CA3187761A1

CA3187761A1 - Methods and systems for reducing risk of air collisions

Info

Publication number: CA3187761A1
Application number: CA3187761A
Authority: CA
Inventors: Michael T. Kezirian
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-07-31
Filing date: 2021-07-30
Publication date: 2022-03-03
Also published as: EP4189430A2; WO2022046350A3; WO2022046350A2; WO2022046350A9

Abstract

The present description is directed to a method for reducing the risk of aircraft encounters or collisions with objects such as debris in airspace featuring identifying the presence or re-entry of objects in the airspace, determining the location of the objects or determining the footprint for re- entering debris, and providing the location or the footprint to air traffic control personnel or offices. The present description also features a computer operated online catalog of the location of objects in the atmosphere and/or the footprint for re-entering objects into the atmosphere along with a computer operated algorithm for describing the location of the objects in the atmosphere and/or the footprint for re-entering objects into the atmosphere.

Description

METHODS AND SYSTEMS FOR REDUCING RISK OF AIR COLLISIONS
FIELD OF THE DISCLOSIIRE
[0001] The disclosure relates to methods and systems for identifying and reducing the risk of air collisions, specifically collisions between aircraft in the airspace and re-entering space debris.
Aircraft can include any airplane, helicopter, launch vehicle, suborbital or orbital spacecraft, drone, high-altitude balloon, sport parachute or other machine capable of flight. Re-entering space debris might include spacecraft, satellites, launch vehicles, meteors, asteroids, other space objects or fragments of one or more of these objects.
RACKGROUND

[0002] Space debris represents a hazard for aircraft. Due to relative speed and associated energy, a collision with one or more fragments of reentering space debris can have catastrophic consequences including the loss of life. The likelihood of an individual aircraft experiencing such a collision is remote. However, the cumulative likelihood of occurrence is sufficient that the hazard warrants implementing protective measures to mitigate the risk. Current vulnerability models show that an impact anywhere on a commercial aviation transport with debris of mass above 300 grams would produce a catastrophic failure, resulting in a loss of the aircraft and the loss of life of all people on board.

[0003] Both reentering meteorites and man-made space debris pose a threat aircrafL Estimates of the total of reentering debris entering annually is shown in Table 1.
Number of Objects and Total Mass Entering the Atmosphere Annually Number/Year Total Mass Object > 100g (tons) Metente 1368O 53 Man-Made Space 2,267 1 40 Debris Table 1

[0004] The number of reentering operating and inactive space objects is also an important factor in assessing risk. Available data is shown in Table 2. For the first seven months of 2020, there were approximately 145 such objects. These numbers of reentries include controlled reentries, including the return of SOyUZ manned capsules, These statistics do not include the stages which have been deorbited rapidly after their launch as part of normal procedures.
Number of Satellites entering the atmosphere Object 2017 2018 2019 2020 (Jan-July) (approx.) --Number of 200 248 323 145 Satellites Table 2

[0005] Air traffic density is also an important variable in assessing aircraft risk. Although there are several methodologies and tools to assess the risk for the public on the ground due to a reentering space debris event, few studies have been performed. for quantifying the risk for aviation. It is important to understand and quantify the effect of space debris to the population, both on the ground and on aircraft.

[0006] Space debris are manmade objects in orbit around the Earth, which no longer serve a useful purpose. The U.S. Space Surveillance Network regularly tracks and maintains in its catalog an estimated 28,21.0 items in orbit (as of January, 2021). The decay duration of the space debris depends on the object's altitude, area-to-mass ratio and solar activity.

[0007] Number of debris objects estimated by statistical models to be in orbit, according to the European Space Agency, as of January 8, 2021 is shown in table 3.
Size of Objects Number of Objects objects greater than 10 cm 34,000 objects from greater than 1 cm to 10 em 900,000 objects from greater than 1 ram to 1 cm 128 million Table 3

[0008] Table 4 below provides general statistics of tracked objects. Note, what is called "payload"
here are satellites, including dead ones; it is the sum of active and debris satellites Number of tracked objects METHODS AND SYSTEMS FOR REDUCING RISK OF AIR
COLLISIONS
ks. , 4'W 111:1 S64:4 2MS
astsc 1=55 Table 4

[0009] The disintegration of the Space Shuttle Columbia on February 1, 2003 identified the seriousness and necessity of reentry safety. It highlighted the need to select vehicle reentry trajectories that minimize the risk to ground populations and the need to take measures to keep air traffic away from falling debris. The Columbia accident demonstrated the need for a deliberate, integrated, and international approach to public safety during reentry operations, particularly for the management of air traffic and space operations.

[0010] The breakup of the Space Shuttle Columbia began at an altitude of about 60 km and led to a "progressive breakup" in which a primary structural failure resulted in large pieces which were followed by smaller pieces that continued to shed off the larger pieces during their descent. Large pieces (landing gear, turbo pumps, etc.) had high ballistic coefficients (defined as the ratio of an object's mass to its drag coefficient times reference area), making them less susceptible to wind and drag.

[0011] Thus, these large pieces fell quickly, reaching the wound within three to five minutes. While there was no protection from these fragments, they comprised a very small part of the total debris field. Smaller pieces (thermal tiles, fragments of the cargo bay doors, etc.) had low ballistic coefficients, and were carried by the wind as they fell. Some developed a small amount of lift as they fell. As a result, these pieces took as long as approximately 40 minutes to reach the ground.
While small and light, some of these pieces were large enough to substantially damage aircraft. Still smaller pieces (similar to confetti and assumed to be harmless to aircraft) remained airborne for over two hours.

[0012] The Columbia accident showed that a Space Shuttle Orbiter failure during reentry could produce risks to aircraft that exceed the threshold that was subsequently established by NASA for safety of the public by several orders of magnitude. Prior to this accident, neither the FAA nor NASA took active precautions to protect uninvolved aircraft from the potential hazards of Space Shuttle debris during a planned reentry.

