http://thespacereview.com/article/1417/2The numbers gameWhat’s in Earth orbit and how do we know?Brian Weeden (bweeden@swfound.org) is a technical advisor for the Secure World Foundation and former US Air Force officer with a background in space surveillance and ICBM operations.Whenever the topic of space debris and satellites in orbit comes up a lot of numbers tend to get thrown around by a lot of different people, and it can be hard to keep all the figures straight. Compounding this is the superficial knowledge (at best) of the subject by many media commentators and the tradition of secrecy by the US military, the organization that has historically been the main keepers of the data on space debris.
This article attempts to shed some light on this subject and will define in detail exactly what stuff is in orbit, how we know what’s up there, and what a satellite catalog is, as well as highlight a few areas of concern with this entire process. In addition, it will make some suggestions for improving the situation in the near future. This is especially important because, as I learned from G.I. Joe growing up, “knowing is half the battle” and right now the world knows a lot less than half of what it should about the space environment.
Sorting through the junkThere are a lot of objects flying around in space and it helps to divide them up into categories. Generally, there are two basic types of objects: natural and man-made (hereafter referred to as artificial). Natural objects consist of meteoroids and micrometeoroids—pieces of asteroids and comets. Given their very small size (usually smaller than a few millimeters in diameter) most of them are not considered to be trackable, especially using ground-based methods. However, they do pose a threat to spacecraft because of their extremely high velocities, sometimes in excess of 70 kilometers per second, although the average is around 20 km/s. These speeds are the result of these natural objects being in orbit around the Sun and not the Earth. Although they are not tracked or cataloged, their population is estimated using statistical models derived partly from examinations of satellites that were brought back to Earth full of tiny holes and impact craters.
The other major category, artificial orbital debris, consists of the leftovers from humanity’s activities in Earth orbit. Every time we put a satellite into space, we end up leaving something behind in Earth orbit. At the very least this is the satellite itself and often times also includes one or more rocket stages and bits of miscellaneous stuff, like explosive bolts, lens caps, and solid rocket exhaust particles. Sometimes these leftover bits themselves shed more pieces through what are called fragmentation events. These events can be minor (a few dozen pieces) to extreme (explosions creating more than a thousand pieces). Within this category of artificial objects we define three basic populations: the trackable, the potentially trackable, and the untrackable.
Table 1 summarizes these definitions and estimated populations. The trackable population is generally defined as those objects ten centimeters in diameter or larger, as these are the current limits of the majority of the currently available tracking sensors. The potentially trackable population is generally defined as those objects between one and ten centimeters in diameter which can be tracked by some current sensors but not often enough to enable cataloging and future prediction at this time. Notably, the Haystack and Goldstone radars operated by the Massachusetts Institute of Technology (MIT) and NASA’s Jet Propulsion Laboratory (JPL), respectively, can track objects down to a few millimeters in size given the right conditions, but they only collect a few hundred hours of data each year. Additional sensors are planned for the near future that could provide the capability to track objects in this category more reliably, such as the S-Band Fence. The untrackable population generally consists of those objects smaller than one centimeter. As with the natural object population, the size of the untrackable artificial population can be estimated using models derived in part from examining satellites brought back from space.
NASA uses the term Micrometeoroid and Orbital Debris (MMOD) to talk about the entire population of natural and artificial objects that could potentially threaten satellites and human activities in space. In general, the main concerns from a safety standpoint are the trackable and potentially trackable populations because of their size. Due to the extremely high orbital velocities, and thus momentum, it is considered impractical to shield against impacts from objects bigger than one centimeter. So objects larger than one centimeter pose a significant risk for total satellite destruction or mission failure. The risk due to potential impacts from objects smaller than one centimeter can be mitigated in some fashion through shielding and satellite design, and generally present risks for only damage to a satellite or subsystem and not total destruction.
Observations, tracks, and catalogsA satellite catalog is a database which contains a list of objects in orbit, information about those objects such as date and country of launch, and orbital data that describes the position of the object. There are multiple satellite catalogs in use across the world, but the most well-known and publicly available catalog is the one maintained by the US military, traditionally referred to as the SATCAT (military shorthand for satellite catalog). This catalog and others like it are a critical part of space situational awareness (SSA), which is knowledge about what’s happening in space.
