AI News, Four new Galileo satellites are now in orbit
- On 18. februar 2018
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Four new Galileo satellites are now in orbit
Europe has four more Galileo navigation satellites in the sky following their launch on an Ariane 5 rocket.
Ariane 5, operated by Arianespace under contract to ESA, lifted off from Europe’s Spaceport in Kourou, French Guiana at 18:36 GMT (19:36 CET, 15:36 local time), carrying Galileo satellites 19–22.
The first pair of 715 kg satellites was released almost 3 hours 36 minutes after liftoff, while the second pair separated 20 minutes later.
ESA is an intergovernmental organisation, created in 1975, with the mission to shape the development of Europe’s space capability and ensure that investment in space delivers benefits to the citizens of Europe and the world.
By coordinating the financial and intellectual resources of its members, ESA can undertake programmes and activities far beyond the scope of any single European country.
Today, it develops and launches satellites for Earth observation, navigation, telecommunications and astronomy, sends probes to the far reaches of the Solar System and cooperates in the human exploration of space.
Four more Galileo navigation satellites ride Ariane 5 rocket into orbit
Unimpeded by rain showers and a dark gray blanket of low clouds, an Ariane 5 rocket thundered away from a European-run space base in the jungle of French Guiana Tuesday to place four Galileo navigation satellites in orbit, an on-target deployment that should improve the location accuracy of new smartphones around the world.
The powerful European-built launcher climbed away from its launch pad in Kourou, French Guiana, seven seconds later as two solid rocket boosters fired to push the 155-foot-tall (47.4-meter) Ariane 5 into the sky.
composite shroud covering the four Galileo satellites at the nose of the Ariane 5 jettisoned just before the mission’s four-minute point, and the rocket’s Vulcain 2 main engine shut off around nine minutes after liftoff.
After coasting more than three hours to the Galileo network’s operating altitude more than 14,000 miles (around 23,000 kilometers) above Earth, the upper stage reignited for a six-minute firing to circularize its orbit at an inclination of 57 degrees, then deployed the four satellites in two pairs.
The spacecraft, each weighing around 1,576 pounds (715 kilograms), will use their own small thrusters to climb into a slightly higher orbit nearly 200 miles (300 kilometers) above their drop-off point.
Once the new satellites are ready for service, the European Commission-owned constellation will have 22 members, 18 of which will be healthy and operational, according to Paul Verhoef, director of navigation at the European Space Agency, which acts as a technical agent and advisor for the multibillion-dollar Galileo program.
Officials hope a software patch that could be installed on ground receivers, including user smartphones, will eventually allow those spacecraft to officially join the active network, Verhoef told reporters before Tuesday’a launch.
Officials announced last December that Galileo navigation signals were publicly available, allowing users in cars, airplanes, and ships to receive positioning data from the European network in conjunction with information already supplied by the U.S. military’s Global Positioning System satellites.
European and U.S. officials have agreed to make current and future generations of Galileo and GPS satellites interoperable, allowing the public to receive signals from both constellations, and combine the data to render more accurate position estimates than possible with just one network.
Three navigation satellites must be in the sky above a user to produce a position estimate, and a fourth is needed to receive an ultra-precise timing signal, which is used in applications like ATM and credit card transactions.
Nevertheless, Galileo was originally designed as a standalone system, and when the four satellites launched Tuesday are operational, the European network on its own will be able to provide navigation services to anyone in the world 95 percent of the time.
The clocks keep precise track of time, allowing the navigation payload to measure how long it takes for a signal to travel between the satellite and a user on the ground, the key measurement needed to generate a position estimate.
Ariane 5 Flight VA240 launches four Galileo satellites
At 3:36 p.m. local time (1:36 p.m. EST / 18:36 GMT) on December 12, 2017, an Ariane 5 rocket lifted off from the European Space Agency (ESA)’s Spaceport in Kourou, French Guiana, carrying four Galileo satellites, bringing the total number of spacecraft in the Galileo constellation to 22.
When the rocket reached an altitude of ten kilometers (6.2 miles), Arianespace’s launch commentator said: “And there they go, blazing a trail across the sky here over the spaceport.” The first pair of satellites was deployed three hours after 26 minutes after liftoff.
