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07.09

The Growing Threat of Space Debris

By Albert Glassman, IEEE Life Member

Introduction

In the early months and years after the Space Age began in October 1957, the main environmental concerns satellite owner/operators had regarding the operational health of their satellites from a physical perspective were meteors (or, more precisely, meteoroids). Since at least a portion of many early satellites' orbits passed through relatively low altitudes, then, as orbit maintenance terminated with end-of-mission, the drag from the upper reaches of the Earth's atmosphere would gently cause these satellites to slowly reenter the atmosphere. Once entering the denser atmosphere (the great incinerator in the sky), the satellites, much like meteors, would "burn-up," though, on occasion, some pieces would reach the ground.

As time passed, space technology advanced, space applications expanded, and, for many years, the Cold War spurred competition in space. Launches of spacecraft became much more frequent. Spacecraft tended to be placed into increasingly higher operational orbits, reaching levels that, thereby, largely eliminated the practical effectiveness of the natural self-cleaning of space offered by atmospheric drag. Additional effort and cost then became required to remove satellites from space at end-of-mission or, at least, from the areas of space densely occupied with operating satellites. Often, removal was shunned.

Thus, the region of outer space around the Earth (much like areas of land, water, and air at various points in time) is becoming polluted. The amount of man-made (or, in today's vernacular, anthropogenic) space system junk and fragments orbiting the Earth has surged over many years, not only from the numerous launches, but, more significantly, from fragmentation of items placed in orbit. Currently, by US Air Force estimates — 19,000 objects (roughly 10 centimeters or larger) orbiting Earth are tracked, of which, 1,300 are active payloads.¹ Others assess there to be about 900 active (i.e., maneuverable) satellites in orbit.²

The collision of the derelict Soviet/Russian communications satellite Cosmos 2251 (a Strela-2M) and the operational commercial Iridium-33 satellite at 790 kilometers above northern Siberia on 10 February 2009 created broader awareness of the space debris problem.³ In addition, on 15 March 2009, a month later, the last minute discovery of a piece of debris about to come dangerously close to the International Space Station (ISS) caused a hurried evacuation of the crew into the docked Soyuz lifeboat, further magnifying space debris concerns.⁴

The limited effectiveness of existing voluntary international debris minimization guidelines may be appreciated by recognizing that China, while participating in the drafting of debris mitigation guidelines at the United Nations, performed an anti-satellite test on 11 January 2007, creating the most space debris from any single event.⁵ Furthermore, Iran and North Korea, whose activities on the World stage are often not well understood, are on the verge of acquiring significant space launch capability. Thus, a great need for a more comprehensive and uniform international commitment to space debris mitigation exists (or, planet Earth may start to look more like Saturn).

What is Space Debris?

Generally, "space debris" refers to any man-made material orbiting the Earth which is no longer operational or useful — including non-functional or decommissioned spacecraft and any fragments thereof, spent rockets, and items cast off during the mission. Also, any of these man-made objects that had orbited the Earth and subsequently reentered the Earth's atmosphere, as well as any portions that survive reentry and reach the Earth's surface, may be referred to as space debris.

Unlike meteors, which are naturally occurring small rocks and particles of matter coming from regions far out beyond the Earth on high speed paths toward Earth and usually burning-up in the atmosphere, space debris is man-made material in orbit around the Earth for at least some period of time. Thousands of spacecraft have been launched into orbit since 1957. These spacecraft and associated rockets become the primary sources of space debris. Since, for many years now, the rate orbiting debris eventually reenters the atmosphere continues to lag behind the rate new debris is introduced, the amount of debris orbiting the Earth continues to increase. Some estimate a debris density in certain regions might soon be reached such that typical occasional collisions among space debris could elevate to a chain reaction of debris forming more debris pieces.⁶

The introduction of space debris results from a variety of events in addition to basic on-orbit retirement of spacecraft. For the typical spacecraft mission, a major piece of debris is the rocket stage that finally places the spacecraft into the orbital region for its operations. If solid fuel is used in the final stage rocket, aluminum oxide slag may be expelled. Small items that might be ejected at start-of-mission include pieces of explosive bolts that held the spacecraft attached to the rocket, separation springs, lens covers, etc. Over time, the sun and other environmental factors may cause spacecraft surface coatings to peel and chip. At end-of-mission, the spacecraft may be maneuvered to reenter the atmosphere, moved to a graveyard orbit, or abandoned in its operational orbit. (Abandonment may not be optional if loss of communications, fuel depletion, etc. may have occurred.)

