Nicholas Johnson is Chief Scientist and Program Manager for NASA’s Orbital Debris Program Office. In July 2008 he was awarded the Department of Defense Joint Meritorious Civilian Service Award for his contribution to Operation Burnt Frost, a mission that involved the interception and destruction of an out-of-control satellite before it could hit the Earth.
NASA Tech Briefs: When was the Orbital Debris Program Office established and what is its primary function?
Nicholas Johnson: The office was established in 1979, first to define the current and future orbital debris environment to support mission operations and spacecraft design, and also to develop orbital debris mitigation measures and policies.
NTB: Can you give us a little more detail about what that involves?
Johnson: Office personnel evaluate all NASA space programs and projects for compliance with agency orbital debris mitigation requirements. The office is also the lead for coordination and cooperation with other U.S. government departments and organizations in the field of orbital debris. As Chief Scientist for Orbital Debris, I also serve as the U.S. technical expert on space debris at the United Nations.
NTB: Exactly what is space debris?
Johnson: Space debris, primarily, is anything in Earth-orbit that no longer has a useful function. That could include a non-functional spacecraft, a derelict launch vehicle upper stage, fragmentation debris, paint flecks, anything you can think of.
NTB: Is space debris just manmade objects, or does it also include natural materials like meteoroids and things like that?
Johnson: Normally when we talk about orbital debris, we’re talking about manmade objects. Meteoroids are in orbit about the sun and we normally refer to them as the natural environment.
NTB: How does one become an expert in space debris? Is there a course of study you can recommend, or do you pretty much learn on the job?
Johnson: Actually, orbital debris is a very small scientific community. Within the U.S., NASA is the principal source of orbital debris expertise and is the only organization which actually characterizes the orbital debris population from the smallest debris — microns — to the largest, which can be tens-of-meters. Personally, I studied physics and astrophysics, but none of my formal education involved orbital debris. I think the vast majority of the folks who are in the field did learn on the job. There is actually one university in the United States — The University of Colorado, Boulder — that is the only U.S. institution to have awarded PhD’s in orbital debris, but only about a half-dozen or so folks have made it through that course. I have been involved in orbital debris research for 30 years in support of a wide variety of U.S. government organizations.
NTB: When it comes to the amount of debris in space, I’ve heard all kinds of figures. I’ve heard that since the launch of Sputnik 1 back in 1957, there have been approximately 28,000 objects put into space, 9,000 of which are still in orbit, and only 6-percent are still operational. To make matters worse, we’re launching approximately 75 new spacecraft per year, adding to the potential problem. How does your office keep track of all this debris and make sure it doesn’t pose a threat to things like the International Space Station, Hubble Telescope, and the Space Shuttle? And are those numbers I have even accurate?
Johnson: Well, they’re a little bit out of date. First off, NASA doesn’t maintain what’s called the U.S. Satellite Catalog. That’s performed by the Department of Defense. We certainly work closely with the DoD in a large number of space surveillance areas.
Since Sputnik 1 there have been more than 4600 space missions launched from around the world that have successfully reached Earth orbit or beyond. The total number of objects which have been officially cataloged by the Department of Defense is now nearly 34,000, of which about 13,000 are still in Earth-orbit. It turns out the Department of Defense is also tracking another 5,000 objects, which they know are out there, but they have not yet officially cataloged them. It’s more of an administrative issue. So, if you’re trying to find a final number of objects that we’re aware of, that we know where they are, it’s somewhere around 18,000.
NTB: How big are most of these objects and how fast are they normally traveling through space?
Johnson: These objects vary in terms of size from about 10 cm or so up to many tens-of-meters. That’s in terms of what can be tracked. Actually there are many smaller objects in orbit which DoD can’t track; they’re down to millimeter, or even micron, size. Their masses, of course, range anywhere from a sub-gram up to many metric tons. In low earth orbit the speeds of orbital debris are 7-8 km/s; in geosynchronous earth orbit the speeds are much less.
NASA relies on the U.S. Space Surveillance Network to track objects larger than about 10 cm in low Earth orbit, up to 2000 km altitude. NASA is responsible for statistically defining the debris environment for smaller objects. Special ground-based radars, including the 70-meter-diameter radio telescope at Goldstone, CA, can detect orbital debris as small as a few millimeters. Returned spacecraft surfaces provide insight into the population of orbital debris smaller than 1 mm.
NTB: Should one of these objects impact the Space Station or a Space Shuttle, what kind of damage could it do?
Johnson: The damage could be negligible, mission-threatening, or catastrophic, depending upon the size of the debris and the location of impact. Debris 10 cm and larger have the potential for completing destroying a spacecraft and creating large amounts of new debris. The accidental collision of two intact spacecraft on 10 February 2009 resulted in the creation of more than 600 large pieces of debris. Debris smaller than 1 mm normally do not affect the operation of a spacecraft.
