GNSS

EGNOS and Galileo on the ambitious Digital Rail agenda

The European Year of Rail brings attention to a number of topics important for improving the role of rail within the EU transport ecosystem. The recently published Policy paper “Challenges for European rail – getting solutions on track” by Jacques Delors Institute, highlights the main challenges and opportunities for the railway system evolution in Europe, focusing on increasing the rail attractiveness and make it the transport of choice for the decades to come.

EGNOS and Galileo are an integral part of the Digital Rail agenda, both freight and passenger transport rely on the European satellite navigation system, improving service provision with more than 150 000 freight wagons in Europe equipped with GNSS-based localization to provide accurate information about the wagon position. Precise location is used for asset and fleet management purposes, becoming a crucial element for efficient supply chain operations, and service to customers with estimated time of goods arrival.

The European GNSS Agency (GSA) continues to support projects and initiatives leading towards potential adoption of EGNOS and Galileo within European Rail Traffic Management System (ERTMS), aiming to decrease the costs linked to the ERTMS deployment and its carbon footprint by reducing the dependency on physical trackside elements that need to be manufactured, installed and maintained for proper train localization.

Last year, the GSA and ESA supported the ERTMS Users Group´s Change Request 1368, aiming to introduce EGNOS as the first step towards future safe use of GNSS for train signaling within ERTMS.

GNSS has the potential to enable a cheaper, more flexible and greener ERTMS, possibly offering also its faster deployment beyond the EU mainline corridors. Outside of Europe, GNSS is already used for fail-safe train localization (e.g. within the Positive Train Control (PTC) in the USA). The role and priorities of the sectorial associations, and especially the EU rail system integrators, will be a key factor for GNSS success within the ambitious Digital Rail agenda, allowing a faster progress towards closing technological gaps and agreeing on the final and best approach towards GNSS inclusion in ERTMS. www.euspa.europa.eu

ESA selects SpacePNT

The European Space Agency (ESA) has selected SpacePNT to develop an advanced spaceborne GPS/GALILEO receiver to demonstrate for the first time, onboard the ESA-SSTL Lunar Pathfinder Spacecraft in orbit around the Moon, the use of terrestrial satellite navigation signals (i.e., GALILEO, GPS) for the purpose of real-time and autonomous orbit determination and Positioning, Navigation and Timing (PNT). The contract includes the development, qualification, and delivery of one protoflight model (PFM) and two engineering models of NAVIMOON receiver.

The NAVIMOON receiver implements very high sensitivity algorithms able to receive and process signals extremely attenuated coming from the spillover around the Earth of the signals transmitted by satellite navigation (SatNav) systems (GALILEO, GPS). Furthermore, it combines these signals’ measurements with advanced on-board orbital forces filters to achieve directly onboard the spacecraft and in real-time an unprecedented target orbit determination accuracy of 100 m rms at Moon altitude, which is well below the typical accuracy that can be achieved today with terrestrial radio ranging that involve the use of costly deep space station ground infrastructures.

Given the high interest in Moon exploration and colonization (over 50 commercial and governmental missions have been announced between now and 2024), it is expected this NAVIMOON receiver technology will play a significant role in the next decade not only on Earth-Moon transfer orbits, but also to provide enhanced PNT services for the Moon users with the deployment of a lunar constellation that will allow the provision of lunar navigation in Moon-obstructed areas.

For this project, SpacePNT will partner with EECL from UK that will work as sub-contractor and will bring their significant space expertise for the electronics design, manufacturing, and qualification. https://spacepnt.com

NASA tests system for aircraft positioning in supersonic flight

NASA recently flight tested a visual navigation system designed to enhance precise aerial positioning between two aircraft in supersonic flight. The Airborne Location Integrating Geospatial Navigation System (ALIGNS) was developed to prepare for future acoustic validation flights of the X-59 Quiet SuperSonic Technology airplane. It is designed to reduce the loud sonic boom, heard on the ground when an aircraft flies at supersonic speeds, to a quiet thump – a technology that will be demonstrated when the X-plane flies over communities starting in 2024.