“Meanwhile, ESA is also working with the European Commission and GSA on dedicated research and development efforts and system design to begin the procurement of the Galileo Second Generation, along with other future navigation technologies.” ESA officials said: “Galileo navigation signals will provide good coverage even at latitudes up to 75 degrees north, which corresponds to Norway’s North Cape—the most northerly tip of Europe—and beyond.” ESA has not only developed satellites for navigation, Earth science, telecommunications, and astronomy, but also the agency has developed deep-space probes such as the Rosetta probe which landed on Comet Churyumov–Gerasimenko.
The complete system consists of: • A space segment of 30 MEO satellites in 3 planes inclined at 56º • A launch segment to place the satellites into their operational orbits • A control ground segment for monitoring and control of the satellites • A mission ground segment managing all mission specific data • A user ground segment of equipment capable of receiving and using Galileo signals Figure 1: The Galileo constellation of 30 spacecraft (image credit: ESA) The Galileo program has been structured into two phases: 1) IOV (In-Orbit Validation) phase: IOV consists of tests and the operation of four satellites and their related ground infrastructure.
two years later, again after highly competitive bidding and based on the performance in WP1, OHB was also able win the space segment Work Order 2 contract, thus increasing the total number of satellites to be built to 22.
Figure 2: Illustration of the Galileo FOC spacecraft (image credit: OHB System) Spacecraft of the FOC series: The production of the spacecraft series, with a delivery schedule of each pair of satellites in periods of 3 months, requires an assembly line production technique to meet the time table.
Figure 3: Galileo FOC solar wing deployment being checked at ESA/ESTEC (image credit: ESA) Legend to Figure 3: The navigation satellite's pair of 1 m x 5 m solar wings, carrying more than 2500 state-of-the-art gallium arsenide solar cells, will power the satellite during its 12 year working life.
Fulfilment of ESA's FOC satellite requirements was achieved through a simple and robust design, leading to a satellite of ~720 kg with a provided power production of 1.9 kW (end of life), which provides navigation signals in L1, E5, and E6 bands, as well as Search-and-Rescue services.
The satellites are integrated in seven modules, depicted also in Figure 5: • the propulsion module (integrated at the propulsion supplier, Moog Inc.) • the solar generator module (integrated at the solar generator supplier) • clock, antenna, and payload core module (integrated at SSTL, OHB's co-prime, responsible for the payload, located in Guildford, UK) • the center and the platform core modules (integrated at OHB's premises in Bremen, Germany).
While in most satellites, the propulsion system is distributed over the entire spacecraft, the modularity intended for Galileo FOC let OHB designers to mount all the propulsion-related systems on one panel, which can be integrated and replaced also late in the MAIT process (as depicted in Figure 4).
Further development work was carried out in two thermal development models that focussed on the two thermally critical areas: firstly, the clock panel, where clock temperature stability was demonstrated, and secondly the area of the travelling wave tubes, where sufficient high dissipation on limited radiator area was validated.
Primary goal is to keep the flow of satellites going, meaning to avoid 'clogging' the production pipeline, as this would have impact on all previous islands, which cannot turn to the next satellite in line, whereas all succeeding islands or stations would 'run dry'.
For larger issues in the production pipeline, there is a so-called 'recovery island' foreseen, which is equipped with all types of ground support equipment which can handle problems that take several days or even weeks to resolve while the rest of the pipeline continues normally.
Table 2: Key parameters of the Galileo spacecraft 7) Figure 6: The main antenna of the FM2 satellite is being inspected at ESTEC prior to mass property testing in August 2013 (image credit: ESA, Anneke Le Floc'h) 8)
The Galileo satellite constellation has been optimized to the following nominal constellation specifications: - Circular orbits (satellite altitude of 23,222 km), orbital inclination of 56°, three equally spaced orbital planes.
It was only a certain time after the separation of the satellites that the ongoing analysis of the data provided by the telemetry stations, operated by ESA and the French space agency, CNES, showed that the satellites were not in the expected orbit.
Figure 7: Photo of the Galileo FOC-3 and FOC-4 satellites fitted onto dispenser (image credit: ESA/CNES/ARIANESPACE-Service Optique CSG) 10) Figure 8: Illustration of satellite configurations in various mission phases (image credit: OHB System)
11) 12) All the Soyuz stages performed as planned, with the Fregat upper stage releasing the satellites into their target orbit close to 23, 500 km altitude, around 3 hours 48 minutes after liftoff.
