General Description

Solar Physics

This category gathers all the products related to solar activity generated by the Tor Vergata University algorithms. The Earth’s ionosphere is affected by very complex mechanisms determined by the occurrence of solar flares and Coronal Mass Ejections (CMEs). They are powered by the release of energy stored in the Sun’s magnetic field:

  • Flares are sudden, eruptive events that occur in the solar atmosphere, usually in correspondence of solar Active Regions (ARs); the chance of a having a major explosive event in a solar AR depends on various features like the free magnetic energy, the AR topology, the flux emergence rate and the helicity and the local dynamics. An occurred flare releases a significant amount of energy in a matter of few minutes and produces a burst of radiation across the electromagnetic spectrum. The classification system of solar flares is based on their according to associated peak flux in the in the x-ray wavelengths;
  • Coronal Mass Ejections are huge magnetic field flux ropes that erupt from the Sun's corona carrying away significant amounts of plasma. As they lift off from the solar atmosphere, they can accelerate up to >3000 km/s, thus sweeping and compressing the slower solar wind, and creating shock waves. In those shocks, energy exchange processes can accelerate particles up to GeV values, creating solar cosmic rays, better known as SEPs. A CME hitting the terrestrial magnetosphere will induce disturbances of the magnetic field (magnetic storm) and can alter the environment in and within the radiation belts.

It is very important for modern space engineering to understand the physical processes behind solar phenomena; better understanding the reasons of sudden energy release in solar events is a fundamental piece of the space weather puzzle.

Currently, IPS generates 20 solar physics products.

Ionosphere

This category collects the products related to the ionospheric activity and generated by the algorithms developed by INGV. The ionosphere is the ionized part of the Earth’s upper atmosphere from about 60 Km to 1000 Km altitude. Ionospheric activity is strongly dependent on the energy absorbed by the solar radiation that excites the gases contained in the atmospheric layers by producing electrical charged “ions”.

The ionospheric electron density affects the propagation speed of the GNSS electromagnetic signals and it is one of the largest contributor to the error budget of GNSS positioning. A typical way of characterizing the ionospheric effect is the generation of Total Electron Content (TEC) geographical maps. TEC is a common descriptive parameter and the delay of a GNSS signal crossing the ionosphere is directly proportional to its value. It represents the total number of electrons integrated between a radio transmitter and receiver along a tube of one meter squared cross section, i.e., the electron number density. It depends on local time, latitude, longitude, season and geomagnetic conditions. The measured TEC is

Moreover, the inhomogeneity of ionospheric electron distribution (i.e. ionospheric irregularities) can cause sudden, rapid and irregular fluctuations of the amplitude and phase of the received signals, termed “ionospheric scintillation”. Given the morphology of the Earth’s magnetic field, the geographic regions in which scintillations are more likely to occur are the polar and the equatorial areas, exacerbating in the low latitude regions. Scintillation can cause degradation on GNSS measurements and, in the worst case, can lead to the loss of lock with the broadcasting satellite, affecting the availability of the GNSS based services.

Currently IPS system generates 63 products related to ionosphere and scintillation activity.

GNSS Receiver Performance

This category gathers all the products related on the effects of ionospheric activity on GNSS receiver performance and generated by Nottingham University algorithms.

Scintillation are rapid fluctuations in the phase and amplitude of the transionospheric radio signal due to small-scale irregularities of the ionosphere. Occurrence of scintillation can increase the root mean square (RMS) of the GNSS receiver tracking error (or jitter), thereby degrading its tracking performance. This tracking error is individual to each satellite-receiver link and propagates into the quality of the estimated position. When it exceeds a certain threshold, loss of lock/cycle slips may occur in the receiver, which can lead to significant degradation in positioning accuracy. The receiver tracking errors show significant correlation with scintillation levels, both at high and low latitudes.

Currently IPS generates 28 products for the GNSS receiver performance category.

GNSS Performance at Application Level

This IPS function, developed by Telespazio, implements nowcast and forecast performance analysis for several classes of GNSS applications, mainly Aviation Services.

The service uses standard GNSS data and forecast models to produce GNSS systems nowcast and forecast performance maps at specific locations, regions or airspace volumes. This analysis is carried out through a volume simulator. This solution implements the following functions:

  • Evaluation of current EGNOS performances in terms of service availability and continuity over the coverage area for several operations, from En-Route to LP/LPV Precision Approaches;
  • Forecast analysis of the expected receiver position error and protection levels (e.g. HPL/VPL) for both ABAS and SBAS avionic solutions; these reports are maps over the entire service coverage area (currently European and worldwide). Forecast report is provided to the users one hour in advance and a new map is generated every 15 minutes. The user can access to several other forecast reports, like xDOP maps, average HPL/VPL maps, aircraft operation availability maps and RAIM-FDE availability maps.

Moreover this service allows to evaluate short-term (from nowcast to 1 hour) and long-term (from daily to yearly) performances of ABAS and SBAS systems to report on the impact of Solar and ionospheric activity on aviation operation, by monitoring a network of at least 30 ground GNSS stations located, when possible, in strategic locations like airports. Input data are retrieved from specific GNSS data providers like IGS, EUREF, etc. More in detail, this service implements the following functions for each station of the monitoring network:

  • Position and integrity analysis:
    • Un-augmented GPS L1 PVT (without integrity);
    • Un-augmented GPS L1 ABAS PVT solution, integrating RAIM-FDE capabilities compliant with RTCA MOPS DO-316;
    • GPS L1 SBAS augmented PVT, emulating the processing of a SBAS-capable airborne receiver compliant with RTCA MOPS DO-229D for bth LP and LPV navigation modes.
  • Performance analysis reports:
    • Position error and integrity analysis provided as plot and report table;
    • Statistical analysis (95% - 99% position error accuracy, PDF/CDF plots, Normality tests, etc);
    • Analysis of satellite geometry (Dilution of Precision parameters timeseries);
    • Availability and continuity diagram for different aircraft operations;
    • Constellation status analysis (URE/URA analysis satellite health status, condition usage in the position calculation, signal power level);
    • Horizontal and vertical integrity diagram (Stanford Diagrams) for both ABAS and SBAS solutions;
    • RAIM FDE performance diagrams.

ips-products Portlet

The RPFs are the processors that are running the nowcast and forecast algorithms; each RPF is tasked to monitor an ionosphere-related effect at user level and report it to the CSPF that will in turn inform users on the criticality of the event. Such iono-related effects are:
  • sun activity, such as sun spots, solar flares, coronal mass ejection, solar energetic particles (RPF-1)
  • ionosphere activity such as Total Electron Content variation, scintillation and travelling ionospheric disturbance (RPF-2, as input to RPF-3)
  • forecast of disturbance at receiver level: loss of lock, position error, tracking error (RPF-3)
  • RPF-4 is the module in charge of monitoring and forecasting the performance of GNSS systems at service level for several classes of users
Among others, RPF-4 also provides specific services to civil aviation users like forecast of the principal performance parameters for ABAS and SBAS applications, integrity, accuracy, availability and continuity.
IPS uses the forecast ionosphere indicators to predict the level of performances achievable by ABAS/SBAS solutions with the aim to improve airspace usage optimization, increasing efficiency and safety, and as a support to the development of both planning and tactical ATM/ATC applications.
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