First, NASA will need to fly the X-59 as part of an acoustic validation phase, to confirm that the aircraft is as quiet as it’s designed to be. This is where ALIGNS comes in. To validate the X-59’s acoustic signature, the team at NASA’s Armstrong Flight Research Center in Edwards, California will need to both measure and visualize its shock waves, which are waves of pressure produced by aircraft as they fly faster than the speed of sound and are heard as sonic booms. Getting accurate measurements of the X-59’s unique shock waves will require a chase aircraft, flying in exact positions relative to the X-59 while both aircraft fly at supersonic speed.

A shock-sensing probe, mounted to the nose of an F-15, will be the primary tool in measuring the X-59’s shock waves. For the probe to take accurate measurements, the F-15 will need to fly in and out of the X-59’s shock waves at precise distances.

“ALIGNS is software that is designed to create a virtual point on the shock wave that is produced from the target aircraft. The pilots will get directional cues on the ALIGNS display to help them steer the F-15 to that specific point in space,” said ALIGNS Principal Investigator Troy Robillos.

“ALIGNS is absolutely going to help us get this done,” says NASA test pilot Jim ‘Clue’ Less. “We’ve flight tested it, we’re going to continue to make it better, and we’ll be ready.”

Matt Kamlet

NASA Armstrong Flight Research Center. www.nasa.gov

STL is an Accurate and Reliable Source for Wide-Area Delivery of Coordinated Universal Time

Satelles, Inc., innovative provider of highly secure satellite-based time and location services, recently announced an important new finding by the U.S. National Institute of Standards and Technology (NIST) about Satellite Time and Location (STL). Following a detailed performance study in 2020, NIST determined that STL is a reliable source of timing that is highly consistent with Coordinated Universal Time (UTC) and is based on a signal that is independent from the GPS and other Global Navigation Satellite Systems (GNSS). The STL service was able to deliver this consistent performance in a deep indoor environment where GNSS signals did not reach.

The results of the study were shared by Dr. Elizabeth Donley, Chief of the Time and Frequency Division at NIST, when she presented at the recent Workshop on Synchronization and Timing Systems (WSTS) conference organized by the Alliance for Telecommunications Industry Solutions (ATIS).

Dr. Donley articulated the details of the study conducted by NIST last year in which a GPS-disciplined clock (GPSDC) and a Satelles EVK-2 evaluation unit with a quartz oscillator comparable to that in the GPSDC were both compared to UTC(NIST), the national time scale in the United States, for a period of 50 days. In this evaluation, the GPS device received its signal from an outdoor antenna whereas the Satelles device was connected to an indoor antenna in a deep indoor environment where GNSS signals were not able to reach.

Time deviation (TDEV) calculations estimated the stability of the two signals with respect to the UTC(NIST) time scale. Based on one day of averaging, the GPS instability was less than two nanoseconds, and the STL instability was only slightly higher at under three nanoseconds (view chart). These measurements demonstrated that STL delivers stability that is comparable to GNSS and does so in an indoor location where GPS signals usually cannot penetrate.

STL delivers a positioning, navigation, and timing (PNT) service from satellites in low Earth orbit (LEO) to back up or augment GPS and other GNSS. www.satelles.com

IIT Roorkee launches free online course on GNSS

IIT Roorkee is launching a free online course on GNSS and Applications on the NPTEL platform. The 4 weeks long course is going to provide a basic understanding about digital elevation models (DEMs) and their application in Civil Engineering and Earth Sciences.

Participants will be given insights into various DEMs, their source, generation techniques, derivatives, errors and limitations.

The courses will begin on 26th July 2021 and will end on 20th August 2021. The registrations are currently open till 2nd August 2021 and can be done through SWAYAM platform. www.iitr.ac.in