[0013] Standard practices have been applied and showed that the probability of one of the exposed aircraft being struck by a piece of falling debris could have been as high as 0.003 to 0.1. This is a range from one in 10 to three in 1,000. The standard practices at the time of the study were provided in the Range Commanders Council (RCC) Standards 321-07

[0014] In the 40 minutes required for the majority of the debris from the Space Shuttle Columbia to fall to the Earth's surface, as many as nine civil aircraft flew through the falling debris. Fortunately, no damage was reported to any of those aircraft, a study conducted by ACA, Inc. (now .ARCTOS) of Torrance, CA applied (what is now a standard) practices and showed that the probability of one of these aircraft being struck by a piece of falling debris could have been as high as 0.003 to 0.1.
This is a range from one in 10 to three in 1,000. The standard practices at the time of the study were provided in the in .R.CC 321-07 "Common Risk Criteria for the National Ranges," published by the Range Commanders Council (RCC).

[0015] After FAA executives were briefed about the potential for aircraft impacts from the Columbia accident, the FAA established procedures to be used as a real-time tactical tool in the event of a Columbia-like accident to identify how to redirect aircraft around space vehicle debris,

[0016] Although the Space Shuttle retired from service in 2011, there are new government and commercial space transportation systems that plan suborbital and orbital operations. These necessarily include launches, reentries and also on-orbit operations. Across this range of vehicles, the available reaction time between space vehicle breakup and entry of debris into the National Air Space can range from zero (if the vehicle is in the air traffic environment at the time of the failure) to upwards of 90 minutes (if the vehicle is nearly in space and at orbital speed at the time of failure).

[0017] Air Traffic Operators will require dependable information and procedures to cope with the sudden onset of such an event and with the short lead-time that will be available until debris enters the airspace. To address those operational needs, FAA has been developing a systematic, standardized space vehicle debris threat management process that can be applied to the variety of space vehicles that will eventually operate in the NAS.

[0018] The procedures established after the Space Shuttle Columbia accident to clear the airspace in case of a space vehicle breakup are only feasible for controlled reentries such as those typically performed for crewed missions, or at the end of a mission by the cargo vehicles that ferry spare parts, consumables, and other items to the International Space Station. The eventual disposal of the International Space Station will require a plan to, potentially first dismantle the structure, and then d.eorbit the entire Station or each segment of the dismantled Station through one or more controlled reentries. In such cases specific maneuvers are planned either to bring the vehicle intact to a preplanned location, at sea or on ground, or to place the debris field, following fragmentation/explosion, away from inhabited areas, like into the SPOUA (South Pacific Ocean Uninhabited Area). Unfortunately, most reentries are uncontrolled.

[0019] Uncontrolled reentries occur as the atmosphere slowly drags an orbiting object deeper into the atmosphere. Moving at speeds greater than 7 km/sec, the object begins to heat as it encounters increasingly significant atmospheric density below the reentry inteiface altitude of about 120 km.
The heating increases as gravity and drag lower the altitude, and eventually low melting point materials reach a condition where they fail. Heating on the primary object and on released fragments continues to increase, and aerodynamic deceleration loads also begin to build.
Aluminum structures have been observed to fail consistently at approximately 78 km altitude, causing a catastrophic breakup of the object. This major breakup phenomenon near 78 km altitude is remarkably independent of vehicle attitude and rates, diameter, shape, and entry flight path angle in between ¨
0.3 and ¨1.5 . High heating rates and aerodynamic forces that produce thermal melting, thermal fragmentation and mechanical fracture during reentry are the primary causes of the various external destruction events.

[0020] There are competing effects that complicate the prediction of whether a given object will survive to impact or demise. However, reentry heating rates are approximately proportional to the velocity cubed and inversely related to the radius of curvature. Thus, small objects released early often demise, unless they have low enough density to slow down rapidly.

[0021] The "footprint" is the area where debris hazards are predicted to "land" given a reentry break-up. A typical footprint for a reentering spacecraft of 5,000 kg or more is approximately 2,000 km long, contained within 35 km of the original ground track. For a reentering launch stage, a typical footprint length is between 100 and 400 km. The major reentry breakup process takes place over a period of approximately 5 min. Objects that survive the reentry environment continue to decelerate and most will approach a terminal velocity proportional to the square root of their ballistic coefficient at about 18 km. From this point, the surviving fragments fall nearly vertically, with their trajectory blown by winds and some additional dispersion potentially due to lift.

[0022] Current forecasts of the time and location of such uncontrolled reentries may have errors of several thousand kilometers and arc available only minutes before reentry_ Consequently, air traffic controllers cannot issue specific "Notice To Airmen" (NOTAMs) on impending reentries.
NOTAMs are effective only when mission planners can provide a specific time and location in advance, as in the case of controlled reentries_ As such, air traffic is subjected to an annual total flux of reentering space debris and meteoroids whose collision risk is not generally controllable.

[0023] in addition to large objects, there are several thousand smaller space debris, resulting from on-orbit fragmentations due to explosions or collisions that reenter annually.