Manned-space has its unique debris contributions. The major difference from robotic missions result from activities of space station occupants. Cosmonauts on early Soviet space stations apparently released various items as part of experiments. Occupants of the Russian space station Mir reportedly tossed out roughly 200 plastic bags of assorted trash.⁷ Tools, gloves, etc. have been lost during space-walks. However, space stations generally are terminated with controlled reentry. The supporting ferry vehicles contribute debris much like robotic missions, except the Soyuz passenger module is designed to return to Earth. The Shuttle drops its external tank and solid rockets before reaching orbit.

Radioactive space debris occurs as well. The Soviet/Russian RORSAT series of satellites are rather notorious ocean reconnaissance spacecraft, carrying high-powered radar whose energy was supplied by an on-board nuclear reactor using enriched uranium. In July 2008, Cosmos 1818, a RORSAT having been retired in its 800 km orbit 21 years previously, appears to have fragmented, or at least is leaking a cloud of reactor coolant, a liquid sodium-potassium (NaK) alloy. Earlier RORSATs operated at much lower orbits and at end-of-life usually sent their reactor cores to a graveyard orbit at about 900 km altitude. About 16 of these 31 reactor cores also have leaked NaK coolant. As a result, about 100,000 NaK globules, measuring 1 to 6 cm, are estimated to be orbiting in the 800-900 km altitude region. The globules likely were radioactive when released, but, probably, are nearly benign now.^{8, 9}

The United States has also contributed to the collection of radioactive material in orbit through the use of Radioisotope Thermoelectric Generators (RTGs) for power systems in Earth-orbiting satellites such as Transit, Nimbus, and LES 8&9.¹⁰ (RTGs usually employ the decay of Plutonium 238 for energy.) Many of these old satellites remain in orbit.

In terms of numerical quantity, however, most space debris originates from the fragmentation of orbiting spacecraft and rocket upper stages — usually, months or years after their missions have ended. Some estimate these events to have occurred over 200 times.¹¹ Most, apparently, were spontaneous.

The mechanisms for spontaneous fragmentations are not fully understood nor absolutely identified in each case. For satellites, these are usually attributed to overpressure caused by solar heating of residual fuel, tanks with gasses for fuel pressurization, or batteries. One space system series that is particularly egregious is the Soviet/Russian EORSAT (the electronic-signal ocean reconnaissance satellite). In the most recent event, Cosmos 2421 fragmented in early 2008; reportedly, now about 22 out of 50 EORSATs launched have exploded.¹² (Some suspect that not all these fragmentations were actually spontaneous.)

For upper stage rockets in orbit, the source of fragmentation is usually assessed to be leaking fuel. The can be spectacular when a rocket is left with large amounts of propellant after a mission failure and the propellant is hypergolic (i.e., the liquid fuel and oxidizer self-ignite upon contact). Astronomers in Australia serendipitously photographed the explosion of the Russian Briz-M upper stage on 19 February 2007, creating about 1,000 pieces of debris.¹³

Other space debris results from collisions among existing debris or between debris and operational satellites. The only collision between two satellites, Iridium-33 and Cosmos 2251, created hundreds of debris pieces in expanding clouds generally moving along the original orbits of the two satellites. Two other collisions involving operational satellites have been documented: the French satellite Cerise had about 4 meters of its gravity gradient boom broken off by a fragment of an Ariane rocket in 1996, and Cosmos 1934 was likely destroyed by a fragment of Cosmos 926 in 1991.³

Another significant source of space debris is intentional fragmentation of satellites. Many assess that certain Soviet military satellites carried explosives that were detonated by ground command at end-of-mission. (Most all of that debris likely has since burned-up in the atmosphere.) Also, in the 1970s through early- to mid-1980s, the Soviets and Americans performed anti-satellite (ASAT) tests. The Soviet ASAT vehicles are believed to have released waves of buckshot at their target satellites, and the United States destroyed its orbiting Solwind solar science satellite with a missile in 1985.¹⁴