A version of the SATCAT is available publicly through the Commercial and Foreign Entities (CFE) program on the Space Track website and provides positional data on the locations of objects in the form of Two-Line Elements (TLEs). Anyone in the world can sign-up for a free account to view, sort, and download this data, with the main restriction being redistribution of the data without prior approval from the Department of Defense (DoD). There are also other websites that have permission to redistribute this data, notably Celestrak and Heavens Above. These two sites receive the same TLEs from the US military that are on Space Track and are authorized to redistribute them, with the main distinction being that Celestrak and Heavens Above sometimes add additional information that isn’t found on Space Track.
Usually in a satellite catalog there is a set of descriptive data for each object. The launch date and launching State are two very important pieces of this data for legal reasons. According to the Liability Convention of 1972, the launching State is considered legally responsible for that object during the launch, on-orbit, and reentry phases and may have absolute liability or fault-based liability for damages caused by the object. The Convention defines the term launching State two ways:
(c) The term "launching State" means:
(i) A State which launches or procures the launching of a space object;
(ii) A State from whose territory or facility a space object is launched;
In the case of the recent Iridium-Cosmos collision, both objects were launched using Russian boosters. However, legally Russia was the launching State for the Cosmos satellite and the United States for the Iridium satellite because a US company, Iridium Satellite LLC, procured the launch and operated the Iridium satellite.
Determining the launching State for each of more than 19,000 objects in orbit currently being tracked is an extremely daunting task. The US military tackles this through a process of “cradle to grave” surveillance, meaning that they attempt to maintain an orbital history of an object from the moment it is launched to the moment it re-enters the Earth’s atmosphere. It should be noted that this does not mean every object is continuously tracked all the time: the technique employed is one of periodic spot checks to determine an object’s position at various points.
The entire process starts with good data coming from a network of sensors. The US military operates a worldwide network of optical and radar sensors called the Space Surveillance Network (SSN). The network is managed by the Joint Space Operations Center (JSpOC) located at Vandenberg Air Force Base in California. Raw data from SSN sensors flows into the JSpOC where they are collated and through a series of calculations turned into equations called element sets that describe the locations and movement of objects in orbit. Keeping the positions of orbital objects in equation form is very useful because it allows the user to propagate the position forwards and backwards in time to see where the satellite was in the past or will be. These element sets are constantly updated through a process known as catalog maintenance1 to make sure that they are as current as possible.
This entire tracking and cataloging process starts with the “birth” of a satellite when it is launched into space. A space launch is simply a more powerful version of a ballistic missile launch, and the Defense Surveillance Program (DSP) satellites in geostationary orbit (GEO) and the Space-Based Infrared Systems (SBIRS) in highly elliptical orbit (HEO) are designed to detect and track both using infrared sensors. By knowing the latitude of the launch site and the heading of the booster, the inclination (or plane of the orbit relative to the Equator) the satellite will end up in can be calculated using some relatively simple trigonometry.
Once the inclination of the object is known, those SSN sensors that will be overflown in the course of an object’s orbit can be determined. These sites are given a heads-up notice and asked to look for a new object or objects coming into their tracking range in that inclination. Once initially detected, the sensor collects a series of observations, called a track, on the object as it passes through the coverage of that particular sensor. These observations are used to determine an initial element set describing the object’s orbit. However, at this point the element set is usually very inaccurate since it only has one track of data covering only a small section of the orbit. So it is passed to subsequent sensors which are tasked to collect addition observations. As more tracks are collected from different points around the object’s orbit the position becomes more and more refined. Once this positional accuracy reaches a certain quality, the object is then ready to be entered into the catalog.
Satellites heading into deep space orbits such as GEO (36,000 kilometers above the Earth) present a different problem as they usually require multiple orbit changes and maneuvers. Some can take several weeks to arrive on station depending on the method used. Each time a maneuver is performed the process of initial discovery by a sensor, creation of an initial element set, and refinement of that element set needs to be repeated. Sometimes the satellite owner-operator will provide a burn plan which has all the scheduled maneuver times and post-maneuver orbital elements. This helps, but still must be verified by sensor observations as these burns don’t always go exactly as planned.
While fairly straightforward for newly launched objects, determining the launching State for a small piece of recently discovered debris is extremely challenging. It could have come from a recent satellite breakup, or be a piece of a breakup of a breakup of a breakup dating back to the beginning of the Space Age. It takes a very knowledgeable and dedicated analyst (along with lots of historical element sets) to be able to propagate an object’s orbit and position back in time through years or decades to match it to where it came from. And only if this process can be done and a launching State determined can the object be entered into the official catalog.