Figure 9: Artist's view of the protective launcher fairing which jettisoned at 3 min 29 sec after launch, revealing the two Galileo satellites attached to their dispenser atop the Fregat upper stage (image credit: Arianespace, ESA)
14) 15) 16) All the Soyuz stages performed as planned, with the Fregat upper stage releasing the satellites into their target orbit close to 23,500 km altitude, around 3 hours and 48 minutes after liftoff.
Next year the deployment of the Galileo system will be boosted by the entry into operation of a specially customized Ariane 5 launcher that can double, from two to four, the number of satellites that can be inserted into orbit with a single launch.
Launch: On November 17, 2016 (13:06 :48 UTC), a quartet of Galileo satellites (Galileo 15-18), each with a mass between 715 kg and 717 kg, and a combined liftoff mass of 2,865 kg, was launched and deployed by Ariane 5 into a circular orbit during a mission lasting just under four hours.
Mission status: • January 29, 2018: With Europe's Galileo satellite navigation system only one launch away from full global coverage, representatives of European industry gathered at ESA/ESTEC in the Netherlands to discuss the transition towards the future Galileo Second Generation.
- Looking further ahead, with the aim of keeping Galileo services as a permanent part of the European and global landscape, a replacement set of Galileo satellites will be required post-2020, serving as transition to a future generation.
- In recent years, innovations have been analyzed and predevelopments performed in various technology fields (system, ground, space, receiver technologies) in order to assess their suitability for future Galileo activities, while ensuring backward compatibility and continuity of Galileo Services.
- In the next eight months, all major public and private stakeholders will be involved in the detailed assessment of the different evolution scenarios and associated technologies, in order to come to decisions on the Transition Program baseline for the evolution towards Galileo Second Generation.
Figure 11: Photo of the Navigation Days audience at ESA/ESTEC (image credit: ESA) • July 4, 2017: Investigators have uncovered the problems behind the failure of atomic clocks onboard satellites belonging to the beleaguered Galileo satnav system, the European Commission said on July 2.
26) - For months, the European Space Agency — which runs the program — has been investigating the reasons behind failing clocks onboard some of the 18 navigation satellites it has launched for Galileo, Europe's alternative to America's GPS system.
- The agency has taken measures to correct both sets of problems, the sources added, with the agency set to replace the faulty component in rubidium clocks on satellites not yet in orbit and improve hydrogen maser clocks as well.
- These new batch satellites are based on the already qualified design of the previous Galileo FOC satellites, except for changes on the unit level – such as improvements based on lessons learned and reacting to obsolescence of parts.
• June 8, 2017: Two further satellites have formally become part of Europe's Galileo satnav system, broadcasting timing and navigation signals worldwide while also picking up distress calls across the planet.
The tests measured the accuracy and stability of the satellites' atomic clocks – essential for the timing precision to within a billionth of a second as the basis of satellite navigation – as well as assessing the quality of the navigation signals.
29) - The report shows the 11 satellites then operating in the Galileo constellation were able to provide healthy signals 97.33% of the time on a per satellite basis, with a ranging accuracy better than 1.07 m and disseminating global UTC time within its signal to within 30 billionths of a second on a 95 percentile monthly basis.
'It was thanks to the tremendous effort of ESA's Galileo team working closely together with colleagues from the Commission and GSA that this milestone could be achieved: the key pillars for reaching are the currently deployed Galileo satellites in combination with the global Galileo ground segment infrastructure, defined and implemented by the ESA team with their respective industry partners.'
- The Initial Service performance levels (Figure 12) achieved by the system are monitored using two complementary monitoring platforms: the Time and Geodetic Validation Facility, an independent precision time-measuring system accurate to a billionth of a second – using an ensemble of atomic clocks located at ESA/ESTEC in Noordwijk, the Netherlands – and the GALSEE (Galileo System Evaluation Equipment), based in Rome, Italy.
The high-quality ranging service enables user level positioning with a typical accuracy of around 3 m on the ground and 5 m in altitude during periods when four satellites are visible.
• March 28, 2017: Eutelsat and GSA (GNSS Agency) Europe signed an 18-year contract covering the preparation and service provision phases for the EGNOS (European Geostationary Navigation Overlay Service) GEO-3 payload that will be hosted on the Eutelsat 5 West B satellite that is due for launch late in 2018.