[0024] Reentry of fragments from launch vehicle are also important to consider as risk to the airspace. Consider the May 5, 2020 launch of a Long March 5B rocket from the Wenchang launch site on China's southern Hainan island. Scientists tracking orbital debris from the launch detected a 20-ton piece of debris from the Chinese rocket as it passed over New York City and Los Angeles before it crashed into the Atlantic Ocean. There were between 15 and 20 minutes of elapsed time from the reentry into the atmosphere and reaching the ocean surface. In May 7-8, 2021, another such Long March 5B launch stage landed in the ocean, with associated debris reaching inhabited villages in Cote d'Ivoire, The core stage of the launch vehicle that is falling to Earth weighs 23 tons and is 10 stories tall. Several large Composite-Overwrapped Pressure Vessels, or COPVs, from SpaceX
rockets have landed in Washington State and off the coast of Oregon in the 2020-2021 time frame.
One such COPPV from the March 4, 2021 launch left a four inch dent in the soil. The COPV in Washington wasn't the only piece of debris to land on US soil in Sping, 201.
An absolute hellstorm of debris rained over SpaceX's Boca Chica, Texas facilities on Tuesday when a Starship prototype exploded mid-air during its attempt to land, marking the fourth explosion of a Mars rocket prototype in a row in Elon Musk's speedy Starship test campaign.

[0025] In the United States, there are many new commercial launch providers which are inexperienced in this field. Many foreign countries are developing government and commercial launch services, often with little experience and few regulations and government oversight. As such, the potential for such anomalous behavior will grow resulting in an increase risk to aircraft.

[0026] One study that attempts to quantify the risk from reentering space debris was performed by The Aerospace Corporation and published in 2019. It considered the number of satellites that would reenter as a result of the proposed large constellations (or mega-constellations) of satellites. Given the cumulative risk from the seven publicly announced mega-constellations (with a cumulative number of satellites calculated to be 15,968), the probability of debris striking a commercial aircraft would be 0.001 per year (1 in 1,000), and without emergency action by pilots, the maximum yearly casualtyexpectation for re-entries of satellites disposed from a single large constellation for people in aircraft could be 0.3 per year (3 in 10). Those estimates would be higher if commercial air traffic were updated to include all worldwide flights. Since the time this study was published, the number of satellites in the proposed constellations has grown. On October 15, 2019, the U.S. Federal Communications Commission submitted filings to the International Telecommunication Union on SpaceX's behalf to arrange spectrum for 30,000 additional Starlink satellites to supplement the 12,000 Starlink satellites already approved by the FCC. In April, 2021, the China Satellite Network Group was founded under state leadership to bundle all activities. According to the plans known so far, more than 20,000 Chinese satellites are to be brought into orbit.

[0027] To mitigate the hazards to users of the airspace, three critical steps must be taken. First, the breakup of the expected reentering debris must be determined in advance to characterize the potential airspace and ground "footprint" threatened in terms of space and time. Second, it is necessary to iteratively forecast the probable space debris reentry critical locations with reference to (high) air traffic density, taking also into account predicted weather conditions. Third, the information must be disseminated in real time to all users in the affected airspace together with specific instructions for avoiding the hazardous region (because the region threatened is usually much shorter in one direction, an informed course correction can greatly mitigate the risk to an aircraft in the vicinity of the falling debris).

[0028] Identifying the reentry of large objects is indeed a difficult task.
From the point of view of the risk evaluation from the airspace to the ground, an uncontrolled satellite can renter anywhere on a large portion of the Earth surface, putting all the locations within the latitude band defined by the orbit inclination into the risk zone. Considering that a reentering satellite in nearly circular orbit completes a full revolution around the Earth in just less than 90 min, even a few days before orbital decay a reentry window still includes many revolutions, overflying most of the planet. Due to the very fast velocity of a low Earth satellite, a relatively small uncertainty in time translates into huge along-track distance uncertainties.

[0029] Usually, the final reentry forecasts issued during the last hour or minutes preceding the actual reentry are based state vector which is 2-3 hours old. Therefore, the predictions issued immediately before reentry maintain a typical along-track uncertainty of half an orbit.
However, even though the final reentry uncertainty window is in practice quite spatially extended along-track, the possible impact time of the satellite fragments at a given critical location may be computed with reasonable accuracy. This allows, for any critical location included in the reentry window, to define a risk time window. In other words, for each critical location included in the reentry window, the debris impact is possible, but not certain; however, in each place, the possible impact may occur only during a specific risk time window, which can be therefore used to plan aircraft trajectories to avoid a collision.

[0030] Included in the New Space economy is the emergence of several companies which track space debris to provide commercial space traffic management services. There are several competitors in this market with different approaches to improve the precision of tracking objects. The capability to predict reentry from attributed objects will improve as new ground-based and space-based methods for tracking are deployed and integrated with the known catalog of objects.

[0031] To provide actionable information to a user in the airspace, there needs to he a procedural mechanism to inform pilots to avoid airspace affected by the hazard of entering space debris. One method is to provide data to the air traffic controllers which can inform airplane operators of the present hazard and provide assistance in minimizing their time in the affected airspace.

[0032] Another option to inform users of the airspace is to utilize real time notification of airspace pilots through an application on internet-connected mobile device. One such service is provided by the company, ForeFlight. This service was created in 2007 by general aviation pilots for the limited purpose of offering weather data for private pilots to assist with flight planning. The platform was expanded to automate flight planning and, today, offers a range of features for recreational pilots, business aviation, military services, and commercial airlines in the United States and around the world. Pilots receive real time updates 'pushed by the ForeFlight service to their mobile phone or tablet' and can have their flight trajectory re-routed, as necessary, to avoid hazards_ Today, this service assists pilots to make real time decisions to respond to weather anomalies and other changes in the airspace. Adding a space debris reentry hazard zone could be a seamless solution to provide pilot notification for the hazard of reentering space debris. Such tools could be in addition to notifications to pilot through air traffic controllers. Such tools could also be used to calculate cumulative risks to aircraft for the hazard of reenteringspace debris. The tools could also calculate the risk to aircraft resulting from the end of life of individual or cumulative risk of constellations of satellites.

[0033] It would be desirable to provide methods and systems for further reducing the risk to aircraft in flight.

