Integrating Air and Space Traffic Management for Aviation and near Space
By: Sanat Kaul
Tags: Air Traffic Management, Space, Aviation, Space Exploration, Freewriting

by Dr Sanat Kaul Chairman, International Foundation for Aviation, Aerospace . and Drones

1.Introduction

This paper will examine and show why it is now necessary for International Civil Aviation Organisation (ICAO) to take over Air and Near Space Traffic Management as technology is similar for both. Further it becomes obligatory for ICAO to do this and Outer Space Treaty of 1957 is silent on the issue of space traffic management..

2.New Space

Travel into upper atmosphere and Outer-space will no longer remain an occasional launch when the Air Traffic Controller informs all aviation traffic to stay clear by issue of a Temporary Flight Restriction (TFR). With the coming of Space Tourism, Sub-orbital Flights, hypersonic aircrafts, high altitude balloons well as UAVs in near future there will be much greater requirement of better management of Upper Air and Near Space. Currently, countries are obliged to manage the air traffic over their sovereign airspace as well as over the Flights Information Region (FIR) over high seas allotted to them by ICAO. The existing technology based on radars is not able to provide good surveillance over High Seas since radars are land based and are unable to provide surveillance over High Seas. Radars find it difficult to cover terrain like Polar Regions or even hill features. Since 1960s with the introduction of Global Positioning System (GPS) by US Air Force the management of Air Traffic is undergoing a change. Global Navigation Satellite System (GNSS), a generic name for constellations like GPS of US, GLONASS of Russian Federation , Bediou of China and local constellation like IRNSS or NAVIC of India have become popular method of navigation not only by aircrafts but in general. ICAO intends to shift from terrestrial navigation to satellite based navigation for aviation. However, there are many issues with satellite based navigation. To begin with GPS signals are weak and subject to interference both natural and motivated. In addition GPS and GLONASS and even Bediou are military satellite constellations and are deliberately made inaccurate for civil purpose. Galileo, the European constellation is supposed to be a civil one but is yet to be fully operational. For Aviation navigation purposes Augmentation satellites are needed like WAAS in the US, EGNOS in Europe and GAGAN in Asia. These satellites are supposed to correct the poor signal and take care of ionosphere disturbances which distort GPS signals with the help of ground stations.

3.Issues Facing Airspace Management:

Presently 70% of earth’s Airspace does not have a continuous air traffic surveillance as radars cannot reach it. In this non-radar Airspaces (NRA), flight surveillance is managed procedurally. To ensure flight safety, large separation distances are mandatory in flight paths passing through NRA. But due to the rise in transoceanic air traffic, a smaller than normal separation distance is already being permitted in some cases. It may also be added that the present surveillance by radars is over only 30% of the earth’s atmosphere that too up to a height of about 50,000 ft which is just over 15 kms (vertical). Even military aircrafts do not go beyond 100,000 ft or about 30 kms vertical above the sea level.

AirSpace and OuterSpace

Space is getting busier then ever with 5–8% growth annually and over 80 launches a year. There are already 1400 satellites in operation. With private sector having major plans for expansion like SpaceX and OneWeb building mega constellations of satellites. Airbus is planning Spaceplanes and Space tourism beginning to take shape withVirgin Galactic, Blue Origin, SpaceX Dragon2, XCOR.

While there is no legally separation between where Airspace ends and Outer Space starts, there are many proposals going around like 100 kms vertical could be the limit of Airspace (based on Karman line proposal)[1]. The major legal difference between the Airspace and Outer Space is that while Airspace above a land territory (including territorial waters) of a country is the Sovereign Airspace of that country as per Article 1 of Chicago Convention of 1944, the Outer Space Treaty of 1967 defines Outer Space (beyond that undefined limit of Territorial Air Space) as the ‘common heritage of mankind’. However, under Art 12 of the Chicago Convention the Air Space over the High Seas is under ICAO and is also treated a ‘Global Commons’ or ‘a common heritage of mankind’ as it is open for all to use. Therefore, both Air Space over High Seas (70% of airspace) and Outer Space can be considered as “Global Commons”. There is, thus, a great commonality between the Chicago Convention and Outer Space Treaty than generally accepted.

Article 28 of the Chicago Convention states that each contracting State shall provide in its territory navigational aids to facilitate international travel by air. However, since Airspace over High Seas is with ICAO, it has to provide the navigational facility. To overcome this responsibility, ICAO has divided the entire Airspace over High Seas into many Flight Information Regions (FIR). After seeking the acceptance of the adjoining country it has allotted FIRs to them. However, no sovereignty is passed on to the state. Currently Air Space Management by a country is at best upto about 30 kms vertical. But with an increasing number of satellites launches and that too from an increasing number of launch vehicles clear rules of the game need to be laid out.

Civil Aviation Navigation Services Organisation (CANSO) has stated in their presentation[2] at a Symposium by ICAO/ UNOOSA in 2017 that while aviation and space are fast growing Industries with great potential the need for cooperation between ATM and STM is now paramount. Clear rules need to be developed and agreed by all stakeholders, to accommodate the requirements of users in traditional airspace, as well as space-bound vehicles travelling to and from space.