30) - EGNOS V3, the second generation of the EGNOS System, will implement a second protected frequency (L5) to offer to the dual frequency safety of life users a more robust and accurate vertical guidance service (increased robustness with respect to the ionosphere), according to the ESA's EGNOS V3 Phases C/D - Summary Statement of Work.
- With the deployment of Galileo and the introduction of new capabilities in GPS, EGNOS V3 will offer improved SoL (Safety of Life) services to the civil aviation community as well as potential new applications for maritime or land users, thus showcasing the system's increased potential to become a leading edge GNSS system in the future.
These failures all seem to have a consistent signature, linked to probable short circuits, and possibly a particular test procedure performed on the ground, with investigations continuing to identify a root cause.
Figure 14: Photo of the Galileo PHM (Passive Hydrogen Maser) clock (image credit: ESA) - Corrective actions: For the remaining 33 RAFS clocks in orbit, the risk of failure is believed to be lower owing to different testing procedures on the ground before launch.
— As ESA Director General Jan Woerner commented during his 18 January press briefing, no individual Galileo satellite has experienced more than two clock failures, so the robust quadruple redundancy designed into the system means all 18 members of the constellation remain operational.
- The impact of RAFS and PHM clock refurbishment on Galileo's launch schedule is under study, but ESA is confident that the clock issues will be resolved and remains committed to launch the next four Galileo FOC satellites before the end of this year.
Even the Russians, with GLONASS, who went with a different signal structure – using FDMA (Frequency Division Multiple Access) with separate satellites using different frequencies – are moving towards the CDMA (Code Division Multiple Access) used by the other systems, meaning different satellites use the same frequencies with coding to differentiate them.'
Surveyors were early adopters, with land surveying that used to take days or weeks being performed within hours, while geologists have gained enormous understanding of earthquakes and the like by measuring ground motion of a few millimeters annually.'
- 'Looking ahead, within 15 years many human-operated vehicles – automobiles, trucks, aircraft and ships – will be self-driving, with one essential element being satellite navigation.'
- But Brad Parkinson warned that such achievements will be at risk if adjacent radio frequencies are turned over to terrestrial users, potentially leading to overlapping interference several billion times stronger than the faint satellite signals.
- 'It's a creeping obligation, internationally, to defend the radio spectrum in order to assure PNT (Position Navigation and Timing) to users worldwide, in order to nurture and support new uses of satellite navigation.'
Parkinson) • December 15, 2016: Europe's Galileo satellite navigation system has entered its initial operational phase, offering positioning, velocity and timing services to suitably equipped users around the globe.
The time between someone locating a distress beacon when lost at sea or in the wilderness will be reduced from up to three hours to just 10 minutes, with its location determined to within 5 km, rather than the previous 10 km.
Because all electromagnetic waves, including radio, travel at a fixed speed – just under 30 cm each billionth of a second – the time it takes for Galileo signals to reach a user receiver yields distance measurements.
This lengthy test phase saw the satellites being run from the second Galileo Control Center in Oberpfaffenhofen, Germany, while their payloads' output was assessed from ESA's Redu center in Belgium, equipped for the tests with specialized antennas for receiving and uplinking signals.
The test campaign measured the accuracy and stability of the satellites' atomic clocks – essential for the timing precision to within a billionth of a second as the basis of satellite navigation – as well as assessing the quality of the navigation signals.
• December 5, 2016: With Europe's Galileo satnav constellation soon to provide initial services, ESA is looking further ahead: its next-stage navigation research program received strong backing during last week's Council at Ministerial level.
37) - In partnership with the EU (European Union), ESA has overseen the creation of two satnav systems: first EGNOS, which improves the precision of US GPS signals over most European territory, in general operation since 2009 and for ‘safety of life' uses since 2011;
- NAVISP will boost Member State industrial competitiveness and innovation priorities in the upstream and downstream navigation sector and it will include investigating the integration of satellite navigation with non-space technologies and complementary positioning and communication techniques.
- NAVISP is structured into three elements, with the first developing new satnav technologies and concepts, the second focused on industrial competitiveness and the third offering support to Member State national programs and activities.
- In a world where satnav-based positioning, navigation and timing services are becoming ubiquitous – underpinning everything from automated drones to precision farming to electricity grids and financial networks – NAVISP will investigate novel ways of making these services more robust and reliable, to facilitate the emergence of competitive European actors.
• November 23, 2016: On 17 November, an Ariane 5 rocket launched four new Galileo satellites (Galileo satellites 15–18), accelerating deployment of the new satellite navigation system.