[0034] The disclosure relates to methods and systems for reducing the risk of air collisions, specifically collisions between aircraft and re-entering space debris.
SUMMARY

[0035] In a first aspect, the present disclosure relates to methods for reducing the risk of air collisions, specifically between objects in the airspace and re-entering space debris by performing the following steps: 1) identifying the presence or re-entry space debris entering the airspace, 2) determining the footprint for re-entering debris (representing the widest area for which debris fragments might pass through the airspace, and the respective time of passage), and 3) notifying users of the airspace by one or both of the following two methods. The information can be provided to air traffic control personnel, automated systems or offices. The air traffic control may then notify the aircraft and/or re-route the aircraft. The information may also be sent directly to pilots operating aircraft using an application on an internet-connected or other wireless-connected mobile device.

[0036] Identifying the presence or re-entry of objects in the airspace may include developing a catalog of all space debris. The catalog may be maintained by taking available data from ground and space-based observatories to improve the precision of the orbital parameters specifying the orbit trajectory (position and velocity) and epoch time.

[0037] Each item will be separately cataloged and will be described by a two-line element set (TLE), or some other comparable description to uniquely specify the orbital parameters. With modification, the data in the Space Track website can be refined (or improved) to provide meaningful predictions to protect the airspace. As such, a database would be generated with updated accuracy of position and velocity as specified by the TLE and its corresponding uncertainty (or covariance). This identifying may also feature routinely propagating the orbit of potential debris objects that may result in a re-entry. This identifying may also feature using orbital mechanics to propagate the object trajectory for the next few hours, the next day, or two days, etc. of one or more objects to calculate the re-entry of such objects.

[0038] The identifying may include identifying re-entry of known objects. This may also include monitoring launch activities around the world and tracking the trajectory of all objects including newly created objects. For example, a typical launch vehicle is comprised of one or more rocket stages and, when the final stage reaches orbit, it releases the fairing (which covers the satellite).
These one or more stages, fairing and other components may become new space objects. During nominal and, especially, during launch anomalies (i.e. failures), there may be many debris objects which nearly reach orbit and create a hazard in the airspace. Usually, there is no ability to control the trajectory or disposal of such objects and they reenter when the natural decay of the orbit results in the object eventually falling through the atmosphere and landing on the ground or in the ocean.

[0039] The determination of the location of the objects or the determination of the footprint for re-entering debris is performed in order to identify what part of the airspace must be closed to aircraft traffic and for what time period. For each re-entering object, a footprint may be calculated. This footprint may be calculated, for instance, by determining how the object will break up as it re-enters the atmosphere and then determining the dispersion of the surviving pieces of the object. For re-entering satellites of known design, it is possible to consider the separate components and assess them individually. For re-entering satellites of unknown specific design, it is possible to estimate or approximate them by size and type (e.g., communications, observation, etc.). A
few components may have a high degree of survivability through re-entry that are common to all spacecraft, for instance, thrusters or engines, pressure vessels, batteries, etc. These may each have a signature on breakup. The footprint that is developed for each object may encompass the potential flight path of the object and, as the object breaks up on re-entry, the respective fragments.
It may also be possible to determine the time period that these objects require to pass through the atmosphere. For example, if a small satellite will re-enter at time t=t0, then all debris objects may for example pass through the airspace between, for instance, t0+10 minutes to t0+25 minutes, and the footprint may be, for instance, 150 km long by 6 km wide in a certain direction from a fixed point.

[0040] The providing of the location or the footprint to air traffic control personnel or offices allows such personnel or offices to notify aircraft and/or re-route aircraft that might otherwise encounter or be impacted by one of the resulting fragments. Algorithms may be developed that automatically calculate the risk of any given aircraft encountering or being impacted by the object. The calculating and the informing of the aircraft may be performed using automated systems.

[0041] In a second aspect, the present disclosure relates to a computer operated online catalog of objects in the atmosphere and their respective two line element, or some comparable comprehensive method to uniquely specify an object's trajectory in Earth orbit. The computer operated online catalog may also include the footprint for re-entering objects into the atmosphere and the corresponding time when objects pass through the atmosphere in this footprint. The orbit may further feature trajectory of motion of the objects and/or velocity of motion of the objects in the atmosphere.

[0042] The computer operated online catalog may be useful for use in methods for reducing the risk of aircraft encounters or collisions with objects such as debris in airspace featuring identifying the presence or re-entry of objects in the airspace, determining the location of the objects or determining the footprint for re-entering debris, and providing the location or the footprint to air traffic control personnel or offices. The air traffic control may then notify the aircraft and/or re-route the aircraft.
When there is a high flux of particles for a specified period of time, air traffic may also issue a Notice to An-men with the appropriate information to alert pilots and flight planners. Alternatively, the location or the footprint may be sent directly to pilots operating aircraft using an application on an internet-connected or other wireless-connected mobile device

[0043] The computer operated online catalog may be useful for aircraft operations such as airlines or other flight planners of aircraft, spacecraft or suborbital spaceflight operators or launch vehicles.
Flight planning may be adjusted to reduce the risk of encounters or collisions with objects such as debris in airspace featuring identifying the presence or re-entry of objects in the airspace, determining the location of the objects or determining the footprint for re-entering debris, and providing the location or the footprint to air traffic control personnel or offices. For example, if a launch vehicle routinely sheds debris in a general vicinity, aircraft operators may chose not to fly in that area during times of launches.

[0044] The identifying the presence or re-entry of objects in the airspace may include developing a catalog of all space debris. The catalog may be maintained by taking available data from ground and space-based observatories to improve the precision of the orbit from publicly available databases, such as the website Space Track. The United States Air Force tracks all detectable objects in Earth orbit, creating a corresponding TLE for each object, and makes publicly available TLEs for many of the space objects on the website Space Track, holding back or obfuscating data on many military or classified objects. The TLE format is a de facto standard for distribution of an Earth-orbiting object's orbital elements.