According to DLR, A German Government Research Agency, within the next two decades commercial Space Traffic will develop into a global multi-billion-Euro market. This emerging market will mainly focus on Suborbital Space Travel (point-to-point connections and vertical ballistic joy rides), Suborbital Cargo Transportation and Satellite Deployment via air launch systems. With the growth of this promising market the need for a safe, efficient and globally (co)operating Space Traffic Management (STM) system will arise

A successful STM system requires the execution of all necessary managing and monitoring & control operations that are mandatory to ensure safe travel of manned and unmanned suborbital space vehicles through space and airspace. One key aspect along this path is the seamless integration of spacecraft into the global Air Traffic Management (ATM) system[3]

4. According to Marshal H Kaplan[4] the implementation and enforcement of space traffic management (STM) policies and regulations will be extremely complex and expensive for governments of spacefaring nations and all users of the near-Earth space domain. Compared to air traffic management, the challenges of managing low-orbital traffic will be orders of magnitude more sophisticated.

The underlying reasons include:

• High orbital speeds of near-Earth satellites, 25 times greater than jet aircraft

• Lack of the ability of satellite to responsively execute avoidance manoeuvres

• Difficulty of assessing real-time and precise collision probabilities

• Presence of millions of uncontrolled and dangerous resident space objects (RSOs) that share the most-congested region of space as operating satellites

• Complexity of reaching an agreement with all spacefaring nations regarding space traffic issues

• Development of regulations that are fair and balanced without excessively restricting space traffic and related operations

• Creation of centralised space traffic controller and enforcement systems

• Achieving satellite operator compliance related to additional onboard traffic management hardware, operational restrictions and licensing processes

All objects in low-Earth orbits (LEOs) are traveling at speeds of over 25,000 kilo-meters per hour, about 25 times faster than today’s jetliners. Satellites share the same space as large and small debris, and everything is moving independently in arbitrary directions. Collisions can occur at relative speeds of up to 50,000 kilometres per hour. Today, there are roughly 1,200 operational satellites in LEO, most of which cannot change course on short notice. Many cannot manoeuver at all. Add to this at least several million passive objects that are completely non-responsive regarding traffic management operations. As a result, we have control over less than 1 percent of a very dangerous population of extremely fast-moving objects all of which are sharing the same space. Clearly, a first step in achieving a complete and successful space traffic management system will be the remediation of the debris problem. Although the complete elimination of debris will not be possible, a sufficient amount of removal and control must be achieved in order to realise safe on-orbit operations for constellation operators. In other words, a permanent space debris elimination and control system must precede effective STM operations.

During the transition period, from today’s situation until an initial STM capability, there must be an international effort to bring the debris situation under control. At the same time, new LEO space systems developers must prepare for a new set of requirements regarding hardware and procedures that will satisfy anticipated STM regulations. For example, every new spacecraft bound for LEO will have to be licensed by the STM authority and incorporate transponders that continuously report the vehicle’s state vector to STM controllers. In order to respond to manoeuver commands, each spacecraft will have to be capable of executing rapid avoidance manoeuvres when commanded to do so. Such implementations will be expensive and add mass to each spacecraft. In fact, space operations will also become more complex.

5.United Nations Committee on Peaceful Uses of Outer Space [5]

The United Nations Committee on Peaceful Uses of Outer Space (UN-COPOUS) has just celebrated its 60th year of existence . Formed in the year 1959 by United Nations General Assembly, it has been able to get five Space related Treaties successfully concluded within its first twenty five years: The Outer-space Treaty of of 1967, their main treaty, has been ratified by 108 number of countries followed by Rescue and Return Agreements of 1968, the Liability Convention of 1972, the Registration Convention of 1976 and finally the Moon Convention of 1979. However, after 1979 Moon Agreement it did not propose any Space Law Treaty.

The UNCOPOUS , therefore, has not been able to keep pace with the growth of Space activities. Since it remains a Committee of the UN, it does not have the advantage of a its own structure. With the huge growth of spacefaring activities there is now an urgent need to have binding regulation for safety, security and environmental protection. The growing and massive problem of Space debris is yet another issue which needs immediate resolution.

6.Future Challenges of Space Traffic Management(STM) — the US approach

Space Traffic Management in the Airspace and Near Space will become a challenge as more and more small satellites enter near space and sub-orbital flights become a reality. United States, the leading Air and Space power in the world today, realising the difficult problem of STM has already designated its Federal Aviation Authority(FAA)/ Commerce Department with the responsibility of laying down rules for commercial space flights. Therefore, by twinning the role of aviation safety management and Outer Space safety management in a single authority, US would bring the desired impact of integrating air and space traffic in a harmonious manner without a legal hitch through up to Low Earth Orbit (LEO).

7.Code of Conduct(CoC) for Space activities

In absence of any acceptable Code of Conduct for Outer Space by way of a UN sponsored regulation, private initiatives have come up. On one end is the US and the other Russia and China together. However, since they have not been able to have a consensus on this issue, it is hanging fire for the last two decades. The issue of CoC concerns both civil and military satellites. It needs to provide freedom of access to all countries and also inherent right to self defence.

Meanwhile European Cooperation for Space Safety Standards(ECSS) is another initiative aimed at developing coherent, single set of user friendly technical standards for use in all European Space activities. At the same time International Organisation for Standards(ISO), with membership of 163 countries has also developed its standards for Space including debris management, re-entry etc. However, ISO standards are voluntary and generic, which does not serve our purpose.

8.Therefore, Space Traffic Management remains an enigma as it remains an unregulated activity from an global point of view. Each spacefaring country decides its own safety norm, rules and regulation and so far there has been coordination between the countries. However, as space activities grow the need for a global regulator is deeply felt.