38) - At the Toulouse space center of France's CNES space agency, a joint ESA–CNES team is now working around the clock to shepherd the four through the critical early orbits, lasting nine days for one pair and 13 days for the other.
• August 9, 2016: Europe's fifth and sixth Galileo satellites, which were salvaged from their faulty launch into working orbits, are set to begin broadcasting working navigation signals for test purposes.
39) - A malfunction in their Soyuz-Fregat upper stage during their 22 August 2014 launch placed the Galileo-5 and -6 into highly elliptical – or elongated orbits – instead of their planned circular medium-Earth orbits.
- The navigation signals will include a signal health status reading that ‘signal component currently in test' and its navigation data validity status will be ‘working without guarantee'.
• June 22, 2016: A sea-based test is demonstrating the potential of extending satnav augmentation coverage into north polar regions, offering a safety-of-life standard of navigation performance to users including shipping or aircraft in flight.
- A 40-strong network of ground monitoring stations perform an independent measurement of GPS signals, so that corrections can be calculated and then passed to users immediately via a trio of geostationary satellites.
- To investigate possible methods for improving SBAS ( Satellite-Based Augmentation System) performance in this Arctic region, the test campaign will assess the benefits of augmentation for various types of satnav signals: single-frequency GPS;
Figure 17: EGNOS covering Europe (image credit: ESA) • April 29, 2016: The Galileo-11 and -12 satellites, launched on Dec. 17, 2015, have been officially commissioned into the Galileo constellation, and are now broadcasting working navigation signals.
41) - The satellites' onboard atomic clocks – while the most precise ever flown for navigation purposes – must be kept synched by Galileo's global ground segment, which also keeps track of the satellites' exact positions in space.
42) - Once safely in orbit and their systems activated, their navigation payloads and search and rescue transponders were subjected to a rigorous process of in-orbit testing, to ensure their performance reached the necessary specifications to become part of the Galileo system.
- The operations team, successfully led by SpaceOpal GmbH, completed the testing campaign few days ahead of schedule, with the satellites beginning to broadcast valid navigation signals on 29 January, 2016.
• December 1, 2015: The Galileo-7 and -8 satellites (FOC-3 and FOC-4), launched on March 27, 2015, completed their commissioning activities and were declared operational, broadcasting navigation signals and, from today, relaying search and rescue messages from across the globe.
New onboard features such as seamlessly swapping between the different atomic clocks – a unique feature in global satnav systems – has been verified, which translates into more robust navigation services.
• November 9, 2015: Europe's fifth and sixth Galileo satellites – subject to complex salvage maneuvers following their launch last year into incorrect orbits – will help to perform an ambitious year-long test of Einstein's most famous theory.
- 'In the meantime, the satellites have accidentally become extremely useful scientifically, as tools to test Einstein's General Theory of Relativity by measuring more accurately than ever before the way that gravity affects the passing of time.'
It has been verified experimentally, most significantly in June 1976, when a hydrogen maser atomic clock on GP-A (Gravity Probe A) of NASA and SAO (Smithsonian Astrophysical Observatory) was launched 10,000 km into space, confirming the prediction to within 140 parts in a million.
- Atomic clocks on navigation satellites have to take into account they run faster in orbit than on the ground – a few tenths of a microsecond per day, which would give us navigation errors of around 10 km per day.
- This new effort takes advantage of the passive hydrogen maser atomic clock aboard each Galileo, the elongated orbits creating varying time dilation, and the continuous monitoring thanks to the global network of ground stations.
• October 2015: Preliminary in-orbit payload performance results: A look is taken at at the initial results of navigation and search and rescue payload operation in orbit of the satellites FOC-1 (FM01) and FOC-2 (FM02) and compared with the predictions and performance in ground tests.
At each output power level the output power was verified against the predictions based on the on-ground measurements of the spacecraft - as measured in TVAC (Thermal Vacuum) and of the antenna as measured both by the supplier and after the integration onto the S/C.
The CMCU (Clock Monitoring and Control Unit) gives the ground segment the capability to adjust the frequency and the phase of the 10.23 MHz reference frequency (used inside the navigation payload and the spacecraft) derived from either of the two clocks (nominally PHM) by measuring the relative phase between these two frequencies over time (phase meter).
