First Operational Pressure Inverted Echo Sounder Retrieved

Sonardyne International, UK, has retrieved its first Pressure Inverted Echo Sounder (PIES) off the coast of Hawaii, USA. This new long-life sensor logging node is designed to accurately measure the average sound velocity through a column of water from the seabed to the sea surface. The information gathered will help oceanographers to better understand the dynamics of the ocean and atmosphere-ocean coupling.


On 24th September 2011, the Sonardyne PIES was free-fall deployed into a 960-metre-deep water channel close to the big island of Hawaii, and commanded to log average sound velocity readings every seven minutes. Now, engineers have returned to the site and recovered the unit by acoustically commanding it to float to the surface under its own buoyancy.

Pressure inverted echo sounding is a technique that works by transmitting an acoustic pulse upwards from a PIES instrument on the seabed. The pulse is reflected off the water-air boundary at the sea surface and returns back down to the seabed where it is detected by the PIES. This enables an exact measurement of the two-way signal travel time to be calculated. At the same instant, an accurate measurement of depth is made using highly precise internal pressure sensors. Average water column velocity can then be calculated directly from the depth (i.e. distance) and travel time data.

Work begins on strengthening EGNOS against solar storms

Europe’s EGNOS satnav augmentation service, employed for an ever-increasing range of uses such as guiding aircraft landings, will be strengthened against the effects of solar storms and its design ‘future-proofed’. The new work order was signed on Friday.
 
The European Geostationary Navigation Overlay Service (EGNOS) uses geostationary satellites and a Europe-wide network of ground receivers to sharpen the accuracy and reliability of US GPS signals over the continent.

EGNOS signals are potentially vulnerable, however, to the effects of high solar activity on the ionosphere – the electrically active upper layers of our atmosphere – which can cause signal ‘scintillations’ and time delays.

And an increase in solar storms is being experienced as the Sun enters the active phase of its 11-year cycle.  

	EGNOS work order signing

This new effort will increase system robustness and service availability against severe ionospheric severe effects that began last year and are expected to continue until the peak of the solar cycle expected in 2013–14.

In addition, while EGNOS began its general service in 2009 and its ‘Safety-of-Life’ signal for aircraft vertical landing approaches became available a year ago this month, the overall system was designed almost a decade ago, so work is also needed to upgrade elements of its communication system to manage technology obsolescence.

The work order also covers planned EGNOS mission evolution, including keeping pace with GPS modernisation, provision of vertical guidance for aircraft landings and extending the EGNOS network to cover North Africa and the Middle East.

This new work order is part of a framework contract signed with Thales Alenia Space France in May 2011.
 

EGNOS ranging station

About EGNOS

Along with Galileo, EGNOS is the other pillar of Europe’s navigation programme. ESA designed the EGNOS system in cooperation with the EC and Eurocontrol.

EGNOS informs users about the current accuracy and integrity (level of reliability) of the system based on the GPS satellites’ orbits, atomic clock accuracy and ionospheric delay.

If the accuracy of the signal falls below a given threshold, users are warned within six seconds.
 

	ESA's EGNOS team

EGNOS is designed against international standards set by the International Civil Aviation Organisation and its development was coordinated with other satellite-based augmentation systems around the world: MSAS in Japan, WAAS in the US, and GAGAN in India.

EGNOS began general use in 2009 – when its control was turned over to the European Commission to be run on a day-to-day basis through the European Satellite Services Provider company, based in Toulouse. The EGNOS Safety-of-Life signal was declared available for aviation in March 2011.
 

ESA is now acting as the design and procurement agent on behalf of the EC for all major EGNOS system changes throughout its operational lifetime, as well as preparing for the next-generation EGNOS expected around 2020. 

Beidou Satnav System Operational

Chinese officials have on 27th December 2011 confirmed that the country's Beidou satellite navigation system is operational, albeit mainly in China, with the goal to offer free, global coverage in place by 2020. At a press conference the China Aerospace Science and Technology Corporation said that Beidou is providing location data and SMS messaging using a network of ten satellites currently in orbit, and another six launches are planned for next year.