Space Traffic Management: some issues

Space Traffic Management is like Air Traffic Management but more. This is so because in the Low Earth Orbit there are over 100,000 pieces of debris over 1cm and higher floating around which can be very harmful to spacecrafts, a situation not found in Airspace. Today United States Air Force(USAF) is monitoring about 20,000 space objects above 10cm. However, USAF is keen to hand over this job to some civil organisation in US, possibly FAA. But will this role remain with US? Maybe another organisation can come up under the overall supervision of UN/ICAO.

9.Extending the role of ICAO to Space Traffic Management

Now we come to role of ICAO in Air Traffic Management and extending the same to Space Traffic Management. Here there are two issues. The first is the legal issue. The Mandate of ICAO by its very name it is meant for Civil Aviation. Yet the Chicago Convention of 1944[6] which is the basis for setting up of ICAO, neither defines what an aircraft is nor defines the upper limits of Airspace. Perhaps, in 1944 there was no need to provide any such definitions. However, the Outer Space Treaty of 1967 also does not define the lower limit for start of Outer Space. Further, aircraft has been defined only in Annexes to ICAO which can be corrected/modified by the Council of ICAO. Therefore, on the legal side there may not be much difficult for ICAO to take on the additional charge of Space Traffic Management but it could be tedious as either a new Annexure on Space will need to be passed or amendments in various Annexes like safety, licensing etc will need to be carried out. This is a matter of detail which can be sorted out.

As Dr Assad Kotaite, the legendary former President of The International Civil Aviation Organisation for 30 years has stated in his book ‘My Memoirs[7]

‘Space: In September 1993, Russian Prime Minister Victor Chermomydrin joined American Vice- President Al Gore in announcing Plans for the International Space Station. The 72-metre by 108-metre Space Station has since been assembled as a series of interlocking modules, serving as a manned platform for scientific research, explorations and technological development, and perhaps above all as a symbol of world peace, as it orbits the planet every 92 minutes, at an altitude of 250 to 263 miles( 402 to424 kilometres). The first Space Station partners were multilateral and government space agencies, but in 2012 the first commercial freighters began docking at the Space Station. I believe that this places us at the dawn of a new age of commercial passenger flights.

‘The first time that sub-orbital flights and space flights were mentioned at an ICAO Assembly was at its Thirty-Fifth Session, in September 2004, when I opened the Assembly with the following words: One hundred years from now, regular passenger flights in sub-orbital space and even in outer space could become commonplace. “Yet we have no precise definition as to where “air space” ends and where”outer space begins. There is no clear indication in international law as to the definition between air space and outer space which would clearly establish whether to apply air law or space law to sub-orbital flights. I believe that the time has come to examine how to apply to sub-orbital and outer-space flights the same kind of global management process that has worked so successfully for international air transport through Chicago Convention.

‘Sub-orbital flight is a natural extension of our current civil aviation-space vessels and space planes will have to fly through current air space to reach low orbit. Sustaining high speeds is no longer a problem: The problem is rather to find the way to enable passengers to endure these speeds in acceptable safety and comfort. I believe that commercial low-orbital flights will one day become widespread. Regulations and standards will need consideration. There is no need for a new agency to develop regulations: drawing on the principles of the Chicago Convention, ICAO is already well-equipped to examine all commercial and technological aspects of sub-orbital flights. New Annexes to the Chicago Convention May be required. The UN has a special Committee on the Peaceful Uses of Outer Space and ICAO has participated in its work”

ICAO was set up as a rule making body in 1947 as an Agency of the United Nations. Over the years it has created 100,000 Standards and many more Recommended Practices(SARP)s as well as detailed Procedures for Air Navigation Services(PANS) and Regional Supplementary Procedures (SUPPS). While it does not possess disciplinary powers, it does a mandatory audit of safety and security of its member countries. An adverse report is sufficiently damaging for the airlines of that county and no country wants a bad report.

However, on the issue of civil aviation each country was empowered by ICAO not only to provide Air Navigation Service to all commercial aircrafts flying over its territory or landing there, but this obligation was extended to many littoral countries by ICAO allotting an FIR to each adjoining country over High Seas. Thus , without having any of its own equipment for Navigation or Surveillance, ICAO was able to get each member country to manage not only its territorial Air Space but also AirSpace which is over the High Seas without any costs it, notwithstanding that AirSpace over High Seas in part of Global Commons and it’s Air Space management is a direct responsibility of ICAO. Of course, those countries that are given to regulate the Airspace over High Seas charge for their services from the airlines and is generally a source of profit for them.

In the case of Space Traffic Management, satellites generally take off vertically from a country ( except for sea launches) and go up OuterSpace without violating any other countries’ AirSpace. But sub-orbital flights may take-off as an aircraft might might pass through other countries.

10. Technical Issues:Global Navigation Satellite System (GNSS)and Space Traffic Management (STM)

GNSS technology is available free to all aircrafts and with the help of Augmentation satellites aircrafts are able to navigate all parts of the earth. However, aircrafts over high seas and polar regions are still unable to keep the Air Traffic Control in the loop with this technology because it requires ground stations.

