What can, or perhaps more importantly should be done to control access to and prevent more debris from building up in the space around Earth?
A Congressional hearing last week tried to add a popular movie-related theme to the issues with a session called: "Space Traffic Management: How to Prevent a Real Life 'Gravity.'" "Gravity" in a nutshell is a movie about what happens to a group of astronauts whose mission is destroyed by orbital debris.
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"While the accuracy of all of the events depicted in the movie 'Gravity' can be questioned, there is no doubt it has made the public more aware of the danger of orbital debris. And that's a good thing. The real world nature of the danger was brought into stark focus by the aftermath of the 2007 anti-satellite test conducted by China. This incident is said to have created an estimated debris population of 150,000 objects larger than 1 centimeter in size. The resulting increase in space debris has made the space environment more hazardous to military, civil, and commercial satellites and spacecraft for years to come," said ranking member of the Space Subcommittee, Donna Edwards.
So what are some of the crucial issues the US government and others are concerned with? Briefly:
- Whose in charge? There are five federal agencies that play a substantial role in orbital debris mitigation and tracking. The National Aeronautics and Space Administration (NASA) has authority over the preponderance of U.S. civil government space missions and has developed a policy and specific procedural requirements for orbital debris mitigation; the National Oceanic and Atmospheric Administration (NOAA) has licensing and regulatory authority over remote sensing spacecraft and a licensing requirement for spacecraft disposal to ensure that applicants comply with U.S. government orbital debris mitigation practices; the Department of Defense's (DOD) Strategic Command (STRATCOM) is responsible for tracking orbital debris; the FCC has jurisdiction for mitigating orbital debris from commercial satellites; and the FAA's Office of Commercial Space Transportation includes orbital debris mitigation regulations in its licensing of commercial launch and reentry vehicles. None have jurisdiction over another.
- Over 70 countries and dozens of companies operate over 1,100 satellites with virtually no regulation.
- A growing trend of multi-payload launches with an ever decreasing satellite size will add to on-orbit congestion. In 2012, 72 new satellites were placed in orbit; in one 7-day period n 2013, 78 new satellites were placed in orbit.
- The trend includes deployment of CubeSats --cube-shaped satellites, 10 centimeters on a side, that are highly capable for their size. In February 2014, the International Space Station (ISS) deployed 33 CubeSats. The SpaceX Falcon-9 ISS cargo resupply mission is programmed to deploy 5 additional CubeSats, including a CubeSat that deploys 104 ChipSats, which are smaller than a credit card.
- Detecting and tracking multiple objects of ChipSat size over 250 miles above the earth is beyond the current capabilities of fielded systems. We anticipate further increase in the complexity of the Space Situational Awareness (SSA) mission through the deployment of hundreds and perhaps thousands of additional small satellites in the next few years-a challenge that will require increasingly capable sensors analytic tools and highly-trained analysts.
- As space debris is generated by humanity's activities in space, it is concentrated in the most heavily used regions of Earth orbit where many active satellites also reside. These regions include the LEO region below 2,000 kilometers (1,200 miles) in altitude and the geostationary Earth orbit (GEO) region, approximately 36,000 kilometers(22,000 miles)above the equator. Of the two regions, LEO currently presents the most pressing challenge for long-term sustainability and increasing collision threats to satellites from space debris.
- There is no international consensus on what the term Space Traffic Management means, nor even what it should be called. For the sake of clarity, Brian Weeden a Technical Advisor with the Secure World Foundation testified that for the sake of his testimony he defined STM as measures taken to minimize the impact of space debris on space activities. Under that definition, the largest element of STM is detecting and mitigating collisions between active satellites and other space objects. While there is some similarity between how this is done in space and air traffic management, the two concepts are not completely analogous. The most important difference between the two is the speed at which objects in space move. The speed of an object in orbit is dictated by its orbital altitude. The lower in altitude an object's orbit is, the faster it must move to avoid being pulled into the atmosphere by the Earth's gravity. At 800 kilometers (500 miles) altitude, an object in orbit travels at approximately 7.5 kilometers per second (17,000miles per hour).
- The most likely scenario for a collision is when two objects in similar orbits at the same altitude cross paths near one of the Earth's poles, and in those cases the combined relative speed can be upwards of 10 to 14 kilometers per second (22,300 to 31,300 miles per hour). Unlike the portrayal in the movie "Gravity," this means that most objects on a collision course in space move too fast for the human eye to see or any human could possibly react to.
- NASA has a process for predicting possible collisions between the ISS and orbital debris. The U.S. standard of protecting occupied spacecraft is to maneuver to avoid an object if it is calculated to have a higher than 1:10,000 chance of hitting the asset. The U.S. standard of protecting occupied spacecraft with a 200 km buffer zone provides less than 30 seconds of separation between the ISS and crossing orbital debris.
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"During my two spaceflights, we flew upside down and backwards to prevent our space shuttle windows from being hit by debris strikes," testified George Zamka, a former NASA astronaut and the current deputy associate administrator in the Office of Commercial Space Transportation at the FAA. But that wasn't enough of course as the space shuttle routinely had dings from space debris.
Zamka stated that as Congress explores the issue of orbital debris and transportation hazards, the FAA urges the Subcommittee to consider at least two possible options, separately or in combination. First, it should look to whether a regulatory agency should authorize transportation on orbit by license. In that scenario, an agency with the proper expertise would, as part of a license evaluation, review the operator's plans and mitigation measures in advance of operations.
In a second scenario that may require additional discussion, we should look to the benefits of an agency with enforcement authority providing notices regarding impending hazards and collisions. An agency with enforcement authority could ensure that maneuvers were carried out, Zamka said.
What do you think?
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