[0045] This identifying may include the position, trajectory (velocity) and epoch time. This identifying may also feature routinely propagating the orbit of potential debris objects that may result in a re-entry. This identifying may also feature orbital propagation using orbital mechanics to determine the trajectory for the next day, two days, etc. of one or more objects to calculate the re-entry of such objects.

[0046] The identifying may include identifying re-entry of known objects. This may include monitoring launch activities around the world and tracking the trajectory of new objects which do not appear in the existing on-orbit catalog. For example, a typical launch vehicle is comprised of many rocket stages, when the final stage reaches orbit, it releases the fairing (which covers the satellite). These stages, the fairing and other debris become new objects.
During nominal and especially during launch anomalies (i.e. failures) there may be many debris objects which nearly reach orbit or reach and orbit and subsequently reenter. These objects create a hazard for users in the airspace.

[0047] The determination of the location of the objects or determination of the footprint for re-entering debris is performed in order to identify the part of the airspace to close to aircraft traffic and for what time period. For each re-entering object, a footprint may be calculated. This footprint may be calculated, for instance, by determining how the object will break up as it re-enters the atmosphere and then the dispersion of the surviving pieces of the object. For re-entering satellites of known design, it is possible to consider the separate components and assess them individually. For re-entering satellites of unknown specific design, it is possible to estimate or approximate them by size and type (e.g., communications, observatory, etc.). A few components may have a high degree of survivability through re-entry that are common to all spacecraft, for instance, thrusters or engines, pressure vessels, batteries, reaction wheels or command moment gyroscopes, etc. These may each have a distinct signature on breakup. The footprint that is developed for each object may encompass the potential flight path of the object and, as the object breaks up on re-entry, the respective fragments. It may also be possible to determine the time period that these objects require to pass through the atmosphere. For example, if a small satellite will re-enter at time t=t0, then all debris objects may for example pass through the airspace between, for instance, t0+10 minutes to to-F25 minutes, and the footprint may be, for instance, 100 miles long by 4 miles wide in a certain direction from a fixed point.

[0048] Thc providing thc location or thc footprint to air traffic control personnel or officcs allows such personnel or offices to notify aircraft and/or re-route aircraft that might otherwise potentially encounter or be impacted by the object. Alternatively, the location or the footprint may be sent directly to pilots operating aircraft using an application on an internet-connected or other wireless-connected mobile device. Algorithms may he developed that automatically calculate the risk of any given aircraft encountering or being impacted by the object. The calculating and informing the aircraft may be performed using automated systems.

[0049] In a third aspect the present disclosure relates to a computer operated algorithm for describing the location of the objects in the atmosphere and/or the footprint for re-entering objects into the atmosphere which may be in communications contact directly to pilots operating aircraft using an application on an internet-connected or other wireless-connected mobile device. The location may be described in terms of position, velocity and epoch time, and may further feature trajectory of motion of the objects and/or velocity of motion of the objects in the atmosphere.
Likewise, the footprint for re-entering objects may be described in terms of position and may further feature trajectory of motion and/or velocity of motion of the re-entering objects in the atmosphere.

[0050] The computer operated algorithm for describing the location of the objects in the atmosphere and/or the footprint for re-entering objects into the atmosphere, which may be in communications contact directly to pilots operating aircraft using an application on an internet-connected or other wireless-connected mobile device, may be useful for methods for reducing the risk of aircraft encounters or collisions with objects such as debris in airspace featuring identifying the presence or re-entry of objects in the airspace, determining the location of the objects or determining the footprint for re-entering debris, and providing the location or the footprint to air traffic control personnel or offices. The air traffic control may then notify the aircraft and/or re-route the aircraft.
[00511 The identifying may include identifying re-entry of known objects. This may include monitoring launch activities around the world and tracking the trajectory of new objects to the on-orbit catalog. For example, a typical launch vehicle is comprised of many rocket stages, when the final stage reaches orbit, it releases the fairing (which covers the satellite). These stages and fairing and other debris become new objects. During nominal and especially during launch anomalies (i.e.
screwups) there may be many debris objects which nearly reach orbit and can create a hazard for the airspace.

[0052] Thc determining thc location of thc objccts or determining thc footprint for rc-cntcring dcbris is performed in order to determine the part of the airspace to close to aircraft traffic and for what time period. For each re-entering object, a footprint may be calculated. This footprint may be calculated, for instance, by determining how the object will break up as it re-enters the atmosphere and then the dispersion of the surviving pieces of the object. For re-entering satellites of known design, it is possible to consider the separate components and assess them individually. For re-entering satellites of unknown specific design, it is possible to estimate or approximate them by size and type (e.g., communications, observatory, etc.). A few components may have a high degree of survivability through re-entry that are common to all spacecraft, for instance, thrusters or engines, pressure vessels, batteries, etc. These may each have a signature on breakup.
The footprint that is developed for each object may encompass the potential flight path of the object and, as the object breaks up on re-entry, the respective fragments. It may also be possible to determine the time period that these objects require to pass through the atmosphere. For example, if a small satellite will re-enter at time t=t0, then all debris objects may for example pass through the airspace between, for instance, t0+10 minutes to t0+25 minutes, and the footprint may be, for instance, 100 miles long by 4 miles wide in a certain direction from a fixed point.
[0053] The providing the location or the footprint to air traffic control personnel or offices allows such personnel or offices to notify aircraft and/or re-route aircraft that might otherwise potentially encounter or be impacted by the object. Alternatively, the location or the footprint may be sent directly to pilots operating aircraft using an application on an internet-connected or other wireless-connected mobile device. Algorithms may be developed that automatically calculate the risk of any given aircraft encountering or being impacted by the object. The calculating and informing the aircraft may be performed using automated systems.
[0054] One option to inform users of the airspace is to utilize real time notification of airspace pilots through an application on internet-connected or other wireless-connected mobile device. Mobile application services enable pilots in flight to make real time decisions to respond to weather anomalies and other changes in the airspace. Adding a reentry hazard zone could be a seamless solution to provide pilot notification for the hazard of reentering space debris.
[0055] The tool can be used to calculate cumulative risks to aircraft for the hazard of reentering space debris. The tools could also calculate the risk to aircraft resulting from the end of life of individual or cumulative risk of constellations of satellites.