GNSS systems are working in Near Space right upto International Space Station and with the ADS-B over Satellite technology developing at high altitudes including Near Space, surveillance technology and AirSpace technology can find common cause in their Integration and joint management of Air and Space traffic up to about 100 km vertical and beyond depending on the technology available. Therefore, technically also merging of AirSpace and Near Space Traffic Management will become realisable within the ICAO requirement of Communications, Navigation and Surveillance/Air Traffic Management (CNS/ATM). Merging the responsibility of Air and near Space traffic management in atmosphere and near space can, therefore, be best left to ICAO with minor tweaking of the Annexes to Chicago Convention as neither the upper limit of Airspace nor the beginning of Outer Space has been defined in any of the Treaties mentioned above. However, some septics like Ruwantissa Aberatne, a legal expert on Space and formerly with ICAO, has stated ‘ it is not prudent to lump air transport and space Transport together by amending an existing Convention, however attractive it might be as a quick fix. Both are very different fields of transport and should be covered by separate multilateral instruments[8] While he sees that an Amendment to the Chicago Convention is required, Dr Assad Kotaite in his book has clearly stated that this is not the case.

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In order to overcome the gaps in continuous surveillance over airspace under use the ICAO Council approved the Global Air Navigation Plan (GANP) with the ultimate goal of a fully harmonised global Air Navigation system with global interoperability as a minimum objective. In order to achieve this it was felt that there is a need to introduce new technology. Use of GNSS as a technology was the obvious answer

11.A new Technology is introduced: ADS-B[9]:

Automatic Dependent Surveillance Broadcast (ADS-B) is a new GNSS based technology that enables aircraft broadcast signals including flight related information i.e., identification, position, altitude, velocity and other relevant information i.e. surveillance on a regular basis to ATCs as well as to other aircrafts. This technology ensures that a moving object in air regularly transmits its position and other details to all other aircrafts and ATCs via the aircraft’s Mode S transponder. However, for accuracy ADS-B also requires ground stations. US has already constructed over 640 ground stations as FAA has announced use of ADS-B (IN) as a compulsory equipment on all aircrafts by 2020. Australia is also doing the same. Terrestrial-based ADS-B infrastructure, therefore, becomes an alternative (or add-on) to radars but not a complete solution to complete Air Traffic Management as it is not available over high seas or polar regions where there are no ground stations

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Shortcoming of ADS-B

ADS-B technology is GNSS based and is able to broadcast the position of an object/ aircraft to the ATC as well as to all other aircrafts in the region giving its flight direction, speed etc While ADS-B technology is considered better than land based Radar technology as it provides a better ground coverage, it also suffers from the same major deficiency as Radars. Both require ground station. As a result both technologies are unable to cover 70% of the earth’s surface ie the High Seas and Polar regions and difficult terrains.

12. Solution to the problem: ADS-B over satellite

DLR experiment

In order to overcome the issues of coverage mentioned above DLR, the German research agency, in 2008 investigated the possibility of monitoring global air traffic from space without ground stations as it could resolve the issues of surveillance in non radar area (NRA) ie the High Seas and Polar regions outlined above. This, they felt, could be achieved by satellites intercepting the information broadcast by aircraft, in this case data from the Automatic Dependent Surveillance — Broadcast (ADS-B), which can then be transmitted to existing ground infrastructure with the help of Mode S transponders on commercial aircraft. This will ensure global surveillance of all air traffic. By 2010 DLR conducted successfully a series of high altitude test flights.

Under the aegis of European Space Agency (ESA) Thales Alenia Space Deutschland GmbH led the “Space Based ADS-B In-Orbit Demonstration (IOD) Payload Development for Air Traffic Surveillance Project”[10] This project was mainly aimed at demonstrating the functionality of this technology under representative space environment conditions, and to verifying the link budget of this payload for the various ADS-B compatible equipment onboard aircraft on different geo-locations.

This was followed on 7th May 2013 by European Space Agency’s (ESA) Proba V experiment (Project for On-Board Autonomy — Vegetation) on board the newest satellite of ESA. Its main task was to provide actual vegetation data to the community and serve as gap filler between the SPOT-VGT and Sentinel-3 satellites. This experiment of the ADS-B receiver on board the satellite was the first experiment of its kind, receiving 1090ES (extended Squitter) ADS-B squitter signals transmitted from aircraft.

The primary goal of the DLR project ADS-B over Satellite was to demonstrate the feasibility of an orbital ADS-B system by means of an In-Orbit Demonstration (IOD) and to evaluate the characteristics and performances which may be important for future space based air traffic control systems. As preparatory missions DLR conducted in 2010 the first of a series of high altitude test flights. During a test flight in northern Sweden a terrestrial ADS-B receiver has been used and basic assumptions regarding the maximum reception distance in NRA could be verified. Based on these trials and pre-development studies a system concept for a space based ADS-B reception has been developed, mostly based on commercial of-the-shelf hardware.

The achieved results of the IOD should take into account the constraints under which this experiment was performed, as there were limitations in cost and time and in particular available resources on the satellite in terms of available power and geometry. Further, the reception of 1090 Extended Squitter ADS-B messages on board of the PROBA-V satellite is mainly affected by the fact that the signal path between a LEO satellite and an aircraft is much longer as the LEO satellite flies at about 820 km altitude while an aircraft flies at 15 kms altitutde, which may lead to a loss of signal quality. In this connection the quality of antenna on board a satellite to receive the ADS-B signals is very important. The same goes with ADS-B receivers

ADS-B over Satellite

ADS-B (Automatic Dependent Surveillance-Broadcast) over Satellite is still in early stages of commercialisation and will overcome the deficiencies to provide a full coverage of surveillance over High Seas and Polar regions of all moving objects in Airspace provided they carry an appropriate transponder.