More recently, as mentioned earlier, China performed an ASAT mission against its aging FY-1C weather satellite at 855 km altitude on 11 January 2007 using a missile, ignoring existing international space debris mitigation guidelines and the requirement for a preceding announcement as stated in Article IX of the Outer Space Treaty. That event created about 2,500 pieces of debris. Furthermore, this tragically occurred at a relatively high altitude and near a heavily used region of space. On 21 February 2008, about a year later, the United States, after announcing its intentions, used a missile to destroy one of its military satellites at just under 250 km altitude. The satellite was nearly fully fueled and uncontrollably descending into the atmosphere. The United States was concerned about potential injury and damage on Earth if some action were not taken. Within about a month, almost all the 360 pieces of debris had reentered the atmosphere and, presumably, were vaporized.¹⁵

Unrelated to spacecraft, one of the most bizarre space debris events occurred in 1963. Under the U.S. DoD project West Ford, short thin copper wire "needle-like" fragments were placed in a 3500 km orbit to act as dipoles. By one account, 480 million of these needles were placed in a band 8 km wide and 25 km long. Much, apparently, remains there, having gathered into numerous clusters.¹⁶

The threat posed by space debris is not limited to outer space. On occasion, aircraft pilots see nearby debris streaking through the atmosphere. Whether those sightings were actually caused by space debris or meteors often tends not to be clear. No aircraft apparently have been hit by falling space debris.

Often, space debris survives the fall through the atmosphere and hits the ground. Lists and photographs of such exist. Perhaps the two best-known occurrences of uncontrolled crashes of spacecraft are those of Skylab, a large U.S. space station, and Cosmos 954, a RORSAT. Skylab, weighing over 80 tons, entered the atmosphere on 11 July 1979 and disintegrated, harmlessly scattering debris over the Indian Ocean and along a 75 x 4400 km strip of western Australia, which, apparently, was largely uninhabited.¹⁷ On 24 January 1978, Cosmos 954 reentered the atmosphere and broke-up, scattering debris over the frozen Canadian wilderness and tundra from Great Slave Lake to Baker Lake in the Northwest Territory. No injuries were reported, but radioactive debris was included in the 120,000 square km area affected.¹⁸

Why is space debris a concern?

To begin with, there is no question that a considerable quantity of anthropogenic material orbits the Earth, which, as the result of a collision, potentially could harm a spacecraft or humans in space. Two regions of space are heavily used and, thus, of greatest concern. One is the low Earth orbit (LEO) regime, an area up to 2000 km altitude with numerous spacecraft in nearly circular orbits with a wide range of orientations. The other is the region around the geosynchronous equatorial orbit (GEO), a circular orbit with 24-hour period located about 35,700 km above the equator.

On average, down to particles under a centimeter in size, spacecraft in LEO are more likely to encounter space debris impacts as opposed to meteor impacts. Since either debris-type at less than a millimeter in size generally poses little or no significant impact threat to spacecraft, space debris generally tends to be more of a concern than meteors, a concern that is growing. On the other hand, in GEO, meteors likely represent a larger fraction of the collision threat than in LEO.

Evidence of debris impact flux in LEO is widely documented. Impact craters are clearly visible on various items brought back to Earth from orbit such as satellites, a Hubble solar panel, and the Long Duration Exposure Facility (LDEF), which accumulated some 30,000 craters after over 5 years in LEO more than 20 years ago.¹⁹ Shuttle windows have had to be replaced many times. Estimates of the space debris population vary greatly, but, generally, a few hundred thousand for debris over one centimeter are assessed and many million for debris over one millimeter. Clearly, the most vulnerable space occupant is a space-walker because spacesuits provide protection against loss of pressure only for small debris (micrometeoroid size); fortunately, no difficulties have been encountered. An example of this concern is NASA's having selected a Shuttle orientation during the recent servicing of Hubble on the basis of protecting the astronauts and Shuttle tiles from debris.²⁰

Note that the dynamics of the meteor and space debris threats differ somewhat — any spacecraft along the path of a meteor is vulnerable, but an element of space debris in the same orbit (i.e., path) as a spacecraft poses little or no threat to the spacecraft. Collisions can occur only if orbits cross. (Strictly speaking, the same is true for the hyperbolic orbits of meteors). Thus, collisions tend to be more rare in GEO, essentially being a single orbit.

An analysis of the event in which the derelict Russian Cosmos 2251 and the operational Iridium 33 collided, demolishing both, might be instructive. The misfortune occurred on 10 February 2009 about 790 km over northern Siberia. In compliance with the UN Registration Convention, the orbit of Cosmos 2251, launched 16 June 1993, was listed as 821 km x 783 km at 74 degrees inclination. Iridium satellites like Iridium-33 (launched on 14 September 1997), all list at 780 km x 780 km at 86.4 degrees inclination. Thus, the orbital altitudes were close, but the orbits would not cross.