[0049] In a fourth aspcct thc prcscnt disclosure relates to a mcthod for rcducing thc risk of aircraft, sub-orbital spacecraft or launch vehicle encounters or collisions with objects such as space debris in airspace by a) identifying the presence or re-entry of objects in the airspace, b) determining the location of the objects or determining the footprint for re-entering debris, and c) providing the location or the footprint to one or more selected from the group consisting of air traffic control personnel or offices, suborbital flight operators, spaceflight launch site operators, administrators of internet-connected or other wireless-connected mobile device applications that assist aircraft pilots and operators with flight planning and avoiding real-time hazards, and aircraft pilots. This aspect may provide a method for reducing the risk of users of the airspace including any airplane, helicopter, launch vehicle, suborbital or orbital spacecraft, drone, high-altitude balloon, sport parachute from encounters or collisions from objects including fragments of reentering space debris and/or launch vehicles featuring a) identifying the presence or re-entry of space debris or remnants of launch vehicles in the airspace, b) determining the spatial (area and altitude) dispersion as a function of time for objects associated with space debris after it reenters the atmosphere or objects associated with launch vehicles, and c) disseminating the information to users of the airspace in order to enable the operators to take corrective action to avoid collision with the identified objects, by doing one or more of the following: notifying controllers (such as airlines, suborbital flight operators, spaceflight launch site operators, and/or others) of aircraft operating in the airspace, notifying air traffic control personnel or offices, and notifying aircraft directly, such as through a wireless-connected device to the operator of aircraft or to the autonomous navigation system controlling aircraft. The notifying may be through a phone, tablet or other mobile application connected through with a cellular, internet, or other wireless service that integrates aircraft flight planning and real-time upgrades of hazards in the airspace.
[0050] In a fifth aspect, the present disclosure relates to a method for reducing the risk of aircraft, sub-orbital spacecraft or launch vehicle encounters or collisions with objects such as space debris in airspace featuring a) identifying the presence or re-entry of objects in the airspace, b) determining the location of the objects or determining the footprint for re-entering debris, and c) providing the location or the footprint to one or more of air traffic control personnel or offices, suborbital flight operators, spaceflight launch site operators, administrators of internet-connected or other wireless-connected mobile device applications that assist aircraft pilots and operators with flight planning and avoiding real-time hazards, and aircraft pilots. In some instances, this aspect features a method for reducing the risk of users of the airspace including any airplane, helicopter, launch vehicle, suborbital or orbital spacecraft, drone, high-altitude balloon, sport parachute from encounters or collisions from objects including fragments of reentering space debris and/or launch vehicles featuring a) identifying the presence or re-entry of space debris or remnants of launch vehicles in the airspace, b) determining the spatial including area and altitude dispersion as a function of time for objects associated with space debris after it reenters the atmosphere or objects associated with launch vehicles, and c) disseminating the information to users of the airspace in order to enable the operators to take corrective action to avoid collision with the identified objects, by doing one or more of the following: i) notifying controllers (such as airlines, suborbital flight operators, spaceflight launch site operators, andJor others) of aircraft operating in the airspace, ii) notifying air traffic control personnel or offices, and c) notifying aircraft directly, such as through a wireless-connected device to the operator of aircraft or to the autonomous navigation system controlling aircraft. The notifying aircraft directly may be performed through a phone, tablet or other mobile application connected through with a cellular, internet, or other wireless service that integrates aircraft flight planning and real-time upgrades of hazards in the airspace.
RETAILED DESCRIPTION

[0051] In the description that follows, the terminology and phraseology used herein is solely used for descriptive purposes and should not be construed as limiting in scope.
Language such as "including," "comprising," "having," "containing," or "involving," and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited, and is not intended to exclude other additives, components, integers or steps.
Likewise, the term "comprising" is considered synonymous with the terms "including" or "containing" for applicable legal purposes. All numerical values in this disclosure are understood as being modified by "about." All singular forms of elements, or any other components described herein including without limitations components of the apparatus are understood to include plural forms thereof. By "aircraft" is meant any machine or device made by man and designed for movement or travel in theair, atmosphere, or space including, for example, airplane, helicopter, launch vehicle, suborbital or orbital spacecraft, drone, or other machine capable of flight. By "space debris" is meant as any suborbital or orbital spacecraft, satellite, launch vehicle, meteor, asteroid, or other space objects or fragments of one or more of these objects.

[0052] The US Air Force maintains a catalogue of objects in Earth orbit that is publicly available through the wcbsitc Space Track. The maintenance of this database includes updating the trajectory when data is available. Because of uncertainties in the atmospheric density and the orientation and dynamics of the reentering body, reentry prediction using this tracking data have an error of approximately 10 percent in time; that is, if an object is observed and an accurate orbit based on that observation is computed one hour prior to reentry, there is a 6 minute error in that prediction. Since this object is traveling at orbital speed (-7.6 km/second), this error translates to an uncertainty in the reentry point of approximately 2740 km, (this is likely an optimistic scenario¨ without special tasking, good estimates of final orbits are generally not computed within one hour of reentry).