This is the reason why there is a disparity between the number of objects listed in the satellite catalog on the Space Track website and the total number reported being tracked. If you log into Space Track and click on the “Box Score” link you will see a chart listing the number of objects launched over all time and still on orbit broken down by launching State. As of July 1, 2009, the total number a cataloged objects still on orbit was just under 14,800.
This number is quite different from the 19,000+ being quoted by military and NASA officials in recent news stories and Congressional testimony (see “The gun pointed at the head of the universe”, The Space Review, June 15, 2009). The difference is that 19,000+ is the total number of objects being tracked, but several thousand of these are pieces of debris for which the launching State has not been identified and thus cannot be entered into the catalog. Crucially, the orbital locations for these 6,000 or so uncataloged (but still tracked) objects are not published by the US military on the Space Track website and thus currently cannot be used in conjunction assessment (predicting close approaches) and collision avoidance analyses by entities other than the US military unless special arrangements are made with the DoD to get this data.
Each object being entered into the US military’s catalog is assigned two unique numbers. The first is known as the satellite number (SATNO) or catalog number and is simply an increment of the total number of objects that have been launched into space. Most people would assume that Sputnik 1 was SATNO 1, but actually the rocket body that placed Sputnik into orbit was cataloged first so Sputnik is actually SATNO 2. The International Space Station (ISS) has been assigned SATNO 25544, based on the Russian Zarya module which was the first piece of the ISS placed into orbit. Each number stays with that object for its entire life and is never reused. Currently, newly cataloged pieces are being assigned numbers over 35,000.
The second unique identifier is the international designator. This number consists of the year the object was launched, the launch number of that year it as on, and which piece it is from that launch. So for example, the Hubble Space Telescope (HST) has the international designator of 1990-037B, meaning it was launched in 1990 on the 37th launch of that calendar year and is the second piece from that launch. 1990-037A is the designator for Space Shuttle Discovery (STS-31) which placed the HST into orbit (and thus was the first piece). 1990-037C belongs to one of the original solar panels which was removed from HST and set adrift by STS-61 during the first servicing mission in 1993.
The object’s designator letter is simply incremented from A through Z. If there are more than 26 pieces from a launch, then it becomes AA through AZ and so on. When dealing with very large number of objects from catastrophic fragmentations, this can get a bit unwieldy. For example, there are over 2,500 pieces currently being tracked from the 2007 destruction of the Chinese Fengyun-1C weather satellite using an anti-satellite (ASAT) weapon. The most recent piece from this event has the international designator 1998-025DJM.
When the SATCAT was first setup, all of the information was being kept in one large database and certain number ranges were set aside for different uses. The number range of 1 through 69,000 was designated as the actual satellite catalog. The range of 70,000 through 79,999 was set aside for the initial element sets used as temporary intermediaries before cataloging as explained earlier. The range 80,000 through 89,999 was set aside for analyst satellites—those objects which are being tracked but cannot be put into the satellite catalog because the launching State hasn’t been determined—and other temporary purposes, such as for burn plans.
Numbers 90,000 through 99,999 were set aside for uncorrelated tracks (UCTs)2 which are observations gathered by sensors that do not correlate to anything in the catalog. The SSN collects on average one hundreds thousands or so UCTs each year for multiple reasons. The sensor site could have been using an outdated catalog that did not have the latest positions for objects. There could have been an error in the tracking software or an optical or radar anomaly. But the most common reason is the population of 300,000 or so objects smaller than ten centimeters that are not consistently tracked. Occasionally, a sensor will track one of these objects as a UCT but not provide enough data to allow another sensor to follow-up.
Without multiple tracks, it is almost impossible to get a stable element set to allow for cataloging and predicting the orbit into the future. Adding more complexity to this are objects which have extreme orbital dynamics due to their unique properties. One example might be a small piece of reflective foil whose orbit fluctuates wildly due to dramatic changes in solar radiation pressure as it rotates. Or the UCT could be one of the many clumps of two-centimeter copper wires and wax left on orbit from Project West Ford, which have very strong radar reflections for their size and unusual orbital dynamics.
The most critical issue with the number ranges is that they are filling up fast. All of the original computer databases used in the US military SSN and at the military command and control centers were hard-coded with a limit of 99,999 entries divided into the ranges outlined earlier. Out of the 69,999 spots allocated for cataloged objects, about half have already been used and growth is accelerating every year. Compounding this situation are the plans to add new sensors to the SSN in the near future that will greatly expand the number of objects tracked. Primary among this is the S-Band Radar Fence, currently scheduled to come on line in 2015, which is predicted to add 100,000 or more new objects in the one to ten centimeter range. While this is indeed a welcome and much-needed expansion of SSA capability, modifying the computer databases and catalog structure across the entire US military system to enable these benefits is a complex and very expensive process.