Airspace is no more the domain of only Aircraft:

Chicago Convention has used the word “Aircraft” without defining it and assumed it as the sole user of airspace , there are now many other users of the airspace. However, these new users are not subject to the requirement imposed upon aircrafts. With new users of airspace similar conditions need to be imposed since surveillance of other than aircrafts is a must for all airspace users and therefore, similar requirements must be imposed on all. The commonality of the instrument falls on ADS-B as it can be put on all objects including balloons and platforms.

Simply put, ADS-B works wherever it is placed, be that on an aircraft, or on a space vehicle, or on a stratospheric balloon, or on a remotely piloted system.

Space borne ADS-B: The Future hope

Only a satellite constellation has the capability to provide a global coverage at any possible flight level, avoiding limitations imposed by terrestrial ADS-B. This could be implemented by receiving ADS-B signals, which are broadcasted regularly by each equipped aircraft, spacecraft or even a balloon giving information on its position, speed, direction etc. by LEO satellites. This data can then be made available to already existing ATC ground infrastructures.

Therefore, a satellite-based surveillance network will provide enhanced Air Traffic Services in areas where the traffic density, the location, or the cost of “conventional” ATC equipment would not justify any installation of radar and/or terrestrial ADS-B. It can also include VHF coverage in fringe areas.

Results: “The Proof of Concept” experiment for ADS-B over Satellite has proved successful. It has successfully validated the principle of detecting even the weak Mode-S transponder transmission from a Low Earth Orbit satellite. With improvement in receivers and antenna the quality could improve.

Signal loss is due to the low signal level resulting from the distance between the receiving satellite at an altitude of approximately 820 km and the transmitting aircraft at an altitude of 12–15 km. Further, RF signal loss is also due to the shapes of the satellite antenna vertical radiation pattern and the aircraft antenna vertical radiation pattern. Corruption of messages by garbling, when several messages arriving at the ADS-B antenna onboard of the satellite at the same time overlap and thus cannot be decoded by the ADS-B receiver. Speed of the satellite of about 27000 km/h, leads to a limit the time of observation for each detected aircraft to about 3 minutes maximum.

Receiver: The ADS-B receiver developed for the PROBA-V in-orbit demonstration provides in its output data no direct signal level measurement values, which mainly would represent the noise level. Instead the receiver provides a correlation gain value for each successfully decoded message, which denotes the performance of the correlation process. It may be added that on June 2013 an Airbus aircraft flying over Scotland was first noticed from space by a new receiver, the ADS-B device of DLR on Proba. In another experiment by DLR when ADS-B over satellite was switched on over 12,000 ADS-b messages were received in two hours with the satellite at an altitude of 820 kms.

Other advantages of ADS-B over satellite is that as the long distance Air Traffic becomes global, it can brings considerable fuel savings, a reduction in green house gases emissions and greater safety of aircraft and passengers.

Commercialisation of ADS-B over satellite for Aviation

Aireon: The first commercial attempt for ADS-B over Satellite for aviation sector was already started in 2014 with the announcement of “Aireon” a joint venture between Iridium Communications, Nav Canada, the Irish Aviation Authority, Italian air traﬃc services provider ENAV, and Danish ATS provider Naviair. Nav Canada also has signed on as Aireon’s ﬁrst customer, and plans to implement space-based ADS-B beginning with its busy North Atlantic airspace. NAV Canada has backed Space-based ADS-B as its major technology for ATM especially over high seas. By March 2014 Aireon had successfully completed qualification testing for the harsh environment of Space. The company produced 81 ADS-B 1090Extended Squitters receiver payloads. It intends to launch 66 satellites into LEO along with six in orbit as spares

With the starting of Aireon as commercial venture for ADS-B-over-satellite, the beginnings of a new era of surveillance of common Air and Near Space integration has, in fact, started. As more commercial companies are taking interest in use of small and nano satellites, only ADS-B transponder may be able to provide the task of integration of Air and Space Traffic Management.

13. The Integration of Air and Space Traffic Management:

While we describe the conventional limit of Airspace as 100 kms in our introduction above, the current commercial air traffic is only up to about 40,000 feet or say 12 kms.

Airspace is currently used by commercial traffic up to about 40,000 feet or say 12 kms above the sea level. Further, From 60,000 (18.3 kms) to 100,000 (30.5 kms) feet it was traditionally used for military operations. Now, however, new commercial operations have started to take place in this airspace which include unmanned free balloons, high endurance UAS and commercial space operations. Air Traffic Services will need to be extended, out of necessity, enhance its role to include the new Aerospace based objects. This will lead to start of integration of aviation and space activities in the upper airspace and beyond. Even space tourism activities propose to go up to 100 kms and beyond into a bit of outer Space. The current set of Radars will be inadequate and new radars for higher altitudes are very expensive. Therefore, new solutions have to be found. Here the new ADS-B over Satellite will be a game changer for aerospace management.