[0053] The uncertainty in the impact zone can be reduced substantially if the object is observed at the primary breakup altitude. If an object is observed before breakup, no major debris has yet been released, so the predicted impact zone must include uncertainties in the atmosphere, vehicle dynamics, etc., for the remaining time before breakup.

[0054] After breakup, there is uncertainty as to whether the observed object is at the toe or heel of the debris footprint, and since the objective is to produce a ground impact zone that will contain the debris with a high level of confidence, the possible ground area affected is larger than the actual debris footprint. For these reasons, the observation altitude that produces an affected area that is closest to the actual debris footprint length is the altitude where the object experiences the primary breakup event. The best predictions of the airspace to be affected by debris are made if the object is observed during re-entry. Thus, the actual re-entry and the prediction is based on trajectory data obtained at the breakup altitude.

[0055] From the point of view of the risk evaluation from the airspace to the ground, an uncontrolled satellite can renter anywhere on a large portion of the Earth surface, putting all the locations within the latitude band defined by the orbit inclination into the risk zone. Considering that a reentering satellite in nearly circular orbit completes a full revolution around the Earth in just less than 90 min, even a few days before orbital decay a reentry window still includes many revolutions, overflying most of the planet. Due to the very fast velocity of a low Earth satellite, a relatively small uncertainty in time translates into huge along-track distance uncertainties.

[0056] Usually, the final reentry forecasts issued during the last hour or minutes preceding the actual reentry are based on a state vector that is at least 2-3 hours old, due to an unavoidable communication and processing delay between the orbit determination epoch and the release of the corresponding reentry prediction. Therefore, the predictions issued immediately before reentry maintain a typical along-track uncertainty of half an orbit. However, even though the final reentry uncertainty window is in practice quite spatially extended along the track, the possible impact time of the satellite fragments may be computed with reasonable accuracy. This allows, for any sub-satellite location included in the reentry window, to define a risk time window. In other words, for each sub-satellite location included in the reentry window, the debris impact is possible, but not certain; however, in each place, the possible impact may occur only during a specific risk time window, which can be therefore used to plan risk mitigation measures on the ground and in the airspace overhead. If the attention is focused on a quite compact and small area of the planet, it is possible to produce additional information useful for the civil protection authorities.

[0057] Successively, the nominal impact times and ground tracks are integrated with a small time dispersion to account for initial conditions variability, a larger time dispersion of tens of minutes to account for the different flight times of fragments with distinct ballistic properties (including small particles not dangerous on the ground, but possibly representing a hazard for aircraft crossing the affected airspace), and a cross-track safety margin to account for the expected dispersion of the fragments and the trajectory residual uncertainties. Applying this method, the ISTI-CNR (Italian Council of Research) has found for the Italian territory, the "risk" time windows typically have an amplitude of about 30-40 minutes, including the airspace crossing from an altitude around 10 km from ground impact.

Claims

WE CLAIM:

1.A method for reducing the risk of aircraft, sub-orbital spacecraft or launch vehicle encounters or collisions with objects such as space debris in airspace comprising:
a) identifying the presence or re-entry of objects in the airspace, b) determining the location of the objects or determining the footprint for re-entering debris, and c) providing the location or the footprint to one or more selected from the group consisting of air traffic control personnel or offices, suborbital flight operators, spaceflight launch site operators, administrators of internet-connected or other wireless-connected mobile device applications that assistaircraft pilots and operators with flight planning and avoiding real-time hazards, and aircraft pilots.

2.T1le method according to claim 1 wherein the a) identifying the presence or re-entry of objects in the airspace comprises developing a catalog of space debris.

3.The method according to claim 1 wherein the a) identifying the presence or re-entry of objects in the airspace compriscs propagating the orbit of potential debris objects that may result in a re-entry.

4.The method according to claim 1 wherein the b) determining the location of the objects or determining the footprint for re-entering debris is performed in order to determine the part ofthe airspace to close to aircraft traffic and for what time period.

5.The method according to claim 1 wherein the b) determining the location of the objects or determining the footprint for re-entering debris comprises calculating a footprint.

6.The method according to claim 1 wherein the c) providing the location or the footprint to air is to traffic control personnel or offices and is performed using automated systems.

7.The method according to claim 1 wherein the c) providing the location or the footprint is to pilots operating aircraft comprises generating notifications through an internet connected or other wireless-connected mobile device.

8.Thc mcthod according to claim 1 further comprising d) providing an algorithm effective to automatically calculate the risk of any given aircraft, sub-orbital spacecraft or launch vehicleencountering or being impacted by the object.

9.A computer operated online catalog of the location of objects in the atmosphere and/or the footprint for re-entering objects into the atmosphere.

10. The computer operated online catalog of the locadon of objects in the atmosphere and/or the footprint for re-entering objects into the atmosphere according to claim 9 wherein the locationis described in terms of its two line elements specifying the orbit and epoch time.

11. The computer operated online catalog of the location of objects in the atmosphere and/or the footprint for re-entering objects into the atmosphere according to claim 9 operable to describethe trajectory of motion of the objects and/or velocity of motion of the objects in the atmosphere.

12. The computer operated online catalog of the location of objects in the atmosphere and/or the footprint for re-entering objects into the atmosphere according to claim 9 operable to describethe footprint for re-entering objects in terms of spatial coordinates, and optionally describe trajectory of motion and/or velocity of motion of the re-entering objects in the atmosphere.

13. The computer operated online catalog of the location of objects in the atmosphere and/or the footprint for re-entering objects into the atmosphere according to claim 8 effective for use in methods for reducing the risk of aircraft encounters or collisions with objects such as debris in airspace featuring identifying the presence or re-entry of objects in the airspace, determining the location of the objects or determining the footprint for re-entering debris, and providing thelocation or the footprint to air traffic control personnel or offices or to aircraft pilots.