Over time, orbit parameters vary due to orbit perturbations and orbit maintenance maneuvers. When the crash occurred, Cosmos 2251 had long since been abandoned, thus terminating its orbit maintenance. The orbit parameters of Cosmos 2251 had become 803 x 767 x 74 degrees and Iridium-33 was at 796 x 785 x 86.4 degrees. Now, an orbit intersection and collision became possible. However, major satellite constellations such as GPS and Iridium use identical orbit sizes and inclinations, potentially resulting in numerous orbit intersections. No ill effects occur here since orbit parameters and satellite phasing are controlled by the satellite operators. (For an animated illustration of the Iridium satellite system, see: www.crystalcommunications.net/satellite/iridium/about_iridium.htm.)

No doubt, over periods when satellite orbits intersect, the probability of collision is low. For example, assume that the same two satellites as above are each about 4 meters long and are approaching each other oriented to result in the longest exposure time. Thus, say Iridium, would be vulnerable to to a collision over a distance of 8 meters around the intersection point. Traveling at nearly 7.5 km/sec, that amounts to an exposure time of 0.001 seconds in every 100 minutes (the orbital period) or one chance of collision in over 6 million on any orbital pass.

Even with the small probability of a collision, such a situation must be watched because of huge financial risk, likely impact on operations, and possible threat to others from new debris. Iridium was doing fine in controlling phasing among its constellation of 66 satellites. However, commercial satellite operators cannot be expected to have worldwide precision tracking capability nor sophisticated analysis resources to determine the precise whereabouts of nearby satellites from other systems, especially if the satellite is abandoned. Precious fuel can be wasted for avoidance maneuvers that are unnecessary. For location information on these other satellites, commercial operators often depend on the Two Line Element (TLE) sets provided by U.S. military. Unfortunately, this data lacks the necessary precision, may not be updated with sufficient frequency, and omits certain satellites.²¹

The GEO regime is more orderly than in LEO and may suffer more from natural debris than man-made debris. Satellites are roughly arranged like a string of pearls. Each satellite has a box along the GEO orbit within which it must reside while operational. Generally, everyone knows their neighbors and usually has good working relationships with them. Occasionally, a satellite will pass by GEO satellites on its way to a specific station in GEO; no difficulties have been experienced. At retirement, most GEO satellites are lofted into a somewhat higher orbit. Several satellites, however, have been left abandoned in GEO. As these age, a threat of fragmentation exists and, as orbit inclination and other orbit parameters drift, a threat of collision could possibly arise. No significant problems are known to have occurred in the GEO regime.²²

In addition to debris concerns in orbit, material that survives reentry potentially poses some threat to people and property. Better tools are needed to assess what might hit the ground and where. The uncontrolled reentry of Skylab and RORSAT scattered debris over a couple hundred thousand square kilometers of land. Intense concern arose around the world as these spacecraft sank lower into the atmosphere because the area of impact remained uncertain until close to the end of the fall. Those impacts fortunately occurred across remote land areas; other uncontrolled reentries have fallen into the oceans. The decision of the United States to perform a low altitude ASAT operation against a wayward military satellite on 20 February 2008 to minimize the danger to life and property generated broad criticism, but the objective was met.

What should be done about this situation?

The ultimate objective guiding responses to remedy the space debris situation must be to sustain the benefits of space for present and future generations. No one wants to pay the penalty of increased shielding. So, responses seek to reduce the likelihood of any type of collision and typically fall into three areas: traffic management (relations with other objects in orbit), code of conduct (primarily, minimizing debris from individual spacecraft missions), and space environment clean-up.

Regarding traffic management, the collision of Iridium-33 and Cosmos 2251 has generated additional attention on space situational awareness (SSA), referred to by some as "international civil space situational awareness" (reflecting the global nature of the problem for the civil/commercial communities). Upgraded SSA is the most achievable near-term accommodation of the space debris threats. A commercial operator usually has good knowledge of where his space assets are but generally has limited ability to determine what dangers may lurk nearby. Congress set up the Commercial and Foreign Entity (CFE) program during 2004.²³ In response, Air Force Space Command provides orbit information in the form of Two Line Element (TLE) sets to registered commercial and foreign users through the Web site space-track.org. (Similar information is publicly available but probably not as accurate.) With special request, Air Force will also provide more precise data and some analysis. However, the military still remains concerned about liability and security.