The Space-Based ADS-B Antenna: The antenna used for ADS-B over Satellite is an antenna array of two elements. Each element is a capacitive fed, shorted patch antenna. There is no direct mechanical bonding between the feeding structure and the patch. This makes the patch assembly very easy. Except for the feeder no dielectric material is used. It has been found that this gives an extra 12% gain increase. The patch antenna is shorted in the center of the patch to the ground plane of the spacecraft structure. This avoids potential charging. The technology for space based antennas is still young and hopefully their will be more improvements

Temporary Flight Restrictions (TFR) : As more and more space launches take place from existing and new launch locations leading to greater demand for declaration of temporary flight restrictions (TFR) the use of TFR will need to be made more sophisticated. Other commercial Expendable Launch Vehicles include Sea Launch Vehicles which operates currently from a floating platform in a remote region of the Pacific Ocean and high altitude Balloons being launched by amateurs and Universities. As more and more countries and private companies start their own launches from their soil or high seas the issue of TFR will become more problematic as the conflict between a growing aviation industry with horizontal requirement of airspace and growing space launch industry with vertical requirement takes place. With Nano and other small satellites getting launch in the thousands per year in future this issue will become very important. For example, Planet Lab, a seven year old company, has already sent 233 satellites into space on a mix of American, Indian, Japanese and Russian rockets. India recently launched 104 satellites in one single launch. Another company One Web in Florida , USA wants to surround the planet with hundreds or even thousands of satellites in the low orbit and form a network accessible to 3 billion people on Earth who lack high-speed internet services. So far very little attention was paid to the airspace above 60,000 feet as this airspace was not particularly important to commercial space or other non-government users. But not any more. More Sea launches will a require more TFR over high seas. It is here that ICAO has to take a proactive stand as it is their mandate and obligation to maintain and encourage growth of safe and orderly traffic in airspace including over High Seas.

Balloons: We are also witnessing frequent launches of unmanned free stratospheric balloons by amateurs and universities that reach the upper airspace for short periods and return. Some larger commercial unmanned free stratospheric balloons that can float above 60,000 feet for several days. These can also cause conflict with other modes of aerospace travel.

In near future we expect supersonic and then hypersonic commercial aircraft will operate at or above 60,000 feet. As a matter of fact, Concorde , the supersonic aircraft flew for over 27 years until 2003. Once occupied by military and space users, this airspace from 60,000 to 100,000 feet is becoming increasingly attractive to commercial users. Further, ELV are giving way to reusable Launch Vehicles (RLV) which have their own requirements. Can the present state of Air Traffic Management based on terrestrial ground equipment like Radars manage it?

Space Vehicles and Reentry issues

Facilitate Integration of Space Operations

Technically integration of air and space traffic management cannot take place unless a common technology is available for surveillance and guidance. Timely and accurate position information is needed to be made available to air and space traffic control systems from all airspace users. There is a particular need for surveillance information on airspace users in the commercial space industry. Further, the integration, even if technically possible, will need acceptance at a political level as global standards will need to be made. ICAO is the obvious institution for it.

As we move towards commercial use of space from Expendable Launch Vehicles to a variety of diverse operational types sharing this upper airspace is a challenge. This is also a tremendous opportunity for ICAO to demonstrate leadership, as is mandated in Chicago Convention of 1944, in airspace integration of both horizontal and vertical kind and support innovation in these developing industries if they are equipped to operate in shared airspace. There is a need to “the development standards and recommended practices between aircraft and space vehicles in sharing of the airspace…This research needs to concentrate at developing more advanced concepts that separate launch and reentry vehicles from other aircraft based on separation standards as opposed to airspace restrictions.” Another aspect is that the presently followed practice of horizontal heights dividing the Airspace will need to adjust to near vertical requirements launch vehicles as well as of Space Tourism vehicles. In order to achieve this goal, space vehicles and other high altitude operations will require onboard equipment that provides adequate communication, navigation and surveillance data to allow for the development of separation standards. ADS-B over satellite comes into play at this juncture as its transponder can be put on all including balloons and UAVs. More so as the efficacy of radars are getting reduced at higher altitudes.

Airspace Class and Requirements: both horizontal and vertical

The need to accommodate a variety of operational types aircrafts, spacecraft’s, rockets, balloons, platforms etc. with different requirements in shared airspace will disrupt the existing system of Air Traffic Control. This requires accurate and reliable detection and tracking information. The reliability of this information is a critical factor in developing separation standards. However, the operational characteristics, including speed, manoeuvrability, trajectory and mission requirements must also be considered in determining separation requirements. Here the role of ADS-B over satellite becomes very important as this technology will provide full coverage of all objects including aircrafts in Airspace provided they are equipped with a transponder. These will include Free Balloons, rocket powered vehicles, ELV, Vertically Launched Reusable Vehicles, Controlled Reentering Vehicles, controlled reusable first stage, reentering vehicle in free fall , High endurance UAVs and others

ADS-B equipment transmits both GPS and barometric attitude information. This allows for validation of the altimetry error that is acceptable in applying existing separation standards. It is important to note that separation standards are based on the position of aircraft and other objects relative to one another, not absolute position. Therefore it is important to ensure that the quality of data received from each airspace user is comparable.It has been confirmed that ADS-B altitude information is superior to barometric and is preferred over barometric even at a height of International Space Station

14.ADS-B over Satellite in Outer Space up to International Space Station (ISS)

Extending GNSS PNT right up to International Space Station(ISS) at about 350 kms in the Space is actually being attempted. Once Space grade receivers are place on a satellite constellation, both CNS/ATM for both upper airspace and near outer space say up to ISS at a height of 350 KM from earth, at least, seems feasible. GNSS PTN is used by ISS to meet altitude determination and enables more precision for space flights operations like rendezvous and docking, station keeping, formation flying and GEO satellite servicing. Using GPS/GNSS on ISS and Crew Rescue vehicles is a challenge being looked into by scientists. The problems of blackouts and multipaths are yet another issue to be tackled. Once these issues are sorted out, it is hoped that ADS-B over satellite will be able to send signals to earth of all moving objects up to that height, be they be satellite or platforms, as long as they have an ADS-B compliant transponder on board. When this is confirmed by trials then there will be full integration of Air Traffic Management between Airspace and near Space.