Figure 19: Seamless switch from RAFS-B to PHM-B resulting in a position ‘jump' of less than 3 cm (image credit: OHB) - Initial measurements of SART (Search and Rescue Transponder): The objective of this (secondary) payload is to receive distress signals transmitted in UHF (406.1 MHz) and upconvert them to L-band and forward them to the earth stations from which then the rescue is organized.
Table 5: SART Test results - The first six FOC satellites have been deployed in orbit, and are all in perfect health, despite the anomalous orbit of satellites FOC-1 (also called FM01) and FOC-2 (FM02) due to an injection failure of the upper stage of the launch vehicle.
45) - The satellites fired their thrusters to drift towards their target orbital positions at around 23, 222 km altitude – helped along in this case by a near-perfect orbital injection to begin with.
• March 13, 2015: ESA is reporting that the sixth Galileo satellite of Europe's navigation system has now entered its corrected target orbit, which will allow detailed testing to assess the performance of its navigation payload.
46) Table 6: Overview of the recovery actions taken by the various teams Figure 20: Corrected orbits of satellites 5 and 6 (image credit: ESA) Legend to Figure 20: The original (in red) and corrected (in blue) orbits of the fifth and sixth Galileo satellites, along with that of the first four satellites (green).
- The revised, more circular orbit means the fifth satellite's Earth sensor can be used continuously, keeping its main antenna oriented towards Earth and allowing its navigation payload to be switched on.
The aim is to raise the lowest point of its orbit – its perigee – to reduce the radiation exposure from the Van Allen radiation belts surrounding Earth, as well as to put it into a more useful orbit for navigation purposes.
48) - The Galileo pair, launched together on a Soyuz rocket on August 22, 2014, ended up in an elongated orbit travelling out to 25,900 km above Earth and back down to 13,713 km.
16, 2014 49) • Oct. 8, 2014: The Independent Inquiry Board, formed to analyze the causes of the launch anomaly, came up with the following conclusion: The root cause of the anomaly on flight VS09 is a shortcoming in the system thermal analysis performed during stage design, and not an operator error during stage assembly.
- Beyond theses corrective actions, sufficient for return to flight, NPO Lavochkin will provide Arianespace with all useful information regarding Fregat's design robustness, which is proven by 45 successful consecutive missions before this anomaly.
- One argument for waiting until mid-2015 for the next launch is that it would give ESA and OHB additional time to put the satellites through a rigorous in-orbit test campaign to debug them before launching additional satellites.
Both satellites – despite the different environment with different orbit period, harsher radiation environment, and in an unforeseen highly elliptical orbit - are in perfect health, no redundancy in any unit or subsystem was lost so far.
While this is good news for the recovery at first look, a second look reveals that even with this large propellant margin aboard, the satellites cannot correct the major injection failure that altered both eccentricity and inclination of the orbit.
The two most urgent problems that FM1 and FM2 are currently facing are identified as: • Earth sensor field of view • Radiation environment The first issue is a result of simple geometry: the Earth sensors aboard are designed for missions in orbits in or above MEO.
With this background in mind, the following tasks are currently being investigated by OHB for ESA to support the re-definition and recovery of the first FOC mission from its injection anomaly caused by Fregat: • Firstly, in order to allow the onboard Earth sensors to become fully operative, it is planned to invest most of the propellant onboard of FM1 and FM2 to raise the orbit's perigee.
The main driving requirements are: • Lifetime: 12 years in MEO for FOC (whereas GIOVE-A was a 27 month mission) • Launch scenario: Dual launch on Soyuz or 4 x launch on Ariane-5 with an effective mass limit of ~730 kg/spacecraft.
industrialization: In order to minimize the recurring costs of production and generate satellites at the required cadence, the payload procurement and AIT (Assembly, Integration and Test) processes have been designed with production optimization as a key driver.
3) Signal generation subsystem: The SGS (Signal Generator Subsystem) is responsible for the generation of ranging and spreading codes, storage and buffering of navigation data obtained from the mission receiver through the CSU and generating the appropriate modulated L-band signals.
Figure 23: Photo of the FGUU (image credit: Galileo GNSS) 4) RF amplification subsystem: The RAS (RF Amplification Subsystem) is designed to meet the following requirements: • Meet the EIRP requirements specified for the Galileo FOC navigation mission • Operate three L-band channels with center frequencies at 1191.795 MHz, 1278.75 MHz and 1575.42 MHz.