Once fully operational, they should cover most of the Asia/Pacific region, and will form the backbone of a global system of over 30 satellites that should be in place by 2020.

According to Ran Cheng of China Aeriospace Science and Technology Corporation, the Beidou service would be free to all and said that the Chinese would be working on interoperability with the US GPS system, Russia's GLONASS and the forthcoming EU Galileo network. An initial version of the interface control documentation has been published online.

He said that the initial service was operating within 25 metres accuracy between 84 degrees to 160 degrees east longitude, 55 degrees south latitude to 55 degrees north latitude, at velocity accuracy of 0.8 metres per second and within 50 nanoseconds for timing. Around 100,000 users are using the service so far, and accuracy will be brought down to 10 metres by next year.

China plans to add many more satellites for a variety of purposes over the coming years, and wants 100 in orbit under the current schedule, according to spokesman Zhao Xiao-chun. Last year China had 19 launches he said, compared to 18 from the US, but behind Russia with 36.

Having its own global positioning system will give Chinese global ambitions a fillip, since the vast bulk of the world currently runs on the US GPS network. Russia has spent billions upgrading and adding to its GLONASS satellite system, initially constructed in the 1980s but which fell into disrepair during the post-Cold War collapse, and this should be operational within a year or so.

The news of China's plans will be causing some furrowed brows at the Pentagon. Global positioning is vital for modern warfare and some of the more excitable members of the military have been suggesting that having an alternative system would let China destroy GPS if war ever came, and the US already has plans for satellites to monitor orbital war.

first navigation signal transmitted to Earth

Europe’s Galileo system has passed its latest milestone, transmitting its very first test navigation signal back to Earth.
 
The first two Galileo satellites were launched into orbit on 21 October. Since then their systems have been activated and the satellites placed into their final orbits, positioned so that their navigation antennas are aligned with the world they are designed to serve.

Last weekend marked the first orbital transmission from one of these navigation antennas. The stage was set, the singer in place and an audience – in the shape of engineers on the ground – was waiting eagerly.

The question was would the singer make music, and if so, would it be in tune?  

	First Galileo test navigation signal

The turn of Galileo’s main ‘L-band’ (1200-1600 MHz) antenna came on the early morning of Saturday 10 December. A test signal was transmitted by the first Galileo satellite in the ‘E1’ band, which will be used for Galileo’s Open Service once the system begins operating in 2014.

To prepare for the test, the payload power amplifiers were switched on and ‘outgassed’ – warmed up to release vapours that might otherwise interfere with operations – before transmission began.

A 20 m-diameter L-band antenna stood ready and waiting at Redu. The antenna is an essential ingredient of Galileo testing, able to assess the shape and quality of the navigation signals, even with the target satellite being 23 222 km up in orbit.
 

20-m diameter antenna at Redu

The signal power and shape was well within specifications. The shape is especially important because its modulation is carefully designed to enable interoperability with the ‘L1’ band of US GPS navigation satellites: Galileo and GPS can indeed work together as planned.

The test campaign is concentrating on the first satellite for the reminder of the year, with the focus moving to the second Galileo satellite from the start of 2012. The plan is to complete In-Orbit Testing by next spring.

The next pair of Galileo In-Orbit Validation satellites will also be launched next year, to form the operational nucleus of the full Galileo constellation. Meanwhile the next batch of Galileo satellites are currently being manufactured for launch in 2014.
 

	Galileo team at Redu

About Galileo

Galileo is an initiative of the European Commission and ESA to provide Europe with an independent global satellite navigation system.

The Galileo satnav system combines the best atomic clock ever flown for navigation – accurate to one second in three million years – with a powerful transmitter to broadcast precise navigation data worldwide. 

Optech Bathymetric Lidar Awarded

Optech has been awarded the MAPPS 2011 Geospatial Excellence Award for Technology Innovation. The award was given to the ALTM Aquarius, a compact solution for mapping coastal and inland waterways. Compatible with the ALTM Gemini system, Aquarius collects simultaneous land and water-depth measurements, enabling wholly complete data sets that span the land/water interface.