14.Rentry issues: The major challenges for the Crew Rescue Vehicle (CRV) as at re-entry into the atmosphere remain. The GPS receiver has to go through the region referred to as the blackout region (between 82 to 67 kms) where RF signals encounter a lot of disturbance due to the Earth’s ionosphere. The RF signals received are much lower signal strength, and typically GPS tracking is reduced to less than 4 satellites for several minutes. The GPS receiver needs to be able to recover the GPS signal following blackout.

15. Mandatory ADS-B over Satellite for all Aviation and Space objects: If we mandate all satellites and other space objects to equip ADS-B over satellite with all vehicles and platforms operations in and through upper airspace with ADS-B over satellite, it will enable all varieties of vehicles to perform more efficiently in upper airspace. ADS-B provides the ability to display these vehicles on controller workstations and provide surveillance data to spaceports and vehicle operators. Simply put, ADS-B works wherever it is placed, be that on an aircraft, or on a space vehicle, or on a stratospheric balloon, or on a remotely piloted system at any height. The technology follows the transponder. The transponder is the key, not the aircraft or the vehicle.

Re-entering stages of a spacecraft (about 75 km), specially the new reuseable type poses new challenges. For reusable launch vehicles, under operator control, there is a need to develop tactical separation standards between aircraft and spacecraft.

16.International Space Station (ISS)

It may also be stated that GNSS PNT is already being used by International Space Station at a height of about 350kms to meet altitude determination and enables more precision for space flight operations like rendezvous and even docking stations keeping, formation flying and GEO satellite servicing. Further, by placing space grade receivers on a satellite constellation like Aireon, it will provide not only 100% global surveillance of all aircrafts but also all other space vehicles(satellites, balloons, platforms etc) and space objects right upto 100 kms and beyond. As Receivers and Antennas improve with quality the transmission of data will also improve.

The most important aspect for the reception of ADS-B messages in space are the receiving conditions for the 1090 MHz extended squitter signal on board the satellite. In comparison to ground based ADS-B surveillance with a range of up to 300 km maximum, the signal path between a LEO satellite orbiting at 820 km altitude and an aircraft is much longer, which results in a low signal level at the ADS-B receiver. Thus the Mode-S signals have to be detected nearly at noise level by a correlation process. The quality of these space based receivers thus becomes very important

17.UNOOSA and ICAO cooperation

1. In 2007 the United Nations Office of Outer Space Affairs (UNOOSA) setup the International Committee on Global Navigation Satellite Systems (ICG) for compatibility/interoperability of GNSS systems and protection of GNSS spectrum, orbital debris mitigation, and orbit de-confliction. The Interagency Operations Advisory Group addresses strategic issues related to inter-agency interoperability, space communications, and navigation matters.

2. ICAO is another source of international governance of GNSS. Its Standards and Recommended Practices (SARPs) for GNSS are found in Amendment 76 to Annex 10 of the Chicago Convention and provide extensive guidance on the technical aspects of GNSS and its application in furtherance of international aviation safety. Integration of commercial space users with aviation users is becoming highly desirable for the present but perhaps, necessary in future. Both ICAO and ONOOSA are seized of the need and have started meeting. Already three joint Conferences have taken place the last one in August of 2017.

3. The objective of full integration of the aviation and rocket based system to maximise airspace efficiency right upto higher levels of airspace and beyond into LEO is very desirable. In such a scenario, a space vehicle operation is a fully integrated with airspace user providing the space operator with assured access to the Airspace and does not disrupt the aviation operators.

4. CONCLUSIONS

Integration of Air and Space Traffic Management at least in the Low Earth Orbit is feasible both Administratively and technically. ICAO can metamorphose into an aerospace body quite easily as pointed out by Dr Kotaite, the legendary President of ICAO. New Standards and Recommended Practices can be made and thereby extend ICAOs coverage to the so called upper AirSpace and up to Low Earth Orbit in an orderly manner as it has already done for aviation. As already mentioned earlier ICAO could create a new Annexe for LEO and make necessary changes and additions in the existing Annexes in order to create/extend SARPs for LEO based safety and traffic management.Further, technology exists to integrate the orderly surveillance and management of air and space traffic by use of GNSS/ADS-B over Satellite.

REFERENCES

1. Chicago: Convention on International Civil Aviation, signed at Chicago on 7th December, 1944 in Chicago known as Chicago Convention.

2. Treaty on Principles Governing the Activities of States in the exploration and use of Outer Space, including the Moon and Other Celestial Bodies, opened for signatures at Moscow, London and Washington, on 27th January, 1967 known as Outer Space Treaty.

3. International Civil Aviation Organisation (ICAO) was setup under Chicago Convention of 1944 and subsequently became a Specialised Agency of the UN. ICAO works within the Chicago Convention and has a membership of 191 Members. The elected council of 36 Member Countries is a permanent elected bodies which makes and approves SARPS (Standards and Recommended Practices)° on a consensus basis to ensure safe and peaceful development of Civil Aviation so that the 100,000 daily flights in the Aviation’s Global Networks operate safely and reliably in every region of the world. As a result of its work it has successfully brought safety to Civil Aviation and made Civil Aviation the safest form of Transportation.