The Space Station is the most heavily protected vehicle ever launched. It can withstand hits by particles up to about 1 cm. The Space Shuttle is a little bit more vulnerable because of its nature and the fact that it has to conduct a reentry successfully. But these particles, if they were to strike either the Space Shuttle or the International Space Station, would typically hit at somewhere around a speed of 10 km/sec, so a very small particle could do a lot of damage.
NTB: What is currently being done to protect these craft from being damaged by space debris, and is there new technology being developed for the future that will provide even better protection?
Johnson: It depends on the vehicle. We’re trying to design robotic spacecraft more robustly. We can shield against particles as large as about 1 cm, although most robotic spacecraft don’t have quite that much shielding onboard.
The primary near-term protection for spacecraft is the limitation of new orbital debris. The U.S. and the international aerospace community have developed specific orbital debris mitigation measures. But when possible, the design of spacecraft can be improved to protect against particles up to about 1 cm. For particles larger than 10 cm, such as those tracked by the Space Surveillance Network, collision avoidance maneuvers are the primary protection. The entire Space Station maneuvered around a piece of debris just last year. For other countermeasures, it’s all in how you fly the vehicle. Debris normally comes from specific directions, so if you put your more sensitive components away from that direction, you’ve got a better chance of surviving.
NTB: Is NASA working on any new technology that will a) reduce the amount of space debris currently floating around out there, and b) prevent future missions from turning into more space debris?
Johnson: Well, we’re looking at “a,” but we can’t do that yet, and we certainly are doing “b” very, very well. What that means is that we’ve been looking at ways to remediate the space environment, but it turns out to be a significant technical challenge as well as an economic challenge. The International Academy of Astronautics is completing a comprehensive study of concepts for the remediation of the near-Earth space environment. When that study is completed, NASA will reevaluate debris removal proposals, but to date, no technique has been found to be both technically feasible and economically viable. It’s hard to find a way to go up and remove debris once it’s in orbit, so NASA and the international community have been focusing for the last 10 to 20 years on better operations and better vehicle designs so that we don’t create debris unnecessarily.
NTB: In July 2008 you received the Department of Defense Joint Meritorious Civilian Service Award for your contribution to Operation Burnt Frost, which was the interception and destruction of an out-of-control National Reconnaissance Office satellite known as USA-193 before it could impact the Earth. Tell us about Operation Burnt Frost and what role you played in it.
Johnson: Burnt Frost was the operation to try to mitigate the threat posed by a crippled Department of Defense spacecraft that contained hazardous material that was about to reenter the atmosphere, components of which would’ve struck the surface of the Earth. I served as the NASA representative to a large U.S. government interagency group charged with assessing the threat posed by the satellite to people on Earth and means of mitigating that threat. NASA contributed to the effort in a variety of ways. We verified that the spacecraft’s propellant tank, containing a large amount of frozen, hazardous hydrazine, would survive an uncontrolled reentry in the atmosphere, potentially exposing multiple people to injury or death. NASA also played a principal role in quantifying the probability of human casualty. In the event that an order was given by the President to engage the spacecraft prior to reentry, NASA evaluated the risk to the International Space Station, the Space Shuttle, and other NASA assets from the resultant, short-lived orbital debris. I worked on a daily basis with the interagency group, visiting U.S. Strategic Command in Omaha, meeting with the President’s Science Advisor, and attending a deputies’ meeting of the National Security Council in the White House. For my efforts, I was awarded the NASA Distinguished Service Medal by the NASA Administrator and the Joint Meritorious Civilian Service Award by the Chairman of the Joint Chiefs of Staff.
NTB: Was that the first time we had ever attempted to intercept a piece of space debris with a surface-launched missile?
Johnson: Yes, it actually was the first time we ever intercepted a piece of space debris. Back in 1985, the U.S. conducted its first and only test of an air-launched anti-satellite system against a Department of Defense satellite called Solwind, which was operational at the time; hence, it was not a piece of orbital debris.
NTB: I imagine this was a lot more challenging.
Johnson: It certainly was. Actually, six weeks prior to the engagement, the United States didn’t have the capability to engage the satellite. We had to completely reconfigure the hardware and the software to even make this possible.
NTB: Exactly what was entailed in doing that? How do you respond so quickly to something like that?
Johnson: It was a phenomenal operation. I really can’t give you the details, but you would be impressed by the dedication and the hard work that people from all over the country, from all of the services, and from the civilian community spent in making that possible.
NTB: I’m sure I would because most people think government agencies tend to get bogged down in bureaucracy. It’s actually quite a tribute that you were able to mobilize that quickly and solve the problem successfully.
Johnson: I’ve been working with the government for nearly 40 years and I’ve never seen people just throw the book out the window and get the job done as well as they did this time.
NTB: Finally, how much risk does space debris pose to people here on Earth?
Johnson: It’s really not that much of a risk. On the average, there’s about one cataloged object per day that reenters the Earth’s atmosphere. Most of it burns up in the atmosphere. Those things which may have surviving components typically fall into the water, or in some desolate region like Siberia, or the Canadian tundra, or the Australian Outback. No one has ever been hurt by any reentering debris.
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