14. The computer operated online catalog of the location of objects in the atmosphere and/or the footprint for re-entering objects into the atmosphere according to claim 9 in communications contact with air traffic control or an aircraft pilot.

15. A computer operated algorithm for describing the location of the objects in the atmosphereand/or the footprint for re-entering objects into the atmosphere.

16. The computer operated algorithm for describing the location of the objects in the atmosphere and/or the footprint for re-entering objects into the atmosphere according to claim 15 whereinlocation is described in terms of spatial coordinates, and wherein trajectory of motion of the objects and/or velocity of motion of the objects in the atmosphere is described.

17. The computer operated algorithm for describing the location of the objects in the atmosphere and/or the footprint for re-entering objects into the atmosphere according to claim 15 wherein the footprint for re-entering objects is described in terms of spatial coordinatcs, and wherein theposition and/or velocity of motion of the re-entering objects in the atmosphere is described.

18. The computer operated algorithm for describing the location of the objects in the atmosphere and/or the footprint for re-entering objects into the atmosphere according to claim 15 useful formethods for reducing the risk of aircraft encounters or collisions with objects such as debris in airspace featuring identifying the presence or re-entry of objects in the airspace, determining the location of the objects or determining the footprint for re-entering debris, and providing the location or the footprint to air traffic control personnel or offices.

19. A computer operated algorithm for describing the location of the objects in the atmosphereand/or the footprint for re-entering objects into the atmosphere according to claim 15 in communications contact with air traffic control or an aircraft pilot.

20. A method for reducing the risk of aircraft, sub-orbital spacecraft or launch vehicle encountersor collisions with space debris in airspace comprising:
a. identifying the presence or re-entry of objects in the airspace, b. determining the location of the space debris or determining the footprint for re-entering space debris, and c. providing the location or the footprint to one or more selected from the group consisting of air traffic control personnel or offices, suborbital flight operators, spaceflight launch site operators, administrators of internet-connected or other wireless-connected mobile device applications that assistaircraft pilots and operators with flight planning and avoiding space debris, and aircraft pilots.

21. A mcthod for rcducing thc risk of uscrs of thc airspacc including any airplane, helicopter, launch vehicle, suborbital or orbital spacecraft, drone, high-altitude balloon, sport parachute from encounters or collisions from objects including fragments of reentering space debris and/or launch vehicles comprising:
a. identifying the presence or re-entry of space debris or remnants of launch vehicles in the airspace, b. determining the spatial dispersion as a function of time for space debris after reentry into the atmosphere or objects associated with launch vehicles, and c. disseminating the spatial dispersion as a function of time for space debris after reentry to users of the airspace to enable corrective action to avoid collision with the space debris.

22. The method according to claim 21 wherein the disseminating the spatial dispersion as a function of time for space debris after reentry to users of the airspace is performed by one ofthe following:
I. notifying controllers of aircraft operating in the airspace, II. notifying air traffic control personnel or offices, or III. notifying aircraft directly via an internet connected or other wireless-connected device to the operator ofaircraft or via an autonomous navigation system controlling aircraft.

23. The method according to claim 22 wherein the notifying is performed via a phone, a tablet, a mobile application connected with a cellular, internet, or wireless service operable to integrate aircraft flight planning and real-time upgrades of hazards in the airspace.

24. A method for reducingthe risk of aircraft, sub-orbital spacecraft or launch vehicle encounters or collisions with space debris in airspace comprising:
a) identifying the presence or re-entry of the space debris in the airspace, b) determining the location of the space debris or determining the footprint for re-entering space debris, and c) providing the location or the footprint of the space debris to one or more selected from the group consisting of air traffic control personnel or offices, suborbital flight operators, spaceflight launch site operators, administrators of internet-connected mobile device applications that assist aircraft pilots and operators with flight planning and avoiding real-time hazards, and aircraft pilots.

25. A mcthod for rcducing thc risk of uscrs of airspace from cncountcrs or collisions from reentering space debris or launch vehicles comprising:
a) identifying the presence or re-entry of space debris or remnants of launch vehicles in the airspace, b) determining spatial dispersion of the space debris or objects associated with launch vehicles as a function of time after it reenters the atmosphere, and c) disseminating the information to users of the airspace in order to enable the operators to take corrective action to avoid collision with the space debris or objects associated with launch vehicles, by performing one or more selected from the gToup consisting of:
i) notifying controllers of aircraft operating in the airspace, ii) notifying air traffic control personnel or offices, iii) notifying aircraft directly.

26. Thc mcthod according to claim 25 wherein the notifying in c) iii) is through a phone, tablet or other mobile application connected through a cellular, internet, or other wireless service that integrates aircraft flight planning and real-time upgrades of hazards in the airspace.

27. A method for reducing the risk of users of the airspace including any airplane, helicopter, launch vehicle, suborbital or orbital spacecraft, drone, high-altitude balloon, sport parachute from encounters or collisions from objects including fragments of reentering space debris and/or launch vehicles comprising:
a. identifying the presence or re-entry of space debris or remnants of launch vehicles in the airspace, b. determining the spatial (area and altitude) dispersion as a function of time for objects associated with space debris after it reenters the atmosphere or objects associated with launch vehicles, and c. disseminating the information to users of the airspace in order to enable the operators to take corrective action to avoid collision with the identified objects, by doing one or more of the following:
I. notify controllers (such as airlines, suborbital flight operators, spaceflight launch site operators, and/or others) of aircraft operating in the airspace, II. notify air traffic control personnel or offices, III. notify aircraft directly, such as through a wireless-connected device to the operator of aircraft or to the autonomous navigation system controlling aircraft.

28. Thc method according to claim 26 wherein the notification in c) iii) is through a phone, tablet or other mobile application connected through with a cellular, internet, or other wireless service that integrates aircraft flight planning and real-time upgrades of hazards in the airspace.