Mirror, mirror on the wall, who has the fairest catalog of them all?While there is no doubt that the US military has the most data on objects in orbit, it is not the only entity keeping track and collecting data. Perhaps the second best network of sensors and independent catalog of orbital positions is kept by the Russian military. In similar fashion to the US, Russia maintains a network of both dedicated space surveillance and additional duty missile warning radars, as well as optical telescopes. Unlike the US, all of the Russian assets are located on the Asian continent. This means that while Russia has excellent coverage over its own territory, particularly for low Earth orbit, it does not have adequate deep space coverage on the other side of the world and very limited coverage of most of the GEO belt.
Recently, the European Council of Ministers approved a plan to study how best to develop a European SSA capability. Initially starting by combining the data from existing European radars and telescopes, the plan might eventually entail building new sensors. China is looking into this problem as well, with their existing optical telescopes and research at the Purple Mountain Observatory located near Nanjing in Jiangsu Province. They have stated that they currently have a catalog of about 100 objects, but have plans to develop a Chinese Space Surveillance System, including building a network of optical sensors. Although unknown exactly to what extent, it is also believed that certain phased array radars managed by the Chinese military are also used for space surveillance. Many other countries have singular telescopes and radar dishes which could be used to track satellites.
But space surveillance and SSA is not limited to governments and militaries. The largest optical space surveillance telescope network in the world is the International Scientific Optical Network (ISON) and consists of 25 scientific and academic instruments at 18 different sites managed by the Russian Academy of Sciences. Additionally, there are hundreds of amateur observers around the world that do an excellent job of tracking the larger, and often classified, objects that governments don’t like to talk about. Armed with binoculars, stopwatches, and backyard telescopes, they can be surprisingly accurate and well informed.
When it comes to judging the “best” catalog, there are two main criteria to consider:
1. The quality of the orbital data, both how accurate the orbital elements are and how often they are updated.
2. The accuracy of the descriptive information, such as what the object is and the launching State.
With regard to the first criterion, the US military undoubtedly has the best catalog in the world, mainly because of the size of the sensor network they can pull data from, the accuracy and quality standards for that data, and the care that is put into maintaining the catalog. There are three caveats to this assessment. First, the satellite catalog released publicly by the US military is not the best it has. The TLEs on Space Track are of a relatively poor accuracy compared to what the US military uses for its own internal analyses and there are at least 6,000 objects being tracked by the US military that do not appear on Space Track because a launching State cannot be identified, as explained earlier in this article.
Second, the US military does not have a monopoly on highly accurate positional data. The mathematical theories and algorithms behind this process are not classified and have been actively discussed in international forums by experts from the US and other countries for decades.
The optical telescopes in the ISON network can generate highly accurate element sets that are on par with the very accurate SP vectors the US military does not release publicly (see “Billiards in space”, The Space Review, February 23, 2009). In a few cases, the US military is actually behind the curve and still using decades-old astrodynamic techniques to create these element sets, mainly because it costs too much to redesign the hardware and software and recertify the system.
There is also the issue of the satellite owner-operator positional data. Anyone who operates a satellite can get very accurate information on its location, either as reported from the satellite itself by the onboard guidance system or through the process of communicating with the satellite. Almost always this positional data collected by the satellite operator is more accurate than anything collected by any third-party sensor and for the most part not being utilized as part of the US satellite catalog.
While there are some technical issues relating to data formats and models that would need to be worked out for this to happen, the main sticking points have traditionally been policy-related. Some commercial operators are uncomfortable dealing with the US military; many would like the data exchange to flow both ways. However, in the past the US military has generally decided not to share data with commercial operators and only provide information about potential issues on the “trust us” model. Ironically, many of these same commercial providers are now cooperating with the SOCRATES-GEO program run by the Center for Space Standards and Innovation because CSSI has found ways to deal with these issues. There are indications the US military may be changing these policies in the near future.
Third, just because the US military has the best current catalog does not mean that it doesn’t have significant room for improvement. In particular, the lack of any sensors on the Eurasian and African continents, in the Southern Hemisphere, and deep space tracking capacity in general are significant handicaps for the US military catalog. For example, the annual European Space Agency report
The Classification of Geosynchronous Objects lists many objects in or near GEO that are not included in the public US military catalog. [3] This list includes 103 dead payloads or rocket bodies listed in the US military catalog without orbital elements and another 67 pieces of debris not listed at all but which can be clearly identified with a particular launch. And as mentioned earlier in this article, the US military catalog currently has hardly any of the estimated hundreds of thousands of objects smaller than ten centimeters in size. The US military is attempting to address both of these issues, mainly through unilateral measures, but is running into financial and bureaucratic difficulties.
