altNicholas 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?