4. The Bridge to Space: CNS Technology for High Altitude operations: Ruth E Stilwell D,P.A, Aerospace Policy Solutions, Hallande Beach,Fl, USA and Nickolas Demidovich, FAA, Washington DC, USA.

5. GNSS AND SUSTAINABLE ACCESS TO SPACE (1)Diane Howard, J.D., LL.M., DCL Embry-Riddle Aeronautical University,600 S Clyde Mossis Blvd, Dayton Beach , Florida; diane.howard@erau.edu (2) Ruth Stilwell, and DPA , Norwich University, 158 Harmon Dr., Noethfield VT USA, rstiwel@norwich.edu

6. First Space-Based ADS-B Satellites in Orbit : Launch Customer Nav Canada has not set Mandate by Mike Collins : News and Media> First Spaced Based ADS-B Satellites in Orbit: www.aopa.org/news-and-media/all-news/2017/january/18/first-space-based-ads-b-satllite-in-orbit

7. ADS-B over satellite The World’s First ADS-B receiver in Space : Conference Paper: 6 authors ;German Aerospace Centre (DLR); T. Delovski, K.Warner,T. Rawlik, J. Behrens. J. Bredemeyer,R.Wendel. DLR-Institute of Space Systems; DLR Institute of Flight Guidance Systems;FCS-Flight Caliberation Services GmBH;HAW — Hamburg Institute of Flight Sciences

8. Spacecraft Reentry Basics: The Aerospace Corporation: www.aerospace.org/cords/all-about-debris-and-rentry/spacecraft-reentry/

9. ADS-B over Satellite: eoPortal; https://directoru.eoportal.org/web/eoportal/satellite-missions/a/ads-b

10.ADS-B : Surveillance Development for Air Traffic Management by Christine Vigier, Design Mana Managemeny

[1] Broadly, most experts say that space starts at the point where orbital dynamic forces become more important than aerodynamic forces, or where the atmosphere alone is not enough to support a flying vessel at suborbital speeds.Historically, it’s been difficult to pin that point at a particular altitude. In the 1900s, Hungarian physicist Theodore von Kármán determined the boundary to be around 50 miles up, or roughly 80 kilometres above sea level. Today, though, the Kármán line is set as “an imaginary boundary” that’s 62 miles up, or roughly a hundred kilometresQ above sea level.

[2] Global Air Traffic Management and Space Traffic by Nico Voorbach, Director ICAO and Industry Affairs : CANSO at ICAO/UNOOSA Aerospace Symposium 29–31st August 2017

[3] Space Traffic Management: dlr.de

[4] | Space Traffic Management: implementation and enforcement by Marshall H. Kaplan — August 31, 2018 Marshall H. Kaplan, Ph.D., is a recognised expert in satellite and launch vehicle systems design and Engineering. He has participated in many new launch vehicle and satellite developments and has served as Chief Engineer on two launch vehicle programs. Dr. Kaplan was a member of the National Research Council’s Committee on Reusable Launch Vehicle Technology and Test Program. He has trained organisations that have won large space systems contracts for military and commercial applications. In his 40+ years of academic and industrial experience, he has served as Professor of Aerospace Engineering at the Pennsylvania State University, was the executive Director of a Space Research Institute and has presented space technology and systems courses in the U.S., Europe, Asia and South America. In addition to publishing over 100 papers, reports, and articles on space technologies, he is the author of several books, including the internationally used text, Modern Spacecraft Dynamics and Control. Dr. Kaplan is an AIAA Fellow and member of the Technical Committee on Space Transportation. He holds advanced degrees from MIT and Stanford University and is a Professor of the Practice in the Department of Aerospace Engineering at the University of Maryland.

[5] The Committee on the Peaceful Uses of Outer Space (COPUOS) was set up by the UN General Assembly in 1959 to govern the exploration and use of space for the benefit of all humanity: for peace, security and development.

[6] The Convention on International Civil Aviation, drafted in 1944 by 54 nations, was established to promote … Known more commonly today as the ‘Chicago Convention’. See History of ICAO and the Chicago Convention at Icao.int

[7] Assad Kotaite, President Emeritus of the Council of International Civil Aviation Organisation: My Memoirs: 50 years of International Diplomacy and Conciliation in Aviation: ICAO 2013

[8] Regulation of Commercial Space Transport : The Astrocizing of ICAO: Ruwantissa Abeyratne: Springer 2015

[9] · ADS-B is a system in which electronic equipment onboard an aircraft automatically broadcasts the precise location of the aircraft via a digital data link. The data can be used by other aircraft and air traffic control to show the aircraft’s position and altitude on display screens without the need for radar : see airservicesaustralia.com

[10] See.ADS-B over Satellite The world’s first ADS-B receiver in Space :Delovski, Toni und Werner, Klaus und Rawlik, Tomasz und Behrens, Jörg und Bredemeyer, Jochen und Wendel, Ralf (2014) ADS-B over Satellite The world’s first ADS-B receiver in Space. Small Satellites Systems and Services Symposium, 26.-30. Mai 2014, Porto Petro, Majorca, Spain. www.Elib.dlr.de