Criticism of the CFE system include accuracy still being inadequate, updates not being sufficiently frequent, inclusion of maneuvers tend not being timely, certain national security satellites that might be relevant to an operator's SSA not being included, and special requests taking an inordinate turn-around time. These shortcomings can make the CFE process seem futile. In frustration, some GEO operators have looked into in-house systems augmented by information from cooperative neighbors. However, problems can exist with using data from other satellite operators because standards are lacking in areas such as accuracy, coordinate systems, terminology, format, and privacy.²¹

Note that various organizations have been dealing with standards for similar space-related data. They could have a role in the SSA standards issue.²⁴ These include the Consultative Committee for Space Data Systems (CCSDS), the Center for Space Standards and Innovation, and the UN's International Standards Organization.

In an effort parallel to CFE, STRATCOM's Joint Space Operations Center had been watching 140 high-priority spacecraft for conjunctions (i.e., close approaches) and computing the probability of collision, but not including Iridium. After the crash, the number was increased to 330, presumably including Iridium, and will further expand to include all maneuverable satellites by 1 October. Two new space tracking systems are coming, the Space-Based Surveillance Satellite (probably, Fall of 2009) and the Space Fence (deployment in 2015), which will greatly increase SSA capability for this program.¹ Nevertheless, to problem is too extensive to solve without international cooperation in terms of resources and commitment. Some suggest an international clearinghouse be established for civil/commercial SSA.

Another space management issue might be limitations on how close to the orbit of another's satellite one might safely set up operations. A related issue would involve who should move and how much when two operational satellites are on a collision course.

Code of conduct efforts has largely dealt with space debris mitigation guidelines. Various versions have been published, e.g., NASA, Inter-Agency Space Debris Coordination Committee, and UN Committee on the Peaceful Use of Outer Space (COPUOS) in 2007. Subsequently, on 12 December 2007, the UN General Assembly adopted the COPUOS guidelines.²⁵ Briefly, they say: limit debris released, minimize potential for spontaneous break-ups, avoid collisions, refrain from intentional destruction, initiate reentry or go to a graveyard orbit at end-of-mission, and deplete energy sources of satellites staying in orbit after end-of-mission (also known as pacification).²⁶

Little has been accomplished to supplement the natural clearing of space debris from the environment beyond controlled reentries and graveyard orbit delivery. The latter obviously leaves debris in space, some of which could possibly fragment. Various space tug schemes to remove dead satellites and spent rocket upper stages exist — such as DARPA's Orbital Express and the life extender/rescue vehicle of the German Aerospace Center (DLR) Robotic Institute. Drag enhancers, magnetic field exploiters, and laser systems have been proposed for LEO debris reduction. Such suggestions tend to be fraught with concerns that more spent rocket motors will be introduced, more debris will be created, an ASAT dual-use capability exists, or they are impractical.²⁷

Conclusions

The amount of space debris in orbit continues to grow. To sustain space as a resource for the many benefits it provides today and those surely coming in the future, a number of activities and commitments must be invigorated. Space situational awareness must be expanded to include at least all operational spacecraft and be available in a reliable and timely manner. International cooperation among spacecraft owner/operators and between them and the tracking/analysis facilities, while maintaining privacy and security, must be encouraged. Standards need to be developed to facilitate information exchanges in this cooperation. Guidelines for space debris mitigation should be maintained and respected. Research for ways to remove debris from space which are effective, affordable, avoid collateral damage, and minimize space warfare concerns should continue. Acceptable procedures to limit the potential for injury and property damage on the ground from uncontrolled reentry of dangerous spacecraft must be found.

References

1. L. James, "Keeping the Space Environment Safe for Civil and Commercial Users," Hearing, U.S. House of Representatives, Space and Aeronautics Subcommittee of the Science and Technology Committee, 28 April 2009.

2. Hearing Charter, "Keeping the Space Environment Safe for Civil and Commercial Users," Hearing, U.S. House of Representatives, Space and Aeronautics Subcommittee of the Science and Technology Committee, 28 April 2009.

