are also able to show that the degree of $\mathfrak{u}$ is minimum among the degrees of all the univariate polynomials in $\rho_2$ solving this problem.

The proposed method is relevant for different purposes, e.g. the computation of a preliminary orbit of an Earth satellite with radar and optical observations, the detection of maneuvres of an Earth satellite, and the recovery of asteroids which are lost due to a planetary close encounter.

This is a joint work with E. Scantamburlo and G. Bau.

Jennifer O'Kane and Simon George

Space weather impacts on the Low Earth Orbit environment

Space weather and solar storms can influence the performance of a variety of technologies, and can also endanger human health and safety. It is the cause of the auroras at the north and south poles, but also has implications on systems such as; Position, Navigation and Timing (PNT) systems, radio communications, transportation networks, the electricity grid, HF communications, and Global Navigation Satellite Services (GNSS). It is therefore vital to understand the effects of space weather on a variety of technologies, and be able to respond appropriately and within a timely manner to mitigate the effects of a space weather event.

Within this presentation, we discuss some of the impacts of space weather that can be particularly problematic, including impacts to low earth orbiting (LEO) satellites. Alongside operational LEO satellites is an abundance of space debris that in itself poses threats to operational satellites. Space debris can damage sensitive electronics within satellites or even disable a satellite, taking it out of operation. We discuss the aerodynamics in the LEO environment on both operational satellites and space debris, and how these may change as a result of space weather events.

David Themens

Space Weather Impacts on the Ionosphere and its Implications
for Radio Navigation and Communications

The plasma in the upper atmosphere, called the ionosphere, has the unique property of being a highly refractive medium for electromagnetic signals in the High Frequency (HF) band (3–30 MHz). This property allows one to use the ionosphere as a reflector for signals in this band, enabling long range (1000s of km) communications, used in commercial aviation operations, as well as enabling long-range remote sensing systems, like Over-the-horizon Radar (OTHR). Due to the dependence of these systems on the ionosphere, however, they are heavily reliant on our capacity to model the ionosphere that their signals propagate through. This, however, is all the more challenging during geomagnetic disturbances or at high latitudes, where the plasma environment can be very dynamic.

In addition to acting as a waveguide for HF signals, the ionosphere can also be highly disruptive for satellite-borne Synthetic Aperture Radar (SAR) applications and Global Navigation Satellite Systems (GNSS), like the Global Positioning System (GPS). As signals from these satellites propagate through the ionosphere, they can be bent by gradients in the plasma and slowed down, ultimately resulting in degraded positioning performance for GNSS and polarization errors for SAR. Small scale irregularities in the ionosphere can also scatter these signals causing interference and signal degradation, which can cause service interruptions. While some of these issues can be “engineered out”, many of them remain an open challenge to the reliability of these technologies and much is yet to be understood regarding how severe space weather events would impact these systems.

In this talk we will explore some of the many mechanisms by which the ionosphere affects space-borne navigation, remote sensing, and communications systems, distinguishing fundamental open challenges from those that have been addressed over the past decades.