The name of the projet demoGRAPE derives from the terms “demo”, wich is about demonstrator, and GRAPE the acronym of GNSS Research and Application for Polar Environment.
- Earth – Sun relations and space weather (high priority)
- Technology: innovation and experimentation (high priority)
- Polar cap dynamics
- Solid Earth dynamics and cryosphere evolution
Polar ionosphere, TEC, scintillations, GNSS, Cloud
The core of the proposed activity is the realization of a demonstrator, DemoGRAPE, which aims to provide on selected case studies an empirical assessment of the delay and of the corruption induced by the ionosphere on satellite signals in the polar regions. The scope is to develop a prototype of a service addressed to the scientific and technological communities that relies on GNSS (Global Navigation Satellite Systems) for their investigations and applications. Commonly, to assess the ionospheric impact on GNSS based technological systems, these communities make use of standard models, which demonstrate to fail at high latitudes. On the other hand the GNSS signals are widely used in different disciplines: DemoGRAPE will demonstrate the usefulness of the proposed system to several scopes, from the applications to positioning, to space weather applications, to solid Earth and polar cap dynamics investigation, to the monitoring of cryosphere evolution, etc. DemoGRAPE will experiment the use of Cloud computing to create an innovative technological tool.
The initiative was born into GRAPE (GNSS Research and Application for Polar Environment), an Expert Group endorsed by SCAR. The international context and the innovative aspects constitute an important legacy that will make the PNRA a pioneer in the frame of the potential services to assist the GNSS operations at the poles.
At high latitudes the ionosphere become often unstable and irregularities on wider scales develop. When sufficiently intense, these irregularities scatter radio waves and generate rapid fluctuations (or scintillation) in the amplitude and phase of radio signals. Amplitude scintillation, or short-term fading, can be so severe that signal levels drop below the GNSS receiver’s lock threshold, requiring the receiver to attempt reacquisition of the satellite signal. Phase scintillation, characterized by rapid carrier-phase changes, can produce cycle slips and sometimes challenge a receiver’s ability to hold lock on a signal. The irregular ionosphere is characterized by heavy TEC (Total Electron Content) gradients which significantly affect the propagation delay of the GNSS signals. Thus, ionospheric scintillation and TEC gradients are significant threats for Global Navigation Satellite Systems (GNSS) operating in the polar latitudes.
DemoGRAPE proposes to join the international efforts spent to monitor and study the high latitude ionosphere to realize a prototype of a service able to assist the GNSS users in the polar regions. The ionospheric models, commonly used to evaluate and/or to remove the ionospheric contribution from the GNSS signals received at ground, are not reliable when applied to polar regions. Countries located at high latitudes often use their own empirical tools to overcome the problem. Nevertheless a common initiative on this subject has not yet been agreed at international level. Also not all the communities have the economical, cultural and technological resources to develop appropriate means. DemoGRAPE is proposed to fill this gap paving the way for the establishment of common standard and procedures in the field.
GRAPE (GNSS Research and Application for Polar Environment) is a SCAR Expert group that intends to intensify the network of collaborations to fulfill a variety of space weather related needs through ad hoc data sharing and models development (www.grape.scar.org). Among the other objectives, GRAPE aims to create and maintain distributed networks of specialized GNSS ionospheric scintillation and TEC monitors at high latitudes to develop ionospheric scintillation climatology, tracking and mitigation models to improve prediction capabilities of space weather.