3. NASA Orbital Debris Quarterly News, 13(2) 1, 2 (2009).

4. NASA Orbital Debris Quarterly News, 13(2) 3 (2009).

5. NASA Orbital Debris Quarterly News, 11(2) 2 (2007).

6. C. Gorski, "Scientists Fear Space Debris Problem Worsening," American Institute of Physics, www.physicist.org, 21 April 2008.

7. N. Johnson, "Monitoring and Controlling Debris in Space," Scientific American, www.sciamdigital.com, August 1998.

8. NASA Orbital Debris Quarterly News, 13(1) 1 (2009).

9. L. David, "Havoc in the Heavens: Soviet-Era Satellite's Leaky Reactor's Legacy," space.com, 9 March 2004.

10. G. Schmidt, T. Sutliff, "Radioisotope Power," NASA Glenn Research Center, 28 September 2008.

11. N. Johnson, "Keeping the Space Environment Safe for Civil and Commercial Users," Hearing, U.S. House of Representatives, Space and Aeronautics Subcommittee of the Science and Technology Committee, 28 April 2009.

12. NASA Orbital Debris Quarterly News, 12(3) 1 (2008).

13. "What's Up in Space — 22 Feb 2007: Major Breakup," spaceweather.com (2007).

14. A. Tan, G. Badahwar, F. Allahdadi, D. Medina, "Analysis of the Solwind Fragmentation Event," AIAA Journal of Spacecraft and Rockets, 33(1) (1996).

15. J. Oberg, "U.S. Satellite Shootdown: The Inside Story," IEEE Spectrum www.spectrum.ieee.org, August 2008.

16. D. Darling, "West Ford," www.daviddarling.info.

17. "Skylab: Re-entry Crisis," Jane's Spaceflight, p. 95 (1984).

18. Q. Bristow, "Operation Morning Light," Geological Survey of Canada, http://gsc.nrcan.gc.ca (1995).

19. A. Whittaker, D. Dooling, "LDEF Materials Results for Spacecraft Applications — Executive Summary," NASA Conference Publication 3261 (1995).

20. F. Morring, "Debris Precautions Set for Hubble Mission," Aviation Week and Space Technology, 27 April 2009.

21. R. DalBello, "Keeping the Space Environment Safe for Civil and Commercial Users," Hearing, U.S. House of Representatives, Space and Aeronautics Subcommittee of the Science and Technology Committee, 28 April 2009.

22. W. Jones, "Space Debris Be Dammed: Intelsat Flies a Satellite 77,000 Kilometers Without a Collision," IEEE Spectrum, www.spectrum.ieee.org, April 2009.

23. Public Law 108-136, Section 913.

24. S. Pace, "Keeping the Space Environment Safe for Civil and Commercial Users," Hearing, U.S. House of Representatives, Space and Aeronautics Subcommittee of the Science and Technology Committee, 28 April 2009.

25. U.N. General Assembly Resolution 62/217, 21 December 2007.

26. M. Krepon, "Space Security" (and attached "Model Code of Conduct for Responsible Space-Faring Nations"), Hearing, U.S. House of Representatives, Strategic Forces Subcommittee of the Armed Services Committee, 18 March 2009.

27. J.C. Liou, N. Johnson, "Risks in Space from Orbiting Debris," Science, vol. 311, 20 January 2006.

Dr. Albert Glassman is an IEEE Life Member and a member of IEEE-USA's Committee on Transportation and Aerospace Policy. In 2008, he served as the Institute of Navigation's AAAS Science Congressional Fellow in the House of Representatives with Rep. Dana Rohrabacher (R-Calif.), a member of the House Science & Technology Committee. In 2007, he was a member of a team headed by Professor John Logsdon, in consultation with NASA managers and former astronauts, that drafted a treaty for international cooperation in protecting the Earth from asteroids, which eventually was submitted to UN COPUOS. Dr. Glassman worked for nearly 20 years in private industry, followed by 20 years in the Department of Defense until his retirement in April 2005. Over those years, he held various positions with space-related responsibilities for analysis, design, launch, space operations, international space, and policy. He was a consultant during 2005-2007. Among national-level projects accomplished, he helped draft President Bush’s 2004 National Security Presidential Directive on Space-Based Positioning, Navigation and Timing. Dr. Glassman holds a Ph.D. in aerospace engineering from UCLA and a J.D. from George Washington University.

Comments on this article may be submitted to todaysengineer@ieee.org.