When it comes to the second criterion, the quality of the descriptive information, the US catalog is also notably lacking. The main issue stems from trying to assess the correct name or mission for an object based on public information, which may be inaccurate, hard to track down, or in a foreign language. Having worked this job in the past and trained these analysts myself, I can tell you that it is extremely challenging. In addition to the high turnover and training issues identified in a previous article, there is the additional issue of naming conventions. The US military has a whole set of naming conventions for various Russian, Chinese, and other foreign boosters and satellites that stem from military intelligence practices. Unfortunately, these names are often quite different from the official public names used by the launching State and sometimes classified.
There are also special cases that are particularly challenging, with perhaps the most serious being new launches. Just because a radar or optical telescope is tracking an object doesn’t mean they know
which object they are tracking, especially if it is newly launched and in a very similar orbit to other pieces from that same launch. Additional information such as size and shape is needed to distinguish between two similar objects and sometimes that information isn’t always available when it comes time to catalog objects. The absolute worst-case scenario is when a booster releases multiple microsatellites. Telling one ten-centimeter cube apart from a dozen others nearby and getting the naming right is very difficult indeed. This can lead to issues where an object gets cataloged as the satellite from a launch when it is actually the rocket body and vice versa. Sometimes these mistakes are not discovered until the piece of debris suddenly maneuvers. The Russian Dnepr-1 booster in particular has had past launch attempts with as many as 18 payloads.
For deep space, often a satellite being launched into the geostationary belt needs to make multiple maneuvers over days or weeks to get to its final orbit. Keeping tabs on all these maneuvers can be difficult, especially if the owner-operator has not made public the sequence of events. Other times satellites in GEO will move to new locations in the belt. Most often this is because they are new commercial satellites that are put into one orbital slot for technical checkout and then weeks or months later moved into an operational slot while the old satellite is maneuvered into the graveyard region.
These are not theoretical problems—they happen every day and the end result is an inaccurate catalog. The operators of Celestrak, who have maintained a list of operational satellites for decades, send a weekly list of discrepancies found in the official Space Track catalog to the JSpOC, a list that is very long indeed.
Perhaps the most controversial issue is the number of currently active satellites. This has come up a few times recently in news articles, briefings, and Congressional testimony. Lieutenant General Larry James, Commander of 14th Air Force and the JSpOC, said in testimony before the House Subcommittee on Science and Aeronautics:
Today we are tracking approximately 19,000 objects; 1,300 active payloads and 7,500 pieces of debris… [and] we conservatively project the number of active satellites to grow from 1,300 to 1,500 over the next 10 years.Currently, the best open source analysis of the number of active satellites comes from a database maintained by the Union of Concerned Scientists. This database is pulled from the public US military satellite catalog, Celestrak, satellite catalog information from other nations including Europe, and amateur observers. As of April 1, 2009, it lists just under 900 active satellites in orbit, including many not officially acknowledged by the US military, giving a disparity of 400 compared to the numbers cited by the US military.
It is unclear where the US military’s number of active satellites comes from. Perhaps there is a difference in naming convention and definition of what an active satellite is. General James cited 19,000 total objects being tracked, of which 1,300 are active payloads but only 7,500 pieces of debris and doesn’t elaborate on what category the other 10,200 objects fall under if they are not active satellites or debris. It could also be that the 1,300 number cited by the US military was derived from unclassified sources so as to not compromise the true number gleaned by military intelligence. One basis for this derivation could be that oft-cited historical “fact” that payloads have made up between five percent and ten percent of the catalog; 1,300 is about seven percent of 19,000.
It takes a village to build a (good) catalogClearly, the issue of maintaining a comprehensive and accurate catalog of objects in Earth orbit is extremely important. Safe and secure operations of satellites and human activities in Earth orbit depend on such information. A good satellite catalog (as measured by the two main criteria outlined earlier) is also essential for monitoring the long-term health of the space environment and devising strategies to protect the long-term sustainability of the space environment.
Despite the issues raised earlier, the JSpOC should be commended for tackling such an extraordinarily difficult mission and doing as well as they have given their existing personnel and resource limitations. The important lesson is that maintaining an orbital catalog is difficult, and asking any organization to do so without also giving them the proper tools and resources is setting that organization up for failure.