Designed as a complementary sensor to Optech's Lidar bathymetry systems, Aquarius provides depth information in relatively shallow water environments not previously accessible to conventional topographic mapping sensors alone.

High-resolution Side-scan Processing

Chesapeake Technology has presented a high-resolution capability for SonarWiz 5 that doubles the resolution of the earlier version. The result for side-scan sonar data is crisper, sharper mosaics, waterfalls and sonar contact images. Christian Mueller, Humminbird’s SAR side-scan operator, said that on a recent search he was able to narrow down almost 70 targets in the survey area to just five, with the first one being a hit.

Surveyors in all types of industries can use high resolution to resolve smaller features and see finer detail to improve productivity, security and safety. For example, Navy Route Surveys can better detect and classify mine-like objects (MLOs). Fisheries researchers will better classify biological habitats. Archeologists will produce clearer images of shipwreck sites (such as the example on the right), and divers will get clearer maps of dive sites.

Galileo satellites handed over to control centre in Germany

Europe’s first two Galileo satellites have reached their final operating orbits, opening the way for activating and testing their navigation payloads.
 
Marking the formal end of their LEOP Launch and Early Operations Phase, control of the satellites was passed yesterday from the CNES French space agency centre in Toulouse to the Galileo Control Centre in Oberpfaffenhofen in Germany.

Oberfaffenhofen, operated by the German Aerospace Center DLR, will be in charge of the satellites' command and control for the whole of their 12-year operating lives.

The two Galileo satellites were launched by Soyuz from French Guiana on 21 October. Three hours and 49 minutes after launch, their Fregat-MT upper stage carried them into their planned 23 222 km orbit, where they were released simultaneously.  

	Galileo satellites ejected from dispenser

At this point, a joint team from CNES and ESA’s ESOC European Space Operations Centre moved into action, beginning the crucial task of bringing the two satellites to life.

The first signals were heard almost simultaneously, confirming they were in good health – but there was still plenty of work to be done to keep them that way.

Like parachutists jumping from an aircraft, they were left tumbling through space. This spinning had to be brought under control before it was safe to deploy the power-giving solar panels, ending the satellites’ reliance on their rapidly dwindling battery power.
 

Galileo LEOP control room, Toulouse

Once the reaction wheels steadied them, the satellites sought the Sun and began recharging their batteries, around 70 minutes after separation.

The thrusters were then tested – an important milestone because the Fregat had carried them most of the way into space but they would have to manoeuvre the last 100 km or so into their planned final orbits by themselves.

The pair then switched from Sun-pointing to Earth-pointing, using infrared sensors that detect our planet as a warm object in cold space.
 

	Oberpfaffenhofen control centre

After that, they settled into their normal mode, with the solar arrays tracking the Sun and the navigation antenna pointed towards Earth.

The section of satellite housing the sensitive atomic clocks – the most accurate ever flown in space for navigation purposes – is kept permanently cool in shadow to help stabilise their performance.

In this configuration, the Toulouse centre commanded a set of thruster firings to relocate the satellites to their intended orbits inclined at 56º to the equator.
 

Galileo IOT L-band antenna at Redu

The handover to Oberpfaffenhofen occurred directly after LEOP was completed, taking place at 22:00 CEST on 3 November.

Ground controllers began by encrypting the telemetry and telecommand links, ensuring secure satellite control. Then they started commissioning the platform, verifying that all prime and redundant subsystems perform as expected.

The next few days will see the navigation payload being switched on, marking the start of Galileo’s In-Orbit Test campaign. This rigorous check of the navigation signals is being conducted from ESA’s ground station in Redu, Belgium.
 

In particular, a 20 m-diameter antenna will measure the precise shape of the navigation signals to a very high degree of accuracy.

Once the navigation payload is fully checked-out and activated, a second Galileo Control Centre in Fucino, Italy – operated by the Telespazio company - will oversee all navigation services.

All the entities participating in these activities - ESOC, CNES, DLR and Telespazio - do so under contract to SpaceOpal, a joint subsidiary company of DLR and Telespazio for Galileo operations.