In this international frame is understandable how the proposed project, DemoGRAPE, would significantly contribute to the GRAPE’s scopes. In fact, DemoGRAPE is designed to be a demonstrator able to provide an empirical assessment of the ionospheric delay and of the corruption of the radio signals due to scintillation over both the poles. These information cannot be easily derived, because the standard ionospheric models, such as the Klobuchar model (Klobuchar, 1987), IRI model (Bilitza, 1997), Nequick model (Radicella and Leitinger, 2001) and others, fail when adopted to reproduce the ionospheric conditions at high latitudes. This is due to the high temporal/spatial variability of the ionosphere at auroral and polar latitudes that makes often unpredictable the conditions of the ionospheric plasma. The disagreement between models and observations have convinced the scientists to rely as much as possible on the empirical assessment of the polar ionosphere derived from actual measurements (see, e.g., Alfonsi et al., 2011). Polar regions are often unevenly monitored, especially over Antarctica, nevertheless last years have recorded an increasing number of observations of the upper atmosphere by means of GNSS receivers. The question is how to structure data and algorithms of the different teams in order to advance the current capabilities in the field. DemoGRAPE is a system based on Cloud computing platform which proposes a solution to that question through the realization of a prototype able to estimate the ionospheric delay and the scintillation conditions over polar regions on the base of the measurements and the algorithms provided by the GRAPE teams. DemoGRAPE is proposed to demonstrate on case studies, selected by the project participants on the base of their expertise and of data availability, the potentialities of a future service that could support different kind of communities united by the common need of a reliable ionospheric estimation. That estimation serves to fulfill a variety of different scopes: from the applications to precise positioning, to the support to remove the ionospheric contribution from the trans-ionospheric measurements (geodesy, space weather, radio glaciology, ice reflectometry, etc…). The letters of support attached (LIV1 and LIV2) testify the interest to the advancements offered by DemoGRAPE.
The technological innovation in respect to the state of the art is the adoption of a smart technology for the design and implementation of a prototype of advanced processors based on the concept of Cloud federation computing (see e-Infrastructure activity, 2011 and Lengert and Jones, 2011). This kind of technology is nowadays a reality and already applied to a wide variety of scientific fields (see Terzo et al. 2011, Mossucca et al. 2012, etc.).
The general purpose of the Cloud Infrastructure is sharing the computational resources and datasets, for transferring data and submitting jobs from several different organizations located in different areas on the world. In this sense the chosen technology fits perfectly the needs of the proposal because it is designed to handle efficiently heterogeneous information stored into different repositories according to diverse formats (for details see the attached description of Cloud solution). As agreed with the GRAPE ionospheric teams, DemoGRAPE is intended to operate on data and algorithms owned by the Italian and international participants (see the attached “LIV1” letters). Historical observations will be enriched with new acquisitions recorded during the project in the Arctic and Antarctic sites offered by the international partners (see the attached “LIV1” letters). The past data sets will be chosen to show “worst cases” during which the ionosphere was highly perturbed and consequently hardly modeled. The new acquisitions will add further crucial information to the existing measurements because acquired with the last generation of instruments in the field (multi-constellation receivers and software receivers). DemoGRAPE will output validated data and added value products obtained running the processors developed ad hoc from the selected algorithms and implemented in the system. The new observations will catch recent events during the peak and the descending phase of the current solar cycle, currently predicted to happen in 2013 with a possible second peak in 2015 (http://science.nasa.gov/science-news/science-at-nasa/2013/01mar_twinpeaks/). During the previous solar cycle the ionosphere was often strongly disturbed in the years following the peak of 2001 as during the Halloween storm in October-November 2003 when the GPS receivers at high latitude experienced long lasting (several hours) outages (see, e.g., Webb and Allen, 2004; Mitchell et al., 2005; De Franceschi et al., 2008). The proposed tool will thus provide the ionospheric scenario through raw and processed data timing with the most active years.
The DemoGRAPE legacy will be:
- Design of the demonstrator based on Cloud infrastructure;
- New measurements by means of multi-constellations hardware and software receivers;
- Data standardization;
- Accessibility to validated data and processors through a dedicated web portal;
- Dissemination of the project to national and international level addressed to students, scientific community, industrial stakeholders, general public.
The general objective of DemoGRAPE is to propose a prototype of a service to support the GNSS operations (for applicative or scientific scopes) over polar latitudes of both the hemispheres.
The specific objectives of the proposed initiative are the followings:
- to highlight the importance of data-driven scenarios to describe realistically the ionospheric conditions at high latitudes;
- to develop procedures for data validation and standardization;
- to develop and implement ad hoc processors on the base of the algorithms made available by different teams;
- to demonstrate the accessibility of the observations acquired at various polar sites by different teams;
- to demonstrate the accessibility of the outputs of processors owned by different teams;
- to propose the cloud computing as the best way to handle heterogeneous data and processors types;
- to propose the cloud configuration as the best method to make accessible data and algorithms keeping the intellectual property of the owners;
- to perform joint measurement campaigns at international level.