One immediate area of concern is that the US military, and government in general, needs to improve how they take constructive criticism on this issue. The flaws and shortcomings of the SATCAT are well known to the analysts that work with it on a daily basis, yet in the past the immediate reaction anytime an outsider pointed out these some issues was one of defensive aggression that immediately shuts down any further cooperation. In the broader context, many of those in the US government who are not working day to day with the catalog unfortunately believe the mission boilerplate—that the JSpOC really does track everything in Earth orbit from cradle to grave. Thus they tend to see any criticism of the catalog or the SSA efforts of the military as unfair, untrue, biased, or based on ulterior motives.
These reactions are unfortunate, and they are compounded by the usual swarm of contractors and private companies that have been drawn to the problem like vultures scenting a fresh kill. Some of these entities actually do have the best interests of the United States and the US military in mind and are honestly looking to help. But others just see SSA as another potentially lucrative funding stream to add to their defense portfolio. Sorting between these two groups is extraordinarily difficult but necessary.
With the recent high profile events of the 2007 Chinese ASAT test, the 2008 destruction of USA 193, and the 2009 Iridium-Cosmos collision, the US is joining other governments around the world in finally realizing the importance of SSA and maintaining an accurate catalog. However, they have yet to find a way of providing the resources to do so without breaking the bank, mainly because they have been primarily focusing on unilateral solutions – each building and operating their own sensor networks.
The United States needs to realize that it is not alone in this effort and there are resources available to help succeed in this mission. In many cases, these resources already exist and bringing them into the process does not necessarily mean huge economic costs. However, it does mean a rethinking of the philosophy behind the approach of SSA as well as policy towards cooperation. Part of this re-thinking is to realize that SSA is not solely a military mission: while it does indeed have a strong military component, it also plays a big role in commercial and civil space affairs. Just as the military does not have a monopoly on space remote sensing imagery, weather data, navigation, or communications, commercial, civil and international players need to be brought into the discussion on SSA and mixed with unilateral military solutions.
One of the great lessons of the Internet Age is that more eyeballs on a problem almost always leads to more accurate information and more timely updates.4 Gone are the days when the prevailing assumption is that a small group of “experts” maintaining a set of data is the best way to go. By opening it up to more people, you greatly increase the chances of finding mistakes and reduce the mind share needed to keep a handle on the data.
Additionally, having large numbers of people looking a data set almost always results in some surprising new ways of analyzing, sorting and creating value from that data. Of course, there are some elements of a satellite catalog that should not be publicly crowd-sourced - in particular intelligence on capabilities and limitations of foreign military satellites. But aside from that small section, the other pieces of data that are already made public and shared (element sets, object names, object type) would benefit.
This means that methods of bringing commercial, civil, and international sources of data into the SSA process to improve the existing satellite catalog need to be explored while simultaneously increasing access to that catalog for international civil and commercial use. At the same time, efforts must be made to separate out and protect information that is truly of a critical, national security nature for the United States and its allies.
Part of this international cooperation and dialog should be on better defining the terms used in SSA, including what information should be in the satellite catalog and what an “active payload” is. Commercial operations and governments should be encouraged to share more data on initial orbits for newly launched objects and especially in-orbit maneuvers of existing objects. Doing so would reduce the workload on SSA systems, improve the accuracy of the satellite catalog, and contribute to trust and transparency.
As is the case with many regimes and problems, knowledge is the key to safe and secure operations in space. A comprehensive and accurate satellite catalog is the essential foundation of this knowledge and enables many other services and functions. While the US military does a yeoman’s job with this mission currently, there are many initiatives that the US government can undertake to improve the situation. The incentive is assured access to and continued use of space for the US, part of which depends on the actions of all the other actors in space. Only when everyone is on the same page of music and understands the space environment can we truly make progress towards space sustainability.
References1. Schumacher, Paul, “Prospects for Improving the Space Catalog”, AIAA Meeting Papers on Disc, September 1996, A9641248, AIAA Paper 96-4290
2. Ibid.
3. R. Choc and R. Jehn, “Classification of Geosynchronous Objects”, Issue 11 (February 2009), European Space Agency, European Space Operations Centre, Space Debris Office.
4. D. Brabham,. “Crowdsourcing as a Model for Problem Solving: An Introduction and Cases”,
Convergence: The International Journal of Research into New Media Technologies (2008) Tracking all the active satellites and orbital debris around the Earth is a challenging task, even for the US Defense Department. (credit: NASA)