The objective of the RAS is to transmit the navigation signals to the ground at a quality and power level high enough for the receiver to track them and prevent interference with the radio astronomy bands and other existing navigation systems.
rescue subsystem: The SAR (Search and Rescue) payload's key function is to receive distress beacon signals at 406.05 MHz, band limit the signal, control its dynamics, convert it to L-band at 1544.10 MHz, and amplify it up to a 5 W output signal.
The key design challenge is to overcome external interfering signals, combined with any internally generated spurs, in combination with large in-band signal dynamics to maintain the payload gain stability.
The SAR payload system will include a transponder that translates the UHF distress beacon signal to the SAR payload output at L-band, for transmission to the MEO system local user terminals, in conjunction with the Galileo SAR antennas and two test couplers.
6) Laser retroreflector array: The laser retroreflector array consists of fused silica corner cubes, which have the geometrical property of turning incoming light rays through 180 degrees so that they return to their source.
SAR/Galileo (Search And Rescue) payload Background: The LEOSAR system, developed by the International COSPAR-SARSAT Program, currently provides accurate and reliable distress alert and location data to help search and rescue (SAR) authorities to assist persons in distress.
57) The inclusion of a SAR (Search And Rescue) payload in the Galileo satellites represents a major opportunity to dramatically enhance the performance provided by this system, it marks a significant expansion of the COSPAS-SARSAT program, a satellite-based network designed to bring help to air and sea vessels in distress.
60) Figure 26: Galileo search and rescue repeater signal (image credit: ESA) The SAR repeaters on these two Galileo satellites are the first of a new class of ‘MEOSAR' repeaters, combining broad field of views with the ability to quickly determine positions.
63) Figure 29: Photo of the SART (Search And Rescue Transponder), image credit: ESA, Kongsberg Norspace The shoebox-sized SART picks up emergency distress calls from the ground or sea and relays them to the nearest rescue center, while also sending a return-link message that help is on the way.
65) - The service is Europe's contribution to the COSPAS–SARSAT international satellite-based locating system that has helped to rescue more than 42,000 people since 1982 – the only system that can independently locate a distress beacon wherever it is activated on Earth.
The distress signal via Galileo arrived at his center 46 minutes before the alert from the existing COSPAS–SARSAT, and the identified position proved to be within 100 m of the crash, rather than the current system's 1.5 km.
66) Figure 30: A helicopter airlift during a Norwegian search and rescue exercise on the Svalbard archipelago (image credit: Sysselmannen på Svalbard–Birgit Adelheid Suhr) 67) Figure 31: Galileo within new system: Like the US GPS and Russian GLONASS, European Galileo satellites are carrying COSPAS–SARSAT MEOSAR (Medium Earth Orbit Search and Rescue) transponders (image credit: NOAA) 68)
Galileo's Ground Segment: The Galileo Ground Segment necessary is one of the most complicated developments undertaken by Europe, having to fulfil strict levels of performance, security and safety: 69) 70) • GMS (Ground Mission Segment): The GMS must provide cutting-edge navigation performance at high speed around the clock, processing data from a worldwide network of stations.
For this purpose, it will use a global network of GSS (Galileo Sensor Stations) to monitor the navigation signals of all satellites on a continuous basis, through a comprehensive communications network using commercial satellites as well as cable connections in which each link will be duplicated for redundancy.
The first is the ODTS (Orbitography Determination and Time Synchronization) function, which will provide batch processing every 10 minutes of all the observations of all satellites over an extended period and calculates the precise orbit and clock offset of each satellite, including a forecast of predicted variations, SISA (Signal-in-Space Accuracy), valid for the next hours.
Indeed, the European Union has deployed a significant Ground Segment infrastructure, which provides localization services for distress alerts transmitted by SAR beacons over a wide area comprising continental Europe, and vast oceanic areas around the continent (Figure 34).
72) Figure 33: Overview of the Search And Rescue function within Galileo (image credit: ESA) The ground segment of the Search and Rescue Service of Galileo consists of 3 receiving ground stations, called MEOLUTs (Medium Earth Orbit Local User Terminal), which receive the distress signals relayed by the Galileo Search and Rescue repeater in the 1544 MHz band.
The stations are networked to share raw data, effectively acting as a single huge 12-antenna station, achieving unprecedented detection time and localization accuracy in relaying search and rescue signals to local authorities.